Evaluation of influenza virus detection by direct enzyme immunoassay (EIA) and conventional methods in asthmatic patients.

ABSTRACT

Throat gargle specimens of fifty-seven acute asthmatic patients (age range 18-40 years) were collected for the study. Thirty-four patients were found influenza virus positive in acute asthma cases. Influenza virus was isolated by conventional culture method on MDCK cell-line and by enzyme immunoassay test (EIA). The EIA negative specimens were retested after virus amplification on MDCK cell-line. Virus shedding and virus surface receptors assay was carried out to determine influenza virus titre. Airway functions were measured by spirometry. A good relationship was observed between the degree of airflow limitation and presence of influenza virus infection (p < 0.001; r = 0.85). A comparable difference in % FEV1 was observed in relation to the symptoms. The patients with greater viral antigen load had lower % FEV1. Two specimens, which were EIA negative, turned out to be positive after amplification on MDCK cell-line. The sensitivity was 98% and specificity was 100%. It was concluded that EIA method is a useful diagnostic tool as it detects influenza viral antigen quickly as compared to conventional methods.