Evaluation of a new rapid influenza A diagnostic test for detection of pandemic (H1N1) 2009 and seasonal influenza A virus.

Background: Rapid influenza A diagnostic tests (RIDTs) play an important role in the clinical setting, especially in the influenza post-pandemic era with three influenza A viruses in circulation.

Objective: Determine the sensitivity and specificity of a new RIDT (FluA Dot) by comparison with BD Directigen EZ FluA+B and CDC rRT-PCR.

Methods: Two sets of experiments were conducted to determine the performance of the new test. (1) Serial dilutions of eight pandemic (H1N1) 2009 (pH1N1) isolates, five seasonal H3N2 isolates, five seasonal H1N1 isolates and three recombinant nucleoproteins were tested by FluA Dot assay, Directigen EZ FluA+B test and CDC real-time RT-PCR. (2) Using CDC rRT-PCR as the gold standard, the clinical sensitivity and specificity of the FluA Dot and Directigen EZ FluA+B were evaluated in nasopharyngeal swab (NPS) specimens of 807 patients presenting with influenza-like illness.

Results: The average analytical sensitivity of FluA Dot (0.06 ng/mL for recombinant nucleoproteins and 2.16 ± 0.85 log 10 TCID(50) for viruses) was approximately 10-fold higher than Directigen EZ FluA+B (1-2 ng/mL for recombinant nucleoproteins and 3.54 ± 0.81 log 10 TCID(50) for viruses), and was approximately 10-fold lower than the CDC rRT-PCR (1.09 ± 0.69 log 10 TCID(50) for viruses). Among 807 NPS specimens tested, the sensitivities and specificities of FluA Dot were 91.1% (95%CI: 86.7-94.4%)/99.7% (95%CI: 98.7-99.9%), and the Directigen EZ FluA+B were 71.9% (95%CI: 65.7-77.6%)/99.8%(95%CI: 99.0-99.9%).

Conclusions: The new test (FluA Dot) exhibit higher sensitivity than Directigen EZ FluA+B both in pH1N1 and seasonal influenza A detection. The promising RIDT can play important roles in influenza diagnosis and therapy.