Better Quick Test Proposed for Strep

A microbiologist who led the team that developed a rapid test for anthrax exposure believes that a similar rapid Strep test should be developed, based on rapid-cycle real-time PCR (polymerase chain reaction). Franklin R. Cockerill III, professor and chair, microbiology, Mayo Clinic (Rochester, MN, USA), presented his comments on a rapid strep test at the annual meeting of the American Association of Clinical Chemistry (AACC) in Orlando (FL, USA).

Dr. Cockerill suggests that the rapid antigen test for strep lacks sensitivity, negative results require a backup culture, and that its sensitivity may be declining. An alternative is rRNA (ribosomal ribonucleic acid) testing, which has enhanced sensitivity but is still not as effective as a culture. His conclusion is that assessing PCR, using the same principle and diagnostic equipment as in the test for anthrax, may be the best test for bacterial strep throat.

Dr. Cockerill believes the LightCycler (Roche, Basel, Switzerland) instrument for PCR-based assays is the optimum equipment to detect the strep A bacterium. In comparing this test with the antigen/culture method, he found that the processing time for 32 samples was 1.5 hours for PCR and up to two days for the antigen/culture method. Personal administrative time was three minutes for PCR and seven minutes for the antigen/culture procedure. Sensitivity was higher in all categories when compared against cultures.