Evaluation of a novel solid-phase immunoassay, Clearview Chlamydia, for the rapid detection of Chlamydia trachomatis

Detection of Chlamydia trachomatis by immunological and genetic methods in female sex workers and the local female population of reproductive age in Mymensingh, Bangladesh

To investigate the accurate prevalence of genital Chlamydia trachomatis infection in Mymensingh, a local area in central-northern Bangladesh, 40 female sex workers (FSW) and 110 sexually active women (SAW, non-FSW) of reproductive age from a local community with clinical symptoms were examined by an immunochromatography test (ICT) and plasmid-based polymerase chain reaction (PCR) during a 1-year period from July 2011 to June 2012 using the endocervical swab as a specimen. By ICT and/or PCR, the C. trachomatis detection rate was 58% and 27% in FSW and SAW, respectively, showing a significant difference (P < 0.01). Two C. trachomatis strains from FSW were determined to be serovar D by ompA-based PCR and sequencing analysis. The highest prevalence was found among women aged 15 to 35 years. A lower socioeconomic status was considered to be an important risk factor for C. trachomatis infection in FSW but not in SAW. This is the first study to determine the prevalence of C. trachomatis infections in FSW and SAW in the same local area in Bangladesh.

Evaluation of direct immunofluorescence assay and cytological examination in comparison to polymerase chain reaction of conjunctival swabs in patients with adult inclusion conjunctivitis

PURPOSE

To evaluate PCR, direct immunofluorescence assay (DIA) and cytological test of conjunctival swabs for the diagnosis of adult follicular conjunctivitis (AFC).

METHODS

Eighty-three adult patients with chronic conjunctivitis and sixteen healthy individuals were included. Conjunctival scrapings underwent PCR, DIA and cytological analysis. Exams were repeated two weeks after treatment application. Sensitivity, specificity and agreement rate with PCR of DIA and Cytology were evaluated and correlated with clinical symptoms/signs.

RESULTS

Cytology test was more sensitive than DIA and presented an acceptable agreement with PCR (K=0.44) in treatment-naïve patients, concerning especially the combination of both conventional exams (K = 0.77). Inferior diagnostic performance of was detected post-treatment, considering the combination as well (K=0.40). Negative post-treatment PCR correlated well with significant relief of symptoms/signs.

CONCLUSION

Combination of Cytology and DIA seems to be a useful diagnostic option for treatment naïve AFC patients. However, PCR remains the most reliable test for post-treatment evaluation.

Clinic-based evaluation of Clearview Chlamydia MF for detection of Chlamydia trachomatis in vaginal and cervical specimens from women at high risk in China

OBJECTIVES

To determine the performance of a rapid Chlamydia trachomatis (CT) test (Clearview Chlamydia MF) compared to the current "gold standard" (Roche Amplicor CT assay) test, and to assess acceptability of the tests to patients.

METHODS

A total of 1497 women at sexually transmitted diseases (STD) clinics or re-education centres in six urban cities (Shanghai, Nanjing, Shenzhen, Guangzhou, Chengdu and Fuzhou) in China participated in the study. Three vaginal and three cervical swabs were collected from each participant. Rapid CT tests were performed locally on the first vaginal and cervical swabs and the results were read independently by two staff members. The second and third swabs were randomised for performing the Roche CT assay at the National STD Reference Laboratory. Acceptability of the rapid tests to patients was determined by asking patients in clinics about their willingness to wait for the results.

RESULTS

The prevalence of CT was 13.2% (197/1497), as determined by the Roche assay with cervical specimens. CT was detected in 78 vaginal and 127 cervical specimens by the rapid test and the positive rates determined with cervical specimens were significantly higher than those with vaginal specimens (p<0.001). There was good agreement between the results read by two independent staff for either vaginal or cervical specimens (both kappa = 0.98, p<0.001). Sensitivities for vaginal and cervical specimens were 32.8% and 49.7%, respectively, and specificities were 99.2% and 97.9%, respectively. The positive predictive value was 85.7% for vaginal and 78.4% for cervical specimens. The vast majority of the patients (99.1%) were willing to wait up to two hours for the results.

CONCLUSION

Clearview Chlamydia MF, while yielding a rapid result and requiring minimal laboratory facilities, had unacceptably low sensitivity compared to a nucleic acid amplification test. Rapid tests yielding results within one hour are generally accepted by the clients.

Development of a membrane strip immunosensor utilizing ruthenium as an electro-chemiluminescent signal generator

A photometric immunosensor that can be used for on-site diagnosis has been constructed. The sensor system was assembled by partially superimposing a nitrocellulose membrane strip (the lower) containing an immobilized antigen on the surface with a glass fiber membrane strip (the upper) including two electrodes on the opposite surfaces. To amplify the signal, we introduced a liposome, containing ruthenium molecules trapped in the core, chemically coupled to an antibody specific to the analyte (e.g. Legionella antigen). In the presence of the analyte, immune complexes were formed by antigen-antibody reactions upon addition of the immuno-liposome into a sample. This mixture was then absorbed by the capillary action from the bottom of the membrane strip. The liposome particles in the complexes were carried by a medium through the antigen pad without interaction, while free immuno-liposome was trapped by immune reactions on the pad surfaces. The aqueous medium influx into the glass pad dissolved a detergent pre-located within the compartment and the liposome rupture thereby released ruthenium molecules into the solution. The molecules were oxidized on the electrode surfaces and produced an electro-chemiluminescence (ECL) in proportion to the analyte concentration. The signal generation based on ECL resulted in an exponential dose-response pattern and the analyte detection limit of 2 ng/ml was approximately 10-fold more sensitive than that obtained from a conventional system.

Follicular conjunctivitis caused by Chlamydia trachomatis in an infant Saharan population: molecular and clinical diagnosis

AIMS

To ascertain the prevalence of acute trachoma as a supposed endemic disease among infants in the Saharan refugee camps of Tindouf (Algeria) and to evaluate the efficacy of treatment with a single dose of azithromycin.

METHODS

527 children aged between 3 and 17 were evaluated in the camp schools in October 2001. All the children were clinically and microbiologically examined, including slit lamp checks of anterior segment and two conjunctival swabs, one for the detection of membrane lipopolysaccharide by quick immunoassay test Clearview Chlamydia MF and the other for the detection of specific DNA by chlamydia plasmid specific polymerase chain reaction (PCR) assay. After examination, a single dose of azithromycin was administered to each child. One month later samples from positive children and 12 random negative children by the first PCR were taken to perform a new PCR assay.

RESULTS

Chlamydia trachomatis was suspected in 2.47% of the children, papillary hypertrophy being the most frequently seen clinical sign. Scarring changes secondary to trachoma were detected in 11.7% of the children. Only four cases (0.8%) were positive to the immunoassay test and 12 cases (2.27%) were positive by PCR. After treatment a second PCR was performed on positive children and they were negative of chlamydia DNA amplification. However, one child who was negative and received the treatment was positive in the second PCR assay.

CONCLUSION

Acute trachoma prevalence is much lower than expected among infants in this Saharan population. The possible reasons could be the recent improvements in hygiene and health care. Cicatricial trachoma is more frequent. The Clearview immunoassay test has very low sensitivity in the detection of this disease. A single dose of azithromycin is sufficient to treat chlamydial conjunctivitis. However, a programme of improvement in hygiene and health care is necessary to prevent re-infection.

Impact of reference standard sensitivity on accuracy of rapid antigen detection assays and a leukocyte esterase dipstick for diagnosis of Chlamydia trachomatis infection in first-void urine specimens from men

A total of 128 previously frozen first-void urine (FVU) specimens from selected asymptomatic men were centrifuged and tested by three Chlamydia trachomatis rapid antigen detection tests and with a leukocyte esterase (LE) dipstick. When the results were compared to those of a reference standard of positivity determined by the Chlamydiazyme enzyme immunoassay as confirmed by a blocking assay, the sensitivities of the Testpack Chlamydia (Abbott), Clearview Chlamydia (Unipath), and Surecell Chlamydia (Kodak) tests and the LE dipstick test were 76.4, 76.4, 67.3, and 88.6%, respectively. Use of the ligase chain reaction (LCR), whose results were confirmed by direct fluorescent-antibody staining of elementary bodies, as the reference standard reduced the sensitivities to 70.9, 67.7, 62.9, and 87.5%, respectively. The specificities by use of LCR as the reference standard were 95.5, 95.5, 100, and 92.4%, respectively. These rapid chlamydial antigen tests performed reasonably well with FVU specimens, but the simple LE dipstick test, which had the highest sensitivity, would have enabled treatment of the greatest number of infected male patients.

Comparison of the PACE 2 assay, two amplification assays, and Clearview EIA for detection of Chlamydia trachomatis in female endocervical and urine specimens

Screening for sexually transmitted diseases (STDs) in a greater proportion of sexually active patients has become an accepted protocol by most health care providers. The purpose of this study was to compare the current test methods for detection of Chlamydia trachomatis used at the University of South Alabama, the PACE 2 assay (Gen-Probe) and the Clearview EIA (Wampole Laboratories), with two amplification technologies, the AMP CT (Gen-Probe) and LCx (Abbott) assays. In addition, a number of demographic parameters were ascertained by asking questions at the time of examination as well as for health care provider concerns and preferences. One urine and four endocervical swab specimens were collected in random order from 787 female patients attending one of four obstetrics-gynecology clinics. Eighty-seven percent of patients had no STD-related symptoms. Patients were considered positive for C. trachomatis if three or more assays (swab and/or urine) were positive. Abbott and Gen-Probe confirmed discrepant results by alternate amplified assays. A total of 66 true-positive specimens were detected by use of the combination of endocervical swabs and urine specimens. After discrepant analysis, sensitivities for endocervical swab specimens for the EIA and the PACE 2, LCx, and AMP CT assays were 50, 81, 97, and 100%, respectively. Sensitivities for the LCx and AMP CT assays with urine specimens were 98 and 81%, respectively. The prevalence of C. trachomatis was 8.4%, as determined by amplification technology. Overall, the amplification technologies were the most sensitive methods with either swab (AMP CT assay) or urine (LCx assay) specimens. The PACE 2 assay offered the advantage of a simpler and less expensive assay with acceptable sensitivity. The clearview CT EIA, while yielding a rapid in-office result, had unacceptably low sensitivity. The wide variation in performance with amplification assays with urine specimens as reported in both this study and the literature obviates the need to clarify optimal parameters for this specimen type.

Preventing pelvic infection after abortion

Pelvic infection is the commonest complication of legal abortion. The presence of lower genital tract infections increases the risk of complications, and women requesting abortion are at significant risk of harbouring sexually transmitted diseases (STD). Prophylactic antibiotic treatment can decrease the rate of post-abortal sepsis, but the optimum regime is unclear. In particular, patients with Chlamydia trachomatis infection, and bacterial vaginosis would appear to be at increased risk, and detection and treatment of these conditions can lower this risk. The opportunity to screen and treat for STD presents itself in this setting, allowing patients and their sexual contacts to benefit, with a decrease in the infected pool in the community.

Use of the polymerase chain reaction for the detection of Chlamydia trachomatis in clinical specimens and its comparison to commercially available tests

A polymerase chain reaction (PCR) was developed to detect Chlamydia trachomatis in genital tract specimens. Two sets of primers for the PCR were used; one set amplifies a region of the plasmid present in all C trachomatis strains and the other amplifies a conserved region of the genome coding for the major outer membrane protein. The sensitivity of these PCRs were compared with each other, and with the sensitivities of antigen ELISA, Clearview and culture. Southern blotting and probing was used to increase sensitivity of detection.

Evaluation of five immunoassays for detection of Chlamydia psittaci in cloacal and conjunctival specimens from turkeys

Five commercially available immunoassays were evaluated for the detection of Chlamydia psittaci in cloacal and conjunctival swabs from industrially raised turkeys: IMAGEN (DAKO Diagnostics, Ely, Cambridgeshire, United Kingdom), Chlamydia CEL-VET IF (Cellabs, Brookvale, Australia), IDEIA (DAKO Diagnostics), CELISA (Cellabs), and CLEARVIEW (Unipath, Bedford, United Kingdom). Results were compared with isolation in Buffalo Green Monkey cells as a reference method. For the conjunctival samples, the sensitivities of the IMAGEN test, the Chlamydia CEL-VET IF test, the IDEIA, the CELISA, and the CLEARVIEW test were found to be 100, 66, 0, 0, and 0%, respectively, as compared to the reference test. Also for the conjunctival samples, the specificities of the IMAGEN test, the Chlamydia CEL-VET IF test, and the IDEIA were found to be 100, 11, and 92.8%, respectively. For the cloacal specimens, the sensitivities of the IMAGEN test, the Chlamydia CEL-VET IF test, the IDEIA, the CELISA, and the CLEARVIEW test were found to be 100, 93.3, 26.6, 0, and 53.3%, respectively. Also for the cloacal specimens, the specificities of the IMAGEN test, the Chlamydia CEL-VET IF test, the IDEIA, and the CLEARVIEW test were found to be 92, 12, 100, and 88%, respectively. The IMAGEN test was the most sensitive and specific direct chlamydia antigen detection test for cloacal and conjunctival samples from turkeys.

Immunoassay: recent developments and future directions

All analytical techniques employed in the biological sciences rely on recognition of the shape and structure of molecules of the substance of interest (the analyte). Such molecular recognition and sensing usually relies on the use other molecules possessing a complementary structure, implying a specific lock and key relationship between the two. Antibodies comprise a class of recognition molecules evolved by nature for the purpose of bodily defence, and are clearly of particular utility in this context. However techniques of increasing sophistication (including the techniques of molecular biology) are currently being developed which enable the artificial construction of antibody-like molecules possessing improved molecular recognition properties which can be harnessed for microanalytical purposes. Oligonucleotide probes likewise exhibit the property of binding to complementary nucleotide sequences, and the techniques of, for example, in situ hybridisation therefore share many features with immunoassay techniques. Microanalytical techniques relying on binding reactions between substances possessing complementary lock and key molecular structures are unlikely to be superseded within the foreseeable future, only the labels used to monitor such reactions, and the means of production of "recognition molecules", being subject to further development. Such techniques already enter into all areas of life, including medicine, agriculture, etc, and are likely to increase further in importance with increasing concern regarding chemically complex contaminants in food, the environment, etc. Developments in this field are clearly directed to slightly differing objectives as indicated in this presentation. These include methodological simplification (making the techniques cheaper and more widely available), improvements in sensitivity (to enable the detection and measurement of substances beyond the reach of current methods) and the construction of transducer-based sensor methods (permitting, inter alia, the monitoring of changing analyte concentrations). However the combination of the "ultrasensitivity" of current single analyte assay methods with the ability simultaneously to determine multiple analytes in the same sample represents, in my view, the next major methodological challenge in this field, and--if successfully addressed--will constitute a quantum advance on present analytical methods. Indeed the development of miniaturised multianalyte binding assay techniques may ultimately comes to be seen as analagous to, for example, the introduction of the word processor, and other similar major technological advances of the past decade.

Evaluation of Clearview and Magic Lite tests, polymerase chain reaction, and cell culture for detection of Chlamydia trachomatis in urogenital specimens

The Clearview Chlamydia test (CV; Unipath Ltd., Bedford, United Kingdom), the Magic Lite Chlamydia test (ML; CIBA Corning, Medfield, Mass.), a polymerase chain reaction (PCR), and cell culture (CC) were evaluated for detection of Chlamydia trachomatis in urogenital specimens. Specimens were collected from 283 men and 724 women visiting the outpatient clinic for Sexually Transmitted Diseases at the University Hospital Rotterdam, Rotterdam, The Netherlands. ML, PCR, and CC were all performed on the same sample to prevent swab-to-swab variability. CV was performed on a separate sample. Analysis of discordant results was performed by application of the following confirmatory assays: first, PCR on the CC, second, ML was repeated, and third, PCR was repeated by using a different DNA extraction protocol. If more than one test was positive, the sample was considered true positive. If only one test was positive, which was confirmed by the confirmatory assay, the sample was also considered true positive. By using these interpretations, the following results were obtained. The sensitivity and specificity of CV for samples from men were 60.4 and 86.3%, respectively. For samples from women, these values were 62.3 and 99.7%, respectively. The low specificity for samples from men was caused by unidentified substances in the swab that was used. The use of CV on samples from men is not recommended by the manufacturer. For samples from women, the specificity of CV was high, but the low sensitivity of CV limits its use for diagnostic purposes. The sensitivities of ML were low for samples from both men and women (68.8% and 50.9% respectively), while specificities were excellent for samples from both groups (100 and 99.9%, respectively). The low sensitivity of ML limits its diagnostic value. The PCR technique was highly specific for samples from both men (99.6%) and women (99.9%). The sensitivity of PCR, however, was unexpectedly low for samples from both groups (men, 87.5%; women, 79.2%), most likely because of the sample treatment method used. The sensitivity and specificity values of CC for samples from men were 95.8 and 100%, respectively. For samples from women, these values were 100 and 99.9%, respectively. In the present study, CC was the most reliable technique for the detection of C. trachomatis.

Home tests to monitor fertility

Industry has been intimately involved in the development of products used in the monitoring of fertility at home. The perspective of industry and the development of such tests including their rationale are presented. The methods taken by industry to utilize current technology in the development of reliable, rapid, one-step tests for urinary human chorionic gonadotropin and luteinizing hormone and the subsequent expansion into other areas are covered.

Comparison of the Clearview Chlamydia test, Chlamydiazyme, and cell culture for detection of Chlamydia trachomatis in women with a low prevalence of infection

Two antigen detection systems, Clearview Chlamydia (Unipath Ltd., Bedford, United Kingdom) and Chlamydiazyme (Abbott Laboratories, North Chicago, Ill.), were compared with culture for the diagnosis of chlamydia infection in women attending gynecological clinics. Chlamydia trachomatis was isolated from 43 (4.5%) of the 965 women tested. In comparison with tissue culture, the Clearview Chlamydia and Chlamydiazyme tests had sensitivities of 79.0 and 74.4%, respectively, and both had a specificity of 99.6%. The results show that the Clearview Chlamydia test is comparable to Chlamydiazyme for the detection of C. trachomatis from endocervical specimens in a population with a low prevalence of infection.

Evaluation of the rapid CLEARVIEW Chlamydia test for direct detection of chlamydiae from cervical specimens

The CLEARVIEW Chlamydia test (Unipath, Mountain View, Calif.), a 30-min immunoassay, was compared to a standard tissue culture technique for the direct detection of chlamydiae from 677 cervical specimens obtained from 667 patients. For data analysis, 15 specimens were eliminated because of toxicity in the culture and 14 were eliminated because of failure of the extracted specimen to migrate in the CLEARVIEW test, one of the latter group being culture positive. Of the remaining 648 specimens, 40 were culture positive, of which 38 were detected by the CLEARVIEW test, and 12 specimens were positive only by the CLEARVIEW test. Therefore, the CLEARVIEW in comparison with culture was easier to perform, more rapid, and in this low prevalence (6.2%) population had a 95.0% sensitivity, 98.0% specificity, and 76.0% positive and 99.7% negative predictive values.