Previous clinical diagnosis of chlamydia helps patients predict outcome of new chlamydia clinical test

Background: As part of an ongoing clinical trial evaluating the effectiveness of an intervention aimed at decreasing STDs in adolescent females, a host of different background measures were collected at baseline. These measures include self-reported behaviors, risk and probability estimates concerning STDs, self-reported prior medical diagnoses, and a Chlamydia trachomatis (Ct) infection assay, among other measures. This analysis examines participants' accuracy in estimating their own chance of chlamydia infection. Methods: Participants were 131 sexually active adolescent females, 79% black, 13% white, mean age 16 (range 13–19), who had been recruited from an adolescent health service. At the time of this study, participants were not primarily being seen for a clinical visit. Participants answered two questions that are examined here: The first asked, “What is the percent chance that you have chlamydia right now,” accompanied by a visual scale ranging from 0% (no chance) to 100% (certainly). The second question asked, “In your life, have you ever been told by a doctor or nurse that you had chlamydia?” Following all questions a vaginal swab was collected by the participant, which was analyzed by polymerase chain reaction (PCR) for Ct. A multiple regression was performed, predicting the outcome of the chlamydia swab test using participants' estimates that they had chlamydia, their self-reported prior diagnosis with chlamydia (dichotomous), and the interaction between these two variables. Results: The regression F(3, 127) = 10.95, p < .01, revealed that participants' estimates of the chance that they had chlamydia significantly predicted outcome of the clinical test, t(127) = 3.34, p < .01. Previous diagnosis with chlamydia alone did not predict outcome of the clinical test, t(127) = −0.84, ns, but the interaction between the two variables significantly predicted clinical outcome, t(127) = −2.07, p < .05. A previous chlamydia diagnosis made participants' own estimates highly predictive of the clinical outcome; the estimates of those who had never been previously diagnosed with chlamydia had very little predictive power. Conclusions: Those participants who had prior experience with a chlamydia diagnosis were much more able to interpret their own risks and symptoms, and arrive at a very accurate estimate of the chance that they had a chlamydia infection. It is important to note that these participants were not seeking care at the time of this study, but that they had enough information to predict clinical outcome of a chlamydia test, especially those who had been diagnosed with chlamydia in the past. Arguably, these are they very patients who are most at risk for long-term sequelae of chlamydia infection, and asking (or having the patient ask) the relevant questions may increase the likelihood that they are identified and treated promptly, and early in the course of infection.