LABORATORY: Testing for Sexually Transmitted Diseases
Symptoms of STDs
Infectious diseases that are transmitted through sexual contact are referred to as sexually transmitted diseases, or STDs. The symptoms and illnesses caused by STDs vary according to the specific infection, the age of the child/adolescent, and the site of the infection. Adolescent girls are often asymptomatic.
Who Should Be Tested
Not all children who have been sexually abused require STD testing. The majority of abuse victims will not have an STD. Only about 5% do, with sexually active adolescents having the highest rates. As a result, the decision to test for STDs must be made on an individual basis. However, because many STDs are asymptomatic, tests are often done during the medical evaluation to exclude a silent infection. While some examiners test all suspected victims for STDs, others limit testing to those whom they believe are at increased risk for infection, such as those with the findings listed below:
A history of:
A sibling or household contact that was diagnosed with an STD
A previous STD
Prior sexual contact
Abuse by multiple perpetrators or by a perpetrator with high risk behaviors, such as crack or IV drug use, prostitution, multiple partners, or a history of STDs
A history of or examination findings consistent with:
Vaginal or urethral discharge
Rectal pain or discharge
Genital ulcers, sores, or warts
Physical indications of vaginal or rectal penetration or a genital injury
A diagnosis of another STD
An age of 13 or older (Tanner 3 or greater)
An inability to follow up at a later time if symptoms develop
The child/adolescent may not offer a reliable enough history to adequately determine risk factors. In cases such as this, individualize the testing based on the information available. If you do not have significant evidence of a recent event, consider a referral to a Child Advocacy Center or other specialized center for further evaluation.
Testing the Suspected Perpetrator
If the sexual abuse victim has been diagnosed with an STD, the suspected perpetrator should be tested, if possible, to determine if that person also has the infection. Interpret this information cautiously. If the suspected perpetrator has already received treatment, the test may be negative. If the test is positive, the information will support the allegations of sexual abuse, although a definitive connection linking the suspected perpetrator to the victim cannot be made. Tests for HIV, syphilis, and blood borne hepatitis will remain positive even after the suspected perpetrator has received medical treatment.
Techniques for Collecting Specimens
Identification of an STD requires an adequate sample, careful specimen handling, and a qualified laboratory. False negative and false positive cultures and tests can occur if errors are made.
The supine position is preferred for the collection of vaginal and urethral specimens. Cervical cultures are recommended in the adolescent while vaginal cultures are sufficient in prepubertal females. In some cases, it may be appropriate to collect vaginal swabs in an adolescent, particularly if the adolescent was not previously sexually active and the insertion of speculum is expected to cause unnecessary distress for the patient. The use of relaxation/distraction techniques and labial or perineal traction maneuvers will assist the medical provider in collecting vaginal specimens without touching the sensitive hymenal tissue. The vaginal wall can be gently swabbed for cultures.
Rectal specimens are best obtained with the patient in the lateral knee chest position. Introduce the swab(s) as far as the rectal crypts (approximately 1 to 1 1/2 inches). Collect specimens prior to a digital rectal examination because lubricating agents will interfere with testing.
Following evidence collection for forensic specimens, STD specimens should be obtained in the following order:
Other indicated specimens based on history and examination
In cases of suspected sexual abuse, it is critical that the tests used to diagnose STDs are recognized as "gold standards."
Cultures for N. gonorrhoeae and C. trachomatis are the "gold standard" for sexual abuse evaluations. Prior to making the diagnosis of an STD in a prepubertal child, the lab must perform additional testing on the culture specimen to be certain of the pathogen's identity. Non-culture screening tests (i.e., enzyme linked immunoassay, DNA probes) should not be used to diagnose an STD in a prepubertal child. Most of these tests have only been utilized and approved for the adult population. The rate of false positive tests can be high when non-culture tests are used in a prepubertal population. Necessary reconfirmation of the specific subtype and further identification of an organism is only possible with culture techniques.
It may be appropriate to use "non-gold-standard" tests for screening, particularly in primary care settings where patient compliance can be assured. Such screening tests are site specific and may be used only to test from certain body sites. Early research utilizing nucleic acid amplification tests (NAATs) looks promising for the future use of these tests for sexually abused children. Currently, a positive NAAT screening of urine or genital swabs must be confirmed by culture prior to diagnosis and treatment.
During the initial examination and follow-up examination, if indicated based on knowledge of last known sexual contact and incubation period of the STD, perform the following:
Collect cultures for N. gonorrhoeae from the pharynx and anus in both sexes, the vagina in girls, and the urethra in boys. Cervical specimens are not recommended for prepubertal girls. For boys, a meatal specimen of urethral discharge is an adequate substitute for an intraurethral swab specimen when discharge is present. In the absence of a known infected offender or symptoms including discharge or dysuria in the male prepubertal victim, the urethral swab for gonorrhea may be deferred. Many experts do not obtain urethral specimens unless there are specific symptoms. If possible, preserve isolates in case additional or repeat testing is required. Some experts recommend using urine NAATs to screen for urethritis in males and vaginitis in females if the child/adolescent's return for confirmatory testing can be assured. Use only standard culture systems for the isolation of N. gonorrhoeae. A positive culture must be confirmed by two additional and unrelated tests. NAATs can be used for screening purposes for gonorrhea but other non-culture methods (e.g., Genprobe) are unacceptable.
Collect cultures for Chlamydia trachomatis from the anus in both sexes and from the vagina in girls. Limited information suggests that the likelihood of recovering Chlamydia from the urethra of prepubertal boys is too low to justify the trauma involved in routinely obtaining an intraurethral specimen. A urethral specimen should only be obtained if urethral discharge or dysuria is present in the male prepubertal victim. A urine NAAT is an appropriate and painless test that can be used as an alternative to the urethral/meatal swab. Pharyngeal specimens for Chlamydia trachomatis are not recommended for either sex because the yield is low and test results can be confused by Chlamydia pneumonia. Perinatally acquired infection may persist beyond infancy at this site. Use only standard culture systems for the isolation of Chlamydia trachomatis and make positive identification by the use of specific antigen testing. Non-culture methods are unacceptable for diagnosis.
If a vaginal discharge is present, obtain cultures, wet mount, and KOH prep of vaginal swab specimens for bacterial vaginosis, Trichomonas vaginalis, and Candida albicans.
When genital lesions are present, consider diagnostic testing for herpes simplex virus or human papillomavirus.
Decisions about serological testing should be made on a case-by-case basis depending on the child/adolescent's risk of infection. Collect and preserve serum for subsequent analysis in case follow-up serologic tests are positive. If the last sexual exposure occurred more than eight weeks prior to the initial examination, sera should be tested immediately for antibody to STDs such as syphilis, blood borne hepatitis, and HIV (with consent).
Test a child/adolescent when significant exposure may have occurred. In New York State, the Department of Health protocol for HIV currently recommends testing and prophylaxis for all victims of sexual assault who are evaluated within 36 hours of the incident. Provide all patients being tested for HIV antibodies with pre- and post-test counseling in compliance with New York State HIV Confidentiality Law (Article ~ 27-F) and obtain written, informed consent.
Nonquantitative detection of HIV is the first step in diagnosing infectivity. In adults and older children, enzyme-linked immunosorbent assay (ELISA) and Western blot assay are used to detect HIV-specific antibodies. These tests are not used for diagnosis in those younger than two years because maternal antibodies are present in neonatal blood. DNA polymerase chain reaction (PCR) and/or viral culturing are the standard detection methods in infants and young children. The patient may be offered rapid HIV testing, using Oraquick or another rapid test. However, initiation of PEP should not be delayed until results are available and should not be denied if the patient refuses testing. For information about HIV prophylaxis, see TREATMENT AND FOLLOW-UP: Sexual Abuse, STD Prophylaxis, HIV.
Considerations Regarding HIV Testing
The incidence of developing HIV infection from a single episode of sexual abuse is very low.
Recommend HIV post-exposure prophylaxis (PEP) to patients reporting sexual assault in which significant exposure may have occurred. Offer PEP as soon as possible following exposure, ideally within one hour and not more than 36 hours after exposure.
Perform baseline HIV testing prior to administration of post-exposure prophylaxis.
Provide counseling to both the adolescent and parent unless the adolescent is determined to have the ability to understand the risks and benefits of testing and treatment. In those situations, ask the adolescent if he/she wishes the parent involved with the counseling.
After counseling and obtaining permission, draw blood and process it per the healthcare facility's policies.
Blood may also be drawn and frozen before counseling. Then, after counseling, a determination can be made regarding having the blood tested.
After an Acute Assault
Following an acute assault:
Offer all victims of sexual assault HIV testing and provide appropriate pretest counseling as required by Public Health Law ~ 27-F.
Do a urinalysis to check for hematuria. If there are symptoms of dysuria, obtain a urine culture and gram stain.
Consider a stool guaiac to test for occult or apparent blood in the stool. When the possibility of anal or intra-abdominal injury is low, the digital rectal examination and guaiac are unnecessary. Collect all evidence and specimens for STDs prior to the digital rectal examination because lubricating agents will interfere with testing.
Perform any diagnostic laboratory or imaging studies to delineate presence and extent of injuries, where indicated.
A serum pregnancy test must be performed in pubertal and post-pubertal females at the initial and follow-up visit to test for pre-existing or subsequent pregnancy.
Test for syphilis, hepatitis B and HIV four to six weeks after the suspected exposure to allow time for antibodies to infectious agents to develop.
Consider serologic tests for the following agents at three months: syphilis, HIV, and hepatitis B and C viruses. At six months retest for HIV and hepatitis C.
Make the choice of tests on a case-by-case basis and discuss the estimated risk of infection with the parent or adolescent. Base any further post-assault testing for STDs or pregnancy on the presence of symptoms, genital lesions, or a history of intercurrent sexual contact. For more information, see Post-Assault Testing and Treatment, Appendix A.