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FDA Clears Rapid Molecular Test for Streptococcus A

Test demonstrates 95% specificity

The Alere i Strep A test (Alere Inc.) has received marketing clearance from the FDA. It is the first molecular test that detects group-A Streptococcus (GAS) bacteria in throat-swab specimens in 8 minutes or less.

Other assays currently in development on the Alere i platform include respiratory syncytial virus, Clostridium difficile, and chlamydia/gonorrhoea.

The Alere i molecular platform was initially cleared for marketing by the FDA for the detection and differentiation of influenza A and B viruses in June 2014. In January 2015, Alere i Influenza A & B became the first molecular test to receive a Clinical Laboratory Improvement Amendments (CLIA) waiver, which allows broad use by health care providers ranging from hospitals and physician offices to clinics and other health care settings.

The Alere i Strep A test detects GAS bacteria in throat-swab specimens using proprietary Molecular in Minutes (MIM) isothermal nucleic acid amplification technology (iNAT). Unlike polymerase chain reaction (PCR) tests, iNAT does not require complex thermocycling or DNA purification and can therefore deliver PCR-caliber results more quickly, according to the manufacturer.

The clinical performance of the Alere i Strep A test was established in a multicenter study conducted in the U.S., in which 481 throat-swab specimens were evaluated with the test and compared with standard bacterial culture. The test’s overall sensitivity and specificity were 95.9% (141/147) and 94.6% (316/334), respectively.

All samples generating discordant results between the Alere i Strep A test and bacterial culture were evaluated by a laboratory-developed real-time PCR assay. Of the six samples negative by the Alere i Strep A test and positive by bacterial culture, four were also negative for GAS by the real-time PCR assay. Of the 18 samples positive by the Alere i Strep A test and negative by bacterial culture, 13 were also positive for GAS by the real-time PCR assay.

GAS bacteria spread through contact with droplets from an infected person’s cough or sneeze, and live in a person’s nose and throat. Most GAS infections cause relatively mild (noninvasive) illnesses, such as strep throat, scarlet fever, and impetigo. More than 10 million noninvasive GAS infections (primarily throat and superficial skin infections) occur annually in the U.S. GAS bacteria can also cause severe and even life-threatening (invasive) diseases. Cases of invasive GAS infections, such as necrotizing fasciitis and streptococcal toxic shock syndrome, occur less often but are associated with higher rates of deaths.

Source: Alere Inc.; April 2, 2015.

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