Low viral load is another factor that may show negative testing. The real time-PCR assay measures the viral RNA in terms of cycle threshold (Ct). It refers to the number of cycles the fluorescent signal requires to become detectable and is inversely proportional to the viral load. The final result is based on the Ct values and values <40 are generally considered positive. So, if the viral load is low, the RT-PCR test may show a negative result, even though the person is showing all the symptoms of coronavirus infection. In such cases, based on the clinical symptoms, doctors rely on a comprehensive analysis of other laboratory tests and X-ray findings.


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