COVID-19 viral and serology testing in New York city health care workers

Abstract

While data continue to emerge around prevalence rates of coronavirus disease 2019 (COVID-19) in the general population, there is limited understanding of infection rates among health care workers (HCWs), a particularly important component of the response to this pandemic as more areas of the world experience surges in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rates.1-3 Viral testing through reverse transcription polymerase chain reaction (RT-PCR) demonstrates active infection, whereas serologic testing for SARS-CoV-2 may answer epidemiologic questions about the prevalence of COVID-19, especially in areas where viral testing has been limited.4,5 Here we provide data showing SARS-CoV-2 antibody prevalence in HCWs working in a hospital in New York City (NYC) during the early pandemic in the United States. The first case in NYC was identified on March 1, 2020, and cases steeply grew over the ensuing weeks. Beginning on April 17, 2020, serologic testing was offered to HCWs who were employed at our 862-bed Manhattan quaternary-care teaching hospital, an affiliated Queens 535-bed tertiary-care community teaching hospital, and an affiliated 180-bed Manhattan nonteaching community hospital. To qualify for testing, HCWs were required to be asymptomatic for 14 days after illnesses consistent with COVID-19, regardless of prior viral testing. The SARS-CoV-2 cyclic enhanced fluorescence assay (CEFA) used (ET Healthcare) was validated against the Food and Drug Administration emergency use authorization–approved New York State (NYS) Department of Health method, showing excellent concordance (n = 145 HCW samples, 95.5% agreement excluding indeterminate results, κ = 0.905; 95% confidence interval [CI], 0.831-0.979). The CEFA also demonstrated excellent specificity (IgG = 98.8% and IgM = 99.4%) using 320 pre-COVID-19 samples.6 The SARS-CoV-2 RT-PCR assay was performed using the cobas SARS-CoV-2 test on the cobas 6800 platform (Roche Diagnostics), which detects SARS-CoV-2 RNA extracted from nasopharyngeal swab specimens. Among the 2,274 HCWs who received a serologic test between April 17, 2020, and May 7, 2020, 35.4% (805/2,274) tested positive for seroconversion of SARS-CoV-2 antibodies, 61.6% (1,401/2,274) tested negative, and 3.0% (68/2,274) were indeterminate Table 1. The majority of HCWs who had seroconverted were either IgG (573/805; 71.2%) or IgG/IgM positive (225/805; 27.9%) Table 2. Of the 2,274 HCWs receiving the serologic assay, 242 (10.6%) had a previous documented RT-PCR viral test. Among this dually tested population, all 68 HCWs (100%) who tested positive for COVID-19 by RT-PCR also tested positive for antibodies Figure 1, demonstrating IgG (47/68; 69.1%) or IgG/IgM (21/68; 30.9%) positivity (Table 2). In comparison, of the 174 HCWs with a negative RT-PCR test, 19.5% (34/174) tested positive for antibodies, reflective of (1) the clinical sensitivity of SARS-CoV-2 molecular assays, which are estimated to be between 58% and 96%, or (2) the timing of the molecular testing.7 Those with positive RT-PCR and serology tests had a higher median age (48 years; interquartile range, 41, 55 years) compared to all others (P < .001). Demographic Characteristics of Health Care Workers Who Received COVID-19 Testing RT-PCR, reverse transcription polymerase chain reaction. aThe P value for the comparison of age between test results is calculated with the use of the Kruskal-Wallis test with median (Q1, Q3). The P value for the comparison of sex, race, and job categories by testing result is calculated with the use of the χ 2 test and Fisher exact test. bJob role descriptors: Physician, NP (nurse practitioner), PA (physician assistant): patient-facing health care providers. Other staff in room: patient-facing health care workers, including nurses, respiratory therapists, phlebotomists. Ancillary staff: non–patient-facing workers on a hospital floor, including desk clerks, couriers, custodial staff, physical/occupational therapists, clinical laboratory workers. Administrative staff: non–patient-facing workers not on the hospital floor working primarily in an office. Other: Non–patient-facing workers that do not fall under previously mentioned categories, including medical school staff, cafeteria workers, non–clinical laboratory workers. Demographic Characteristics of Health Care Workers Who Received COVID-19 Testing RT-PCR, reverse transcription polymerase chain reaction. aThe P value for the comparison of age between test results is calculated with the use of the Kruskal-Wallis test with median (Q1, Q3). The P value for the comparison of sex, race, and job categories by testing result is calculated with the use of the χ 2 test and Fisher exact test. bJob role descriptors: Physician, NP (nurse practitioner), PA (physician assistant): patient-facing health care providers. Other staff in room: patient-facing health care workers, including nurses, respiratory therapists, phlebotomists. Ancillary staff: non–p