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

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