Diagnosis of COVID is performed by PCR methods, but their capacity is limited by the requirement of high-level facilities and instruments. The loop-mediated isothermal amplification (LAMP) method has been utilized for the detection of isolated virusspecific RNA. Preliminary data suggest the possibility of isothermal amplification directly from respiratory samples without RNA extraction. All patients admitted to our hospital were screened for SARS-CoV-2 by routine. Respiratory samples were tested by variplex system based on LAMP method directly without RNA extraction and by PCR. Primary endpoint was the falsenegative rate of variplex test compared with PCR as gold standard. In 109 patients variplex test and PCR assay were performed simultaneously. Median age was 80 years and male/female ratio was 40/60%. The prevalence of PCR-confirmed COVID diagnosis was 43.1%. Variplex test was positive in 13.8%. False-negative rate of variplex test compared with PCR was 83.0%. The potential of LAMP technology using isolated RNA has been demonstrated impressively by others, and excellent sensitivity and specificity of detecting SARS-CoV-2 has been reported. However, without RNA extraction, the variplex test system failed to reliably detect SARS-CoV-2 directly in respiratory samples.

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Diagnosis of COVID is performed by PCR methods, but their capacitiy is limited by the requirement of high-level facilities and instruments. The loop-mediated isothermal amplification (LAMP) method has been utilized for the detection of isolated virus-specific RNA. Preliminary data suggest the possibility of isothermal amplification directly from respiratory samples without RNA extraction.All patients admitted to our hospital were screened for SARS-CoV-2 by routine. Respiratory samples were tested by variplex system based on LAMP method directly without RNA extraction and by PCR. Confirmation or exclusion of clinical COVID diagnosis was based on history, examination and findings. Primary endpoint was the false negative rate of variplex test compared to PCR.A total of 153 patients were included in the study. Median age was 79 years and male/female ratio was 45%/55%. Prevalence of clinical COVID diagnosis was 61.4%. Variplex test and PCR assay was positive in 15.0% and 45.5%, respectively. In 109 patients variplex test and PCR assay were performed simultaneously. False negative rate of variplex test compared to PCR was 83.0%.The potential of LAMP-technology using isolated RNA has been demonstrated impressively by others and excellent sensitivity and specivity of detecting SARS-CoV-2 has been reported. However, without RNA extraction the variplex test system failed to reliable detect SARS-CoV-2 directly in respiratory samples.

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