From the Guidelines
The next step for a patient with a positive TB gold test is to undergo a chest X-ray to rule out active tuberculosis disease. If the chest X-ray is normal, the patient likely has latent tuberculosis infection (LTBI) and should be evaluated for preventive therapy. The standard preventive treatment regimen is isoniazid 300mg daily for 6-9 months, or alternatively, rifampin 600mg daily for 4 months, or isoniazid plus rifapentine weekly for 3 months 1. Before starting treatment, baseline liver function tests should be obtained, especially for patients with risk factors for hepatotoxicity. During treatment, patients should be monitored monthly for medication side effects and adherence. It's essential to understand that a positive TB gold test indicates the immune system has been exposed to Mycobacterium tuberculosis, but doesn't differentiate between latent infection and active disease. Without treatment, approximately 5-10% of people with LTBI will develop active TB disease in their lifetime, with the highest risk occurring within the first two years after infection. Treating LTBI significantly reduces this risk of progression to active disease, which is why preventive therapy is recommended despite the absence of symptoms.
Some key points to consider:
- A positive TB gold test result should prompt further evaluation to rule out active tuberculosis disease 1.
- The QuantiFERON-TB Gold test, the QuantiFERON-TB Gold In-tube test, and the T-SPOT TB test are approved by the FDA as aids for detecting latent M. tuberculosis infection 1.
- Prior vaccination with bacillus Calmette-Guérin may result in a positive TST result, whereas there is less cross-reactivity with IGRA 1.
- Annual testing should be considered for those who have negative results by TST but are at ongoing risk for exposure to tuberculosis 1.
In terms of treatment, the most recent and highest quality study recommends the following regimens for LTBI:
- Isoniazid 300mg daily for 6-9 months
- Rifampin 600mg daily for 4 months
- Isoniazid plus rifapentine weekly for 3 months 1
It's crucial to note that these regimens may vary depending on the patient's specific situation and risk factors. Therefore, it's essential to consult with a healthcare professional to determine the best course of treatment.
From the FDA Drug Label
Isoniazid is recommended as preventive therapy for the following groups, regardless of age. Candidates for preventive therapy who have HIV infection should have a minimum of 12 months of therapy. Candidates for preventive therapy who have fibrotic pulmonary lesions consistent with healed tuberculosis or who have pulmonary silicosis should have 12 months of isoniazid or 4 months of isoniazid and rifampin, concomitantly
The next step for a patient with a positive Tuberculin (TB) gold test is to consider preventive therapy with isoniazid, depending on the patient's risk factors and age. The specific treatment duration and regimen will depend on the individual's circumstances, such as HIV status, presence of fibrotic pulmonary lesions, or other medical conditions that increase the risk of tuberculosis 2.
- Key considerations include:
- HIV infection status
- Presence of risk factors (e.g., silicosis, diabetes mellitus, immunosuppressive therapy)
- Age and membership in high-incidence groups
- Results of the tuberculin skin test (induration size) The patient's healthcare provider will need to weigh the risk of hepatitis against the risk of tuberculosis and make an individualized decision regarding preventive therapy 2.
From the Research
Next Steps for a Patient with a Positive Tuberculin (TB) Gold Test
- The patient should undergo further evaluation to determine if they have active or latent TB infection 3
- A chest x-ray, tissue culture, and acid-fast staining may be performed to confirm the diagnosis, although these tests have their limitations 3
- Immunologic tests, such as the QuantiFERON-TB Gold In-Tube test, may be used to measure the production of IFN-gamma by TB-specific T lymphocytes, which can help differentiate between active and latent TB infection 4
- The patient's treatment plan will depend on the severity of their disease and their HIV status, with HIV-positive patients requiring more careful monitoring and treatment 4
- Sputum quality can impact the yield of TB diagnostic tests, and pre-sputum collection interventions may be necessary to improve sputum quality and increase the chances of detecting M. tuberculosis 5
Diagnostic Considerations
- The Tuberculin skin test (TST) lacks specificity and reliability, and may not accurately diagnose TB infection 3
- The QuantiFERON-TB Gold In-Tube test has certain advantages over the TST, but its reactivity may decrease over time, especially in patients undergoing treatment for active TB 4
- Nucleic acid amplification technology and serological tests may also be used to diagnose TB, but these tests have their own limitations and may not be suitable for all patients 3