Latent Tuberculosis

Pt from Asia with h/o DM, HIV, bariatric surgery, solid organ transplant, homelessness, and incarceration presents for health maintenance exam. Works in the healthcare industry and reports ongoing substance abuse including smoking, injection drug use. Weight <90% of ideal body weight on exam.

• Screening

  • No h/o BCG vaccine and reliable for follow-up: Mantoux tuberculin skin test (PPD) positive

  • H/o BCG vaccine or unlikely to return for PPD check: Interferon-gamma release assay (QuantiFERON-TB Gold) positive

• Obtain CXR to rule out fibrotic changes, active disease

• Treatment

  • Offer once-weekly isoniazid 15 mg/kg (max dose 900 mg) and rifampin (weight-based dosing guidelines) x 12 weeks

  • If evidence of active disease on CXR, transition to active disease regimen

  • Prophylax close contacts with isoniazid 15 mg/kg (max dose 300 mg) qd x 9 months

• Pt counseled about concern for progression to active disease due to risk factors including DM, immunocompromised state, continued substance abuse, and h/o bariatric surgery

• Pt advised that without treatment, latent TB will convert to active disease in 10% of cases

Notes

TB screening tests include PPD and interferon-gamma release assay (QuantiFERON-TB Gold)

• Positive in cases of both latent and active TB

• Tuberculin skin test (sensitivity 90%, specificity 80%)

  • > 15 mm: Positive for all patients

  • > 10 mm: Positive for patients

    • Children < 4 years old

    • From regions where TB is common

    • Who work in setting where TB is common

    • IV drug users

  • > 5 mm: Positive for patients

    • Who are immunocompromised (e.g. HIV, transplant recipient, prescribe ≥ 15 mg prednisone daily, etc.

    • With direct exposure to active TB

    • With fibrotic changes on CXR

• QuantiFERON-TB Gold (sensitivity 80%, specificity 99%)

  • Not recommended for children younger than 5 years

  • CDC recommends against use for confirmatory testing after positive PPD

Latent TB

• Risk factors for contracting infection include living abroad, working in healthcare, institutionalization (e.g. homeless shelter, prison), and immunocompromised state (e.g. HIV, solid organ transplant)

• Non-symptomatic and cannot be spread to others

• CXR in latent TB may be normal or show calcified granulomas

• Twelve week course of  isoniazid/rifapentine is as effective as 9 month course

Active Tuberculosis

Pt with h/o immunocompromised state, latent TB presents with hemoptysis x3 weeks. Reports fatigue, night sweats, and chest pain exacerbated by cough. Fever, weight loss, lymphadenopathy on exam.

• Labs

  • Positive TB nucleic acid amplification and sputum acid fast bacilli (AFB) smear

  • Obtain CBC, CMP; consider 4th generation HIV test

  • Patient HIV positive: Obtain CD4 count

• Imaging

  • CXR shows upper-lobe nodular opacities, hilar adenopathy, and patchy consolidation likely representing pleural effusion and/or pulmonary infiltrates

  • Consider CT to r/o disseminated disease

• Drug susceptible TB treatment

  • Initial intensive phase (2 months)

    • Rifampin 600 mg daily; pt counseled that urine may appear red due to medication

    • Isoniazid 300 mg daily

    • Pyrazinamide 1,000 mg daily

    • Ethambutol 800 mg daily

  • After intensive phase, continue rifampin 600 mg daily and isoniazid 300 mg daily for  7 months

• Refer to infectious disease

• Report case to local health department

• Patient’s social circumstances may allow transmission to other community members: Admit to hospital and initiate airborne infection precautions including negative pressure room
  

Notes

• Infection and transmission

  • See latent tuberculosis for risk factors associated with acquiring TB

  • Airborne and highly contagious

    • If a patient lives alone and contact with other community members can be limited, hospital admission may not be warranted

    • Healthcare workers should wear N95 mask

• Diagnosis

  • Definitively made with one of the following

    • Positive NAA

    • Two positive AFB smears regardless of NAA

  • If definitive diagnosis cannot be made, treat based on screening test results and clinical judgement

• CXR

  • Abnormalities generally seen in posterior upper lobes or superior lower lobes

  • Hilar adenopathy is only observed in one third of cases

• Treatment

  • In patient <55 kg lean body mass, refer to weight-based dosing

  • Rifampin can turn urine red, but the pt may not notice because ethambutol can cause loss of color vision