Testing Both Blood and Urine for Zika

In May, FDA granted an emergency use authorization for the RealStar Zika virus RT-PCR kit, made by Altona Diagnostics GmbH (Hamburg, Germany). The test is meant to provide detection of RNA from Zika in serum from human blood, or urine. (The urine is collected alongside a patient-matched serum specimen.)

The workings of the RealStar test, as described in the FDA authorization letter, involve a primer and dual hydrolysis (Taqman ) probe. Purified nucleic acids are first reverse transcribed into cDNAs. The process has the probes anneal to specific target sequences located between the respective forward and reverse primers. "During the extension phase of the PCR cycle, the 5' nuclease activity of Taq polymerase degrades the probes, causing the reporter dye to separate from the quencher dye, generating fluorescent signals. With each cycle, additional reporter dye molecules are cleaved from their respective probes, increasing fluorescent activity," the FDA letter says.

The tests go to labs certified to perform high complexity tests under the U.S.'s Clinical Laboratory Improvement Amendments of 1988, or by similarly certified non-U.S. labs.

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