Directigen Flu A + B test versus viral culture and reverse transcription-PCR for diagnosis of influenza virus type A and type B

ABSTRACT

In our study, 60 sputum specimens were collected from patients suffering from upper and lower respiratory tract manifestations with a mean age of 44.5 years. Out of the 60 patients, 49 patients had developed pneumonia as a complication. In addition to 20 specimens were collected from apparently healthy subjects matching in age with the patient group. All specimens were subjected to Directigen Flu A+B assay, viral culture on Madin Darby canine kidney cell and reverse transcription-PCR [RT-PCR] for demonstration of influenza type A and B. Directigen Flu test had a detection rate of 18.3% for influenza type A and 26.6% for influenza B. Viral culture had a detection rate of 20% and 26.6% for influenza type A and influenza type B respectively. While RT-PCR had a detection rate of 16.6% and 25% for influenza virus type A and B respectively. The sensitivity, specificity and positive and negative predictive value was[66%, 0%, 72.7%, 0% for influenza A virus and 75%, 0%, 75%, 0% for influenza type B by Directigen Flu A + B test. While the resolved sensitivity, specificity and positive and negative predictive value of RT-PCR was 100%, 83.3%, 100%, 60% for influenza A virus and 100%, 93.7%, 100%, 80% for influenza type B. Directigen Flu test is rapid, easy, reliable test that can be used for diagnosis and discrimination between influenza type A and type B infections. But it lacks specificity in some patients, thus, it requires confirmation by tissue culture and RT-PCR to rule out false-positive results: