Evaluation of FASTPlaqueTB-RIF, a rapid, manual test for the determination of rifampicin resistance from Mycobacterium tuberculosis cultures.

SETTING: Two Mycobacteriology Reference Laboratories in Johannesburg (Laboratory 1) and Cape Town (Laboratory 2), South Africa. OBJECTIVE: To determine the ability of the FASTPlaqueTB-RIF test to correctly identify rifampicin susceptibility on strains of Mycobacterium tuberculosis cultured on solid media. DESIGN: A comparative study of FASTPlaqueTB-RIF and conventional drug susceptibility methods, with selection bias to include sufficient rifampicin resistant strains. RESULTS: Rifampicin susceptibility results were available for 191 strains of M. tuberculosis. Eighty-one strains were found to be rifampicin resistant and 110 strains were rifampicin susceptible by conventional methods. The sensitivity, specificity and overall accuracy for the FASTPlaqueTB-RIF were 100%, 97% and 98% at Laboratory 1, and 100%, 94% and 97% at Laboratory 2. CONCLUSION: FASTPlaqueTB-RIF offers a performance comparable to the gold standard proportion methods of rifampicin susceptibility testing, as well as the advantage of the speed of results that the newer methods deliver, without the need for specialised equipment. This makes FASTPlaqueTB-RIF a rapid test for rifampicin resistance suitable for widespread application.