Clinical evaluation of single-swab sampling for rapid COVID-19 detection in outbreak settings in Dutch nursing homes.

PURPOSE: To assess whether one swab can be used to perform both the antigen-detection rapid diagnostic test (Ag-RDT) and reverse transcriptase polymerase chain reaction (RT-PCR) for COVID-19 detection during an outbreak in the nursing home (NH) setting. METHODS: The single-swab method (SSM), where the Ag-RDT is performed with the transport medium used for RT-PCR, was evaluated in three Dutch NHs and compared to the laboratory setting. We collected Ag-RDT and RT-PCR results, NH resident characteristics and symptomatology. In addition, two focus groups were held with the involved care professionals to gain insight into the feasibility of the SMM in the NH setting. RESULTS: In the NH setting, the SSM had a sensitivity of 51% and a specificity of 89% compared to RT-PCR. These were lower than in the laboratory setting (69% and 100% respectively). Yet, when stratified for cycle threshold values, the sensitivity became comparable between the settings. Symptoms occurred more frequent in the Ag-RDT+ group than Ag-RDT- group. Resident characteristics did not differ between these groups. Based on the focus groups, the SSM was feasible to perform if certain requirements, such as availability of staff, equipment and proper training, were met. However, the rapid availability of the test results were perceived as a dilemma. CONCLUSION: The advantages and disadvantages need to be considered before implementation of the SSM can be recommended in the NH setting. For the vulnerable NH residents, it is important to find the right balance between effective testing policy and the burden this imposes.

Symptom- and Prevention-Based Testing of COVID-19 in Nursing Home Residents: A Retrospective Cohort Study.

Nursing homes (NH) residents with COVID-19 can either be tested because of presence of core symptoms (S-based) or because of transmission prevention (TP-based). The investigated study sample included all NH residents who underwent SARS-CoV-2 RT-PCR testing between March 16, 2020 and May 31, 2020 (n = 380). Clinical symptoms, temperature, and oxygen saturation were extracted from medical records, 7 days before to 14 days after testing. COVID-19 was confirmed in 81 (21%) residents; 36 (44%) S-based and 45 (56%) TP-based: 45. Cycle threshold (CT) values did not differ between the groups. In the 7 days prior to the test falling (32%), somnolence (25%) and fatigue (21%) occurred in both groups. Two days before the test, we observed a stronger decrease in oxygen saturation and an increase in temperature for the S-based group compared to the T-based group that remained up to 10 days after testing. Residents within the S-based group were 2.5 times more likely to increased mortality within 30 days than residents in the TP-based group (HR, 2.56; 95% 1.3-5.2). Although, 73% of the T-based group did eventually develop core symptoms. Thus, attention to falling and daily measures of temperature and oxygen saturation can contribute to earlier detection.