SARS-Cov2 Infection Detection by Polymerase Chain Reaction and Serologic Testing in Clinical Practice.

Murad, Douglas; Chandrasekaran, Sukantha; Pallai, Ajaya; Garner, Omai B; Denny, Christopher T

Patients with SARS-Cov2 can be diagnosed by polymerase chain reaction (PCR) during the time of acute infection or later in their clinical course by detection of virus specific antibodies. While in theory complementary, both PCR and serologic tests have practical shortcomings. A retrospective study was performed in order to further define these limitations in a clinical context and to determine how to best utilize these tests in a coherent fashion. A total of 3,075 patients underwent both PCR and serology tests at UCLA in the study period. Among these, 2731 (89%) had no positive tests at all, 73 (2%) had a positive PCR test and only negative serology tests, 144 (5%) had a positive serology test and only negative PCR tests, and 127 (4%) had positive PCR and serology tests. Approximately half of the patients with discordant results (i.e. PCR positive, serology negative or vice versa) had mistimed tests in reference to the course of their disease. PCR positive patients who were asymptomatic or pregnant were less likely to generate a detectable humoral immune response to SARS-Cov2. On a quantitative level, the log number of days between symptom onset and PCR cycle threshold (Ct) values were positively correlated. However, there was no apparent relationship between PCR Ct and serologic AU/ml results.