Accuracy of the Rapid Test Kit Antigen for SARS CoV 2 Infection during the COVID 19 Pandemic in Sibu, Sarawak

Introduction  Sarawak (particularly Sibu) suffers from a third wave of SAR-Co-2 infection since January 2021 with average daily cases of about 100; rapid test kit antigen (RTK-Ag) has been used to provide a faster turn-around-time result. However, there are concerns regarding its accuracy. This study aims to determine the accuracy of the RTK-Ag in a high-prevalent community setting.    

Method  We identified patients who had RTK-Ag from Sibu Division Health Office and Sibu Hospital between January and May 2021 and compared them with the formal reverse transcriptase polymerase chain reaction (rt-PCR) results done within 24 hours. We calculated and analysed the accuracy parameters of the RTK-Ag against rt-PCR.    

Results  There were 758 patients with RTK-Ag tests, and 629 patients had rt-PCR within 24 hours of the former. The sensitivity, specificity, negative predictive value, and positive predictive value of RTK-Ag were 83.78%, 99.32%, 93.63% and 98.10%, respectively. The agreeability was near perfect (Kappa coefficient 0.868, p <0.001). Among the true positives, the cyclic threshold (Ct) value for E and RdRp genes were significantly higher (p<0.001) in the RTK-Ag negative group (34.80 (IQR: 13.490) and 36.46 (IQR: 15.920) respectively).    

Discussion/Conclusion  RTK-Ag has good sensitivity and specificity for mass screening during a high prevalent community setting, particularly in detecting patients with low Ct value. Based on our results, we suggest the RTK-Ag positive results be accepted to detect those infected with SARS-CoV-2 infection. In contrast, those with RTK-Ag negative results should undergo rt-PCR if they remained as high-risk cases.   

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