Performance of rapid influenza diagnostic tests (QuickVue) for influenza A and B Infection in India

Abstract

Background: Rapid point-of-care (POC) tests provide an economical alternative for rapid diagnosis and treatment of influenza, especially in public health emergency situations.

Objectives: To test the performance of a rapid influenza diagnostic test, QuickVue (Quidel) as a POC test against a real-time polymerase chain reaction (RT-PCR) assay for detection of influenza A and B in a developing country setting.

Study design: In a prospective observational design, 600 patients with influenza-like illness (ILI) or with severe acute respiratory illness (SARI) who were referred to the Influenza Clinic of a tertiary care hospital in Srinagar, India from September 2012 to April 2013, were enrolled for diagnostic testing for influenza using QuickVue or RT-PCR. All influenza A-positive patients by RT-PCR were further subtyped using primers and probes for A/H1pdm09 and A/H3.

Results: Of the 600 patients, 186 tested positive for influenza A or B by RT-PCR (90 A/H1N1pdm09, 7 A/H3 and 89 influenza B), whereas only 43 tested positive for influenza (influenza A=22 and influenza B=21) by QuickVue. Thus, the sensitivity of the QuickVue was only 23% (95% confidence interval, CI: 17.3-29.8) and specificity was 100% (95% CI: 99.1-100) with a positive predictive value (PPV) of 100% (95% CI 91.8-100) and a negative predictive value (NPV) of 74.3% (95% CI: 70.5-77.9) as compared to RT-PCR.

Conclusions: The high specificity of QuickVue suggest that this POC test can be a useful tool for patient management or triaging during a public health crisis but a low sensitivity suggests that a negative test result need to be further tested using RT-PCR.

Figure 1

Relationship between Ct values by RT-PCR and influenza positivity by Quickvue. The Ct values obtained for RT-PCR for influenza specific PCR (X-axis) are plotted against percent positivity by Quickvue test (Y-axis). Lower Ct values (proxy for high viral loads) correlated with higher positivity by Quickvue assay.