Lack of utility of a Limulus amoebocyte lysate assay in the diagnosis of urethral discharges in men

We evaluated a Limulus amoebocyte lysate assay (LALA) test kit for the diagnosis of gonorrhea in 883 unselected men with urethral discharge. Results were compared with those of Gram-stained smears and Martin-Lewis cultures. Of 331 men with gonococcal urethritis and 552 men with nongonoccal urethritis, 125 (37.8%) and 503 (91.1%), respectively, could not be evaluated by LALA owing either to insufficient discharge specimen to perform the test (569 or 64.4%) or to other exclusion criteria (59 or 6.7%). Of 255 LALA-evaluable discharges, LALA correctly diagnosed 252 (98.8%), compared with 244 (95.7%) for the Gram-stained smear. However, the Gram-stained smear also correctly diagnosed 96.5% of 456 men with insufficient discharge for LALA testing. The clinical utility of the LALA test kit is severely limited by performance criteria that exclude the majority of unselected men with urethritis. In addition, it is more technically cumbersome, time consuming, and costly than Gram-stained smears. Further test modifications are unlikely to overcome these inherent disadvantages of LALA.