Background: The QuickVue influenza test, a rapid diagnostic method, detects influenza antigen by immunochromatographic assay. In a nested case-control study, the presence of viral RNA on the QuickVue test strip was checked using reverse transcriptase-polymerase chain reaction (RT-PCR). Methods: QuickVue test strips from 30 patients who attended the Hajj pilgrimage in Mecca, confirmed to have influenza by RT-PCR on nasal swabs collected in lysis buffer, were selected as cases, and another 30 strips from influenza-negative patients were chosen as controls after matching for age, sex, and risk factors of influenza. Test strips from both cases and controls were subjected to RT-PCR testing 9 months after bedside testing. Results: Eight cases (27%) and 1 control (3%) were positive for influenza by the QuickVue test at point of care (P = 0.03). Later, when the test strips were subjected to RT-PCR, 6 of 8 influenza-positive QuickVue strips detected the presence of influenza RNA, and the only positive strip from the controls was also confirmed to have influenza. Thus, the presence of influenza was confirmed in 8 of 9 QuickVue positive strips with substantial agreement between bedside QuickVue testing and subsequent RT-PCR testing on the strips (κ coefficient, 0.8; 95% confidence interval, 0.6-1). Conversely, there was only slight agreement between RT-PCR on lysis buffer and RT-PCR on QuickVue strips (κ coefficient, 0.2; 95% confidence interval, 0.03-0.3). Conclusion: Our pilot study demonstrated that the QuickVue test strips if saved rather than discarded can be used to reevaluate discordant results.
- J coefficient
- Nested case-control study
- Point-of-care testing
- Reverse transcriptase-polymerase chain reaction