The Limulus amoebocyte lysate assay for prediction of chlamydial infection in males with non-gonococcal urethritis: an evaluation.

Chlamydia trachomatis produces small amounts of an endotoxin-like material. The Limulus amoebocyte lysate assay was used to evaluate chlamydial cell cultures and also the exudates from adult male patients with non-gonococcal urethritis, as a possible method to subdivide this condition into chlamydial and nonchlamydial urethritis. In vitro endotoxin assays were conducted in McCoy cell media using the Limulus assay, and endotoxin levels were consistently 10-fold less at 24 h than at 0, 48, 72, and 96 h, which may be accounted for by the unique growth cycle of chlamydia. In 75 males with non-gonococcal urethritis, urethral exudates were collected, serially diluted and assayed for endotoxin content. Of these, 27 (36%) had positive chlamydial cultures and 48 were negative. There was no statistically significant correlation between the level of endotoxin present and a positive or a negative culture for C. trachomatis (P greater than 0.05). Sensitivity and specificity of the assay were only 59% and 56%, respectively, at a 1 in 8 dilution; it was not useful in predicting chlamydial culture results in male patients with non-gonococcal urethritis.