Enzyme immunoassay compared with cell culture and immunofluorescence for detecting genital chlamydia

Periodic health examination, 1996 update: 2. Screening for chlamydial infections. Canadian Task Force on the Periodic Health Examination

OBJECTIVE

To update the 1984 recommendations of the Canadian Task Force on the Periodic Health Examination on the routine screening of asymptomatic patients for infection with Chlamydia trachomatis.

OPTIONS

Screening, with the use of culture or nonculture tests, of the general population, of certain high-risk groups or of all pregnant women; or no routine screening.

OUTCOMES

Rates of asymptomatic and symptomatic chlamydial infection, perinatal complications, longterm complications of infection (i.e., pelvic inflammatory disease, infertility and ectopic pregnancy), coinfection with other sexually transmitted diseases, disease spread, hospital care, complications of therapy and costs of infection and of screening.

EVIDENCE

Search of MEDLINE for articles published between Jan. 1, 1983, and Dec. 31, 1995, with the use of the major MeSH heading "chlamydial infections," references from recent review articles and recommendation by other organizations.

VALUES

The evidence-based methods of the Canadian Task Force on the Periodic Health Examination were used. Advice from reviewers and experts and recommendations of other organizations were taken into consideration. Prevention of symptomatic disease and decreased overall costs were given high values.

BENEFITS, HARMS AND COSTS

The greatest potential benefits of screening asymptomatic patients for chlamydial infections are the prevention of complications, especially infertility and perinatal complications, and the prevention of disease spread. There is no evidence that screening of the general population for chlamydial infections leads to a reduction in complications, and screening may increase costs. However, there is evidence that annual screening of selected high-risk groups and of pregnant women during the first trimester is beneficial in preventing symptoms and reducing the overall cost resulting from infection.

RECOMMENDATIONS

There is fair evidence to support screening and treatment of pregnant women during the first trimester (grade B recommendation) as well as annual screening and treatment of high-risk groups (sexually active women less than 25 years of age, men or women with new or multiple sexual partners during the preceding year, women who use nonbarrier contraceptive methods and women who have symptoms of chlamydial infection: cervical friability, mucopurulent cervical discharge or intermenstrual bleeding; grade B recommendation). There is fair evidence to exclude routine screening of the general population (grade D recommendation).

VALIDATION

These recommendations are similar to those of the US Preventive Services Task Force and the US Centers for Disease Control and Prevention, Atlanta.

SPONSOR

These guidelines were developed and endorsed by the Canadian Task Force on the Periodic Health Examination, which is funded by Health Canada and the National Health Canada and the National Health Research and Development Program. The principal author (H.D.D.) was supported in part by the Ontario Ministry of Health and the Canadian Infectious Diseases Society Lilly Fellowship.

Detection of Chlamydia trachomatis in semen by antibody-enzyme immunoassay compared with polymerase chain reaction, antigen-enzyme immunoassay, and urethral cell culture

OBJECTIVE

To compare the results obtained by four different techniques for the detection of Chlamydia trachomatis in the male genital tract.

DESIGN

Prospective study.

SETTING

Andrology unit of a university hospital.

PATIENTS

Male infertility patients.

INTERVENTIONS

Analysis of semen samples and urethral swabs for the presence of C. trachomatis by recombinant antibody-enzyme-linked immunosorbent assay (rELISA), polymerase chain reaction (PCR), antigen-enzyme immunoassay (EIA) and McCoy cell culture.

MAIN OUTCOME MEASURE

Detection of C. trachomatis.

RESULTS

In 57 of 205 semen samples (27.8%) immunoglobulin A-antibodies against C. trachomatis were found. In contrast, only 1 of 56 semen samples (1.8%) was positive for C. trachomatis-DNA by PCR, only 1 of 139 semen samples (0.7%) was positive by antigen-EIA, and only 4 of 173 urethral swabs (2.3%) grew C. trachomatis in cell culture.

CONCLUSIONS

The discrepancy of positive results found by the antibody-rELISA and direct methods for the detection of C. trachomatis indicates successful eradication of the microorganism in > 90% of antibody-positive men. Therefore, detection of antibodies against C. trachomatis in seminal plasma appears to be of limited diagnostic value.

Comparison of an enzyme immuno assay (Antigenz Chlamydia) with cell culture for the detection of genital chlamydial infection in high and low risk populations

OBJECTIVE

To evaluate a new enzyme immuno assay, Antigenz Chlamydia, for the detection of chlamydial antigen in urogenital samples using cell culture as the gold standard for comparison and direct immuno fluorescence to aid resolving the discrepancies.

SUBJECTS

212 men and 303 women attending an STD clinic and 404 women of child bearing age attending gynaecological clinics.

RESULTS

Sensitivity, specificity, predictive value of positive result and predictive value of negative result of the new test were 77.6%, 99.0%, 94.3%, and 95.7% respectively in the high risk population with a prevalence of 16.5%. In the low risk population the figures were 84.2%, 94.5%, 43.2% and 99.2% respectively with a prevalence of 4.7%.

CONCLUSION

Antigenz Chlamydia is an easy and quick test to perform. The test is suitable for use in high risk and low risk populations provided all positive samples are confirmed.

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.

Preliminary evaluation of "Clearview Chlamydia" for the rapid detection of chlamydial antigen in cervical secretions

Clearview Chlamydia (Unipath) is a rapid monoclonal antibody based latex immunodiffusion test for detecting chlamydial antigen in endocervical specimens. The assay does not require specialised equipment or extensive training and takes less than 30 minutes from sample to results. The clinical performance of Clearview Chlamydia was evaluated with 478 paired endocervical swabs from patients attending a genitourinary medicine clinic. In the first part of the study, 221 non-randomised specimens were tested by cell culture (1st swab) and Clearview (2nd swab) whereas in the second part of the study 257 randomised swabs were examined by Clearview, cell culture and immunofluorescence. The overall prevalence of chlamydial infection was 8.8% and the sensitivity, specificity, positive and negative predictive values for Clearview were 85.7%, 99.1%, 90% and 98.6%. The test requires further evaluation to establish its role in the management and control of chlamydial infection.

Comparison of the Kallested Pathfinder EIA, cytocentrifuged direct fluorescent antibody, and cell culture for the detection of Chlamydia trachomatis

A total of 203 duplicate endocervical samples collected from patients at an adolescent health care center were tested for the presence of Chlamydia trachomatis by cell culture, Pathfinder enzyme immunoassay (EIA) (Kallestad) and cytocentrifuged direct fluorescent antibody (DFA). Compared to cell culture, the Pathfinder assay demonstrated a sensitivity and specificity of 85.2% and 100%, whereas the DFA procedure demonstrated to be 92.6% sensitive and 99.4% specific.

Is a test of cure necessary following treatment for cervical infection with Chlamydia trachomatis?

Tests of cure (TOC) were performed on specimens from 106 women following treatment for chlamydial infection of the cervix. 91 women attended for the first TOC with enzyme immunoassay (EIA) within one week of finishing antibiotics. Three were EIA positive, 88 were EIA negative. These three women were subsequently EIA and culture negative although they received no further antibiotics. Ninety women returned for the second TOC with EIA and culture between seven and 27 days after completing treatment. All the results were negative. Routine TOC is unnecessary following appropriate antichlamydial therapy. If TOC is indicated antigen-detection methods should not be used immediately after finishing antibiotics as misleading positive results may be obtained. EIA or culture at one week or later after treatment is reliable.

Comparison of an enzyme immunoassay (Ortho) with cell culture and immunofluorescence for the detection of genital chlamydial infection

An enzyme immunoassay (EIA) test (Ortho Diagnostic Systems Ltd) was evaluated against cell culture for the detection of chlamydial genital infection. Specimens were obtained from 409 patients (204 men and 205 women). Sensitivity, specificity, predictive value of a positive result (PVP) and predictive value of a negative result (PVN) for the new test compared to cell culture were respectively 73.1%, 93.8%, 63.3% and 96% for men and 80%, 95.6%, 71.4% and 97.2% for women. Discrepancies were further evaluated by repeating the EIA, and by direct immunofluorescence (IF) on the EIA transport buffer. The sensitivity, specificity, PVP and PVN of the EIA against the combination of cell culture and direct IF were respectively 76.7%, 96%, 76.7% and 96% for men, and unchanged for women. Overall agreement between the EIA and the combination of cell culture and direct IF was 93.4%. The EIA is rapid and simple to perform and does not require elaborate equipment.

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

Two commercial test kits, Pharmacia Chlamydia EIA (PhEIA) and IDEIA Chlamydia Test, for the identification of Chlamydia trachomasis and McCoy cell culture were compared in urogenital specimens. The sediments of the transportation buffers of specimens with discordant results were investigated for elementary bodies (EB) with fluorescein-labelled antichlamydial antibodies. The prevalence of chlamydial infection among the men was 16% (48 of 293), 47 culture positive and one EB positive, and among the women 10% (10 of 97), 10 culture positive. In men, the sensitivity of PhEIA, IDEIA and culture was 71%, 40% and 98%, respectively. In women, irrespective of site, corresponding figures were 100%, 80% and 100%. The specificity and positive predictive values were 100% for both enzyme immunoassays in men and women. The low sensitivity of IDEIA could not be explained by the degree of infection as measured by the number of inclusion bodies in cell culture, the presence of antigen as measured by the number of EBs or the sampling order.