What are the next steps for a 31-year-old male with a low positive Tuberculin (TB) test result and a negative Quantiferon TB Plus test, with no symptoms and no known risk factors for TB infection?

From the Guidelines

No further action is needed for a 31-year-old male with a low positive tuberculin skin test (TST) and a negative Quantiferon TB Plus test who has no symptoms and no risk factors for TB infection. This combination of test results most likely represents a false positive TST rather than true TB infection. The Quantiferon TB Plus is a more specific test than the TST and helps rule out TB infection in cases where the TST may be falsely positive, which can occur due to prior BCG vaccination or exposure to non-tuberculous mycobacteria. The negative Quantiferon result is particularly reassuring in the absence of symptoms or risk factors, as stated in the guidelines for using interferon gamma release assays to detect Mycobacterium tuberculosis infection 1.

Key Considerations

• The patient's low positive TST result is likely a false positive, given the negative Quantiferon TB Plus test and the absence of symptoms or risk factors.
• The Quantiferon TB Plus test is more specific than the TST and helps to rule out TB infection in this scenario.
• The guidelines recommend that a single positive IGRA or TST result should not be taken as reliable evidence of M. tuberculosis infection in healthy persons with a low likelihood of infection and no risk factors 1.

Next Steps

• Educate the patient about TB symptoms (persistent cough, night sweats, weight loss, fever) and advise them to seek medical attention if these develop in the future.
• No preventive TB treatment (such as isoniazid) is indicated in this scenario, as treating someone without true infection would expose them unnecessarily to potential medication side effects without benefit.
• The patient can be reassured that the combination of a low positive TST and a negative Quantiferon TB Plus test, in the absence of symptoms or risk factors, does not require further action or treatment.

From the FDA Drug Label

Candidates for preventive therapy who have HIV infection should have a minimum of 12 months of therapy. Recent converters, as indicated by a tuberculin skin test (≥ 10 mm increase within a 2-year period for those < 35 years old; ≥ 15 mm increase for those ≥ 35 years of age). The risk of hepatitis must be weighed against the risk of tuberculosis in positive tuberculin reactors over the age of 35 However, the use of isoniazid is recommended for those with the additional risk factors listed above (1-6) and on an individual basis in situations where there is likelihood of serious consequences to contacts who may become infected.

The patient has a low positive Tuberculin test result and a negative Quantiferon TB Plus test, with no symptoms and no known risk factors for TB infection. Given the patient's age (31 years) and the absence of risk factors, the next steps would be to:

• Repeat the tuberculin skin test to confirm the results, as the initial result is a low positive.
• Assess for risk factors that may have been missed, such as recent travel or exposure to someone with TB.
• Consider a chest radiograph to evaluate for any signs of pulmonary disease.
• Monitor the patient's symptoms and repeat testing if necessary. The patient does not meet the criteria for preventive therapy with isoniazid based on the provided information 2.

From the Research

Next Steps for a 31-year-old Male with a Low Positive Tuberculin (TB) Test Result and a Negative Quantiferon TB Plus Test

• The patient has a low positive TB test result, which may be a false positive, especially since he has no symptoms and no known risk factors for TB infection 3.
• The Quantiferon TB Plus test result is negative, which suggests that the patient may not have a latent TB infection 4.
• However, the performance characteristics of the QFT-Plus test have not been evaluated in certain patient populations, such as immune compromised patients, patients taking immunosuppressive drugs, pregnant women, and individuals younger than 18 years of age 4.
• The patient's PCP should consider the following next steps:
  • Confirmatory repeat testing on a new specimen is recommended, as suggested by the ATS/IDSA/CDC Clinical Practice Guidelines (2017) 3.
  • The patient should be evaluated for any clinical conditions that may affect the interpretation of the TB test results, such as diabetes, silicosis, chronic renal failure, and hematological disorders 4.
  • The patient's medical history and risk factors for TB infection should be reassessed to determine the likelihood of a false positive result 5, 6.
• It is essential to note that the diagnosis of latent TB infection is complex and requires careful interpretation of test results, medical history, and risk factors 7, 5, 6.

Considerations for Interpretation of Test Results

• The tuberculin skin test (TST) has a low specificity, which can lead to false positive results, especially in BCG-vaccinated individuals or those infected with non-tuberculous mycobacteria 4.
• The QuantiFERON TB Plus test has a higher specificity than the TST, but its performance characteristics have not been fully evaluated in certain patient populations 4, 5, 6.
• The results of the TB tests should be interpreted in the context of the patient's medical history, risk factors, and clinical presentation 3, 7, 5, 6.

Clinical Decision-Making

• The patient's PCP should use their clinical judgment to determine the best course of action, taking into account the patient's test results, medical history, and risk factors 3, 7, 5, 6.
• The PCP should consider consulting with a specialist in tuberculosis or infectious diseases if they are unsure about the interpretation of the test results or the management of the patient 3, 7, 5, 6.