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Analytical and clinical evaluation of a heat shock SARS-CoV-2 detection method without RNA extraction for N and E
Alfredo Bruno1, Domenica de Mora2, Byron Freire-Paspuel3
1Instituto Nacional de Salud Pública e Investigación "Leopoldo Izquieta Pérez", Guayaquil, Ecuador; Universidad Agraria del Ecuador, Guayaquil, Ecuador.
Background:
The COVID-19 pandemic has caused significant supply shortages worldwide for SARS-CoV-2 molecular diagnosis, like RNA extraction kits.
Objective:
The aim of our study was to evaluate the clinical performance and analytical sensitivity of a simple SARS-CoV-2 diagnosis protocol based on heat shock without RNA extraction using both "CDC" (N gene) and "Charite" (E gene) RT-qPCR protocols.
Results:
1,036 nasopharyngeal samples, 543 of them SARS-CoV-2 positive, were analyzed. The heat shock method correctly identified 68.8% (232/337) and 89.4% (202/226) of SARS-CoV-2 positive samples for N gene and E gene, respectively. Analytical sensitivity was assessed for heat shock method using the CDC RT-qPCR protocol, obtaining sensitivity values of 98.6%, 93.3% and 84.8% for limit of detection of 100.000, 50.000 and 20.000 viral RNA copies/mL of sample.
Conclusions:
Our findings show that a simple heat shock SARS-CoV-2 RT-qPCR diagnosis method without RNA extraction is a reliable alternative for potentially infectious SARS-CoV-2 positive patients at the time of testing. This affordable protocol can help overcome the cost and supply shortages for SARS-CoV-2 diagnosis, especially in developing countries. In Ecuador, it has been used already by laboratories in the public health system for more than 100.000 specimens.
