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Publication: Utility of Covid-19 point of care antigen tests in low-middle income settings
Goga, A Mayne, E.S Woeber, K Takuva, S Nsibande, D Lekalakala, M Jaumdally, S Mutevedzi, P Vreede, H Daniels, B.B
Goga, A
Mayne, E.S
Woeber, K
Takuva, S
Nsibande, D
Lekalakala, M
Jaumdally, S
Mutevedzi, P
Vreede, H
Daniels, B.B
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Abstract
Background:
Access to SARS-CoV-2 polymerase chain reaction (PCR) testing is a bottleneck globally, especially in low-and middle-income countries (LMICs). Reliable point-of-care (POC) diagnostics for coronavirus disease 2019 (COVID-19) are cheaper and easier to scale-up than PCR especially in LMICs, and will facilitate interruption of transmission. We report the field-based effectiveness of rapid point-of-care (POC) antigen COVID-19 tests during the beta and delta waves, in South Africa.
Methods:
We enrolled symptomatic, ambulatory persons under investigation (PUIs) aged 18 years and older, presenting for SARS-CoV-2 diagnosis at public health facilities in three provinces, South Africa. All patients completed a questionnaire regarding symptoms. Nasopharyngeal swabs were taken and processed for SARS-CoV-2 PCR testing using either GeneXpert (Cepheid, USA), or with a manual assay (ThermoFisher TaqPath assay or Seegene Allplex assay) on a real-time PCR platform at routine, accredited National Health Laboratory Service laboratories, as per routine national protocols. Concomitantly, trained study staff performed three facility-based POC antigen tests on a nasal/nasopharyngeal swab, as recommended by the manufacturer. Asymptomatic contacts of people with confirmed COVID-19 were recruited into the asymptomatic study arm and rapid tests and PCR were performed. The sensitivity (S), specificity (Sp), positive (PPV) and negative predictive (NPV) values of tests for PUIs and contacts were calculated using PCR as the reference standard.
Results:
Between Oct 2020-2021 1816 participants were enrolled;472 (26%) tested PCR or rapid test positive;235 positives (49.8%) and 532 negatives were followed up at 5-14 days;574 asymptomatic contacts were enrolled, of which 21 (3.7%) were PCR positive. Performance of the three antigen tests are shown in Table 1∗.
Conclusion:
In a real world setting, during the beta and delta waves, compared with PCR the sensitivity of rapid antigen tests ranged from 35-68%. This may reflect low viral loads at diagnosis. Further work will compare antigen test performance in patients with high versus lower cycle threshold (Ct) values. Meanwhile, PCR testing capacity needs urgent scale-up in LMICs and improved POC diagnostics are needed to facilitate COVID-19 diagnosis in LMICs.
Description
Poster-T05 presented at the 29th Conference on Retroviruses and Opportunistic Infections (CROI), 12–16 February 2022: Virtual.
Date
2022-02-16
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Databases of international organizations
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Keywords
COVID-19 testing,South Africa,Diagnosis,Nasopharyngeal swab,Beta and delta waves,Point of care