The Establishment of the Spiking Method to Evaluate the Rapid Diagnostic Test Antigen (Ag-RDT) Product for COVID-19 Detection

The quality control of the COVID-19 Rapid Diagnostic Test (Ag-RDT) product is regarded as one of the government’s responsibilities. The Indonesian government establishes rules for Ag-RDT post-market validation, where it should be performed by two designated laboratories, using the spiking technique. The usage of this technique raises concerns, especially if it does not represent the precise product quality, due to the sample dilution. In addition, the requisite of using fresh samples that should be prepared for less than 48 hours is considered costly and time-consuming. In response to this, we tested two samples from different age groups on the Ag-RDT brand recommended by the World Health Organization (WHO); Panbio™ Covid-19 Ag Rapid Test (Abbott) and standard Q Ag-RDT (SD Biosensor, Roche). In both Ag-RDT products, the samples observed in the cycle threshold (Ct) values≤25 groups exhibit >80%sensitivity and >97% specificity as in compliance with the WHO recommendation. Meanwhile, as observed in the Ct>25 groups, the sensitivity of the two Ag-RDT products was below 25%, which was not in compliance with the WHO recommendation. Overall, this study indicated that the Spiking technique is eligible to be used for evaluating the performance of Ag-RDT, especially at Ct≤25. Additionally, the samples’ life span of up to 2 weeks of storage at -80oC can be used for post-market validation of Ag-RDT. Furthermore, the quality control assay for longer sample storage is interesting to be carried out.