The BinaxNOW antigen detection assay on CSF samples for diagnosis of pneumococcal meningitis

Introduction The BinaxNOW pneumococcal antigen detection assay is an immuno-chromatographic technique where the cell wall polysaccharide instead of capsular polysaccharide is the target. Although intended for use on urine samples, its role in diagnosis of pneumococcal meningitis has been reported by many others. The current study explores its accuracy when compared with real-time PCR. Methodology CSF samples from suspected meningitis cases were processed for Gram stain and culture following standard protocols. Antigen was detected by BinaxNOW antigen detection assay for Streptococcus pneumoniae . Previously published primers and protocols were used for real-time PCR targeting autolysin ( lyt A) gene and was considered as the gold standard test. Results Among the 74 samples tested, pneumococcal antigen was detected in 21.6% (16/74) and qPCR in 11 (14.9%) samples. Antigen detection assay had higher sensitivity (90.9%) when compared with culture (45.5%) while the positive predictive value was the lowest (62.5% and 100% for culture). It was in substantial agreement with the gold standard test with kappa coefficient of 0.685 and an accuracy of 90.5%. Conclusions The BinaxNOW pneumococcal antigen detection test can be employed for initial screening of samples or point-of-care test owing to its substantial agreement with real-time PCR.