Direct tuberculosis drug susceptibility testing: time-saving and cost-effective in detecting MDR-TB.

Abstract

Recent advances have made molecular diagnosis of tuberculosis (TB) and drug susceptibility testing (DST) possible, but the high costs involved present a huge challenge. The refinement and improvement of affordable methods therefore remain a priority. Conventional indirect DST is inexpensive and reliable, but time-consuming. A direct DST method for the direct testing of sputum samples without culture has been developed to reduce the time required for DST, but there have been conflicting results. Direct and indirect DST against isoniazid and rifampicin were performed on 208 sputum smear-positive specimens, 186 from newly diagnosed patients and 22 from previously treated patients; respectively 169 and 180 of the direct and indirect DST results were reportable. In comparison with indirect DST, direct DST resulted in a saving of on average 10.5 days. The time to direct DST results was inversely correlated with the number of acid-fast bacilli in the sputum samples. Direct DST is highly sensitive, reliable, cost-effective and time-saving in comparison with indirect DST.