Maximising the efficiency of surveillance for COVID-19 in dialysis units in South Africa: The case for pooled testing

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Maximising the efficiency of surveillance for COVID-19 in dialysis units in South Africa: The case for pooled testingTo the Editor: The COVID-19 epidemic in South Africa (SA) is currently in a growth phase with high incidences in most major cities. [1] Patients who are dependent on chronic renal dialysis care, including peritoneal dialysis and haemodialysis, are chronically un well and usually have multiple comorbidities including hypertension, diabetes and cardiovascular disease.These comorbidities are known to increase the risk of adverse outcomes for COVID-19, including hospitalisation with high care or intensive care admission, and/ or death.[2] Haemodialysis patients throughout the country require facility-based support three times a week, and a typical dialysis visit is ~4 hours.[3] Asymptomatic stages of SARS-CoV-2 infection necessitate the assumption that all staff and patients in a dialysis unit are potential carriers of the coronavirus or are vulnerable to infection.[4] Viral shedding of SARS-CoV-2 includes expiration of infectious droplets and droplet nuclei that can be prevented by the use of face masks and other precautions including spatial arrangements and hand hygiene.[5,6] A holistic approach is necessary to reduce risks and mitigate consequences of SARS-CoV-2 infection.While screening checklists and temperature monitoring contribute to early detection in a dialysis unit, further monitoring techniques are necessary to identify staff and patients infected with COVID-19.In our current dialysis setting, we have found that some patients are unwilling to report mild symptoms, as this can result in the inconvenience of a delayed session and increased costs of testing as required by current triage recommendations.[7] There is also the fear of stigmatisation associated with a positive test among staff and patients.Testing all haemodialysis patients and unit staff at regular intervals may be helpful where COVID-19 tests are readily available and affordable.However, in SA, waiting times for results can currently be up to a week, and shortages of reagents are known to be a problem.Shortfalls in SA have been compounded by unfocused community testing and superfluous testing outlined in guidelines that are not well co-ordinated with SARS-CoV-2 risks and testing infrastructure.[8] Pooling samples from many patients and testing these pooled samples rather than conducting individual tests reduces test kit requirements.A recent simulation analysis has found that pooledsample polymerase chain reaction analysis strategies will save substantial resources for COVID-19 compared with individual testing.[9] When pooling samples, the prevailing incidence and group size are considered, to determine most efficient fit in the epidemic context.[10] Haemodialysis unit staff are already sorted into shifts and patients are already cohorted, providing initial strata for pooling.Current COVID-19 prevention protocols limit crossover between staff shifts and patient cohorts.Pooled testing offers an affordable approach for COVID-19 surveillance of haemodialysis unit staff and vulnerable patients.As patients are at continued risk of COVID-19 transmission, multistage pooling is required.

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