Improving evaluations of T-cell assays for diagnosing active Mycobacterium tuberculosis infection.

摘要

Evaluations of T-cell assays for diagnosing active Mycobacterium tuberculosis (TB) infection were recently published in the Journal of Infection by Liao et al., Kim et al. and Clark et al. (December 2009). These evaluations presented evidence of T-cell assays clinical accuracy, i.e. can the tests detect the presence and absence of active TB infection. Unfortunately, knowledge of T-cell assays clinical accuracy offers only moderate help in deciding if the tests are clinically useful in an individual patient. To better understand clinical usefulness, evaluations should investigate how a patient's management is altered by their use, that is: does the test help you treat the patient quicker, cheaper, or better; does it make no difference or does it lead to harm? At present the debate about T-cell assays for diagnosing active TB infection seems focused on their clinical accuracy. A simple Medline search, based on the term ELISPOT and Tuberculosis, demonstrates this. This search identified seven studies into the clinical accuracy of T-cell assays to diagnose active TB infection. Only one reported clinical usefulness. It included just seven patients with active TB, with the T-cell assays prompting early initiation of anti-tuberculous therapy in three patients. This provides preliminary evidence that despite the limitations of the T-cell assays: their clinical sensitivity being reported as low as 70% by Liao et al., their clinical usefulness is worthy of investigation.