Utility of latex agglutination test (LAT) in detecting acute bacterial meningitis against culture as gold standard

Background: Bacterial meningitis is a medical emergency. It is a major cause of death and disability worldwide. Immediate steps must be taken to establish the cause and initiate effective therapy. Though Gram staining is essential in diagnosis of meningitis, some cases may be missed. Culture and latex agglutination tests (LATs) help to overcome this disadvantage. Objective: This study was conducted to find out the sensitivity of the LAT in acute bacterial meningitis against culture as the gold standard. Materials and Methods: Cerebrospinal fluid (CSF) samples were collected aseptically in dry, sterile bottles from all cases of bacterial meningitis by lumbar puncture from August 2011 to December 2013. They were subjected to cell count, Gram staining, culture and LAT. Results: Out of 538 samples, aetiological agents were identified by Gram stain and culture or LAT in 52 cases. Streptococcus pneumoniae was isolated in 22 (42%), Haemophilus influenzae type b in 14 (26.9%), Neisseria meningitidis in three (5.6%), Group B streptococci in three (5.6%), Klebsiella pneumoniae in six (11.5%), Acinetobacter baumannii in two (3.84%) and Escherichia coli in two (3.84%) cases. In the present study, the LAT for H. influenzae type b; Streptococcus pneumoniae; Neisseria meningitidis A, B, C, Y and W135; Group B streptococci; and E. coli K1 antigen had a sensitivity of 74.1%, specificity of 95.8%, positive predictive value 52.1% and negative predictive value 98.3%. Conclusion: LAT cannot replace the utility of culture. Despite its drawbacks, LAT is a simple, rapid procedure, suitable to be used as an adjunct laboratory test for establishing the aetiological diagnosis of bacterial meningitis, particularly in partially treated cases.