Head-to-head comparison of nasal and nasopharyngeal sampling using SARS-CoV-2 rapid antigen testing in Lesotho

• Published in: PloS one Vol. 18; no. 3; p. e0278653
• Main Authors: Labhardt, Niklaus D, González Fernández, Lucia, Katende, Bulemba, Muhairwe, Josephine, Bresser, Moniek, Amstutz, Alain, Glass, Tracy R, Ruhwald, Morten, Sacks, Jilian A, Escadafal, Camille, Mareka, Mathabo, Mooko, Sekhele M, de Vos, Margaretha, Reither, Klaus
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 02.03.2023; Public Library of Science (PLoS)
• Subjects: Accuracy; Adult; Antigens; Biology and life sciences; Biosensors; Child; Coronaviruses; COVID-19; COVID-19 - diagnosis; Diagnostic systems; Disease transmission; Engineering and Technology; Female; HIV; Hospitals; Human immunodeficiency virus; Humans; Immune system; Laboratories; Lesotho; Male; Medical diagnosis; Medical tests; Medicine and Health Sciences; Nasopharynx; Nose; People and Places; Polymerase chain reaction; Research and Analysis Methods; Rural areas; Sampling; SARS-CoV-2; Sensitivity; Severe acute respiratory syndrome coronavirus 2; Testing; Tuberculosis; Lesotho; South Korea; United States > US; Africa
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0278653

To assess the real-world diagnostic performance of nasal and nasopharyngeal swabs for SD Biosensor STANDARD Q COVID-19 Antigen Rapid Diagnostic Test (Ag-RDT). Individuals ≥5 years with COVID-19 compatible symptoms or history of exposure to SARS-CoV-2 presenting at hospitals in Lesotho received two nasopharyngeal and one nasal swab. Ag-RDT from nasal and nasopharyngeal swabs were performed as point-of-care on site, the second nasopharyngeal swab used for polymerase chain reaction (PCR) as the reference standard. Out of 2198 participants enrolled, 2131 had a valid PCR result (61% female, median age 41 years, 8% children), 84.5% were symptomatic. Overall PCR positivity rate was 5.8%. The sensitivity for nasopharyngeal, nasal, and combined nasal and nasopharyngeal Ag-RDT result was 70.2% (95%CI: 61.3-78.0), 67.3% (57.3-76.3) and 74.4% (65.5-82.0), respectively. The respective specificity was 97.9% (97.1-98.4), 97.9% (97.2-98.5) and 97.5% (96.7-98.2). For both sampling modalities, sensitivity was higher in participants with symptom duration ≤ 3days versus ≤ 7days. Agreement between nasal and nasopharyngeal Ag-RDT was 99.4%. The STANDARD Q Ag-RDT showed high specificity. Sensitivity was, however, below the WHO recommended minimum requirement of ≥ 80%. The high agreement between nasal and nasopharyngeal sampling suggests that for Ag-RDT nasal sampling is a good alternative to nasopharyngeal sampling.