Detection of Chlamydia trachomatis endocervical infection in asymptomatic and symptomatic women: Comparison of deoxribonucleic acid probe test with tissue culture

Rapid detection of genetic mutations using the chemiluminescent hybridization protection assay (HPA): overview and comparison with other methods

The detection of genetic mutations is of paramount importance for the study, diagnosis, and treatment of human genetic disease. Methods of detection generally fall into one of two categories: those to scan for unknown mutations and those to detect known mutations. This review focuses on methods for the detection of known mutations. The hybridization protection assay (HPA) is described in detail. The HPA method utilizes short oligonucleotide probes covalently labeled with a highly chemiluminescent acridinium ester (AE). The assay format is completely homogeneous, requiring no physical separation steps, and can rapidly and sensitively detect all single-base mismatches as well as multiple mismatches, insertions, deletions, and genetic translocations. When very low copy number targets are assayed, HPA is coupled with transcription-mediated amplification (TMA), an isothermal method that amplifies DNA or RNA targets. Other methods that are described for the detection of known mutations include hybridization with sequence-specific oligonucleotides, hybridization to oligonucleotide arrays, allele-specific amplification, ligase-mediated detection, primer extension, and restriction fragment analysis. The advantages and limitations of each of these methods are discussed. Methods to scan for unknown mutations are briefly described.

Prevalence of Chlamydia trachomatis infection in a low-risk population in Hungary

BACKGROUND AND OBJECTIVE

Chlamydia trachomatis is the leading cause of nongonococcal urethritis and cervicitis in women. Because of the recent increases in the numbers of new cases and severe consequences, there is an urgent demand for the introduction of sensitive and specific rapid diagnostic methods.

GOAL

A multicenter examination involving seven centers was sponsored by the Hungarian Ministry of Health and Welfare in order to provide a survey of Chlamydia trachomatis in the gravid population. 6,161 women were tested between 1994 to 1995.

STUDY DESIGN

The seven centers were selected with regard to different aspects, from developed and less developed areas in the capital, two large provincial towns, and various other provincial regions reflecting either an industrial or an agricultural background. The nucleic acid hybridization method (PACE 2 Gen-Probe, San Diego, CA) was introduced in this low-risk population for the examination of Chlamydia trachomatis. In one center, a further two methods, antigen detection by ELISA (SYVA, CA) and cultivation on the McCoy cell line (staining with SYVA FITC-labeled antichlamydia monoclonal antibody), were applied.

RESULTS

International surveys and experience indicate that the proportion of the population threatened by Chlamydia trachomatis is above 10%. The overall average incidence of Chlamydia trachomatis cases in this low-risk gravid population was 5.74%. The data from the different centers ranged between 1.6% and 9.7%. The chlamydia-infected Hungarian gravid population is below the critical 10%, but there is one Hungarian county where the value is close to 10%.

CONCLUSIONS

In this provincial, industrial area, the number of unmarried and divorced gravida in a low economic situation is disproportionately high. For this disadvantaged population, permanent Chlamydia trachomatis screening was suggested. In the other centers, screening of pregnant women for Chlamydia trachomatis and the treatment of positive cases and their partners were suggested for pathological gravida with preterm labor and preterm rupture of the membranes.

Detection of Chlamydia trachomatis in urethral and urine samples from symptomatic and asymptomatic male patients by the polymerase chain reaction

To evaluate the commercially available polymerase chain reaction (PCR) assay Amplicor (Roche Molecular Systems, USA) for diagnosis of Chlamydia trachomatis infection, urethral and urine swabs from a total of 344 male patients were tested and the results compared with those obtained by the nonisotopic hybridization assay Pace 2 (Gen Probe, USA) for urethral samples and by the enzyme immunoassay EIA MicroTrak (Syva, USA) for urine. Discrepant results were analyzed by a repeated test run using a major outer membrane protein-derived primer PCR, by the probe competition assay, and by the direct immunofluorescence test (DIF). Thirty-nine men (11.3%) were chlamydia positive, based on the results of all tests from both sampling sites. The rate of detection of chlamydia in urethral specimens by Amplicor and the Pace 2 was 79.5% and 61.5%, respectively, while the rate of detection in urine sediment was 75% for both Amplicor and EIA. In the first run of the PCR, a high number of false-negative results for unfrozen samples was observed, decreasing the sensitivity of Amplicor in urine to 47.3%. The results of the study indicate that Amplicor detects more infected individuals compared with other tests and is suitable as an alternative diagnostic test for chlamydia infections, using not only urethral specimens but also urine specimens. However, the finding of false-negative results when using Amplicor on unfrozen samples must be further investigated.

Cervico-vaginal Chlamydia trachomatis infection in pregnant adolescent and adult women. A morphologic and immunofluorescent study

We studied the incidence of cervical Chlamydia trachomatis (CT) in 65 adolescents aged between 14 and 19 years and 65 adults aged 20 years or more. All subject were more than three months advanced in a normal pregnancy. Two samples for cytology were obtained from each patient, one ecto- and endocervical, with Ayre's spatula and cytobrush, and one only endocervical with cytobrush. The first one was examined after Papanicolaou staining and the second one was examined with the easily performed immunofluorescence reaction to CT (IF)--Microtrak, SYVA. Twenty seven adolescent patients (41.5%) and fourteen adults (21.5%) had a positive IF test for CT; the rate in adolescents was significantly higher (P < 0.01) than in adults. The Papanicolaou (Pap) stained slides, examined blind for evidence of CT infection showed a sensitivity of 70.7%, a specificity of 95.5% and positive and negative predictive values of 87.8% and 87.6% respectively. Seven adolescents showed cytological signs of Papillomavirus (HPV) infection, and six of them were also CT positive; five had signs of HPV infection and 4 of them were CT positive.

Comparison of the Syva MicroTrak enzyme immunoassay and Gen-Probe PACE 2 with cell culture for diagnosis of cervical Chlamydia trachomatis infection in a high-prevalence female population

Culture is currently considered the "gold standard" for detecting Chlamydia trachomatis infections. We evaluated the Syva MicroTrak enzyme immunoassay (EIA) and Gen-Probe PACE 2 tests, which detect chlamydial antigens and rRNA, respectively. These assays were compared with each other and with culture for the detection of C. trachomatis in cervical specimens obtained from 217 women attending a clinic for sexually transmitted diseases. The prevalence of infection was 22.1% by culture. The sensitivity, specificity, and positive and negative predictive values were 79.2, 98.2, 92.6, and 94.3%, respectively, for EIA. For PACE 2, the respective values were 77.1, 97.6, 90.1, and 93.7%. After corrections for two false-negative cultures, the sensitivities and specificities were 80 and 99.4%, respectively, for the EIA and 78 and 98.8%, respectively, for the probe assay. Quantitative evaluation of the results showed that false-negative results with either assay were associated with cultures that had low inclusion counts or were negative without subpassage. Analysis of nonculture results revealed that 2.3% of the EIA results and 4.6% of the probe assay results were within +/- 30% of the respective assay cutoff values. These included four false-negative (one EIA and three probe) and two false-positive (one EIA and one probe) results. The Syva MicroTrak EIA and the Gen-Probe PACE 2 assay are comparable to but significantly less sensitive than culture. Use of a grey zone may help identify the need for repeat or confirmatory testing.