Lack of specificity of Chlamydiazyme for detection of vaginal chlamydial infection in prepubertal girls

Medical and legal implications of testing for sexually transmitted infections in children

Testing for sexually transmitted infections (STIs) in children presents a number of problems for the practitioner that are not usually faced when testing adults for the same infections. The identification of an STI in a child can have, in addition to medical implications, serious legal implications. The presence of an STI is often used to support the presence or allegations of sexual abuse, and conversely, the identification of an STI in a child will prompt an investigation of possible abuse. The purpose of this paper is to review the epidemiology of child sexual abuse, including the epidemiology of major STIs including Neisseria gonorrhoeae, Chlamydia trachomatis, syphilis, herpes simplex virus (HSV), Trichomonas vaginalis, and human papillomavirus, and the current recommendations for diagnostic testing in this population.

Appropriate use of nonculture tests for the detection of sexually transmitted diseases in children and adolescents

The introduction of nucleic acid amplification tests (NAATs) has been the most important advance in the diagnosis of sexually transmitted diseases (STDs) since tissue culture replaced inoculation of eggs for culture and isolation of Chlamydia trachomatis from clinical specimens. Because nucleic acid amplification is exquisitely sensitive, theoretically capable of detecting as little as a single gene copy, and highly specific, it offers the opportunity to use noninvasive sampling (ie, urine). This ability in turn means that these tests might be used in nontraditional settings, such as schools and in the field, which may be very helpful in providing services to homeless adolescents. However, none of these tests is approved or recommended by the manufacturers for rectal specimens from adults, and they are not approved for rectogenital specimens from children. In addition to medical implications, the identification of a sexually transmitted disease (STD), especially in a young child, also has legal implications. Because of the legal implications, the highest specificity is needed and is more important than is sensitivity in this situation. Data on the use of these tests in prepubertal children are insufficient to permit their use at this time. What may be appropriate for screening a sexually active adult in an STD clinic may not be appropriate for evaluating a child victim of suspected sexual abuse. Although missing possible sexual abuse is a major concern, the ramifications of a false-positive test for an STD, which can lead to erroneous reports of sexual abuse and possibly unjustified prosecution and incarceration, also must be considered.

Inappropriate use of nonculture tests for the detection of Chlamydia trachomatis in suspected victims of child sexual abuse: A continuing problem

The introduction of nonculture tests for detection of Chlamydia trachomatis has revolutionized the management of chlamydial infections in sexually active adolescents and adults. However, these tests are insufficiently specific for use in genital and rectal sites in children; false-positive tests can be frequent. We report here 4 cases involving inappropriate use of nonculture tests in children in New York City during 1998. Two cases involved the use of enzyme immunoassays with vaginal specimens. In both cases the initial results were positive, however, cultures for C trachomatis performed later were negative. In the third case, the DNA probe test for C trachomatis was used. The fourth child was being evaluated for sexually transmitted diseases after rape. Although the pediatrician sent a rectal culture to a large commercial laboratory it was later determined that the laboratory was using an enzyme immunoassay for culture confirmation leading to a false-positive result. At the least the use of these inappropriate tests resulted in unnecessary retesting and at the worst, unnecessary hospitalization, erroneous reports of sexual abuse and possibly unjustified prosecution and incarceration. Because of the social and legal implications it is important that practitioners be aware of these recommendations and require that commercial laboratories adhere to approved C trachomatis culture methods.

False-positive enzyme immunoassay test results for Chlamydia trachomatis because of contact of the collection swab with agar

BACKGROUND

We noted an increased incidence of false-positive Chlamydia trachomatis enzyme immunoassay results using the Abbott IMx SELECT C. trachomatis EIA test when a single swab was used for urethral sampling for both gonococcal culture inoculation and chlamydial detection.

GOALS

To evaluate if contact of the enzyme immunoassay collection swab with an agar produces false-positive chlamydial enzyme immunoassay results.

STUDY DESIGN

Samples containing agar-based culture media were tested by two enzyme immunoassays and a ligase chain reaction technique.

RESULTS

We report false-positive chlamydial enzyme immunoassay results using the Abbott IMx SELECT C. trachomatis EIA test if the collection swabs are in contact with gonococcal culture media (Modified New York City agar, chocolate, Thayer-Martin, or GC-lect) before insertion of the swab in the transport media of the enzyme immunoassay. The other assay results were negative.

CONCLUSIONS

Using a single collection swab to screen for genital infections with gonococcal cultures and chlamydial enzyme immunoassay is inappropriate because it may lead to false-positive chlamydial enzyme immunoassay results, at least with the Abbott IMx SELECT C. trachomatis EIA test, incurring public health and financial consequences.

Sexually transmitted diseases in sexually abused children: medical and legal implications

Sexually transmitted diseases (STDs) may be transmitted during sexual assault. In children, the isolation of a sexually transmitted organism may be the first indication that abuse has occurred. Although the presence of a sexually transmissible agent from a child beyond the neonatal period is suggestive of sexual abuse, exceptions do exist. In this review I discuss the issues of the transmissibility and diagnosis of STDs in the context of child sexual abuse. Rectal or genital infection with Chlamydia trachomatis among young children may be the result of perinatally acquired infection and may persist for as long as 3 years. A major problem with chlamydia testing in the context of suspected sexual abuse in children has been the inappropriate use of non-culture tests. Although the new generation of nucleic acid amplification tests have shown high sensitivity and specificity with genital specimens from adults, data on use of these tests on any site in children are practically non-existent. Bacterial vaginosis (BV) has been identified among children who have been abused and among those who have not been abused. However, many of the methods used to diagnose BV in adults have not been evaluated in children. Recent studies of perinatal infection with human papillomavirus (HPV) have been inconclusive. HPV DNA has been detected at various sites in children who have not been abused. The relation to the development of clinically apparent genital warts is unclear. Although HIV can be acquired through sexual abuse in children, the exact risk to the child and which children should be screened is still controversial.

Diagnosis of chlamydial infection in the pediatric population

The genus Chlamydia now contains 4 species, 2 of which, Chlamydia trachomatis and C. pneumoniae are important human pathogens. Both organisms cause infections in children and adults, but infection in children pose a unique set of problems. As C. trachomatis is primarily a sexually transmitted disease, the presence of rectal or genital infection in a prepubertal child has been used as evidence of sexual abuse. Although there are several categories of non-culture tests that have bear approved for genital sites in adults, these tests are not approved for these sites in children. Of these tests in rectal and vaginal specimens in children have been associated with a high rate of false positives. C. pneumoniae is emerging as a frequent cause of community acquired pneumonia in adults and children. Because culture is not generally available, serologic diagnosis is used more frequently. However, currently available serologic methods appear to be insensitive in children. The availability of a commercial PCR test will greatly facilitate the diagnosis of C. pneumoniae infections in children.

Acceptability and usefulness of vaginal washes in premenarcheal girls as a diagnostic procedure for sexually transmitted diseases. The Child Protection Centre at the Winnipeg Children's Hospital

OBJECTIVE

To assess the suitability of vaginal washes as specimens for sexually transmitted disease diagnosis and determine the usefulness of PCR technology for Chlamydia trachomatis diagnosis in prepubertal girls.

STUDY DESIGN

Paired sets of vaginal secretions were collected with swabs and by vaginal wash from 138 prepubertal girls for evaluation because of alleged sexual abuse. Detection by culture of Neisseria gonorrhoeae and C. trachomatis was compared between the two sampling techniques. PCR techniques were also used to test 29 vaginal wash specimens for C. trachomatis.

RESULTS

In the prepubertal girls N. gonorrhoeae was detected in two wash specimens but in only one swab specimen; C. trachomatis was detected by culture in both paired specimens from two children and by PCR in vaginal washes from both of the two children positive by culture; PCR identified two other infected children.

CONCLUSIONS

A vaginal wash technique coupled with newer molecular amplification technology may be useful in the assessment of sexually abused children.

Diagnostic methods for intracellular pathogens

Diagnosis of infection with Chlamydia pneumoniae is difficult and the optimal diagnostic procedure has yet to be established. C. pneumoniae is more difficult to isolate in tissue culture than C. trachomatis. Attention must be paid to the site from which the specimen is taken, and all specimens should be processed within 24 h or stored at 4 C. Serologic diagnosis largely depends on microimmunofluorescence testing which, despite proposed criteria, still has a large subjective component. Serology has limitations in terms of both sensitivity and specificity and antibodies may be difficult to detect in individuals with positive C. pneumoniae cultures. Non-culture methods include enzyme immunoassays, fluorescent-antibody techniques and DNA probes. The most promising appears to be PCR. Co-infection of C. pneumoniae and other respiratory organisms seem to be common.

Pediatric gonococcal infection: case report demonstrating diagnostic problems in remote populations

The inability of Neisseria gonorrhoeae to survive prolonged transit times and hostile ambient temperatures has made its detection at referral laboratories by cultural methods untenable. In this situation, reliance upon antigen detection systems is attractive but when these tests are performed on vaginal specimens from children, false positive results are a significant concern. Some of the difficulties associated with the investigation of a gonococcal infection resulting from sexual abuse of a child in an isolated community are illustrated in this report.

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.

Sexually transmitted diseases and child abuse

The diagnosis in a child of any infection that is usually sexually transmitted in adults should raise the suspicion of possible sexual abuse. We know sexual abuse is a common childhood experience. The American Academy of Pediatrics Committee on Child Abuse and Neglect has rated the implications of sexually transmitted diseases for diagnosing sexual abuse (Table 6).

Value of confirmation of Chlamydiazyme enzyme immunoassay results in the detection of Chlamydia trachomatis

The specificity of an EIA (Chlamydiazyme, Abbott) for detection of Chlamydia trachomatis was evaluated by means of a monoclonal antibody blocking reagent (Abbott) and a direct fluorescent antibody test (DFA) (Micro Trak, Syva). Of the 12,864 tested specimens from the urethra and cervix, 666 (5.2%) were positive. When retested with the same technique 625 (4.9%) were again positive. The result in 514 (4.0%) specimens was verified by means of the blocking reagent. Of specimens with absorbance values just below the established cut-off limit (0.07-0.114), 31 of 79 (39.2%) were specifically inhibited, increasing the rate of positive results by 0.25%. The results confirmed with the blocking reagent were in agreement with those obtained by DFA. The findings show that verification of positive Chlamydiazyme results is strongly advisable, in particular in specimens from the cervix.

False-positive Chlamydiazyme results during urine sediment analysis due to bacterial urinary tract infections

Our study examined whether urinary tract infections (UTIs) would cause false-positive results when urine sediment was tested with the Chlamydiazyme (CZ) system. Thirty-six infected urine samples and fifteen controls were studied. All controls were negative. Forty-seven percent of Escherichia coli UTIs (n = 30) and 100% of Klebsiella pneumoniae UTIs (n = 4) were positive on CZ testing of urine sediment. Nine E. coli UTIs positive by CZ were negative by direct fluorescent-antibody staining. When suspensions of the pure cultures were analyzed, 47% of E. coli and 100% of K. pneumoniae samples were CZ positive. False-positive results were not related to organism biotype or urine characteristics, including pH, specific gravity, and leukocyte count. We conclude that the presence of a UTI and also bacterial contamination must be ruled out prior to urine sediment testing.

Effect of endocervical specimen quality on detection of Chlamydia trachomatis and on the incidence of false-positive results with the Chlamydiazyme method

Duplicate endocervical swabs were collected from 1,675 patients to assess the effects of variations in specimen quality on Chlamydiazyme (Abbott Laboratories) detection of Chlamydia trachomatis and the incidence of false-positive results. One swab (at random) from each patient was tested for C. trachomatis antigen by using the standard Chlamydiazyme procedure. A 200-microliter volume of 0.9% saline was added to the other swab from each patient. After vortexing, 20 microliters was smeared on a slide for Papanicolaou (Pap) staining and the remaining specimen was then tested with the Chlamydiazyme assay. The Chlamydiazyme result was positive for 170 (10.1%) and 165 (9.8%) of the stained and unstained duplicate specimens, respectively (no significant difference). Pap stains on smears from 1,536 (91.7%) of the patients were analyzed, and endocervical and/or metaplastic (E-M) cells were detected in 789 (51.4%) smears. Of these 1,536 stained and analyzed specimens, 150 (9.8%) were Chlamydiazyme positive but only 132 (88.0%) of the positive results were confirmed by repeating the test and using a monoclonal blocking antibody (Abbott). Confirmed Chlamydiazyme-positive results were obtained from only 34 (4.6%) of 747 specimens lacking E-M cells but from 98 (12.4%) of 789 specimens containing the cells (P less than 0.001). Of the 150 initially Chlamydiazyme-positive results obtained with Pap-stained, analyzed specimens, 12 (26.1%) of 46 were falsely positive from specimens lacking E-M cells but only 6 (5.8%) of 104 were falsely positive from specimens containing E-M cells (P less than 0.01). C. trachomatis antigen was detected significantly more frequently and false-positive results were significantly less common from specimens in which E-M cells were detected.