Utility of Latex Agglutination Test in the Laboratory Diagnosis of Bacterial Meningitis

Kim, Mi Na; Pai, Chik Hyun

Abstract

BACKGROUND: Latex agglutination (LA) test has been ordered frequently on cerebrospinal fluid (CSF) specimens to identify etiologic agents of bacterial meningitis as early as possible, but its use is still controversial. To assess the clinical utility of LA tests, 54 consecutive cases of bacterial meningitis were reviewed retrospectively in a tertiary care hospital in Seoul.
METHODS
A total of 54 patients with bacterial meningitis of Streptococcus pneumoniae (21 cases), Haemophilus influenzae (17), Neisseria meningitidis (5), Streptococcus agalactiae (11) were identified by a search of the hospital computer files from 1989 through 1997 in Asan Medical Center. The medical records of each patient were reviewed for CSF parameters (cell count, protein, glucose), the results of Gram stains, cultures, and LA tests, and history of antibiotics prior to the procurement of the CSF specimens. We also evaluated the yield of LA tests performed during the 12-month period from July 1996 through June 1997 and searched the hospital computer files for the CSF parameters of 215 patients on whom LA tests were done in the month of July 1997.
RESULTS
Gram stains and cultures were positive in 21 (70.0%) and 29 (96.7%), respectively, of 30 cases without prior antibiotic treatment, compared to only 4 (16.7%) and 7 (29.2%), respectively, of 24 cases with prior antibiotic treatment (P<0.001). Latex agglutination tests were positive in 12 (92.3%) of 13 without and 16 (80.0%) of 20 cases with prior antibiotic treatment. Of the 54 cases of bacterial meningitis the etiology was established by cultures and/or LA tests in 36 and only by LA test in 12, and the remaining six cases were transferred from other hospitals with diagnosis. The LA tests yielded only 6 positive cases (0.5%) from the 1,212 specimens of CSF received in 1996-97. On the review of CSF parameters, 27 (96.4%) of 28 patients with positive LA had leukocyte count of > OR =50/ L compared to 122 (56.7%) of 215 patients with LA tests performed in the month of July 1997.
CONCLUSIONS
The LA test is highly sensitive for the laboratory diagnosis of bacterial meningitis. It is a valuable test, particularly when the patient has a history of prior antibiotic treatment. The low yields of the LA tests could be improved by limiting the tests to those specimens with leukocyte counts of > OR =50/ L.