Screening urine samples by leukocyte esterase test and ligase chain reaction for chlamydial infections among asymptomatic men

Using urinary leucocyte esterase tests as an indicator of infection with gonorrhoea or chlamydia in asymptomatic males in a primary health care setting

To evaluate a leucocyte esterase test as a predictor of gonorrhoea or chlamydia in asymptomatic Aboriginal males at the Central Australian Aboriginal Congress Male Clinic (Ingkintja), first-void urine samples and clinical information were collected from consecutive asymptomatic males presenting to the Ingkintja in Alice Springs between March 2008 and December 2009. Urine was tested immediately with a leucocyte esterase test dipstick and then by polymerase chain reaction for gonorrhoea and chlamydia. Among the 292 specimens from asymptomatic males, 15.4% were positive for gonorrhoea or chlamydia. In this group, compared with polymerase chain reaction result for gonorrhoea or chlamydia, leucocyte esterase test alone and in combination with age ≤35 years showed sensitivities of 66.7% and 60%, specificities of 90.7% and 94.7%, positive predictive values of 56.6% and 67.5%, negative predictive values of 93.7% and 92.8% and the area under receiver operating characteristics curve values of 0.79 and 0.85, respectively. Leucocyte esterase tests can reasonably be used as a basis for immediate empirical treatment for gonorrhoea or chlamydia in asymptomatic central Australian Aboriginal men under 35 years of age.

Should asymptomatic men be included in chlamydia screening programs? Cost-effectiveness of chlamydia screening among male and female entrants to a national job training program

OBJECTIVE

To compare the cost-effectiveness of various chlamydia screening strategies within a population of male and female youth entering a national job training program.

STUDY DESIGN

Cost-effectiveness analysis of various chlamydia screening strategies among a cohort of 4000 female and male New England job training students. Strategies for women include (a) no screening, (b) universal endocervical DNA probe screening, (c) universal urine based NAAT screening, and (d) universal endocervical NAAT screening. Strategies for men include (a) no screening, (b) selective urine NAAT screening of leukocyte esterase (LE)-positive urines, and (c) universal urine-based NAAT screening.

RESULTS

Universal endocervical NAAT screening of women and universal urine NAAT screening of men were the most effective and cost-effective strategies individually and in combination. Endocervical NAAT screening of women prevented 23 more cases of PID and saved $27,000 more than endocervical DNA probe screening. Likewise, universal urine NAAT screening of men prevented 21 more cases of PID in their female partners and saved $16,000 more than selective urine NAAT screening of LE positive men.

CONCLUSIONS

Use of a sensitive NAAT to screen both men and women for chlamydia upon entry to a National Job Training Program is cost-effective, cost-saving, and provides a public health opportunity to substantially reduce chlamydia infections among youth at risk for sexually transmitted diseases.

Performance of urine leukocyte esterase in asymptomatic male youth: another look with nucleic acid amplification testing as the gold standard for Chlamydia detection

PURPOSE

To re-evaluate the sensitivity and specificity of leukocyte esterase (LE) for screening adolescent and young adult males for Chlamydia trachomatis using a nucleic acid amplification test (NAAT) as the gold standard.

METHODS

This study was conducted at two Massachusetts Department of Youth Services sites and one Job Corps site. Recently admitted asymptomatic sexually active male youth aged 14 to 25 years (mean 16.6 years) were recruited between January 2001 and July 2003 (N = 1008). Participants provided first part voided urine specimens for testing with LE and Chlamydia NAAT. The sensitivity, specificity, and positive and negative predictive value of urine LE for identification of Chlamydia infection were determined using NAAT as the gold standard.

RESULTS

Fifty-seven (5.7%) participants were infected with Chlamydia as defined by a positive NAAT. Defining trace + as the LE cut point resulted in sensitivity and specificity of 57.9% and 78.3%, respectively. Defining 1+ as the cut point resulted in sensitivity and specificity of 47.4% and 96.1%, respectively.

CONCLUSIONS

Urine leukocyte esterase is a moderately sensitive method to screen for Chlamydia. Nevertheless, a substantial proportion of infections are not detected with LE screening. When feasible, urine NAAT provides a much more sensitive and equally noninvasive method of detecting Chlamydia. However, if LE is used as an initial screen followed by NAAT confirmation of LE positive samples, we recommend using trace LE as the cut point for positive results.

The clinical and economic consequences of screening young men for genital chlamydial infection

BACKGROUND

Wide-scale application of urine-based screening of asymptomatic men for chlamydial infection has not been thoroughly assessed.

GOAL

The goal was to compare clinical and economic consequences of three strategies: (1). no screening, (2). screening with ligase chain reaction (LCR) assay of urine, and (3). prescreening urine with a leukocyte esterase test (LE) and confirming positives with LCR.

STUDY DESIGN

We used a decision analytic model.

RESULTS

At a chlamydia prevalence of 5%, the no screening cost was US dollars 7.44 per man screened, resulting in 522 cases of pelvic inflammatory disease (PID) per 100000 men. LE-LCR was most cost-effective, preventing 242 cases of PID over no screening at an additional cost of US dollars 29.14 per male screened. The LCR strategy prevented 104 more cases of PID than LE-LCR but cost US dollars 22.62 more per male screened. For this to be more efficient than LE-LCR, the LCR assay cost needed to decline to <or=US dollars 18.

CONCLUSION

At a chlamydia prevalence of 5%, LE-LCR is the most efficient use of resources. If LCR cost decreases or chlamydia prevalence increases, the LCR strategy is favored.

Chlamydia trachomatis infection in asymptomatic men

BACKGROUND

The epidemiology of Chlamydia trachomatis infection in men is not well defined, especially among those who are asymptomatic or show no signs of infection. Established C. trachomatis screening programs for women have demonstrated the benefit of routine screening in reducing prevalence over time, but the yield and benefit of screening asymptomatic men are unclear.

METHODS

Cross-sectional study of C. trachomatis prevalence and associated risk factors among men tested at sexually transmitted disease (STD) clinics in Alaska, Idaho, Oregon, and Washington. We analyzed data from 43,094 men universally tested from 1997 to 1999 at 103 STD clinics, and assessed age-specific prevalence of infection, controlling for signs of infection (urethritis diagnosed by clinician) and report of sexual contact to a person with an STD (defined as "contact").

RESULTS

Overall prevalence of C. trachomatis was 10.3%. Age-specific prevalence was highest among men aged 18 to 19 years and lowest among those aged >29 years, regardless of signs of infection upon examination or contact to a person with an STD. If these factors and age <25 years had been used to direct C. trachomatis testing at STD clinics, 59% of men would have been tested and 91% of positives would have been detected.

CONCLUSIONS

Using either the presence of clinical signs or report of a sex partner with an STD in combination with selective screening of all men aged <25 years detects the majority of infections and, in our population, would have considerably reduced the number of negative tests performed.

The accuracy and efficacy of screening tests for Chlamydia trachomatis: a systematic review

Screening women for lower genital tract infection with Chlamydia trachomatis is important in the prevention of pelvic inflammatory disease, ectopic pregnancy and infertility. This systematic review aims to state clearly which of the available diagnostic tests for the detection of C. trachomatis would be most effective in terms of clinical effectiveness. The review included all studies published from 1990 onward that evaluated diagnostic tests in asymptomatic, young, sexually active populations. Medline and Embase were searched electronically and key journals were hand-searched. Further studies were identified through the Internet and contact with experts in the field. All studies were reviewed by two reviewers and were scored by Irwig's assessment criteria. Additional quality assessment criteria included a documented sexual history and recording of previous chlamydial infection. The reviews were subjected to meta-analysis and meta-regression. The 30 studies that were included examined three types of DNA-based test--ligase chain reaction (LCR), PCR and gene probe--as well as enzyme immuno-assay (EIA). The results showed that while specificities were high, sensitivities varied widely across the tests and were also dependent on the specimen tested. Pooled sensitivities for LCR, PCR, gene probe and EIA on urine were 96.5%, 85.6%, 92% and 38%, respectively, while on cervical swabs the corresponding sensitivities of PCR, gene probe and EIA were 88.6%, 84% and 65%. Meta-analysis demonstrated that DNA amplification techniques performed best for both urine and swabs in low prevalence populations. We conclude that nucleic acid amplification tests used on non-invasive samples such as urine are more effective at detecting asymptomatic chlamydial infection than conventional tests, but there are few data to relate a positive result with clinical outcome.

Sexually transmitted diseases and human immunodeficiency virus-discordant partnerships among men who have sex with men

Sexually active men who have sex with men (MSM) at 5 Seattle clinics were assessed for bacterial sexually transmitted diseases (STDs), human immunodeficiency virus (HIV)-discordant partnerships, sexual behavior, and drug use. Of the HIV-positive men, 45% reported having HIV-negative sex partners and 42% reported having sex partners with unknown serostatus during the past 2 months, whereas 14% and 57% of HIV-negative men reported having HIV-positive and unknown-serostatus sex partners, respectively. Correlates of sex partners with unknown serostatus were recruiting sex partners at bathhouses or parks. Gonorrhea, chlamydia, or syphilis was diagnosed in 12% of HIV-positive and 13% of HIV-negative MSM, and the rates did not differ between men with HIV-concordant and HIV-discordant partnerships. High prevalences of bacterial STDs and HIV-discordant partnerships emphasize the need for interventions to foster serostatus discussion, condom use, fewer anonymous partners, and STD screening.

Effectiveness of a mobile medical van in providing screening services for STDs and HIV

This retrospective study assesses the efficacy of a mobile medical van in screening high risk individuals and identifying new cases of HIV and other sexually transmitted diseases (STDs) in an urban setting from July 1996 through March 1997. High risk sex and drug use were common, while consistent condom use was rare. Relatively few patients were screened for STDs; positive cases represented only a small proportion of the STD cases identified in the study community. The mobile program, however, accounted for 11.5% of all HIV tests conducted at public test sites in the city. Mobile medical programs have the potential to improve STD and HIV control efforts by providing services to high risk individuals who may lack access to care elsewhere. Doing so, however, will require more active case finding techniques, including new, less invasive techniques to test asymptomatic individuals.

Urine-based screening for Chlamydia trachomatis in men attending sexually transmitted disease clinics

BACKGROUND

Nucleic acid-amplified tests for Chlamydia trachomatis are accurate but costly. Screening strategies for asymptomatic men are needed.

GOAL

To assess C trachomatis screening strategies for asymptomatic males.

STUDY DESIGN

Men attending a sexually transmitted disease clinic were tested for C trachomatis with ligase chain reaction and culture, and for urethral inflammation with urine leukocyte esterase and urethral Gram stain.

RESULTS

C trachomatis prevalence was 5.5% among 1,625 asymptomatic men. Ligase chain reaction increased detection by 49% among men without urethral inflammation. An age of younger than 25 years and urethral inflammation were associated with positive ligase chain reaction results. The negative predictive value of urine leukocyte esterase was highest among older men, but urethral Gram stain was equally sensitive in predicting infection regardless of age. An age of younger than 30 years or urethral inflammation identified the highest proportion of infections (92%) and reduced the percentage of men screened by 43%.

CONCLUSIONS

Urine ligase chain reaction increased C trachomatis detection, particularly among men without urethral inflammation. Testing all asymptomatic men younger than 30 years is optimal, whereas negative urine leukocyte esterase or urethral Gram stain results in men 30 years or older support no testing.

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.

Noninvasive screening for genital chlamydial infections in asymptomatic men: Strategies and costs using a urine PCR assay

OBJECTIVE

To evaluate cost saving strategies to screen for genital chlamydial infection in men using polymerase chain reaction (PCR) technology.

METHODS

Men with no urethral symptoms presenting to a sexually transmitted disease (STD) clinic were recruited. Study participants underwent a questionnaire interview. Urethral swabs were taken to perform a smear for polymorphonuclear leucocytes (PMN) and for the detection of Chlamydia trachomatis by culture and PCR. First-catch urine was collected for a leukocyte esterase test (LET) and PCR.

RESULTS

C trachomatis infection was detected in 36 of 463 (7.8%) men. LET and PMN were positive in 10 (28%) and 12 (33%) infected men, respectively. Risk factors for chlamydial infection were younger than age 25 years, LET-positive, PMN-positive and STD contact (P<0.001). The direct cost of genital chlamydial infection in men in Canada has been previously estimated at $381/case. Based on a sensitivity of 90% for urine PCR, the estimated direct cost of testing all participants to detect 32 cases was $453/case. Using risk factors recommended in the Canadian STD Guidelines (age younger than 25 years, new partner, STD contact or unprotected sex), the same number of cases would have been detected by testing only 384 men at $376/case. Using age younger than 25 years or STD contact as the screening criterion, 78% of those infected would have been detected at $259/case, and no new cases would have been detected by adding LET-positive or PMN-positive as risk factors.

CONCLUSION

Targeted screening for chlamydial infection using urine PCR assay and risk factors recommended in the Canadian guidelines could substantially reduce the cost of screening at a STD clinic setting. LET and PMN smear did not appear to be useful indicators of chlamydial infection in this population.

Reappraising the value of urine leukocyte esterase testing in the age of nucleic acid amplification

BACKGROUND

The leukocyte esterase (LE) test has a limited role in determination of empiric therapy for male patients screened for urethritis because of its poor positive predictive value in low (< 5%) prevalence settings. The recent advent of nucleic acid amplification testing of first-void urine (FVU) has dramatically increased the ease with which widespread screening for Chlamydia trachomatis and Neisseria gonorrhoeae can be performed, but the costs of such testing may be prohibitive. The LE test may therefore have a role in management of urethritis because of its high negative predictive value.

OBJECTIVES

To determine the sensitivity, specificity, and positive and negative predictive value of LE testing for the diagnosis of N. gonorrhoeae and C. trachomatis in male FVU specimens in a low-prevalence urban setting using a commercial polymerase chain reaction (PCR) as the gold standard.

METHODS

Data were obtained on men presenting to an urban sexually transmitted disease clinic over a 16-month period. Patients were included if an FVU had been tested for the presence of LE using a rapid dipstick, read by an automated urine analyzer, and the sample (either an FVU or urethral swab) had then been processed for the detection of N. gonorrhoeae and C. trachomatis by PCR.

RESULTS

Of 301 assessable patients, there were 14 cases of gonorrhoea, 21 cases of chlamydia, and 1 case of dual infection detected by PCR. Most men (245/301; 81.4%) were asymptomatic, of whom 12 of 245 (4.9%) had an infection detected compared with 24 of 56 (42.9%) in the symptomatic men (P < 0.001). Using a "< or = trace" cutoff, the overall value for the sensitivity of the LE test was 77.8% (95% confidence interval, 60.4-89.3), specificity 80.8% (75.4-85.2), positive predictive value 35.4% (25.2-47.1), and negative predictive value 96.4% (92.8-98.3).

CONCLUSIONS

The negative predictive value of the LE test may be of use in determining which patients should proceed to specific diagnosis by nucleic amplification methods (e.g., PCR or ligase chain reaction). By limiting testing to patients with positive LE results, cost savings may be made, enabling the technology to be used in a wider community setting. The value of the LE test in higher prevalence populations with access to nucleic amplification testing remains to be established.

Comparison of performances of two commercially available tests, a PCR assay and a ligase chain reaction test, in detection of urogenital Chlamydia trachomatis infection

The diagnostic performance of a PCR test (Roche Cobas Amplicor CT/NG Test) and that of a ligase chain reaction (LCR) test (Abbott LCx Chlamydia trachomatis assay) were compared by using endocervical and urethral swab specimen culture as a reference test. First-void urine (FVU) and endocervical and urethral swab specimens were collected from 1,015 unselected patients attending a sexually transmitted disease clinic and a clinic for adolescents in Helsinki, Finland. Chlamydia trachomatis was cultured from samples from the endocervix or urethra. PCR was performed with fresh and frozen urine and the culture transport medium. LCR was performed with fresh and frozen urine and LCx swab transport medium. Diagnostic consistency and diagnostic accuracy were statistically tested. The test results were identical for 984 patients (97%). Discrepant results were observed for 31 patients. Overall, LCR and PCR showed excellent kappa coefficients of consistency for both swab and FVU specimens (0.93 and 0.95, respectively). Sixty-one patients (6%) were culture positive. Testing of FVU by LCR or PCR increased the overall positivity rates to 7.0 and 7.7%, respectively. While PCR of FVU detected the greatest number of C. trachomatis infections (sensitivity, 96.1%), for some PCR-positive FVU specimens the results could not be confirmed (specificity, 99.6%). PCR and LCR were more sensitive than culture (sensitivities, 92 and 93% versus 79% for culture) in the diagnosis of genital C. trachomatis infection. In conclusion, both tests can be recommended for use in the clinical laboratory and for the screening of asymptomatic C. trachomatis infections.

The inhibitory effect of phosphate on the ligase chain reaction used for detecting Chlamydia trachomatis

AIMS

To examine the detection limit of the ligase chain reaction kit for Chlamydia trachomatis, to study the inhibitory effect of phosphate on the ligase chain reaction, and to clarify the mechanism of inhibition.

METHODS

Three reference serovars of C trachomatis--D/UW-3/Cx, F/UW-6/Cx, and L2/434/Bu--were used to test the sensitivity of the chlamydia ligase chain reaction. Comparison was made of the inhibition by phosphate before and after DNA amplification. Phosphate in up to 2.4 mM concentration was added to specimens of C trachomatis serovar D (1 to 50 inclusion forming units (IFU)/reaction) before DNA amplification to examine the concentration dependency of phosphate inhibition of the ligase chain reaction.

RESULTS

The detection limits were 0.6 IFU/reaction for serovar D/UW-3/Cx and F/UW-6/Cx, and 0.4 IFU/reaction for L2/434/Bu. Phosphate inhibited the ligase chain reaction only when it was added before the amplification stage. The specimens containing chlamydia at 1 to 50 IFU/reaction were negative when the concentration of phosphate added at the prethermocycle stage was more than 1.2 mM.

CONCLUSIONS

Ligase chain reaction analysis is a reliable method of diagnosing C trachomatis infection because of its high sensitivity. It would be clearly superior to the currently used methods if the problem of inhibitors could be eliminated. The mechanism of inhibition of the ligase chain reaction by phosphate was thought to be blockade of the amplification of the target DNA. The efficacy of the ligase chain reaction could be inhibited by phosphate in the urine, so duplicate dilution analysis of some negative specimens should be useful.

The usefulness of screening for chlamydial trachomatis infection with cervical mucus leukocyte esterase

OBJECTIVE

To evaluate the ability of leukocyte esterase dipstick test (LET) performed in cervical mucus to predict direct immunofluorescent (DIF)-verified Chlamydia trachomatis (Ct) cervical infection.

METHOD

Eighty women with inflammatory cervico-vaginal smear were submitted to both an endocervical smear, to verify Ct cervicitis by DIF technique; and a cervical mucus sample to perform LET. Results of LET and DIF were matched.

RESULTS

Among 30 Chlamydial positive subjects, cervical mucus esterase test was positive in 28 (93.3%); while among 50 Chlamydial negative controls, esterase test was negative in 43 subject (86%). The sensitivity, specificity, positive and negative predictive values for LET were 93.3%, 86%, 80% and 95% respectively.

CONCLUSION

Cervical mucus LET is a simple, cost effective screening test, with promising accuracy, for Ct cervical infection among women with inflammatory cervico-vaginal smears.

False-negative results of a ligase chain reaction assay to detect Chlamydia trachomatis due to inhibitors in urine

The aim of this study was to assess the presence of inhibitors in urine specimens causing false-negative results in a commercial Chlamydia trachomatis gap-filling ligase chain reaction (Gap-LCR) assay. On testing of urine samples by the Gap-LCR assay and urethral swab specimens by cell culture, 73 (19%) Chlamydia trachomatis positive subjects were detected among 382 men attending a clinic for sexually transmitted diseases. In 56 subjects, the agent was detected in both the urine and the urethral samples, while 309 subjects were negative in both tests. In seven subjects urine samples were Gap-LCR positive (confirmed by a different Gap-LCR assay), but the corresponding urethral swab samples were cell culture-negative. In another ten subjects the urethral swab samples were cell culture positive, but their urine samples were Gap-LCR negative. Subsequent re-analysis of the urine samples including the addition of external Chlamydia trachomatis DNA indicated full or partial inhibition in nine of the cell culture-positive Gap-LCR negative subjects. When urine preparations were freeze-thawed and diluted prior to testing, Chlamydia trachomatis was detected in six of the ten initially Gap-LCR-negative samples. Gap-LCR inhibitors were present in at least nine (12%) of the 73 urine preparations from the Chlamydia trachomatis positive individuals. Identification of samples containing Gap-LCR inhibitors and subsequent processing to reduce the inhibition increased the sensitivity of the test from 86% to 95%.