Comparison of Pharmacia Chlamydia EIA, IDEIA and cell culture in the detection of urogenital chlamydial infection

Magic Lite Chlamydia immunoassay in urogenital samples and urine versus chlamydial culture

Magic Lite Chlamydia assay (commercial test kit for the identification of Chlamydia trachomatis) was evaluated on urogenital samples and urine with chlamydial culture as the reference method. The sediment of the transportation buffer of specimens which were Magic Lite positive but culture negative or toxic was investigated for elementary bodies with fluorescein-labelled anti-chlamydial antibodies. The prevalence of chlamydial infection among the 577 men investigated was 13.7% as estimated by culture and direct immunofluorescence and 6.4% among the 173 women. In order to improve the sensitivity a cut-off value below that recommended by the manufacturer was used. The sensitivity of Magic Lite in male urethral specimens was then 60.8% and that in female urethral/cervical specimens 90.9%. The specificity was 99.6% and 100%, respectively. In urine specimens the sensitivity of Magic Lite was 63.3% (men) and 63.6% (women). The specificity was 99.4% and 100%, respectively. The sensitivity of Magic Lite on male urethral specimens was related to the number of inclusion bodies per well in culture and it was higher among men attending with clinical findings of urethritis (69%) than among asymptomatic men sampled as a screening procedure (36%) (P < 0.05). Corresponding differences between the sexes and between those with and without symptoms were not noted for Magic Lite applied on urine samples.

Prevalence of urogenital Chlamydia trachomatis infection in El Salvador. I. Infection during pregnancy and perinatal transmission

One-hundred and twenty-nine pregnant women in labour (age range 15-46 years; median age 23) and 42 infants born to chlamydia-positive mothers (age range 5-15 days; median age 10) were investigated to estimate the prevalence and incidence, respectively, of Chlamydia trachomatis infection in San Salvador, El Salvador. Urethral and cervical samples were obtained from all women and conjunctival specimens were taken from both eyes of each child. The chlamydial antigen was detected with the commercial Pharmacia Chlamydia EIA kit. Direct immunofluorescence (DFA) (Syva MicroTrak) was used for confirmation. In the newborns both EIA and DFA tests on direct preparations from ocular smears were performed on all the samples. The prevalence of chlamydial infection in pregnant women was 44% (57/129). The incidence of chlamydial infection in neonates was 64% (27/42), and the majority of the infected children (56%) had conjunctivitis. Referring to individuals rather than specimens the sensitivity of EIA tests on conjunctival samples from the infants was low (37%) as compared with 91% on urethral and cervical specimens from the pregnant women.

Laboratory techniques for the diagnosis of chlamydial infections

Yolk-sac inoculation of embryonated eggs was superseded 25 years ago by the use of cell cultures (often McCoy) for the isolation of Chlamydia trachomatis. Centrifugation of specimens onto the cell monolayers was shown to increase sensitivity, but little of late has further improved sensitivity which is at least ten-fold greater than that of eggs. However, culture is slow and labour intensive so that non-cultural techniques without these drawbacks have come to dominate. Direct fluorescent antibody (DFA) tests are rapid and have sensitivities that range from 70% to 100% for men and 68% to 100% for women, and specificities that range from 87% to 99% for men and 82% to 100% for women; if the tests are read by competent observers the values are at the top end of the ranges. The detection rate may be enhanced even further by relatively low-speed centrifugation of specimens before staining. Skilled reading is not a feature of enzyme immunoassays (EIAs) which according to the literature have sensitivities that range from 62% to 97% for men and 64% to 100% for women, and specificities that range from 92% to 100% for men and 89% to 100% for women. However, comparison against poor reference tests is responsible for most of the higher values and the clinician should not be misled into believing that EIAs have excellent sensitivity; the lower values in the ranges are closer to reality. Furthermore, EIAs that are being designed for use by general practitioners should be regarded with the greatest caution since lack of sensitivity means that chlamydia-positive patients will go undetected. The polymerase chain reaction (PCR) is not bedevilled by insensitivity but it is no more sensitive than the most sensitive cell culture or DFA tests. PCR is unsuitable for routine diagnosis but has a place as a research tool. For men, examination of "first-catch" urine samples by the best of the non-cultural procedures provides an acceptable non-invasive approach to diagnosis; for women, the value of examining urine may be less, but needs to be thoroughly tested. However, there is little doubt that a Cytobrush used to obtain cervical specimens holds no practical advantage over a swab. Serological tests are reliant on the provision of paired sera for making a diagnosis; high antibody titres in single sera may be suggestive of an aetiological association in deep-seated chlamydial infections (epididymitis, arthritis, salpingitis, etc), but unequivocal interpretation is unusual, particularly in an individual case, since the distinction between a current and past infection is problematical.

Gonorrhoea and urogenital chlamydial infection in female prostitutes in Tegucigalpa, Honduras

The prevalence of gonorrhoea and urogenital chlamydial infection was investigated in female prostitutes in Tegucigalpa, Honduras. Epidemiological data were recorded according to a standardized questionnaire. The median age of the prostitutes was 27 years and the median period of prostitution was 2-4 years. Most of the women (91%) had no occupation other than prostitution and 57% of them had not even completed primary school. In 233 cases when both gonococcal culture and chlamydial antigen detection with a commercial EIA kit were performed the prevalence of gonorrhoea was 25% (59) and that of chlamydial infection 31% (72). Both diseases were recorded in 9%. The women who had been prostitutes for 2 years or longer had gonorrhoea (P less than 0.01) or chlamydial infection (P less than 0.05) less frequently than those who had practised prostitution for a shorter time period. Among 70 different gonococcal isolates from 241 prostitutes, 40 (57%) belonged to serogroup W II/III. Most (83%) of the 30 W I isolates were beta-lactamase producing (PPNG) like 42% of the W II/III isolates. All non-PPNG isolates, except one had decreased susceptibility to benzylpenicillin (MIC greater than or equal to 0.125 mg/l) and all isolates were susceptible to spectinomycin. Four out of five isolates from the throat were PPNG and the fifth had a benzylpenicillin MIC of 0.5-2.0 mg/l.