Rapid evaluation of female patients exposed to gonorrhea by use of the Limulus lysate test

The Limulus amoebocyte lysate (LAL) assay was used to evaluate 115 females who were named as sexual contacts by men with culture-proven gonorrhea. These patients were treated for gonorrhea before laboratory confirmation, as recommended by the Centers for Disease Control, because of the lack of rapid screening tests and the serious consequences of undetected infection. For the LAL assay, endocervical samples were collected with depyrogenated cotton-tipped swabs, and the swabs were placed in 10 ml of diluent to assay for endotoxin; the negative predictive value of the LAL assay at this dilution was 100%. Incubation was carried out at 37 degrees C for 30 min; positive or negative results were indicated by gelation or lack of gelation, respectively. Lysate sensitivity was 0.3 ng/ml, with an Escherichia coli endotoxin standard. Single endocervical cultures and the LAL assay were both positive in 71 patients, but the Gram stain was positive in only 36 (50.7%) of these cases. For the 44 culture-negative cases, the LAL assay was negative in 21 (47.7%). Thus, the LAL assay was able to selectively exclude approximately half of the culture-negative gonorrhea contacts and would have spared these patients inappropriate therapy and contact tracing, without excluding culture-positive gonorrhea cases.