Treatment of Latent Tuberculosis Infection (LTBI)
This patient has latent tuberculosis infection (LTBI), not active disease, and should be treated with a short-course rifamycin-based regimen: 3-4 months of daily isoniazid plus rifampicin (Option B) or 3 months of rifampicin alone. 1, 2, 3
Key Diagnostic Findings
This patient has:
- Positive IGRA test indicating TB infection 2, 3
- Normal chest X-ray excluding active pulmonary TB 1, 2
- No clinical signs or symptoms of active disease 2, 3
- Known exposure to active TB case (the maid) 4
This clinical picture confirms LTBI, not active tuberculosis disease. 2, 3
Why Not the Other Options
Option A (4 medicines for 6 months then 2 medicines for 3 months): This is treatment for active tuberculosis disease, not LTBI. Active TB requires multi-drug therapy with isoniazid, rifampin, pyrazinamide, and ethambutol. 1, 5 This patient has no evidence of active disease.
Option C (4 medicines for 6 months): Again, this is for active TB disease, which has been excluded by normal chest X-ray and absence of symptoms. 1, 5
Option D (1 medicine for 6 months): While 6-9 months of isoniazid monotherapy was historically used for LTBI 1, 3, current guidelines favor shorter rifamycin-based regimens due to better completion rates and similar efficacy. 1, 2
Recommended Treatment Regimens for LTBI
The European Respiratory Society recommends the following preferred regimens for LTBI: 1
3-4 months of daily isoniazid plus rifampicin (most closely matches Option B) 1, 2, 4
- Isoniazid 5 mg/kg (max 300 mg daily) plus rifampin 10 mg/kg (max 600 mg daily) 4
3 months of rifampicin alone 1
- Alternative when isoniazid cannot be used
3 months of weekly rifapentine plus isoniazid 1, 2
- Requires directly observed therapy
These shorter regimens have significantly higher completion rates compared to 6-9 months of isoniazid monotherapy. 6
Critical Monitoring Requirements
Monthly clinical monitoring is essential: 4
- Assess for hepatotoxicity symptoms: nausea, vomiting, abdominal pain, dark urine, jaundice 3, 4
- Monitor adherence to treatment 4
- Baseline and periodic liver function tests every 2-4 weeks, especially if risk factors for liver disease exist 1, 3
Add pyridoxine (vitamin B6) 25-50 mg daily to prevent peripheral neuropathy when using isoniazid. 3, 4
Important Clinical Pitfalls
Never use single-drug therapy if there is any suspicion of active TB disease, as this rapidly leads to drug resistance. 2, 7 This is why excluding active disease with chest X-ray and clinical evaluation is mandatory before starting LTBI treatment. 2, 3
Given the known exposure to an active TB case, treatment should be initiated promptly rather than adopting a "watch and wait" approach. 4 Close contacts with positive IGRA should receive LTBI treatment regardless of other factors. 4
The patient's exposure should be reported to public health authorities for contact investigation. 4