Does Digital Vaginal Examination Using Lubricant Have an Impact on Testing for Chlamydia trachomatis by Polymerase Chain Reaction?

Abstract

IN MANY CLINICAL SITUATIONS, it is convenient and efficient for the healthcare provider to perform a bimanual pelvic examination before a vaginal speculum examination, and more comfortable for the patient. These situations include uterine sizing and cervical evaluation before outpatient dilation and curettage as well as cervical examination of pregnant patients evaluated for preterm labor for rapid assessment and triage. Some practitioners also use vaginal lubricants on the blades of a speculum to decrease patient discomfort. There is concern, however, that these lubricants may interfere with the sensitivity of vaginal and cervical microbiologic testing. Part of this concern presumably arises from the active ingredient in bacteriostatic gel: a 0.25% concentration of chlorhexidine, which is a substance used for its antimicrobial properties. The performance of any diagnostic test relies on adequate sample collection. Excess cervical mucus and blood, for example, may interfere with adequate endocervical sampling for Chlamydia trachomatis.1 Sensitivity of culture and antigen detection tests for chlamydia is greatly affected by specimen adequacy. Chlamydia testing using polymerase chain reaction (PCR) does not require viable organisms, so it was believed that specimen adequacy would be less critical in testing by PCR. However, one study demonstrated a 75% reduction in the sensitivity of chlamydia PCR testing performed on inadequate versus adequate endocervical samples.2 The use of a lubricant before specimen collection could affect the ability to obtain an adequate sample by decreasing the absorbency of the swab, diluting the number of organisms in the sample, or directly inhibiting the PCR assay. Because no data is currently available regarding the effect of lubricants on STD testing, this study was designed to investigate the impact a lubricant containing no chlorhexidine may have on C trachomatis PCR testing. From January 1997 to May 1998, women at least 18 years of age with positive test results for chlamydia on routine screening by PCR testing (Amplicor C trachomatis test; Roche Diagnostics, Branchburg, NJ) who had not yet been treated were recruited for participation in this study approved by the institution review board. Nonpregnant women attending the Magee-Womens Hospital Emergency Department and Ambulatory Care Clinics were eligible to enroll. Exclusion criteria involved use of an antibiotic or spermicide within 3 weeks of the original positive PCR test and previous hysterectomy. After informed consent was obtained, a sterile unlubricated vaginal speculum was placed in the vagina. A Dacron swab was inserted into the endocervix, rotated for 10 seconds, and placed in PCR transport media. The speculum then was removed, and the entire contents of a 3-g package of sterile water-soluble lubricating jelly containing no chlorhexidine were placed on a gloved hand for bimanual examination of the pelvic organs (Operand, Prichard, WV). The unlubricated speculum was then reinserted, and a second endocervical sample was collected for chlamydia PCR testing in the same fashion. The chlamydia PCR assay was performed according to the manufacturer’s recommendation (Amplicor C trachomatis test; Roche Diagnostics). All the patients were treated The authors thank Marijane A. Krohn, PHD for statistical assistance. Supported by the Irene McLenahan Young Investigator Research Award, Magee-Womens Hospital, Pittsburgh, Pennsylvania. Received for publication August 29, 2000, revised June 28, 2001, and accepted July 17, 2001. From the Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine and Magee-Womens Research Institute, Pittsburgh, Pennsylvania