PCR testing cycles (FOI)

Request

Please provide a timeline of CT (cycling threshold) rates and alterations since the beginning of Covid-19 PCR testing.

Was 40 thermal cycles used consistently since the start. If not, when was the cycle rate changed, to what rate, and how many times.

Response

The number of cycles has remained constant at 40.

The difference between the thermal cycles quoted in response to previous FOI requests and the most recent response is due to the number of cycles needed to reach an end point for the PCR testing method used by the OpenCell equipment who provide the island service for non-hospital patients.

PCR test thermal cycles and false positives (FOI)

OpenCell use Viral RNA Extraction using the Maxwell® HT Viral TNA Kit which uses magnetic beads to extract the viral RNA qPCR preparation and analysis, and the RealStar® SARS-CoV-2 kit for the rt-PCR process, on the qTower from AnalytikJena.

The FOI request referred to in the above link was completed by both the OpenCell service and by the hospital. In the hospital Cephid Gene Xpert analyser is used which requires 45 thermal cycles to reach its end point as per the manufacturer’s instructions.