Dillner J, Elfström KM, Blomqvist J, Engstrand L, Uhlén M, Eklund C, Boulund F, Lagheden C, Hamsten M, Nordqvist-Kleppe S, Seifert M, Hellström C, Olofsson J, Andersson E, Falk AJ, Bergström S, Hultin E, Pin E, Pimenoff VN, Hassan S, Månberg A, Nilsson P, Hedhammar M, Hober S, Mattsson J, Arroyo Mühr LS, Lundgren KC
J. Infect. Dis. 224 (1) 14-20 [2021-07-02; online 2021-02-14]
Whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) positivity among asymptomatic subjects reflects past or future disease may be difficult to ascertain. We tested 9449 employees at Karolinska University Hospital, Stockholm, Sweden for SARS-CoV-2 RNA and antibodies, linked the results to sick leave records, and determined associations with past or future sick leave using multinomial logistic regression. Subjects with high amounts of SARS-CoV-2 virus, indicated by polymerase chain reaction (PCR) cycle threshold (Ct) value, had the highest risk for sick leave in the 2 weeks after testing (odds ratio [OR], 11.97; 95% confidence interval [CI], 6.29-22.80) whereas subjects with low amounts of virus had the highest risk for sick leave in the 3 weeks before testing (OR, 6.31; 95% CI, 4.38-9.08). Only 2.5% of employees were SARS-CoV-2 positive while 10.5% were positive by serology and 1.2% were positive in both tests. Serology-positive subjects were not at excess risk for future sick leave (OR, 1.06; 95% CI, .71-1.57). High amounts of SARS-CoV-2 virus, as determined using PCR Ct values, was associated with development of sickness in the next few weeks. Results support the concept that PCR Ct may be informative when testing for SARS-CoV-2. Clinical Trials Registration. NCT04411576.