Based on reviews of available data, WHO has recommended against using tests that do not provide reliable information for diagnosing TB. In 2011, WHO recommended that commercial serologic tests should not be used for the diagnosis of pulmonary and extrapulmonary TB because the commercial serodiagnostic tests available at that time provided inconsistent and imprecise findings; there was no evidence that using those commercial serological assays improved patient outcomes; and the tests generated high proportions of false positive and false negative results, which may have an adverse impact on the health of patients (17).19
WHO recommendations are specific for intended uses and, sometimes, even an approved test is not recommended to be used for a specific purpose. For example, NAATs (e.g. Xpert MTB/RIF, Xpert Ultra or Truenat) are not recommended for use in monitoring the response to treatment. Also, in outpatient settings, WHO recommends against using LF-LAM to assist in the diagnosis of active TB in:
- HIV-positive adults, adolescents and children without first assessing TB symptoms;
- HIV-positive patients without TB symptoms and with an unknown CD4 cell count, or without TB symptoms and a CD4 cell count greater than or equal to 100 cells/mm3; and
- HIV-negative individuals.
Similarly, WHO recommends that, in low- and middle-income countries, interferon-gamma-release assays may be used to aid in the detection of latent TB infection. However, such tests should not be used for the diagnosis of pulmonary or extrapulmonary TB, or for the diagnostic work-up of adults (including HIV-positive individuals) suspected of active TB.