RNA Biosignatures in Adolescent Patients in a Pediatric Emergency Department with Pelvic Inflammatory Disease

Pelvic inflammatory disease (PID) consists of infection and inflammation of the upper female genital tract. PID typically begins in the lower genital tract in the vagina and cervix and then spreads to the upper genital tract including uterus, fallopian tubes, ovaries, and peritoneum 1-3. PID is thought to be largely a polymicrobial infection, but several sexually transmitted organisms have been implicated including Neisseria gonorrhoeae and Chlamydia trachomatis. It has been suggested that other organisms may also be involved in the development of PID including Trichomonas vaginalis 4 and Mycoplasma genetalium 5, 6. If untreated, PID can lead to long term complications in young women including ectopic pregnancy, chronic pelvic pain, and infertility1. Because the consequences of under-recognition and under-treatment of this condition are severe, the Centers for Disease Control and Prevention (CDC) have maintained broad diagnostic criteria for PID to ensure that cases are not missed 7. The current minimum diagnostic criteria for PID in a sexually active female include the presence of lower abdominal pain and any of the following: cervical motion tenderness, adnexal tenderness, or uterine tenderness7. This clinical diagnosis can be particularly difficult in the adolescent population, where discomfort with pelvic examination is common and pain can be difficult to interpret8-10. Although PID may be challenging to diagnose in the adolescent female population, these patients represent a high risk group: PID has been shown to be more common in adolescent females, particularly those with early sexual intercourse and lower socioeconomic status 9, 11. The ability to diagnose PID is critical in the pediatric emergency department, which has been shown to be an important source of accessing health care for high risk adolescents, and where lower abdominal pain is a common chief complaint12. In addition to the long term complications of a missed PID diagnosis mentioned above, there are also potential complications with over-diagnosis such as inappropriate antibiotic use and unnecessary health care resource utilization. Because of the dangers involved with both over and under-diagnosis of PID in the adolescent emergency department population, the development of novel methods to improve the accuracy of diagnosis of PID is essential. Over the past decade, the development of RNA based microarray technology has allowed clinicians to contemplate new ways to approach such diagnostic dilemmas. There are preliminary data in several areas including acute infection, inflammatory bowel disease, and childhood cancer which suggest that broad evaluation of the human immune response to disease as measured by RNA expression patterns may correctly identify distinct patient sets 13-17. The array technology collapses a set of signals into a metric for which accurate quantitation and analytic methods have been validated18. Signals that may have been modest individually can be amalgamated into a measurable signature and thus may have superior function diagnostically. It has been established that unique patterns of inflammatory gene expression can be identified in pathologic specimens from different abdominal processes including appendicitis and inflammatory bowel disease 19, 20. Furthermore, it has been suggested that proteomic based strategies might be effective ways of identifying surgical causes of abdominal pain in adolescent females21. The peripheral immune response to organisms associated with PID is much less well studied. However, there are data in animal models which suggest that unique T cell populations are involved in the immune response to Chlamydia trachomatis and Neisseria gonorrhoeae infection 22, 23. More recently, it has been shown that differential peripheral immune responses to Chlamydia trachomatis may predict upper vs. lower genital tract disease24 and also that endometrial inflammation by T, and B cells is associated with Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis infection 4. Further, genetic polymorphisms in Toll-like receptors have been suggested to play a role in Chlamydia trachomatis infection and PID 25. These data suggest that a detailed analysis of gene expression in peripheral leukocytes of adolescent girls with PID may yield important information about the inflammatory response in these patients, and may ultimately lead to the development of novel diagnostic tools. In this study, we compared RNA biosignatures in adolescent female patients with PID to those in healthy control patients.