Update of diagnostic methods in tuberculosis (TB)

Abstract

The WHO aims to reduce the number of deaths from TB by 95% and decrease its incidence rate by 90% between 2015 and 2035. The recommended rapid diagnostic tests are accurate and cost-effective, allow for a prompt start to treatment, and influence other outcomes that are important to the patient. To detect latent infection, the tuberculin skin test and interferon γ release (IGRA) tests are used. Although IGRA is an expensive test, it has greater specificity and is not affected by previous exposure to the BCG vaccine, among other advantages. For the diagnosis of active TB, smear microscopy is commonly employed. Culture is a more sensitive, but also more complex method. It constitutes the definitive diagnosis and allows phenotypic sensitivity tests to be performed. TB-LAM has limited sensitivity; however, unlike other methodologies, it has shown promising results in individuals living with HIV and CD4 T-cell counts below 200/mm³. Finally, among the molecular biology-based tests, commercial methods using real-time PCR allow mass diagnosis and sensitivity testing to first- and second-line drugs to be conducted within a few hours of receiving the sample. These are highly sensitive and specific tests, and their use is recommended as the initial diagnostic test in both pulmonary and extrapulmonary TB cases.