Expanded gold standard in the diagnosis of Chlamydia trachomatis in a low prevalence population: diagnostic efficacy of tissue culture, direct immunofluorescence, enzyme immunoassay, PCR and serology

Aftermath of Chlamydia Trachomatis - The Tip of an Iceberg in Female Reproductive Health

OBJECTIVE

The magnitude of infertile couples worldwide was found to be 60-80 million. Genital infection due to Chlamydia trachomatis (C. trachomatis) is one of the most prevalent sexually transmitted infections (STIs) which may present as PID, leading to ectopic pregnancy, infertility or other adverse health outcomes. This study was done to assess the prevalence of C. trachomatis infections among female patients with infertility using real time PCR (RT-PCR) and to compare the findings of molecular testing with hysterosalpingography (HSG) and ultrasonography (USG).

MATERIAL AND METHODS

50 endocervical swabs were collected from women of reproductive age group attending infertility clinic and stored at -80 ºC. DNA extraction was done with Helini bacterial mini spin kit and tested for C. trachomatis DNA by RT-PCR kit.

RESULTS

Of the 50 patients, 43 (86%) had primary infertility, and 7 (14%) had secondary infertility. Three (6%) were positive for C. trachomatis by RT-PCR. Two had primary infertility and one had secondary infertility.

CONCLUSION

Routine screening of C. trachomatis even in high-risk populations is not available in developing countries like India. The World Health Organization recommends syndromic approach for case management. Hence, a cost-effective, highly sensitive and specific test is the pressing priority in resource poor settings.

Molecular Approaches to the Diagnosis of Chlamydia

Chlamydia trachomatis is known as the most common bacterial infection agent to pass with sexual transition. This microorganism is an obligatory intracellular parasite. A variety of infections are caused by C. trachomatis, including trachoma, pneumonias in newborns, genital and urinary tract infections, and lymphogranuloma venereum (LGV), which is caused by LGV strains. The diagnosis of Chlamydia trachomatis can be made by cultures and isolations, antigens and antibodies (direct fluorescence, enzyme immunoassays), hybridization, or polymerase chain reaction (PCR). Each year, infection and diagnosis rates increase in the developed world. Since Chlamydia is mostly asymptomatic, screening, and treatment are a key to detecting cases. Polymerase chain reaction (PCR), ligase chain reaction (LCR), and nucleic acid sequence-based amplification (NASBAa) molecular methods can be used for the detection, low concentration, quantification, and identification of organisms. While the traditional PCR method confirms its existence, it can quantify real-time PCR (RT-PCR). This method (RT-PCR) may have low sensitivity among variants of the same species. Also, PCR scans, which receive urine service, offer great advantages. PCR from initial void urine (FVU) samples is highly sensitive in detecting the organism. Urine Chlamydia screenings are more acceptable in large populations and asymptomatic detections.

Chlamydia trachomatis and Genital Mycoplasmas: Pathogens with an Impact on Human Reproductive Health

The most prevalent, curable sexually important diseases are those caused by Chlamydia trachomatis (C. trachomatis) and genital mycoplasmas. An important characteristic of these infections is their ability to cause long-term sequels in upper genital tract, thus potentially affecting the reproductive health in both sexes. Pelvic inflammatory disease (PID), tubal factor infertility (TFI), and ectopic pregnancy (EP) are well documented complications of C. trachomatis infection in women. The role of genital mycoplasmas in development of PID, TFI, and EP requires further evaluation, but growing evidence supports a significant role for these in the pathogenesis of chorioamnionitis, premature membrane rupture, and preterm labor in pregnant woman. Both C. trachomatis and genital mycoplasmas can affect the quality of sperm and possibly influence the fertility of men. For the purpose of this paper, basic, epidemiologic, clinical, therapeutic, and public health issue of these infections were reviewed and discussed, focusing on their impact on human reproductive health.

Screening tests: a review with examples

Screening tests are widely used in medicine to assess the likelihood that members of a defined population have a particular disease. This article presents an overview of such tests including the definitions of key technical (sensitivity and specificity) and population characteristics necessary to assess the benefits and limitations of such tests. Several examples are used to illustrate calculations, including the characteristics of low dose computed tomography as a lung cancer screen, choice of an optimal PSA cutoff and selection of the population to undergo mammography. The importance of careful consideration of the consequences of both false positives and negatives is highlighted. Receiver operating characteristic curves are explained as is the need to carefully select the population group to be tested.

Genital Chlamydia trachomatis: an update

Chlamydia trachomatis is the most common cause of curable bacterial sexually transmitted infection (STI) worldwide. It manifests primarily as urethritis in males and endocervicitis in females. Untreated chlamydial infection in man can cause epididymitis and proctitis. Though most women with Chlamydia infection are asymptomatic or have minimal symptoms, some develop salpingitis, endometritis, pelvic inflammatory disease (PID), ectopic pregnancy and tubal factor infertility. It is associated with an increased risk for the transmission or acquisition of HIV and is also attributed to be a risk factor for the development of cervical carcinoma. Early diagnosis and treatment of infected individuals is required to prevent the spread of the disease and severe sequelae. Traditionally, tissue culture was considered the gold standard for the diagnosis. However, with the availability of newer diagnostic techniques particularly molecular methods which are not only highly sensitive and specific but are cost-effective also, the diagnosis has became fast and easy. The purpose of this review is to study the various aspects of genital C. trachomatis infection. Also the advances related to the clinical picture, various diagnostic modalities, prevention, treatment, drug resistance and control measures will be dealt with.

Seropositivity of Chlamydia trachomatis among saudi pregnant women in makkah

OBJECTIVE

To determine the seroprevalence rates of immunoglobulin G (IgG) and immunoglobulin M (IgM) to Chlamydia trachomatis in Saudi pregnant women.

SUBJECTS AND METHODS

Using enzyme-linked immunosorbent assay (ELISA), a total of 1600 serum samples were tested for antibodies to Chlamydia trachomatis known to cause a variety of clinical syndromes in women and newborn infants.

RESULTS

Chlamydia trachomatis IgG antibodies were detected in 8.7% and IgM antibodies were found in 1.5% of different age groups.

CONCLUSION

Pregnant Saudi women have low prevalence rate of Chlamydia trachomatis IgG antibodies and lower prevalence for Chlamydia trachomatis IgM.

Chlamydia trachomatis diagnostics

Nucleic acid amplification (NAA) assays for the diagnosis of Chlamydia trachomatis infections started to appear in the peer reviewed literature about 12 years ago and during that period we have seen an incredible effort put into the development and evaluation of commercially developed NAA kits to diagnose and treat infections.

Evaluation of the microparticle enzyme immunoassay Abbott IMx Select Chlamydia and the importance of urethral site sampling to detect Chlamydia trachomatis in women

OBJECTIVE

To evaluate the commercial microparticle enzyme immunoassay (MEIA), Abbott IMx Select Chlamydia, for the detection of Chlamydia trachomatis in women and to compare its performance with endocervical cell culture. Also, to determine whether sampling the urethral site is an important part of chlamydial diagnosis in women.

SETTING

The Auckland, Manukau, and Waitakere Sexual Health Clinics, Auckland, New Zealand and the Department of Clinical Microbiology, Auckland Hospital, Auckland, New Zealand.

PATIENTS

The study population consisted of 622 consecutive women who attended the three sexual health clinics.

METHODS

The IMx Chlamydia assay was performed on an IMx analyser, following a specimen treatment procedure. All reactive samples from the IMx Chlamydia assay were confirmed using the IMx Chlamydia blocking antibody reagent. The Syva direct fluorescent antibody (DFA) test was used to aid in resolving discrepancies. The cell culture technique was performed in shell vials using cycloheximide treated McCoy cells, which were stained using a fluorescein conjugated monoclonal antibody.

RESULTS

When compared against the endocervical cell culture, the IMx Chlamydia had a sensitivity of 82.1% (23/28) and a specificity of 99.3% (590/594). When compared against an expanded gold standard, the IMx Chlamydia and endocervical cell culture had sensitivities of 84.4% (27/32) and 87.5% (28/32), specificities of 100% (590/590) and 100% (590/590), positive predictive values of 100% (27/27) and 100% (28/28), negative predictive values of 99.2% (590/595) and 99.3% (590/594), and accuracies of 99.2% (617/622) and 99.4% (618/622), respectively. The prevalence rate by endocervical cell culture and the expanded gold standard were 4.5% and 5.1%, respectively. Additional urethral cell culture testing revealed a further nine patients positive from this site only, giving a 28% (9/32) increase in the number of patients diagnosed for chlamydia, thus giving an overall prevalence of 6.6% (41/622).

CONCLUSIONS

The IMx Chlamydia assay is an easy and rapid test to perform, it is cost effective, and shows similar performance to endocervical cell culture in the female population studied and is thus an excellent alternative to culture for the diagnosis of C trachomatis. The study also showed the importance of urethral site sampling in these women, as endocervical testing alone will underestimate the prevalence of chlamydial genital infection.

Lowering the cut off value of an automated chlamydia enzyme immunoassay and confirmation by PCR and direct immunofluorescent antibody test

AIMS

To increase the sensitivity of an automated chlamydia enzyme immunoassay by significantly lowering its cut off value, and to maintain specificity by confirmation with polymerase chain reaction (PCR) and direct immunofluorescent antibody test (DFA).

METHODS

Over five months, the cut off value of the enzyme immunoassay used to screen urogenital samples for chlamydia antigen was reduced from 80 to 10. Samples with a test value of 10 or above were further tested with a commercial PCR assay. All samples during the first three months and discrepant samples during the last two months of the study were also tested with the DFA.

RESULTS

3250 urogenital swabs (1246 urethral, 1335 endocervical, 669 pooled urethral/endocervical) from 1246 males and 2004 females were processed. Using the manufacturer's recommended cut off of 80, the enzyme immunoassay identified chlamydia antigen in 134 samples (4.1%). Using the lower cut off value of 10 and either PCR or DFA as the confirmatory test, Chlamydia trachomatis was identified in 178 samples (5.5%). Thus, 45 additional positive samples were identified and the confirmed detection rate was increased by 33.8% (45/133). Excluding equivocal PCR results, the concordance between DFA and PCR was 91.8%. This strategy increased the detection rate by 2.1% in men and 0.9% in women (significant only in men). In female patients, pooled urethral/endocervical swabs as a specimen gave a significantly higher yield than endocervical swabs regardless of whether the lower cut off strategy was used.

CONCLUSIONS

This strategy of significantly lowering the cut off test value with confirmation on the same specimen by either PCR or DFA is feasible and cost effective. The use of pooled urethral/ endocervical specimens in females should be considered routinely as detection rate was significantly improved.

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.

Comparison of an automated enzyme immunoassay with a direct fluorescent antibody test and polymerase chain reaction for the detection of Chlamydia trachomatis in diagnostic specimens from male patients

Endourethral swabs and first-pass urine (FPU) samples from 148 male patients were tested for Chlamydia trachomatis by an automated enzyme immunoassay (EIA) (Vidas; bioMérieux, France), a direct fluorescent antibody (DFA) test (MicroTrak; Syva, USA) and two polymerase chain reaction (PCR) methods. Chlamydia trachomatis was considered present if a specimen was positive by at least two methods. This expanded criterion identified 27 patients (18%) as truly infected. One of the PCR methods was most sensitive for both types of specimen. When the recommended cut-off value of Vidas was reduced by 50%, its sensitivity on endourethral swabs was comparable to that of the DFA test, but the DFA test performed better with FPU. In general, FPU was suitable only for PCR.

Detection of Chlamydia trachomatis infections in women by Amplicor PCR: comparison of diagnostic performance with urine and cervical specimens

We used the Roche Amplicor PCR assay to compare urine and cervical swabs as sample material in the detection of Chlamydia trachomatis causing genital infections. The diagnostic performance of Amplicor PCR was compared with that of cell culture and the Gen-Probe PACE 2 assay with cervical specimens. If discrepant from other results, the specimens negative by PCR were diluted and reanalyzed to reveal PCR inhibitors. Of 666 patients, 39 (5.9%) were confirmed to have chlamydial infection. The respective sensitivity and specificity of Amplicor PCR were as follows: urine specimens, 82.0 and 99.7%; cervical specimens, 82.0 and 99.8%. Those for cell culture with cervical specimens were 84.6 and 100%. For the Gen-Probe PACE 2 assay, the sensitivity and specificity with cervical specimens were 79.5 and 100%, respectively. Without the effect of PCR inhibitors, the sensitivity of PCR with urine would have been 97.4%. Provided that the problems currently caused by inhibitors will be solved, the Amplicor PCR assay with urine specimens offers a tempting alternative for the diagnosis of C. trachomatis infection in women.