Respiratory

Pulmonary tuberculosis: diagnosis, treatment, and public health reporting

Clinical Overview and When to Suspect Pulmonary Tuberculosis

— Cough ≥2–3 weeks, especially with night sweats, weight loss, hemoptysis, fevers, or anorexia

— Any patient with the above PLUS an epidemiologic risk factor

— Foreign-born from high-prevalence regions (Asia, Africa, Latin America, Eastern Europe) — accounts for ~70% of US cases

— HIV (single greatest risk factor for reactivation)

— Close contacts of active TB cases

— Homelessness, incarceration, long-term care, IV drug use

— Healthcare workers, mycobacteriology lab personnel

— Immunosuppression: anti-TNF therapy, chronic steroids, transplant, ESRD, post-gastrectomy, silicosis, diabetes

— Primary: lower/mid lung infiltrate + hilar adenopathy, often in children/HIV

— Reactivation: upper-lobe cavitary disease in adults

Pulmonary tuberculosis (TB) is infection of the lung by Mycobacterium tuberculosis, transmitted via aerosolized droplet nuclei and remaining a leading global infectious killer despite low US incidence (~2.5/100,000).

When to suspect in the US ambulatory setting:

Key risk groups (Step 3 favorites):

Pathophysiology in one breath: Inhaled bacilli → alveolar macrophages → primary Ghon focus (often middle/lower lobes) → hematogenous seeding → containment as latent TB infection (LTBI) in 90%; reactivation typically in upper-lobe apical-posterior segments due to high O₂ tension.

Primary vs reactivation:

Step 3 management: Any patient suspected of pulmonary TB in clinic or ED must be placed in an airborne isolation (negative-pressure) room with N95 respirators before further workup — do not wait for imaging.

Board pearl: A homeless man with 6 weeks of cough, hemoptysis, and a 15-lb weight loss is TB until proven otherwise — CXR, sputum AFB ×3, and isolation come first; broad-spectrum antibiotics for "pneumonia" without isolation is the wrong answer.

Key distinction: LTBI = asymptomatic, non-infectious, normal CXR, positive IGRA/TST. Active TB = symptomatic and/or radiographic disease, potentially infectious. They are managed completely differently.

Presentation Patterns and Key History

— Initially dry, becomes productive

— Hemoptysis in cavitary disease — can be massive if a Rasmussen aneurysm erodes

— Pleuritic chest pain if pleural involvement

— Low-grade fevers, drenching night sweats requiring sheet/clothing changes

— Anorexia and unintentional weight loss (often >10 lb)

— Fatigue, malaise

— Country of origin and date of US arrival; travel to endemic regions

— TB exposure: known contact, shelter, prison, healthcare work

— Prior TB or LTBI treatment — completion status, regimen, drug resistance

— Prior TST/IGRA results and prior BCG vaccination (affects TST interpretation, not IGRA)

— HIV status and CD4 count; other immunosuppression (anti-TNF, steroids, transplant)

— Comorbidities: diabetes, ESRD, silicosis, malignancy, malnutrition

— Substance use: tobacco, alcohol, IV drugs

— Housing, occupation, household composition (children, immunocompromised)

— Cervical lymphadenitis (scrofula), back pain (Pott disease), sterile pyuria (renal TB), meningitis, pericarditis

— Extrapulmonary disease is more common in HIV and children

Classic constitutional triad: chronic cough, night sweats, weight loss — present in the majority of active pulmonary TB.

Symptom timeline: Symptoms are subacute to chronic (weeks to months), distinguishing TB from bacterial CAP (days) and viral URI.

Cough characteristics:

Systemic symptoms:

Targeted history (high-yield on Step 3):

Extrapulmonary clues that change the picture:

HIV-coinfection caveat: Advanced HIV (CD4 <200) often presents atypically — lower-lobe or miliary infiltrates, lack of cavitation, negative TST, and a higher likelihood of normal or near-normal CXR. Maintain suspicion despite atypical features.

Board pearl: A foreign-born taxi driver with 2 months of cough, 12-lb weight loss, and a recent emigration from India — order CXR + sputum AFB + IGRA + HIV test; do not anchor on "smoker's cough."

Step 3 management: Always document the public health risk assessment (contacts at home, work, daycare) at the index visit — it drives later contact investigation.

Physical Exam Findings and General Assessment

— Cachexia, temporal wasting, pallor

— Low-grade fever (often 99–101°F); high fevers possible

— Tachypnea and mild hypoxemia in advanced disease

— Often normal or minimal findings despite extensive radiographic disease (a classic teaching point)

— Possible apical/posterior crackles ("post-tussive rales")

— Bronchial breath sounds or amphoric breathing over a cavity

— Dullness, decreased breath sounds, and pleural rub if tuberculous pleural effusion

— Cervical and supraclavicular lymphadenopathy (scrofula) — firm, matted, sometimes draining

— Generalized lymphadenopathy raises concern for HIV co-infection or miliary TB

— Spine tenderness, kyphosis → Pott disease

— Sterile pyuria, flank pain → genitourinary TB

— Meningismus, cranial neuropathies → TB meningitis (basilar predilection)

— Pericardial rub, elevated JVP, pulsus paradoxus → TB pericarditis (think in HIV)

— Hepatosplenomegaly, choroidal tubercles on fundoscopy → miliary TB

— Erythema nodosum, phlyctenular conjunctivitis → hypersensitivity reactions to primary TB

— Vitals: temperature, RR, SpO₂ on room air, weight (track for response)

— Look for signs of complications: massive hemoptysis, tension pneumothorax (from cavity rupture), or sepsis physiology in disseminated disease

— Mental status changes → consider CNS TB or hyponatremia from SIADH

— Oral candidiasis, Kaposi sarcoma, dermatologic signs of immunosuppression should prompt HIV testing if not already done

General appearance:

Pulmonary exam — frequently underwhelming:

Lymphatic exam:

Extrapulmonary clues to seek:

Hemodynamic and severity assessment:

HIV-specific findings:

Key distinction: Unlike bacterial pneumonia where exam often correlates with imaging, in TB the CXR and CT typically look far worse than the lung exam — a quiet chest with a destroyed upper lobe is classic.

Board pearl: Choroidal tubercles on fundoscopy are pathognomonic for miliary TB — always examine the eyes in a febrile patient with diffuse micronodular CXR pattern.

Step 3 management: Document baseline weight and oxygen saturation at diagnosis — both are tracked monthly during therapy as response markers.

Diagnostic Workup — Initial Labs, Imaging, and Microbiology

— Reactivation TB: upper-lobe apical-posterior infiltrates, cavitation, fibronodular scarring, volume loss

— Primary TB: mid/lower-lobe consolidation + ipsilateral hilar adenopathy ± pleural effusion (especially in kids)

— Miliary TB: diffuse 1–3 mm nodules throughout both lungs

— Healed TB: apical fibrosis, calcified granulomas, Ranke complex (calcified Ghon focus + node)

— HIV with CD4 <200: may show lower-lobe, diffuse, or normal CXR

— Three sputum specimens collected ≥8 hours apart, at least one early-morning, before initiating therapy

— Each sent for: (1) AFB smear (acid-fast stain), (2) mycobacterial culture (gold standard, takes 2–6 weeks), (3) nucleic acid amplification test (NAAT), typically Xpert MTB/RIF

— Xpert MTB/RIF detects MTB DNA and rifampin resistance in ~2 hours — CDC recommends NAAT on at least one specimen for any patient with suspected pulmonary TB

— Induced sputum with hypertonic saline (preferred next step)

— Bronchoscopy with BAL ± transbronchial biopsy

— Early-morning gastric aspirates in young children

— HIV test — mandatory for every patient with TB

— CBC, CMP (baseline LFTs and creatinine before drug therapy), uric acid, hepatitis B/C serologies, pregnancy test

— Vitamin D level (often low; supplementation considered)

— Diabetes screen (HbA1c) — bidirectional risk

Imaging — Chest X-ray (PA + lateral):

Chest CT: Use when CXR is equivocal or to characterize cavitation, tree-in-bud (endobronchial spread), or rule out alternatives. Not required for diagnosis but commonly obtained.

Microbiology — the diagnostic core:

If sputum is unobtainable:

Adjunctive labs:

TST and IGRA help establish prior infection but do not confirm active disease and may be negative in 20–25% of active TB (anergy).

Board pearl: A positive AFB smear is not specific for TB — nontuberculous mycobacteria (NTM) also stain acid-fast. NAAT distinguishes MTB from NTM and is the rapid answer on Step 3.

Step 3 management: Place in airborne isolation, send 3 sputum AFB + 1 NAAT + culture, order HIV, baseline LFTs/Cr, and notify the local health department on clinical suspicion — do not wait for culture.

Diagnostic Workup — Confirmatory Testing and Drug Susceptibility

— Liquid media (MGIT, BACTEC) yields growth in 1–3 weeks; solid media (Löwenstein-Jensen) takes 3–6 weeks

— Required for drug susceptibility testing (DST) — phenotypic susceptibility to isoniazid, rifampin, ethambutol, pyrazinamide (RIPE), and second-line drugs when indicated

— Xpert MTB/RIF detects rifampin resistance rapidly

— Xpert MTB/RIF Ultra has improved sensitivity, especially in paucibacillary or HIV disease

— Line-probe assays and whole-genome sequencing for INH and second-line resistance — done at reference labs

— Preferred over TST in BCG-vaccinated patients and those unlikely to return for TST reading

— Detects IFN-γ release to MTB-specific antigens (ESAT-6, CFP-10) — not affected by BCG

— Cannot distinguish latent from active disease

— Read at 48–72 hours; induration, not erythema

— Cutoffs:

— ≥5 mm: HIV, recent contact, fibrotic CXR, transplant/immunosuppression (≥15 mg/d prednisone or anti-TNF)

— ≥10 mm: foreign-born, IVDU, healthcare workers, prisoners, children <4, high-risk medical conditions

— ≥15 mm: no risk factors

— Thoracentesis: lymphocyte-predominant exudate, ADA (adenosine deaminase) >40 U/L supportive, low glucose, pleural fluid AFB often negative

— Pleural biopsy has higher yield than fluid culture (granulomas + culture)

— Lymph node FNA/excision, CSF (high protein, low glucose, lymphocytosis, ADA), urine, bone, pericardial fluid as clinically indicated

Mycobacterial culture remains the diagnostic gold standard:

Molecular drug-resistance testing:

IGRA (QuantiFERON, T-SPOT.TB):

Tuberculin skin test (TST/PPD):

Pleural TB workup:

Extrapulmonary sampling:

Key distinction: Smear-positive = highly infectious and requires strict isolation; smear-negative but culture-positive = less infectious but still active disease requiring full treatment.

Board pearl: Pleural fluid AFB smear and culture are notoriously low yield (<30%); pleural biopsy with histology + culture is the high-yield move on a Step 3 vignette of lymphocytic effusion with elevated ADA.

Step 3 management: Always obtain DST on the initial isolate, even if you start empiric RIPE — results guide regimen adjustment at week 6–8.

Risk Stratification and Initial Management Logic

— Active pulmonary TB (clinical + radiographic + micro): full 4-drug therapy, isolation, reporting

— Latent TB infection (LTBI): positive IGRA/TST, no symptoms, normal CXR → 3–4 month preventive regimen

— Suspected active TB pending workup: empiric isolation + RIPE if clinical suspicion is high and delay would risk transmission or deterioration

— Pulmonary or laryngeal disease, cavitary disease, AFB smear-positive sputum = highly infectious

— Extrapulmonary only (no lung involvement) = generally not infectious

— Hospitalize if hypoxia, hemoptysis, hemodynamic instability, inability to self-isolate, suspected MDR-TB, or unstable comorbidity

— Most stable patients can be managed outpatient with home isolation in coordination with public health

— Stay home, no visitors, separate bedroom, mask when others present

— Continued until: receiving effective therapy ≥2 weeks, clinical improvement, and 3 consecutive negative AFB smears on different days

— Standard of care for all active TB in the US — improves adherence, reduces resistance and relapse

— Administered by health department; video-DOT acceptable

— LFTs, creatinine, CBC, HIV, hepatitis B/C, pregnancy test

— Visual acuity and color vision (ethambutol baseline)

— Weight (drug dosing is weight-based)

— Prior TB treatment, contact with known MDR case, immigration from high MDR prevalence country, HIV with TB exposure

— In these patients, expand empiric regimen and obtain expedited molecular DST; consult TB specialist

Diagnostic categorization drives management:

Infectiousness assessment:

Inpatient vs outpatient decision:

Home isolation criteria:

Directly Observed Therapy (DOT):

Baseline assessments before starting RIPE:

Resistance risk factors that change empiric regimen:

CCS pearl: Order — airborne isolation, sputum ×3 (AFB, NAAT, culture), HIV, LFTs/Cr/CBC, hepatitis panel, pregnancy test, visual acuity, weight, CXR. Notify health department. Start RIPE empirically if suspicion is high.

Board pearl: A patient who "feels better" after 2 weeks of RIPE is not cured — total duration is 6 months minimum; stopping early is the leading cause of relapse and acquired resistance.

Pharmacotherapy — First-Line RIPE Regimen

— Rifampin (or rifapentine in newer regimens) 600 mg daily

— Isoniazid (INH) 5 mg/kg (max 300 mg) daily + pyridoxine (B6) 25–50 mg to prevent neuropathy

— Pyrazinamide (PZA) 25 mg/kg daily

— Ethambutol 15–20 mg/kg daily

— Intensive phase (months 0–2): all four drugs daily

— Continuation phase (months 2–6): INH + rifampin; can use thrice-weekly DOT

— Extend to 9 months if: cavitary disease on initial CXR and positive culture at 2 months; CNS TB (9–12 months); bone/joint TB (6–9 months)

— Isoniazid: hepatotoxicity, peripheral neuropathy (B6 prevents), drug-induced lupus, sideroblastic anemia, CYP inhibition

— Rifampin: hepatotoxicity, orange body fluids (urine, tears — counsel!), flu-like syndrome, thrombocytopenia, potent CYP3A4 inducer (warfarin, OCPs, methadone, ARVs, DOACs)

— Pyrazinamide: hepatotoxicity (most hepatotoxic), hyperuricemia/gout, arthralgia, photosensitivity

— Ethambutol: optic neuritis (red-green color blindness, decreased acuity) — dose-related, usually reversible

— 3HP: weekly INH + rifapentine ×12 weeks (DOT)

— 4R: daily rifampin ×4 months

— 3HR: daily INH + rifampin ×3 months

— 6–9H: daily INH ×6–9 months (legacy option)

Standard regimen for drug-susceptible pulmonary TB: RIPE for 2 months, then RI for 4 months (total 6 months):

Phases:

2022 alternative — 4-month rifapentine-moxifloxacin regimen (CDC-endorsed for select adults/adolescents ≥12 yr with drug-susceptible pulmonary TB, non-cavitary or limited disease, non-pregnant, HIV with CD4 ≥100 on appropriate ART): rifapentine + INH + PZA + moxifloxacin daily for 8 weeks → rifapentine + INH + moxifloxacin daily for 9 weeks.

Key drug-specific toxicities (memorize):

LTBI regimens (preferred to longest):

Board pearl: Counsel every patient that rifampin turns urine, tears, and contact lenses orange — this is harmless but expected; also warn about OCP failure and recommend a backup method.

Step 3 management: All TB drugs are given once daily on an empty stomach when possible to maximize absorption; rifapentine is the exception (with food).

Drug-Resistant TB, Drug Interactions, and Special Pharmacologic Issues

— Mono-resistant: to one first-line drug

— MDR-TB: resistant to at least INH + rifampin

— Pre-XDR: MDR + resistance to any fluoroquinolone OR a second-line injectable

— XDR-TB: MDR + resistance to a fluoroquinolone AND additional Group A drug (bedaquiline or linezolid)

— Refer to TB expert/state public health

— BPaL or BPaLM regimen (bedaquiline + pretomanid + linezolid ± moxifloxacin) for 6 months has revolutionized care for pulmonary MDR/pre-XDR TB

— Older regimens: ≥4 effective drugs for 15–24 months based on DST

— Bedaquiline: QT prolongation, hepatotoxicity

— Linezolid: myelosuppression, peripheral and optic neuropathy, serotonin syndrome

— Fluoroquinolones (moxi, levo): QT, tendinopathy, dysglycemia

— Cycloserine: psychosis, seizures

— Aminoglycosides (amikacin): ototoxicity, nephrotoxicity

— Rifampin induces CYP3A4 → lowers levels of: warfarin, OCPs, methadone, statins, azoles, DOACs, tacrolimus, most HIV protease inhibitors and many NNRTIs

— In HIV co-infection: substitute rifabutin for rifampin when using PIs or certain ARVs

— INH inhibits CYP → raises phenytoin, carbamazepine, warfarin levels

— Start TB therapy first; initiate ART within 2 weeks if CD4 <50, within 8 weeks if CD4 ≥50

— Watch for IRIS (paradoxical worsening) — treat with NSAIDs or corticosteroids; do not stop ART or TB therapy

— Indicated in TB meningitis and TB pericarditis — reduces mortality and constrictive complications

— Not routinely used in pulmonary TB

Drug-resistance definitions:

MDR-TB management:

Key second-line agents and toxicities:

Critical drug interactions (Step 3 minefield):

HIV co-infection (TB-HIV) timing of ART:

Adjunctive corticosteroids:

Board pearl: A TB patient on warfarin started on RIPE will see INR plummet from rifampin's CYP induction — monitor INR weekly and increase warfarin dose preemptively.

Step 3 management: Any rifampin resistance on Xpert MTB/RIF is a red flag for MDR-TB — broaden empiric therapy and consult public health immediately while awaiting full DST.

Special Populations — Elderly, Renal, and Hepatic Impairment

— Often present atypically: nonspecific weight loss, failure to thrive, cognitive change, lower-lobe disease

— Higher reactivation risk due to immunosenescence, comorbid diabetes, malnutrition, institutionalization

— Greater risk of drug-induced hepatitis (especially INH) — baseline and monthly LFTs more critical

— Polypharmacy raises rifampin interaction concerns (warfarin, statins, DOACs, antiplatelets)

— INH and rifampin: no dose adjustment (hepatically cleared)

— Pyrazinamide and ethambutol require dose-interval adjustment — give thrice weekly (25 and 15–25 mg/kg respectively) after dialysis on dialysis days

— Avoid aminoglycosides if possible; use cautiously with levels

— Increased risk of ethambutol optic neuritis in CKD — monitor vision closely

— INH, rifampin, and PZA are all hepatotoxic; PZA is the worst offender

— In mild/moderate liver disease: standard regimen with close LFT monitoring (every 2–4 weeks)

— In decompensated cirrhosis (Child-Pugh C) or active hepatitis: drop or limit hepatotoxic drugs

— Options: rifampin + ethambutol + fluoroquinolone ± second-line agent for 12–18 months

— Avoid PZA entirely in severe liver disease

— Consult hepatology and TB specialist

— Hold all hepatotoxic TB drugs if: ALT >3× ULN with symptoms (nausea, jaundice, RUQ pain) or ALT >5× ULN asymptomatic

— Once LFTs normalize, rechallenge sequentially — usually rifampin first, then INH, then PZA last (or omit PZA)

— Worsens TB outcomes; tighter glycemic control improves cure rates

— Rifampin reduces sulfonylurea efficacy; may require insulin

Elderly patients:

Renal impairment (CrCl <30 or dialysis):

Hepatic impairment:

Monitoring for drug-induced liver injury (DILI):

Diabetes:

Pyridoxine (B6) supplementation is mandatory for: elderly, diabetics, alcoholics, malnourished, HIV, CKD, pregnancy, breastfeeding — to prevent INH neuropathy.

Board pearl: Any TB patient with new RUQ pain, nausea, or jaundice during therapy → stop INH/rifampin/PZA, check LFTs, rule out other causes (hepatitis serologies, alcohol, acetaminophen), and resume sequentially once recovered.

Step 3 management: Baseline LFTs are mandatory; routine monthly LFTs are required for those with risk factors (age >35, alcohol use, HIV, pregnancy, postpartum, viral hepatitis, baseline LFT abnormalities).

Special Populations — Pregnancy, Pediatrics, and HIV

— Active TB in pregnancy must be treated — untreated disease is far more dangerous than therapy

— First-line regimen: INH + rifampin + ethambutol for 9 months (PZA traditionally avoided in US pregnancy guidelines due to inadequate teratogenicity data, though WHO endorses its use)

— Pyridoxine 25–50 mg/day mandatory during pregnancy and breastfeeding

— Streptomycin and other aminoglycosides are contraindicated (fetal ototoxicity)

— Fluoroquinolones generally avoided unless MDR-TB

— Breastfeeding is safe and encouraged on first-line therapy; drug levels in milk are subtherapeutic for infant treatment

— Defer LTBI treatment postpartum in most low-risk women

— Treat during pregnancy if: HIV co-infection, recent contact with infectious TB, or recent conversion — INH + B6 ×6–9 months preferred

— Children often have primary disease: hilar adenopathy, lower-lobe infiltrate, paucibacillary

— Sputum hard to obtain — use induced sputum or early-morning gastric aspirates ×3

— Higher risk of progression to disseminated and CNS TB, especially under age 5

— Same RIPE regimen, weight-based; ethambutol may be omitted if disease is mild and no resistance suspected

— Contacts: any child <5 exposed to active TB → window prophylaxis with INH until repeat TST/IGRA at 8–10 weeks post-exposure

— BCG vaccine: not routinely given in the US; protects against severe pediatric TB (meningitis, miliary), less so adult pulmonary disease

— Test every TB patient for HIV; test every newly diagnosed HIV patient for LTBI/TB

— Start TB therapy first, then ART within 2 weeks (CD4 <50) or 8 weeks (CD4 ≥50); CNS TB delay ART to 8 weeks regardless

— Use rifabutin instead of rifampin with most PIs

— Watch for IRIS in first 3 months of ART

Pregnancy:

LTBI in pregnancy:

Pediatrics:

HIV co-infection:

Board pearl: In a pregnant patient with active pulmonary TB, the wrong-answer choices are "delay treatment until postpartum" and "include streptomycin" — correct answer is INH + rifampin + ethambutol + B6 for 9 months, start now.

Key distinction: LTBI in pregnancy → usually defer treatment to postpartum; active TB → treat immediately.

Complications and Adverse Outcomes

— Cavitation with secondary bacterial or fungal (aspergilloma/mycetoma) superinfection

— Massive hemoptysis from erosion into bronchial arteries or Rasmussen aneurysm (pulmonary artery pseudoaneurysm in a cavity) — life-threatening, requires bronchial artery embolization

— Bronchiectasis and traction in healed apical fibrosis

— Pleural effusion, empyema necessitatis (chest wall extension)

— Pneumothorax from cavity rupture

— Tracheobronchial stenosis, fistulae

— Post-TB lung disease: chronic dyspnea, obstructive/restrictive pattern, recurrent infections

— Aspergilloma in old cavities — hemoptysis years later

— Miliary TB, TB meningitis (basilar, cranial neuropathies, hydrocephalus), Pott disease (spinal kyphosis, cord compression), pericarditis with constriction, renal, adrenal (Addison disease), GI, peritoneal, lymphatic

— SIADH from pulmonary disease

— Adrenal insufficiency from adrenal involvement — think in TB patient with hypotension, hyponatremia, hyperkalemia

— Drug-induced hepatitis (INH/rifampin/PZA)

— Optic neuritis (ethambutol)

— Peripheral neuropathy (INH without B6)

— Acquired drug resistance from inadequate therapy

— IRIS in HIV co-infected patients starting ART

— Rifampin-induced flu syndrome, thrombocytopenia, AIN

— Transmission to contacts — especially household, healthcare, congregate settings

— Outbreaks in shelters, prisons, schools

— Untreated active TB: ~50% mortality

— Treated, drug-susceptible TB: <5% mortality in HIV-negative

— MDR/XDR-TB and HIV co-infection significantly increase mortality

Local pulmonary complications:

Pulmonary destruction sequelae:

Extrapulmonary spread:

Endocrine/metabolic complications:

Treatment-related adverse outcomes:

Public health consequences:

Mortality:

CCS pearl: A TB patient on RIPE who develops new jaundice → stop all hepatotoxic drugs, check ALT/AST/bilirubin/INR, rule out viral hepatitis and drug overdose, and rechallenge sequentially once LFTs return to <2× ULN.

Board pearl: Massive hemoptysis in a TB patient with a cavity = Rasmussen aneurysm — stabilize airway (intubate with bleeding side down), CT angiography, and emergent bronchial artery embolization by IR; surgery is last resort.

When to Escalate — Hospitalization, ICU, and Consultation

— Hypoxia (SpO₂ <90% on room air), respiratory distress, or need for supplemental oxygen

— Hemoptysis (especially massive — >200 mL/24h or any hemodynamic compromise)

— Inability to tolerate oral intake or PO medications

— Severe drug toxicity (jaundice, hepatitis)

— Unstable comorbidities (decompensated CHF, ESRD on dialysis, decompensated cirrhosis)

— Inability to self-isolate (homeless, shelter without isolation capacity, household with young children or immunocompromised contacts who cannot be relocated)

— Suspected or confirmed MDR/XDR-TB

— Diagnostic uncertainty requiring bronchoscopy or biopsy

— Respiratory failure requiring mechanical ventilation

— Massive hemoptysis with airway compromise

— Septic shock (rare but seen in disseminated TB)

— TB meningitis with altered mentation, seizures, or hydrocephalus

— Severe IRIS in HIV co-infection

— Negative-pressure room with ≥6–12 air exchanges/hour and HEPA filtration

— N95 or PAPR for all staff entering; patient wears surgical mask when transported

— Continue until 3 negative AFB smears on consecutive days, ≥2 weeks of effective therapy, and clinical improvement

— Infectious disease/TB specialist: all MDR/XDR cases, HIV co-infection, pediatric, pregnant, treatment failure, severe disease

— Pulmonology: for bronchoscopy, complex airway disease, hemoptysis

— Public health department: mandatory for every confirmed or suspected case — they coordinate DOT, contact tracing, and reporting

— Interventional radiology: bronchial artery embolization for massive hemoptysis

— Thoracic surgery: refractory cavitary disease, destroyed lung, persistent positive cultures despite optimal therapy (rare)

Outpatient management is the rule for stable, adherent, drug-susceptible TB patients who can self-isolate at home.

Hospitalization indicated for:

ICU criteria:

Airborne isolation in hospital:

Consultations:

CCS pearl: A hospitalized smear-positive patient should not leave the negative-pressure room for unnecessary tests; bring portable imaging or schedule tests at end-of-day with airborne precautions.

Step 3 management: A patient with TB who is being discharged must have confirmed DOT arrangement with the health department, a follow-up appointment within 1–2 weeks, and refills for at least 1 month of medications before leaving the hospital.

Key Differentials — Other Pulmonary Infections

— Acute onset (days), lobar consolidation, productive purulent sputum, responds to standard antibiotics

— Sputum Gram stain and culture differ from AFB

— Key distinction: TB is subacute/chronic (weeks–months); CAP is acute

— Postmenopausal women with bronchiectasis (Lady Windermere syndrome — MAC in RML/lingula)

— Tall, thin men with COPD and apical cavities (MAC, M. kansasii)

— AFB smear-positive but NAAT negative for MTB

— Treatment: macrolide-based regimens for many months, not RIPE

— Not reportable, not transmitted person-to-person (with rare exceptions)

— Histoplasmosis (Ohio/Mississippi valleys): cavitary apical disease can mimic TB; urine antigen, serology

— Coccidioidomycosis (Southwest US, "Valley fever"): nodules, cavities; serology

— Blastomycosis (Midwest, Southeast): mass-like consolidation; skin lesions

— Aspergillus: aspergilloma in pre-existing TB cavity; chronic necrotizing aspergillosis

— HIV with CD4 <200; diffuse bilateral ground-glass infiltrates, hypoxia out of proportion, elevated LDH

— Coexists with TB in HIV; consider both

— Poor dentition, aspiration risk, air-fluid level on CXR, foul-smelling sputum

— Responds to amoxicillin-clavulanate or clindamycin

Bacterial pneumonia (typical CAP):

Nontuberculous mycobacterial (NTM) disease (M. avium complex, M. kansasii, M. abscessus):

Endemic fungal infections:

Pneumocystis jirovecii pneumonia (PCP):

Anaerobic lung abscess:

Lung abscess from Staphylococcus aureus (post-influenza, IVDU with right-sided endocarditis with septic emboli) — multiple cavities, often bilateral

Melioidosis (Burkholderia pseudomallei) in returning travelers from Southeast Asia, Northern Australia — upper-lobe cavitation, can mimic TB exactly

Board pearl: AFB smear-positive sputum with negative MTB NAAT in a postmenopausal woman with bronchiectasis = MAC, not TB — do not start RIPE, do not isolate; refer to ID for NTM workup.

Key distinction: TB is reportable and transmissible; NTM and fungal pneumonias generally are not — public health response differs entirely.

Key Differentials — Non-Infectious Mimics

— Smoker with chronic cough, hemoptysis, weight loss, cavitary upper-lobe mass

— Overlapping demographics and symptoms — TB and lung cancer can coexist

— CT with contrast, bronchoscopy with biopsy distinguishes

— Always consider cancer when "TB" doesn't respond to therapy

— Bilateral hilar lymphadenopathy ± upper-lobe reticulonodular infiltrates

— Non-caseating granulomas on biopsy; elevated ACE; hypercalcemia

— Negative AFB, negative IGRA usually — but TB must be ruled out before starting steroids

— Upper-lobe cavitary nodules, sinusitis, glomerulonephritis

— c-ANCA/PR3 positive; rapid course

— IV drug use, right-sided endocarditis (tricuspid)

— Multiple peripheral nodules, some cavitating, often bilateral

— Blood cultures positive; TTE/TEE shows vegetations

— Acute pleuritic pain, hemoptysis, wedge-shaped peripheral opacity

— CT-PA confirms

— CF, ciliary dyskinesia, immunodeficiency, post-infectious

— Chronic cough with copious sputum, recurrent infections

— Upper-lobe fibronodular disease in miners, sandblasters, foundry workers

— Silicosis dramatically increases TB risk — screen all silicotic patients with IGRA/TST

— Asthma with central bronchiectasis, eosinophilia, elevated IgE, positive Aspergillus precipitins

— Subacute cough, migratory patchy consolidations, responds to steroids — but rule out TB first

Lung cancer (especially squamous cell carcinoma):

Sarcoidosis:

Granulomatosis with polyangiitis (GPA):

Rheumatoid lung nodules in seropositive RA — can cavitate, mimic TB nodules

Septic pulmonary emboli:

Pulmonary infarct from PE:

Bronchiectasis (non-TB causes):

Silicosis and pneumoconioses:

Allergic bronchopulmonary aspergillosis (ABPA):

Cryptogenic organizing pneumonia (COP):

Board pearl: A patient "treated for TB" who isn't getting better — reconsider the diagnosis: was it really TB (re-review microbiology), is it MDR-TB, or is it lung cancer/sarcoid/GPA masquerading as TB?

Step 3 management: Before empirically starting corticosteroids for presumed sarcoidosis or COP in an at-risk patient, rule out active TB and treat LTBI — steroids in undiagnosed TB cause catastrophic dissemination.

Long-Term Plan — Completion, LTBI Therapy, and Secondary Prevention

— Standard 6-month regimen: 182 doses (or appropriate intermittent equivalents)

— Completion within 9 months for the standard regimen; missed doses must be made up

— Documented by DOT records

— Clinical improvement (symptoms resolved, weight gain)

— Sputum culture conversion to negative by 2 months (or repeat AFB negative)

— Completion of full prescribed regimen

— No routine surveillance CXR unless symptomatic

— Educate patient on relapse symptoms — return promptly if cough, fevers, weight loss recur

— Relapse rate <5% with completed susceptible-strain therapy

— All household and close contacts of an infectious case must be evaluated

— Contacts with positive IGRA/TST and normal CXR → LTBI treatment

— Preferred regimens (short-course): 3HP (weekly INH-rifapentine ×12 wk), 4R (daily rifampin ×4 mo), or 3HR (daily INH-rifampin ×3 mo)

— Initial-negative contacts: repeat IGRA/TST at 8–10 weeks (window period)

— Annual influenza vaccine, pneumococcal vaccines (PCV20 or PCV15+PPSV23), COVID-19

— Smoking cessation (smoking worsens TB outcomes and recurrence)

— Diabetes optimization, HIV ART continuation, nutrition support

— USPSTF recommends LTBI screening in adults at increased risk (foreign-born from high-prevalence countries, residents of high-risk congregate settings)

— Annual screening for healthcare workers in specific exposure settings

— Provide patient with a wallet card listing TB diagnosis, drugs taken, dates, susceptibility — useful for future immigration, employment, or healthcare encounters

Treatment completion is defined by total doses taken, not calendar time:

Cure criteria:

Post-treatment follow-up:

LTBI treatment as secondary prevention:

Vaccinations and comorbidity management:

Screening for at-risk groups (USPSTF/CDC):

Documentation and patient records:

Board pearl: A positive IGRA in a US-born, low-risk patient should prompt repeat testing or careful clinical correlation before committing to 3–4 months of therapy — but in any high-risk patient, treat LTBI to prevent reactivation.

Step 3 management: At treatment completion, document the date, total doses, final culture status, and provide a written summary to the patient and PCP; no routine post-treatment CXR or sputum is required in asymptomatic patients.

Follow-Up, Monitoring, and Counseling

— Symptom review: cough, fevers, weight, energy, side effects

— Weight (drug doses adjusted if significant change)

— Adherence verification via DOT logs

— Visual acuity and red-green color discrimination (while on ethambutol)

— Inquire about jaundice, RUQ pain, nausea, peripheral numbness, joint pain, rash

— Sputum AFB smear and culture monthly until two consecutive negatives

— Culture at 2 months is the critical milestone:

— Positive 2-month culture + initial cavitation → extend continuation phase to 7 months (total 9 months)

— Positive culture beyond 4 months suggests treatment failure → DST, adherence review, broaden regimen

— Baseline LFTs, creatinine, CBC, uric acid for everyone

— Routine monthly LFTs if: age >35, alcohol use, viral hepatitis, HIV, pregnancy/postpartum, baseline abnormality, symptoms

— Visual acuity at baseline and as needed for ethambutol toxicity

— ALT >5× ULN asymptomatic or >3× ULN symptomatic → stop INH/rifampin/PZA, work up alternative causes, resume sequentially

— Visual changes → stop ethambutol immediately, ophthalmology referral

— Severe rash, drug fever, hematologic toxicity → individualized

— Importance of completing full course; risk of resistance with stopping early

— Take medications on empty stomach when possible

— Avoid alcohol during therapy (hepatotoxicity)

— Rifampin colors body fluids orange; OCP failure — use barrier method

— Report any visual changes, jaundice, persistent vomiting, severe rash, or numbness immediately

— Stay in home isolation until cleared by public health

— Contact investigation typically completed within 7–14 days

— DOT continued throughout treatment

— Some states require completion-of-therapy reporting

Monthly follow-up during therapy (standard cadence):

Microbiologic monitoring:

Laboratory monitoring:

When to hold drugs:

Counseling priorities:

Public health follow-up:

CCS pearl: Order monthly LFTs, sputum AFB + culture, weight, visual acuity check, and adherence assessment as standing follow-up orders for the duration of therapy.

Board pearl: The single best predictor of cure and prevention of acquired resistance is DOT adherence — emphasize it on every visit and in test answers.

Ethical, Legal, and Patient Safety Considerations

— TB is a nationally notifiable disease in all US states

— Suspected and confirmed cases must be reported to the local/state health department, typically within 24 hours of suspicion (varies by jurisdiction)

— Reporting triggers contact investigation, DOT enrollment, and outbreak surveillance

— Failure to report violates state public health law and can result in legal sanctions

— HIPAA permits disclosure to public health authorities without patient consent

— Patients should be informed that reporting will occur, but consent is not required

— Most patients adhere voluntarily, but state public health law permits civil detention of patients with infectious TB who refuse treatment or isolation and pose a transmission risk

— Process requires due process — court order, least-restrictive setting, periodic review

— Used as last resort after extensive case management, social work, and behavioral interventions

— LTBI treatment is preventive — patients can decline; ensure they understand the lifetime reactivation risk (~5–10%)

— Pregnant patients with active TB must be informed of treatment risks vs untreated disease risks — treatment is strongly recommended

— Healthcare workers with TB exposure require IGRA at baseline and 8–10 weeks; positive converters need LTBI treatment

— Workplace transmission triggers an institutional infection control review

— Discharge of a TB patient from inpatient to outpatient requires:

— Confirmed health department handoff with DOT plan in place

— Adequate medication supply (≥1 month)

— Documented follow-up appointment within 1–2 weeks

— Confirmed safe home isolation conditions

— Communication with PCP and DOT provider

— Patients lost to follow-up are a leading cause of treatment failure and MDR-TB emergence

— Foreign-born and immigrant populations may fear immigration consequences — reassure that TB treatment does not jeopardize immigration status and many programs provide free care regardless of insurance

— Use professional medical interpreters; do not use family members

Mandatory reporting:

Confidentiality vs public health:

Involuntary detention/quarantine:

Informed consent edge cases:

Occupational exposure:

Transition-of-care risks (Step 3 favorite):

Stigma and equity:

Board pearl: A homeless patient with active TB who repeatedly refuses isolation and therapy can be legally detained under state public health authority — the correct first step is escalating case management and engaging the health department, not immediate court order.

Key distinction: Reporting is mandatory and not subject to patient refusal; treatment can be refused but isolation may be enforced when public risk is high.

High-Yield Associations and Rapid-Fire Facts

Reactivation site: apical-posterior segments of upper lobes (high O₂ tension); superior segment of lower lobes second most common

Ghon focus = primary parenchymal lesion; Ghon complex = Ghon focus + ipsilateral hilar adenopathy; Ranke complex = calcified Ghon complex (healed primary)

Caseating granulomas with central necrosis on histology = TB until proven otherwise (also: histoplasmosis, syphilis)

Sterile pyuria in a young patient = think renal TB (or Chlamydia urethritis)

Pott disease: thoracolumbar spine, anterior vertebral body destruction, gibbus deformity, cold abscess

Scrofula: cervical TB lymphadenitis — children more often have NTM scrofula; adults more often TB

Choroidal tubercles = pathognomonic for miliary TB

Erythema nodosum + phlyctenular conjunctivitis = hypersensitivity reactions to primary TB

Addison disease in developing world = TB adrenalitis (autoimmune in developed world)

SIADH is a recognized complication of pulmonary TB

Silicosis + TB = "silicotuberculosis"; silica impairs macrophage function — screen aggressively

TNF-α inhibitors (infliximab, etanercept, adalimumab) reactivate latent TB — screen with IGRA before initiating

BCG vaccine: live attenuated M. bovis; given in high-prevalence countries; causes false-positive TST but not IGRA

INH metabolism: hepatic acetylation by NAT2; "slow acetylators" at higher risk of neuropathy and hepatotoxicity

Rifampin = potent CYP3A4 inducer; rifabutin = milder, used with HIV PIs

PZA requires conversion to active form by mycobacterial pyrazinamidase; resistance via pncA mutation

Ethambutol inhibits arabinosyl transferase (cell wall); optic neuritis is dose-dependent

Quantiferon vs T-SPOT: both IGRAs; T-SPOT counts spot-forming cells; both use MTB-specific antigens (ESAT-6, CFP-10)

TB meningitis CSF: lymphocytic pleocytosis, low glucose, elevated protein, elevated ADA — adjunctive dexamethasone reduces mortality

TB pericarditis: adjunctive steroids reduce constrictive pericarditis

Lady Windermere syndrome: MAC (not TB) in RML/lingula in elderly women — a TB-mimic

Board pearl: A patient on infliximab for Crohn disease who develops fevers and a miliary CXR pattern has reactivation miliary TB — confirm with sputum/blood/bone marrow, start RIPE, hold the TNF inhibitor.

Step 3 management: Before any biologic immunosuppression, screen for LTBI with IGRA and treat positive results for at least 1 month before initiating the biologic.

Board Question Stem Patterns

— Foreign-born adult, 3 months of cough/night sweats/weight loss, CXR with upper-lobe cavitation

— Right answer: Airborne isolation, sputum ×3 for AFB/NAAT/culture, HIV test, baseline labs, notify health department, empiric RIPE if high suspicion

— Wrong answers: Outpatient azithromycin; await culture before isolation; CT-guided biopsy first

— Patient about to start adalimumab for psoriasis or RA

— Right answer: IGRA and CXR before starting biologic; if IGRA positive and CXR normal → treat LTBI (3HP or 4R) for at least 1 month before biologic

— CD4 <200, atypical CXR (lower-lobe or normal), positive sputum AFB

— Right answer: Start RIPE first, then ART within 2 weeks if CD4 <50, 8 weeks if higher; monitor for IRIS

— Patient on RIPE develops jaundice, RUQ pain, ALT 8× ULN

— Right answer: Stop INH, rifampin, PZA; continue ethambutol if needed; rule out viral hepatitis; rechallenge sequentially after LFTs normalize

— TB patient on warfarin or OCPs starts rifampin

— Right answer: Rifampin induces CYP3A4 → INR will drop; OCPs will fail — adjust warfarin and use barrier contraception

— Active TB in pregnancy

— Right answer: INH + rifampin + ethambutol + pyridoxine for 9 months; avoid streptomycin; treat now, do not defer

— Newly diagnosed TB; what next?

— Right answer: Report to local health department immediately; initiate contact investigation; arrange DOT

— Postmenopausal woman with bronchiectasis and RML disease, AFB smear positive

— Right answer: NAAT negative for MTB → MAC, not TB; treat as NTM

— Patient refuses isolation/treatment and lives in shelter

— Right answer: Engage public health for intensive case management; legal detention is last resort

— Positive sputum culture at 4 months

— Right answer: Repeat DST, evaluate adherence (DOT records), broaden regimen, consult TB expert — consider MDR-TB

Stem 1 — The classic vignette:

Stem 2 — The TNF inhibitor patient:

Stem 3 — The HIV patient with cough:

Stem 4 — The drug toxicity stem:

Stem 5 — The drug interaction stem:

Stem 6 — The pregnant patient:

Stem 7 — Public health/reporting:

Stem 8 — The "is it TB?" differential stem:

Stem 9 — The non-adherent patient:

Stem 10 — The treatment failure stem:

Board pearl: When a Step 3 vignette mentions "from [high-prevalence country]" + chronic respiratory symptoms, TB is on the differential until ruled out.

One-Line Recap

Pulmonary TB is a reportable, transmissible, granulomatous infection that demands prompt airborne isolation, sputum-based diagnosis with NAAT plus culture and DST, 6 months of RIPE under directly observed therapy, HIV co-testing, public health notification, and contact investigation — with all longitudinal monitoring, drug-toxicity vigilance, and special-population adjustments handled in tight coordination with the local health department.

Recognition: Chronic cough + constitutional symptoms + risk factor (foreign-born, HIV, contact, congregate setting) → isolate first, then sputum AFB ×3 + NAAT + culture + HIV + CXR.

Treatment: RIPE for 2 months → INH/rifampin for 4 months (total 6); extend to 9 months for cavitary disease with positive 2-month culture or CNS/bone disease; pyridoxine with INH always.

Monitor: Monthly sputum until conversion, monthly symptoms/weight/LFTs if risk factors, visual acuity on ethambutol, drug interactions (rifampin = CYP3A4 inducer).

Public health: Mandatory reporting, DOT for everyone, contact investigation with IGRA/TST at baseline and 8–10 weeks, LTBI treatment for positive contacts and immunocompromised patients before biologics.

Step 3 management: The transition from inpatient to outpatient must include confirmed health department handoff, DOT enrollment, medication supply, and follow-up within 1–2 weeks — lost-to-follow-up is the leading driver of acquired MDR-TB.

Board pearl: The most commonly missed "right answer" on Step 3 TB questions is report to the health department — when in doubt, that's almost always part of the correct management bundle alongside isolation and empiric RIPE.