After confirmed exposure to Mycobacterium tuberculosis, what immediate medical evaluation, screening, and treatment steps are recommended?

What to Do After TB Exposure

After confirmed TB exposure, immediately undergo tuberculin skin testing (TST) or interferon-gamma release assay (IGRA), followed by clinical evaluation for active disease, and if negative, repeat testing at 8-10 weeks post-exposure to detect delayed conversion. 1

Immediate Actions (Within 7 Days of Exposure)

Step 1: Initial Testing and Evaluation

• Obtain a TST (5 TU purified protein derivative by Mantoux method) or IGRA as soon as possible after learning of the exposure, regardless of any previous test results 2
• Undergo prompt clinical evaluation including detailed history, physical examination, and chest radiograph to rule out active TB disease 2, 1
• If you have respiratory symptoms (cough >2-3 weeks, bloody sputum, night sweats, weight loss, fever), provide sputum samples for acid-fast bacillus smear and culture 2, 3

Step 2: Obtain Source Patient Information

• Identify the drug-susceptibility pattern of Mycobacterium tuberculosis from the source patient's isolate—this is critical for guiding your preventive or curative therapy 2, 1
• Document this susceptibility pattern in your medical record for future reference if you develop active disease 2

Interpreting Your Initial Test Results

If Initial TST/IGRA is Positive (≥5 mm induration)

• You are considered at risk for newly acquired infection and require chest radiograph and medical evaluation for active TB 2, 4
• If chest radiograph and clinical evaluation are negative for active disease: Begin preventive therapy immediately with one of these FDA-approved regimens 5:
  • Preferred: Isoniazid 300 mg daily plus rifapentine weekly for 3 months 6
  • Alternative: Rifampin 600 mg daily for 4 months 4, 6
  • Standard: Isoniazid 300 mg daily for 9 months (12 months if HIV-infected or have fibrotic lesions on chest X-ray) 5, 7

If Initial TST/IGRA is Negative

• Critical caveat: A negative test during the first 8 weeks post-exposure does NOT rule out infection—the immune system requires 8-10 weeks to mount a detectable response 1
• You must undergo repeat testing 8-10 weeks (ideally 12 weeks) after the last exposure 2, 1
• If the repeat test is positive (conversion), this indicates infection occurred during the exposure period and you require full treatment for latent TB infection 1, 5

High-Risk Contacts Requiring Immediate Prophylaxis

Even with negative initial testing, certain groups should begin preventive therapy immediately after active disease is excluded 1:

Children Under 5 Years Old

• Start treatment immediately (isoniazid 10 mg/kg/day) after ruling out active disease, even with negative initial testing 5
• This "window prophylaxis" is mandatory because young children are at extreme risk for severe disseminated TB and TB meningitis 1
• Continue therapy until repeat testing at 12 weeks post-exposure 5

HIV-Infected or Immunocompromised Persons

• Begin preventive therapy immediately after excluding active disease, regardless of initial test results 2, 1
• HIV-infected contacts require minimum 12 months of preventive therapy 2, 5
• TST reaction ≥5 mm is considered positive in HIV-infected persons 2, 4

Close Contacts of Infectious TB Patients

• If you had intense exposure (prolonged close contact in poorly ventilated spaces), consider immediate prophylaxis after excluding active disease 2

Follow-Up Protocol

At 8-10 Weeks Post-Exposure

• Mandatory repeat TST/IGRA for all contacts with initial negative results 2, 1
• If this second test is positive, begin full treatment for latent TB infection 1, 5
• If negative and asymptomatic, no further testing is required 1

Ongoing Monitoring

• Learn and monitor for TB symptoms: persistent cough, bloody sputum, night sweats, weight loss, fever 2, 3
• Seek immediate medical evaluation if any symptoms develop, even years later 2, 4
• If you cannot complete preventive therapy, you should not be excluded from work but must understand your elevated risk and seek prompt evaluation for any TB symptoms 1

Special Considerations Based on Exposure Intensity

Highest Priority (Most Intense Exposure)

• You had prolonged close contact with the source patient in poorly ventilated spaces 2
• You are a household member or caregiver 2
• You participated in congregate activities with the source patient (e.g., choir, card games, shared living spaces) 2

Lower Priority (Less Intense Exposure)

• Brief or casual contact in well-ventilated areas 2
• Testing expanded to this group only if high-intensity contacts show evidence of transmission 1

Critical Pitfalls to Avoid

• Never assume a negative test during the first 8 weeks post-exposure rules out infection—this is the most common and dangerous error in TB contact management 1
• Do not delay prophylactic treatment in high-risk contacts (young children, HIV-infected persons) while waiting for the 8-10 week repeat test 1
• Do not skip the repeat test at 8-10 weeks if your initial test was negative—conversions frequently occur during this window period 2, 1
• Always obtain drug-susceptibility data from the source patient before starting therapy—treating with isoniazid when the source has isoniazid-resistant TB renders your preventive therapy ineffective 2, 1

Monitoring During Preventive Therapy

• Monthly assessment for adverse reactions, particularly hepatotoxicity (nausea, vomiting, abdominal pain, jaundice) 4
• Baseline liver function tests and monthly monitoring if you are over 35 years old 4
• Report any symptoms immediately to your healthcare provider 4