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Cycle Threshold to Test Positivity in COVID-19 for Return to Work Clearance in Health Care Workers
Sandra Domeracki1, Robert N Clapp, Kristopher Taylor
1Occupational and Employee Health Section and Infectious Disease Section, Medical Service and Laboratory Medicine Service, San Francisco Veterans Affairs Health Care System (Ms Domeracki, Dr Clapp, Mr Taylor, Dr Lu, Dr Lampiris, Dr Blanc); Occupational and Environmental Health Nursing, Community Health Systems, School of Nursing (Ms Domeracki); Division of Occupational and Environmental Medicine (Dr Clapp, Dr Blanc); Department of Laboratory Medicine (Dr Lu); and Division of Infectious Disease (Dr Lampiris), Department of Medicine, University of California San Francisco, San Francisco, California.
Objective:
To ascertain whether reverse transcriptase polymerase chain reaction (RT-PCR) cycle amplifications until detection, the cycle threshold (Ct), could help inform return to work (RTW) strategies for health care workers (HCWs) recovering from COVID-19 infection.
Methods:
Sequential Ct data from COVID-19 nasal pharyngeal (NP) RT-PCR testing in all COVID-19 positive HCWs at a single institution. Analysis of Ct in relation to time until negative testing for RTW clearance.
Results:
Data for 12 employees showed that time elapsed until RT-PCR test-based RTW clearance ranged from 7 to 57 days (median, 34.5 days). Lower initial Ct correlated with the total time elapsed until clearance (r = -0.80; P = 0.002).
Conclusion:
Considering the RT-PCR Ct, which correlates with the estimated viral load, may help inform RTW planning and decision making beyond solely relying on dichotomized positive/negative results.
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