Effects of Patient Characteristics on Diagnostic Performance of Self-Collected Samples for SARS-CoV-2 Testing

Abstract

We evaluated the performance of self-collected anterior nasal swab (ANS) and saliva samples compared with healthcare worker-collected nasopharyngeal swab specimens used to test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We used the same PCR diagnostic panel to test all self-collected and healthcare worker-collected samples from participants at a public hospital in Atlanta, Georgia, USA. Among 1,076 participants, 51.9% were men, 57.1% were >50 years of age, 81.2% were Black (non-Hispanic), and 74.9% reported >1 chronic medical condition. In total, 8.0% tested positive for SARS-CoV-2. Compared with nasopharyngeal swab samples, ANS samples had a sensitivity of 59% and saliva samples a sensitivity of 68%. Among participants tested 3-7 days after symptom onset, ANS samples had a sensitivity of 80% and saliva samples a sensitivity of 85%. Sensitivity varied by specimen type and patient characteristics. These findings can help physicians interpret PCR results for SARS-CoV-2.

Keywords: 2019 novel coronavirus disease; COVID-19; Georgia; SARS-CoV-2; United States; anterior nasal; coronavirus disease; coronaviruses; respiratory infections; saliva; self-collected; sensitivity; severe acute respiratory syndrome coronavirus 2; viruses; zoonoses.

Figure 1

Flowchart of patient enrollment and sample results for investigation of the effects of patient characteristics on self-collected and healthcare worker–collected samples for severe acute respiratory syndrome coronavirus 2 testing, Atlanta, Georgia, USA. ANS, anterior nasal swab; NPS, nasopharyngeal swab; QC, quality control.

Figure 2

C_t values of self-collected and healthcare worker–collected samples for severe acute respiratory syndrome coronavirus 2 testing, Atlanta, Georgia, USA. PCR completed using CDC 2019-nCoV Real-Time Reverse Transcriptase PCR Diagnostic Panel (15). A) ANS and NPS samples at PCR target N1. B) ANS and NPS samples at PCR target N2. C) NPS and saliva samples at PCR target N1. D) NPS and saliva samples at PCR target N2. ANS, anterior nasal swab; C_t, cycle threshold; NPS, nasopharyngeal swab.

Figure 3

C_t values of self-collected and healthcare worker–collected samples for N1 target of severe acute respiratory syndrome coronavirus 2 PCR, Atlanta, Georgia, USA. PCR completed using CDC 2019-nCoV Real-Time Reverse Transcriptase PCR Diagnostic Panel (15). Horizontal lines within boxes indicate medians; box tops and bottoms indicate 25th and 75th percentiles; whiskers indicate the range. ANS, anterior nasal swab; C_t, cycle threshold; NPS, nasopharyngeal swab.