What is the next course of action for a patient with a positive Tuberculosis (TB) screening test result using the Mantoux skin test (also known as Purified Protein Derivative (PPD) test)?

From the Guidelines

For a patient with a positive TB skin test, the next step is to perform a chest X-ray to check for active tuberculosis infection, and consider obtaining an interferon-gamma release assay (IGRA) blood test to confirm the skin test result, especially if the patient has received BCG vaccination previously. This approach is based on the guidelines provided by the American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America, as outlined in the study published in the American Journal of Respiratory and Critical Care Medicine 1.

Key Considerations

• If the chest X-ray is normal and there are no symptoms suggesting active TB, the patient likely has latent TB infection (LTBI) 1.
• Treatment for LTBI typically involves isoniazid 300mg daily for 6-9 months, rifampin 600mg daily for 4 months, or the combination of isoniazid 900mg plus rifapentine 900mg weekly for 12 weeks (3HP regimen) 1.
• During treatment, monitor for medication side effects, particularly hepatotoxicity, with regular liver function tests.
• The positive skin test indicates the patient has been exposed to TB bacteria and developed an immune response, but doesn't necessarily mean they have active disease.

Radiographic Evidence of Prior Tuberculosis

• Persons with a positive tuberculin PPD skin test who have radiographic findings consistent with prior pulmonary tuberculosis are at increased risk for the subsequent development of active tuberculosis 1.
• The optimum treatment for patients with latent tuberculosis infection and abnormal chest radiographs consistent with prior tuberculosis is 9 months of INH, as recommended by the guidelines 1.

Decision to Initiate Treatment

• The decision to initiate combination antituberculosis chemotherapy should be based on epidemiologic information, clinical, pathological, and radiographic findings, and the results of microscopic examination of acid-fast bacilli (AFB)–stained sputum and cultures for mycobacteria 1.
• If the suspicion of tuberculosis is high or the patient is seriously ill, combination chemotherapy using one of the recommended regimens should be initiated promptly, often before AFB smear results are known and usually before mycobacterial culture results have been obtained 1.

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 course of action for a patient with a positive Tuberculosis (TB) screening test result using the Mantoux skin 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 infection: minimum of 12 months of therapy
• Fibrotic pulmonary lesions or pulmonary silicosis: 12 months of isoniazid or 4 months of isoniazid and rifampin, concomitantly
• Other risk factors: treatment may be considered on an individual basis, weighing the risk of hepatitis against the risk of tuberculosis 2

From the Research

Next Course of Action for a Patient with a Positive TB Screening Test Result

The next course of action for a patient with a positive Tuberculosis (TB) screening test result using the Mantoux skin test (also known as Purified Protein Derivative (PPD) test) involves several steps:

• Confirming the diagnosis: The gold standard for diagnosis of active TB disease is microbiological confirmation by culture of Mycobacterium tuberculosis (MTB) 3.
• Further testing: Interferon γ release assays (IGRA) can be used as an adjunct to diagnosis of active TB disease, but they do not have sufficient sensitivity or specificity to exclude or confirm active TB disease 3.
• Medical evaluation: A medical evaluation is necessary to determine if the patient has active TB disease or latent TB infection (LTBI) 4.
• Treatment: If the patient is diagnosed with active TB disease, treatment with anti-TB medications is necessary 4.
• Contact investigation: If the patient is diagnosed with active TB disease, a contact investigation should be conducted to identify individuals who may have been exposed to the patient 5.

Considerations for Patients with Prior Positive TST Results

Patients with prior positive TST results may benefit from prophylaxis after repeat exposure to infectious TB 5.

• Risk factors: Certain risk factors, such as age < 5 years, household exposure, and exposure to infectious patients, increase the risk of developing active TB disease 5.
• Prophylaxis: Receipt of more than 1 month of treatment for latent TB infection following the current contact investigation can be protective 5.

Comparison of TST and IGRA

IGRAs, especially T-SPOT.TB, are more effective at detecting TB infection than TST 6.

• Sensitivity: T-SPOT.TB is significantly more sensitive than TST 6.
• Specificity: The specificity of T-SPOT.TB is higher than the specificity of TST, but there is overlap between confidence intervals 6.