Strain differentiation of Neisseria gonorrhoeae by reverse passive hemagglutination

Reverse passive hemagglutination tests for rapid diagnosis of snake envenomation

Reverse passive hemagglutination (RPHA) tests for the detection of six major poisonous snake venoms of Thailand were studied. Three different species of red blood cells i.e., sheep (SRBC), human (HRBC) and chicken (CRBC) were sensitized with protein A-affinity purified rabbit antivenom IgG using chromic chloride as a coupling reagent. The properties of these sensitized erythrocytes with regard to sensitivity, specificity, stability to venom enzymes and storage etc., were studied and compared. The sensitivities of the RPHA tests in venom detection were 2 to 635 ng/ml. Cross-reactions were observed with heterologous venoms at concentrations at least 62 times higher than those observed with homologous venoms. After treatment with glutaraldehyde, the coupled red blood cells showed reduced sensitivity but were stable at 4 degrees C from 1 to 12 months depending upon the antibody and the species of erythrocytes. The entire test required 60 to 120 min. The RPHA using fresh SRBC correctly identified various venoms in 48 of 59 (81.3%) serum samples and 16 of 26 (61.5%) wound swabs. Venom mis-identifications were made in 2 sera (3.4%). In a comparison of 24 paired serum and wound swab samples, more positive identifications were made with serum than with swab samples but the difference was not statistically significant (p > 0.05).

Enzyme immunoassay for diagnosis of gonorrhea

An enzyme immunoassay (EIA; Gonozyme [Abbott Laboratories]) for gonococcal antigen was assessed for the rapid diagnosis of gonorrhea. Patients attending two sexually transmitted disease clinics were tested by EIA and culture on Thayer-Martin medium. EIA was highly effective in detecting gonococcal infection among symptomatic men, with 70 of 75 (93.3%) culture-positive men having positive tests and no false-positive reactions. The performance of the test was not as good in detecting cervical gonorrhea; the best result obtained was a sensitivity of 87% (33 of 38) for EIA compared with culture. EIA false-positives occurred at a relatively low rate for women, with the test having a specificity of ca. 97%. The test clearly is capable of detecting gonococcal antigen in cervical and urethral specimens, but its role in routine diagnosis is not clear. Its performance seems equal to that of the Gram stain for men, but it seems to be less sensitive than culture for cervical gonorrhea--a drawback in high-risk populations. The low false-positive rate could be an important issue in screening low-prevalence populations.

Detection of Neisseria gonorrhoeae antigen by a solid-phase enzyme immunoassay

The Gonozyme test (Abbott Laboratories) is a new enzyme immunoassay for detecting Neisseria gonorrhoeae antigens in specimens from the urethra in men and the endocervix in women. To evaluate the usefulness of the assay 249 patients were investigated. The results obtained with the immunoassay were compared with those of culture and microscopy of Gram-stained smears. The sensitivity and specificity of the test were high in men with urethritis and acceptable in different groups of women. As the sensitivity of the Gonozyme test was much higher than that of microscopy for endocervical specimens it might be useful as a rapid screening test for the detection of gonorrhoea in women.