Cytobrush in collection of cervical specimens for detection of Chlamydia trachomatis.

Methods of collecting endocervical samples for the detection of Chlamydia trachomatis were evaluated. We compared Calgiswab and cytobrush for isolation in cell culture and Dacron swab and cytobrush for direct fluorescent-antibody (DFA) testing for 632 females attending a sexually transmitted disease clinic. An additional specimen for enzyme immunoassay (EIA) was also collected. True-positives were identified as tissue culture positive and/or both DFA and EIA positive. Use of the cytobrush significantly improved the sensitivity of both the culture (69% with swab and 100% with cytobrush) and DFA testing (68% with swab and 85% with cytobrush). The EIA sensitivity was 85%. The specificity of each test was greater than or equal to 98%. The cytobrush appears to be the superior method for the collection of cervical samples from nonpregnant women.     

Evaluation of a nonisotopic probe for detection of Chlamydia trachomatis in endocervical specimens.

A nonisotopic probe (Gen-Probe PACE; Gen-Probe, Inc., San Diego, Calif.) for detection of Chlamydia trachomatis in endocervical specimens was evaluated in 344 women attending a dysplasia clinic or an obstetrics clinic and 158 women who visited an emergency room. For each patient, the probe, a tissue cell culture, and a direct immunofluorescent-antibody test (DFA; MicroTrak; Syva Co., Palo Alto, Calif.) were used. C. trachomatis was detected in 54 specimens by at least one method. Forty-four, 44, and 37 specimens were positive by culture, probe, and DFA, respectively, and 31 were positive by all three methods. Considering culture-positive plus both probe- and DFA-positive results as the "gold standard," we determined the overall sensitivity, specificity, and positive and negative predictive values of the probe to be 80, 98, 82, and 98%, respectively. These values were 94, 98, 84, and 99%, respectively, in emergency room patients and 71, 98, 80, and 97%, respectively, in clinic patients. The sensitivities, specificities, and negative predictive values of the DFA and probe were comparable. The positive predictive values of the DFA in all patients and in emergency room and clinic patients were 97, 100, and 95%, respectively. Given the number of probe-positive results that were not confirmed by culture, we do not recommend using the Gen-Probe PACE to screen for C. trachomatis in women with a low to moderate risk for infection.     

Rapid antigen detection assay for identification of Chlamydia trachomatis infection.

A rapid antigen detection test was compared with direct fluorescent-antibody staining and with tissue culture isolation for the detection of Chlamydia trachomatis infections in 507 women. The sensitivities observed were 75, 76, and 84%, respectively, with specificities of > 99%.     

Comparison of the Clearview Chlamydia, the PACE 2 assay, and culture for detection of Chlamydia trachomatis from cervical specimens in a low-prevalence population.

The Clearview Chlamydia assay (Wampole Laboratories, Cranbury, N.J.), the PACE 2 DNA probe assay (GenProbe, San Diego, Calif.), and culture were compared for their abilities to detect Chlamydia trachomatis from cervical specimens in a population with a low prevalence (3.9%) of chlamydial infections. A consensus reference method was used. The consensus reference method defined a positive specimen as one with a positive culture result or positive by both of the two nonculture methods. Of the 940 specimens tested, 37 were positive; 36 were positive by culture, 28 were positive by the PACE 2 assay, and 27 were positive by the Clearview assay, giving sensitivities of 97.3, 75.5, and 72.9%, respectively, and specificities of 100, 97.1, and 98.9%, respectively. There was a direct correlation between the number of inclusion-forming units detected by culture and the ability of the two nonculture methods to detect the positive specimens.     

Evaluation of Syva enzyme immunoassay for detection of Chlamydia trachomatis in genital specimens.

Detection of Chlamydia trachomatis infection was evaluated by culture and a new Syva enzyme immunoassay (EIA) in 1,012 patients at two Baltimore, Md., sexually transmitted disease clinics. The overall chlamydia prevalence determined by culture was 12%. For 506 fresh cervical and urethral specimens, the sensitivity of Syva EIA was 90% and its specificity was 94% compared with culture. Discordant Syva EIA results were further evaluated by staining the sediment in centrifuged culture transport media and Syva EIA transport tubes with a fluorescent monoclonal antibody to C. trachomatis to detect elementary bodies. Reanalysis of the data after use of this technique to resolve discordant results increased sensitivity and specificity to 92 and 96%, respectively. A subsample of 307 fresh cervical specimens was also tested in a three-way comparison using Abbott Chlamydiazyme, Syva EIA, and culture. In this sample, compared with culture, the sensitivity and specificity of Syva EIA were 87 and 95%, respectively, and for Chlamydiazyme they were 77 and 98%, respectively. Syva EIA is a 4-h, easy-to-perform enzyme-linked immunosorbent assay which has a high sensitivity with fresh genital specimens and offers an excellent alternative to culture.     

Clinical evaluation of a new polymerase chain reaction assay for detection of Chlamydia trachomatis in endocervical specimens.

A clinical evaluation of the Amplicor polymerase chain reaction (PCR) assay for the detection of Chlamydia trachomatis in endocervical swabs (Roche Molecular Systems, Branchburg, N.J.) is described. This new clinical system used one-step sample preparation, amplification with biotinylated cryptic plasmid primer pairs (CP24-CP27), uracil-N-glycosylase (AmpErase), and a microtiter format for amplicon capture and detection. Culture with McCoy cells in duplicate 1-dram (3.697-ml) vials with fluorescent immunostaining was the reference system. Endocervical swab samples from 945 women provided 74 culture-positive specimens, of which PCR detected 71. The initial PCR result was positive for 12 additional specimens. Arbitration of the PCR-positive, culture-negative samples by PCR with major outer membrane protein primers, duplicate culture, elementary body direct fluorescent-antibody staining, and DNA extraction PCR showed that all 12 samples were positive for chlamydia, raising the number of truly positive samples from 74 to 86. After arbitration the true sensitivities of PCR and culture were 96.5 and 86%, respectively (P = 0.02). Specificities for both were 100%. For PCR, the positive and negative predictive values were 100 and 99.7%, respectively. Total test efficiency was 99.7%. A high-test-volume (121 samples) timing study with all items included in the College of American Pathologists work load method indicated that this PCR format took approximately 3 min per sample. Because of the high sensitivity, specificity, and improved ease of handling, we found PCR to be a good alternative to culture for detection of C. trachomatis.     

Detection of PCR inhibitors in cervical specimens by using the AMPLICOR Chlamydia trachomatis assay.

To determine that susceptibility of AMPLICOR Chlamydia trachomatis PCR to inhibitory factors possibly present in cervical specimens, we obtained cervical specimens from 200 gynecology patients attending our outpatient clinic. The prevalence of C. trachomatis infection was 4.1%, as determined by cell culture. All AMPLICOR specimens were tested in one procedure as described by the manufacturer, and after the specimen was spiked with C. trachomatis, several other pretreatment protocols were used. Complete inhibition of the PCR was observed in 38 (19%) cervical specimens. Heat treatment at 95 degrees C, freeze-thawing, or 10-fold dilution of the samples reduced the initial inhibition to 9, 16, or 9%, respectively. A combination of heat treatment and 10-fold dilution reduced the inhibition to 4% of the samples. A second specimen type (swabs inoculated in 0.2 M sucrose phosphate buffer [2SP]) was also evaluated. A 10-fold dilution of the spiked 2SP specimen resulted in an inhibition rate of 6%, which was comparable to that obtained by centrifugation of the 2SP specimen prior to processing. Furthermore, it was shown that the inhibition was not correlated with blood contamination. Processing the specimens on the day of collection or the day after resulted in a higher inhibition rate than did delayed processing (27.6 versus 15.5%, respectively). An inverse correlation was found between the concentration of C. trachomatis added to the sample and the rate of inhibition observed. The inhibition was partly correlated with the pH of the cervical mucosa. Decreased inhibition was found at pH values of > or = 7.5. The effects of blood, pH, and delay in processing were all evaluated by using the AMPLICOR specimen. We conclude that the susceptibility of AMPLICOR C. trachomatis PCR to inhibiting factors in cervical specimens can be significantly reduced if the pretreatment procedure includes heat treatment or the use of 2SP transport medium. Also, a 10-fold dilution of the clinical specimen followed by heat treatment will largely prevent the inhibition of this PCR.     

Development of a novel quantitative real-time assay using duplex scorpion primer for detection of Chlamydia trachomatis

A novel quantitative real-time PCR method using the duplex scorpion primer for detection of Chlamydia trachomatis DNA was developed and validated. The assay employs a duplex primer; its most important feature is the intramolecular probe-target interaction. The assay had many prominent characteristics. (i) The duplex probe is simpler to synthesize and significantly easier to purify than TaqMan probe because that the fluorescent dye pair and the quencher pair are in different oligonucleotides. (ii) The method has high sensitivity, specificity, intra- and interassay reproducibilities. (iii) The assay has a quantitative dynamic range of 25 to10(9) genome copies per reaction mixture. (iv) The scorpion system can identify 98.6% samples in the validation panel without retest. There were 81 positive samples and 67 negative samples, which were confirmed by two FDA-approved NAATs (the Roche Amplicor PCR assay, Abbott LCR kit) and our new method. Any two positive results out of the possible three-comparator results would define the infected-patient gold standard. Of the positive samples, 79 (97.5%) were found positive (ranging from 31 to 227,648 copies/microl, M=4219 copies/microl), whereas no negative samples were found positive by the assay. A quantitative, fast, and easy-to-handle diagnostic approach such as the MOMP-based real-time PCR described here might improve the detection of C. trachomatis infection.     

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

Clearview Chlamydia (Unipath Limited, Bedford, United Kingdom) is a rapid immunoassay for the direct detection of Chlamydia trachomatis antigen. This assay was evaluated against the tissue culture method by using 376 paired endocervical specimens. The Clearview assay had a sensitivity of 93.5% and a specificity of 99% when it was compared with the tissue culture method. This assay does not require specialized equipment or trained personnel and yields results within 30 min from the time that a specimen is collected.     

Evaluation of chlamydiazyme enzyme immunoassay for detection of Chlamydia trachomatis in urine specimens from men.

Paired first-voided urine and urethral swab specimens were collected from 540 men attending sexually transmitted disease clinics in three geographic locations. Urine specimens were tested for the presence of Chlamydia trachomatis by commercial enzyme immunoassay (Chlamydiazyme), and the results were compared with those of urethral swab cultures. Overall prevalence of urethral C. trachomatis by culture was 14%, and the Chlamydiazyme assay had an overall sensitivity of 83%, a specificity of 96%, a positive predictive value of 76%, and a negative predictive value of 97%. Sensitivity was greater (94%) in those culture-positive samples with a high antigen load (> or = 20 inclusion-forming units per coverslip) than those with a lower antigen load (68%). Assay of urine specimens from men attending sexually transmitted disease clinics by Chlamydiazyme appears to be a reliable, noninvasive method of detection of C. trachomatis infection, and further evaluation of its performance in asymptomatic and low-prevalence populations is indicated.     

Evaluation of a direct fluorescent antibody test for detection of Chlamydia trachomatis in endocervical specimens. Brief report

A total of 160 endocervical specimens collected from 72 symptomatic and 82 asymptomatic women attending a gynecology outpatient clinic were investigated for genital Chlamydia trachomatis infection by the use of tissue culture and DFA test. The infection rate was 42% for symptomatic and 23% for asymptomatic patient groups. The sensitivity rates of the DFA test in the symptomatic and asymptomatic groups were 84% and 75%, while the specificity rates were 89% and 95%, respectively. The DFA test had an overall sensitivity of 80% and specificity of 93%. There was 90% agreement between the two techniques. Therefore, DFA is recommended as an alternative to tissue culture where laboratory facilities are limited and genital chlamydial infections are highly prevalent.     

Evaluation of three immunoassays for detection of Chlamydia trachomatis in urine specimens from asymptomatic males.

The performances of three commercially available immunoassays (Chlamydiazyme/Antibody Blocking Assay [Abbott Diagnostics, Abbott Park, Ill.], IDEIA [Analytab Products, Plainview, N.Y.], and Microtrak EIA [Syva Co. Palo Alto, Calif.]) were evaluated for the detection of Chlamydia trachomatis in urine specimens from asymptomatic males. Assay results were compared with direct specimen immunofluorescence (DFA) analysis of urine sediment (Syva Microtrak; Syva Co.), which was chosen as the study confirmation assay. An overall Chlamydia prevalence of 7% (24 of 340) was found in our study population, with peak incidences occurring in the adolescent (8 of 93 specimens) and young adult (11 of 146 specimens) age groups. Sensitivity and specificity data among the Chlamydiazyme, IDEIA, and Microtrak enzyme immunoassays (EIAs) were determined to be 79.1 and 99%, 91.7 and 98%, and 95.8 and 99%, respectively. The Microtrak EIA and IDEIA products demonstrated sensitivities and specificities equal to or greater than those claimed for urine specimens. The diagnostic accuracies of these assays on asymptomatic subjects, along with the ease of this collection method, suggest a role for these products as screening tools. The sensitivity of the Chlamydiazyme assay was lower than that claimed previously in symptomatic patients, with 5 of 24 positive specimens demonstrating false-negative results. In those cases, centrifugation of the original immunoassay aliquot material and then DFA examination confirmed specimen positivity. Urine immunoassay screening in combination with DFA confirmation (which was chosen because it has antibody epitopic specificity different from that of the primary assay) provides a high degree of diagnostic precision. The use of noninvasive collection methods could result in greater testing compliance among asymptomatic males and, subsequently, could reduce the incidences of both symptomatic and silent chlamydial infections.     

TestPack Chlamydia, a new rapid assay for the direct detection of Chlamydia trachomatis.

TestPack Chlamydia (Abbott Laboratories) is a rapid enzyme immunoassay for the direct antigen detection of Chlamydia trachomatis in endocervical specimens. The assay is self-contained, requires no specialized equipment, and yields results in less than 30 min. The clinical performance of TestPack Chlamydia versus chlamydial cell culture was evaluated with a total of 1,694 paired endocervical specimens. Discordant samples were further investigated by immunofluorescent staining and by Chlamydiazyme immunoassay, with confirmatory procedures. The sensitivity of TestPack Chlamydia with less-than-48-h-old specimens was 76.5%, while culture sensitivity was 86.7%. TestPack Chlamydia specificity was determined to be 99.5%. These results indicate that TestPack Chlamydia is an accurate test for chlamydial infection, with a positive predictive value of 96.2%. This assay is suitable for low-volume chlamydial testing in physician offices, clinics, and smaller laboratories.     

Evaluation of a novel PCR-based diagnostic assay for detection of Mycobacterium tuberculosis in sputum samples.

We report on a PCR-based assay we have developed for the detection of Mycobacterium tuberculosis in sputum samples. One hundred sputum specimens, which included 34 culture-positive and 66 culture-negative specimens, were evaluated with this system. Of the 34 culture-positive specimens, 31 were PCR positive, and 60 of the culture-negative specimens were PCR negative. An internal standard has been included in the assay system to monitor PCR inhibition and to confirm the reliability of the PCR assay.     

Validation of roche COBAS Amplicor assay for detection of Chlamydia trachomatis in rectal and pharyngeal specimens by an omp1 PCR assay

Screening guidelines for men who have sex with men (MSM) recommend testing of extragenital sites (pharyngeal and rectal) for gonorrhoea and chlamydia. Testing of specimens from these sites is not validated by most commercial nucleic amplification tests, such as the COBAS Amplicor assay. To investigate the utility of the COBAS Amplicor assay for detection of Chlamydia trachomatis in extragenital specimens, this study developed and evaluated confirmatory tests using the omp1 gene as an alternative target for amplification by PCR. Of anal and throat swabs collected from men in male-only saunas, 52 swabs that tested C. trachomatis positive by COBAS Amplicor and 30 swabs that tested as negative were included for confirmatory omp1 PCR testing. A total of 49 (94%) COBAS Amplicor-positive samples were confirmed by the omp1 PCR. A substantial proportion of specimens were confirmed by using a nested omp1 PCR (27%). Not confirmed by any omp1 PCR were three anal swabs (6%). It is most probable that these samples contained lower bacterial levels that were near or below the detection level of the omp1 PCR assays. The findings of this study support the confident reporting of C. trachomatis detected by COBAS Amplicor in extragenital specimens and support the utility of this assay as a screening test for MSM.     

Evaluation of the digene hybrid capture II CT-ID test for detection of Chlamydia trachomatis in endocervical specimens

The performance characteristics of the new signal amplification-based Hybrid Capture (HC) II CT-ID test system (Digene, Silver Spring, Md.) with endocervical specimens were compared to those of tissue culture and PCR (AMPLICOR CT PCR; Roche Molecular Systems, Branchburg, N.J.) for detection of Chlamydia trachomatis in 587 women. HC II CT-ID identified 62 of 65 confirmed C. trachomatis-positive patients (sensitivity of 95.4%) and was negative for 517 of 522 patients who were negative by culture and PCR (specificity of 99.0%). Twelve of the 65 confirmed positive patients were negative by culture but were identified by both HC II CT-ID and PCR (sensitivity of culture was 81.5% [P < 0.01]). In comparison, PCR detected 59 of 65 positive specimens (sensitivity of 90.8%) and had a specificity of 99.6% (520 of 522). These results demonstrate that the Digene HC II CT-ID test is a highly sensitive and specific assay for the detection of C. trachomatis infection in endocervical specimens.     

Performance of a nonisotopic DNA probe for detection of Chlamydia trachomatis in urogenital specimens.

The Gen-Probe PACE 2 assay (GP), a nonisotopic DNA probe, was evaluated by using cell culture as the method of reference. Specimens were collected from 260 men and 482 women visiting the outpatient department for sexually transmitted diseases at the University Hospital in Rotterdam, The Netherlands. The prevalences of Chlamydia culture-positive men and women were 13.2 and 8.6%, respectively. Sensitivity values for the male and female patients were 70.6 and 92.7%, respectively. Specificity values for these groups were 98.2 and 97.7%, respectively. Sensitivity was significantly lower when the number of inclusions in cell culture was low. Samples which showed a discordance between cell culture and GP results were retested by the polymerase chain reaction. If the results of the polymerase chain reaction were considered as the points of reference, the sensitivity and specificity of both GP and cell culture could be calculated. The performance of GP for females was comparable to that of cell culture. In males, the sensitivity of GP was considerably lower than that of cell culture (77.2 versus 91.4%), while specificity was somewhat higher (99.6 versus 99.1%). Compared with cell culture, the GP is a relatively simple and rapid test that is suitable for diagnosing Chlamydia infections in urogenital specimens.     

Comparison of Digene hybrid capture 2 and conventional culture for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in cervical specimens

Digene's Hybrid Capture 2 (HC2) CT/GC, CT-ID, and GC-ID DNA tests were evaluated by comparison to traditional culture methods for detecting Chlamydia trachomatis and Neisseria gonorrhoeae infections in 669 cervical specimens from high-risk female populations attending two sexually transmitted disease clinics. For detection of either or both infections, the HC2 CT/GC test algorithm had 93.8% sensitivity and 95.9% specificity compared to those of culture. After resolution of discrepant results by direct fluorescent-antibody (DFA) staining or PCR assay, the relative sensitivity and specificity of the HC2 CT/GC test algorithm increased to 94.8 and 99.8%, while the values for culture were 83.6% (McNemar's P value, 0.0062) and 100%, respectively. For detection of the individual pathogens, the relative sensitivities for the HC2 CT-ID and GC-ID tests were 97.2 and 92.2% and the specificities were greater than 99% compared to culture adjucated by DFA staining and PCR. Test performance varied at the two clinics: the HC2 CT/GC algorithm, CT-ID, and GC-ID tests had significantly higher sensitivities (McNemar's P value, <0.05) than that of culture for the population at one clinic as well as for the combined populations. At the other clinic, the HC2 tests performed as well as culture.     

Enzyme amplified immunoassay: a novel technique applied to direct detection of Chlamydia trachomatis in clinical specimens.

Endocervical swabs from 212 women and urethral swabs from 100 men were tested by the routine methods for McCoy cell culture and simultaneously by a novel enzyme amplified immunoassay test to detect chlamydia antigen. Overall correlation of the amplified test with culture was 96.5%. The test proved to be a suitable screening procedure for genital chlamydial infection, particularly for large numbers of specimens or in cases in which culture was not available.     

Evaluation of a rapid assay for detection of Chlamydia trachomatis infections in outpatient clinics in South Kalimantan, Indonesia

A multicenter cross-sectional survey was conducted comparing a commercially available chlamydial optical immunoassay (OIA) to the chlamydial ligase chain reaction (LCR). Endocervical samples from 415 outpatients visiting clinics from three hospitals in South Kalimantan, Indonesia, were evaluated. Relative to the LCR, the overall sensitivity and specificity of the OIA were 31.6 and 98.9%, respectively. The sensitivity of the OIA varied among the three hospital laboratories, ranging from 20 to 50%. The OIA performance was slightly lower on samples from patients attending dermatovenereology clinics than on samples from nondermatovenereology clinic patients. The results indicate that the OIA did not perform well compared to LCR.