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POINT-OF-CARE ANTIBODY TESTS for COVID-19: FIELD-BASED PERFORMANCE, SOUTH AFRICA
Topics in Antiviral Medicine ; 30(1 SUPPL):331-332, 2022.
Article in English | EMBASE | ID: covidwho-1880280
ABSTRACT

Background:

SARS-CoV2 antibody testing is an important auxillary test especially for retrospective diagnosis or in patients with long COVID-19 or multisystem inflammatory syndrome of childhood. Epidemiological serology studies may also assist public health planning. Access to formal laboratory testing is not universal in many low-and middle-income (LMIC) countries and rapid lateral flow antibody tests are an attractive alternative. Performance of these tests has been inconsistent. A large-scale study was undertaken in South Africa, during the beta and delta waves, to assess the field-based performance of rapid point of care (POC) COVID-19 antibody tests.

Methods:

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 were enrolled at baseline. All patients completed a questionnaire regarding symptoms. Nasopharyngeal swabs were taken and processed for SARS-CoV-2 PCR testing using a GeneXpert (Cepheid, USA), or manual assay (ThermoFisher TaqPath assay or Seegene Allplex assay) on a real-time platform at routine accredited National Health Laboratory Service laboratories as per routine national protocols. Concomitantly, trained study staff performed three facility-based POC lateral flow antibody tests on a on a fingerstick sample and blood was collected for formal serology. POC tests were selected following a rapid in-laboratory evaluation. Asymptomatic contacts of people with confirmed COVID-19 were recruited into the asymptomatic study arm and rapid tests and PCR were performed. PCR and rapid positive patients and 500 negative controls were followed up at 5-14 days. Antibody tests were compared with formal serology performed on 2 platforms-Euroimmun (Euroimmun, Lubeck) IgA and IgG anti-S antibodies and Abbott Architect IgG test.

Results:

The sensitivity (S), specificity (Sp), positive (PPV) and negative predictive (NPV) values of tests for PUIs and contacts were calculated (Table 1)∗. Analyses using serology as a reference are forthcoming.

Conclusion:

Compared with PCR, performance of rapid POC COVID-19 antibody tests was poor with low sensitivity. This may reflect the patient cohort tested as humoral responses typically develop from day 7-14. The tests are unlikely to be useful for acute diagnosis but sensitivity may improve at later timepoints and further follow up data will be analysed by duration of symptom onset, severity of symptoms and wave (beta versus delta).
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Collection: Databases of international organizations Database: EMBASE Type of study: Clinical Practice Guide Topics: Long Covid Language: English Journal: Topics in Antiviral Medicine Year: 2022 Document Type: Article

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Collection: Databases of international organizations Database: EMBASE Type of study: Clinical Practice Guide Topics: Long Covid Language: English Journal: Topics in Antiviral Medicine Year: 2022 Document Type: Article