In a recent publication in the American Journal of Infection Control, CITF Leadership Group member Dr. Mel Krajden and colleagues in British Columbia conducted a serological survey of long-term care (LTC) residents and staff following outbreaks at two facilities. The authors found that people who had previously tested negative for SARS-CoV-2 by RT-PCR (nasal swab) later tested positive for antibodies via a blood sample, showing that more people may had been infected than previously thought. These findings are important as they can inform rapid yet effective COVID-19 responses in LTC facilities.
- Among individuals with a negative RT-PCR or no previous SARS-CoV-2 diagnostic test, those who reported myalgias (muscle aches and pains), headache, and loss of appetite were found positive using a serological COVID test.
- Symptomatic cases assessed with the US Centers for Disease Control’s probable case definition were associated with seropositivity more often than those assessed using the Canadian, European and World Health Organization case definitions.
- A wider case definition, with low threshold for symptoms in LTC settings when considering isolation of symptomatic staff and residents, would be effective.
- Symptomatic staff and residents should be subject to serology testing, despite several negative tests for COVID-19.
Long-term care (LTC) facilities have been hit hard by the COVID-19 pandemic. Time is of the essence when trying to control a COVID-19 outbreak as residents of these facilities are exceptionally vulnerable. The authors of this study, from the British Columbia Centre for Disease Control, the Provincial Health Services Authority of British Columbia and the University of British Columbia, sought to evaluate how many residents and staff were infected with SARS-CoV-2 by comparing results of RT-PCR by nasopharyngeal swab tests to serological test results. Additionally, as nasopharyngeal testing is not always available or timely and case definitions are therefore used to mitigate risk, this study sought to assess the current case definitions for COVID-19 given that the elderly may not always present with the classic expected symptoms.
The authors found that 39% of participants tested positive for SARS-CoV-2 by blood sample after a negative nasopharyngeal swab result or no previous test. Myalgias (body aches and pains), headache, loss of appetite, were often associated with positive antibody tests. This shows that positive COVID-19 cases are going undetected via RT-PCR, potentially due to symptoms outside of the expected case definition. Often these participants had three or more negative nasopharyngeal swabs.
The authors suggest adopting a wider case definition with low threshold for symptoms in LTC settings when considering isolation of symptomatic staff and residents. Further, symptomatic staff and residents with several negative tests for COVID-19 should be subject to serology testing. These findings have implementations for the future as those working in health and infection control may need to alter their outbreak inclusion criteria.
Vijh R, Ghafari C, Hayden A, Schwandt M, Sekirov I, Morshed M, Levett P, Krajden M, Boraston S, Daly P, Lysyshyn M, Harding J, Mclennan M, Chahil N, Mak A, Mckee G. Serological survey following SARS-COV-2 outbreaks at long-term care facilities in metro Vancouver, British Columbia: Implications for outbreak management and infection control policies. Am. J. Infect. Control. 2021 May;49(5):649-652. doi: 10.1016/j.ajic.2020.10.009.