What is the treatment for a positive Tuberculosis (TB) test result?

Treatment for Positive Tuberculosis (TB) Test

For a positive TB test, the recommended treatment is isoniazid (INH) daily for 9 months or rifampin daily for 4 months for latent TB infection, after active TB disease has been ruled out through chest radiography and clinical evaluation. 1, 2

Initial Evaluation After Positive TB Test

• All individuals with a positive tuberculin skin test (TST) must undergo chest radiography and clinical evaluation to exclude active TB disease before initiating treatment for latent TB infection (LTBI) 1
• Symptoms suggestive of TB (cough, fever, night sweats, weight loss) warrant prompt evaluation regardless of TST status 1
• Collection of sputum specimens for mycobacteriologic testing should be considered for those with abnormal chest radiographs or symptoms 1
• The presence of any symptom suggestive of TB plus any abnormality on chest radiography offers the highest sensitivity to identify active TB 3

Interpretation of Positive TB Test Results

• A positive TST is defined as ≥5 mm induration for:
  • HIV-infected persons
  • Recent contacts of TB cases
  • Persons with organ transplants or immunosuppression 1
• A positive TST is defined as ≥10 mm induration for:
  • Residents of high-risk congregate settings
  • Healthcare workers
  • Immigrants from high TB burden countries 1, 3
• A positive TST is defined as ≥15 mm induration for persons with no known risk factors 3

Treatment for Latent TB Infection

• After ruling out active TB, treatment for LTBI should be initiated with one of these regimens:

  • Isoniazid daily for 9 months (preferred regimen) 2
  • Rifampin daily for 4 months 2, 4
  • 3-month weekly rifapentine plus isoniazid 3, 4
  • 3-4 month daily isoniazid plus rifampicin 3

• Patients with fibrotic pulmonary lesions consistent with healed tuberculosis should receive 12 months of isoniazid or 4 months of isoniazid and rifampin 2

• HIV-infected persons with positive TB tests should receive a minimum of 12 months of therapy 2

Monitoring During Treatment

• Liver function tests should be monitored every 2-4 weeks during treatment, especially for:

  • HIV-infected persons
  • Pregnant women
  • Persons with history of liver disease
  • Regular alcohol users 1, 3

• Patients should be educated about symptoms of hepatotoxicity (nausea, vomiting, jaundice) and instructed to stop medication and seek medical attention if these develop 1

• Patients receiving isoniazid should also receive pyridoxine (vitamin B6) to prevent peripheral neuropathy, especially HIV-infected persons 1

Special Considerations

• Patients on immunosuppressive therapy (including biologics) should receive treatment for LTBI before continuing or initiating biologic therapy 1

• For patients from areas with high TB drug resistance (>10% background resistance), more aggressive treatment may be needed 3

• Single-drug therapy should never be used for active TB disease, as this can lead to drug resistance 5, 6

Common Pitfalls and Considerations

• A positive TB test indicates infection but does not distinguish between latent infection and active disease 7, 8

• Interferon-gamma release assays (IGRAs) like QuantiFERON-TB Gold and T-SPOT.TB may be preferred over TST in BCG-vaccinated populations due to higher specificity 1, 8

• Without treatment, LTBI will progress to active TB disease in approximately 5-10% of affected people 4

• Both suspected and confirmed cases of LTBI and TB disease must be reported to local or state health departments 4