Findings from this nationally representative sample of US young adults suggest that the vast majority of STD-positive participants (~89%) had concordant self-reports of recent penile/vaginal sex that matched their STD-positive status. At the same time, however, the findings suggest that more than 10% of STD-positive participants had discrepant results. This means they had a positive STD test but reported abstaining from sex in the previous 12 months. It is interesting to note that ~6% of STD-positive participants reported no lifetime history of penile/vaginal sex.
In controlled analyses, it was intriguing that reporting penile/vaginal sex in the previous 12 months increased the odds of testing positive for 1 of 3 STDs by only ~2.1 times. In a logistic regression model, an obtained odds ratio of this magnitude would represent a modest effect. In this case then it can be said the value of young adults' self-report to the prediction of a positive test result was only modest. This counterintuitive finding suggests that sole reliance on young adults' self-reported penile/vaginal sexual activity as a marker for STD acquisition risk may be imprecise and, further, could be problematic. From a national behavioral surveillance perspective, researchers should be cautious about making inferences regarding STD risk among this population on the basis of responses to self-report surveys assessing recent sexual activity.
Although the findings indicate discrepancies between young adults' positive STD status and their self-reported sexual behavior, the use of a disease marker (ie, STDs), although representing an objective and quantifiable marker of sexual behavior, is not without controversy, nor is it a panacea for avoiding bias associated with self-report. With respect to intervention studies, it is important to recognize that reliance on incident STDs as a measure to evaluate the efficacy of an STD/HIV risk-reduction program may not be an appropriate outcome for every study. It is unlikely, for instance, that the incidence of STDs will be changed in a short-term study conducted in a population with little sexual activity or in a community with a low prevalence of STDs. Conversely, populations with a high degree of sexual activity and a high prevalence of STDs are ideal for studying the effects of behavioral interventions on STD incidence. Moreover, studies that incorporate STDs as the primary outcome measure will need to be conducted with sufficiently large samples to provide sufficient statistical power to detect differences in STD incidence.
With respect to observational studies, the use of STDs as a marker of risky sexual behavior may not reflect the true prevalence of risk behaviors in a population. Indeed, being a marker of disease, STD prevalence, observed in cross-sectional studies, or STD incidence observed in longitudinal studies, may represent a marked underestimate of actual sexual risk behaviors (eg, proportion of young adults who are sexually active or frequency of sexual intercourse) in a young adult population. Acquiring an STD is not only a function of unprotected sexual intercourse, but also reflects the prevalence of STDs in young adults' socio-sexual network, risk of sex partners (ie, concurrency), and frequency and proficiency of correct condom use.
The lack of associations regarding discrepancies between STD status and self-reported sexual behavior is striking. Although it may be reasonable to expect that discrepancies in reporting would vary by gender, race, age, or education, this was not observed. In essence, discrepant reporting may be likely among young adults regardless of gender or race. Thus, future research should test novel assessment techniques designed to minimize occurrences of discrepant reporting for diverse populations of young adults.
From a clinical standpoint, the discrepancies between STD positivity and self-reported sexual behavior identified in this nationally representative sample suggest that routine STD screening may be beneficial and necessary to reduce STD morbidity among young adults. In addition, given that no sociodemographic characteristics differentiated young adults with discrepant results (ie, STD-positive but reported no recent penile/vaginal sex) from those without (ie, STD-positive but reported penile/vaginal recent sex), routine screening for common STDs may be useful for all young adults, regardless of self-reported sexual history, race, gender, or age.
The study is not without limitations, and plausible alternative hypotheses that may explain, in part, the finding of discrepancies in having a laboratory-confirmed STD and young adults' self-reported abstinence. Foremost is the absence of a baseline measure of STD status. Specimens were collected only as part of the wave 3 assessment; thus, the STDs identified are “prevalent” STDs, not necessarily incident infections. Also, only urine specimens were collected for STD testing, which generally only detect STDs acquired through penile/vaginal sex, thereby not detecting STDs transmitted through other means of sexual contact (ie, anal sex or oral/genital sex). Although urine tests could capture urethral infections acquired through anal sex among men who have sex with men,19
no information was collected about this behavior. Second is the duration of the time interval from the wave 2 to the wave 3 assessment. The question used to categorize participants into those with sexual experience and those who were abstinent is based on the wave 3 retrospective assessment of young adults' previous 12 months. Thus, given that the time interval between wave 2 and wave 3 assessments is longer than 12 months, coupled with the fact that STD specimens were not collected in wave 2, participants could be accurate and reliable in their reporting of abstinence (over the previous 12 months) at wave 3 and still have an STD because the infection could have been acquired before the 12 month assessment interval, at a time when they may have been sexually active (eg, wave 2). Although studies that report on persistent C trachomatis
infections among women suggest it can persist for more than 1 year if left untreated,20,21
these same studies also report that among asymptomatic women, ~50% of C trachomatis
infections clear within 1 year of infection, and 82% within 2 years of infection. In addition, clearance rates differed by age of first sex, oral contraceptive use, and serotype,21
and none of these studies report on persistence of infection in males, or clearance rates in males. Thus, we have no way to accurately estimate how often persistent infections occurred in this mixed gender sample of young adults. In addition, the accuracy of the STD tests used in the Add Health study is less than perfect, and therefore some false-negatives and false-positives were inevitable. It is difficult to estimate the rate of false-positives as these data were obtained from a nationally representative community-based sample and most available estimates of the sensitivity and specificity of the STD assays are based on clinic samples. However, the false-positive rate (typically computed by subtracting a test's specificity from 1) was likely quite small, as reported specificities for the STD assays used by Add Health are as high as 98.9% to 100% in several studies.22–24
Another limitation is the length of the interval that assessed young adults' sexual behavior. Given the length of the reporting interval, the previous 12 months, young adults' retrospective recall could be inaccurate (they did have sex, but do not recall having sex), making the assessment of sexual behavior unreliable. In this case, the data would still be invalid; however, the source of bias would be attributable to poor recall, not volitional underreporting of sexual behavior, which is also a likely source of bias. Indeed, recent data suggest that shorter recall periods yield more reliable reports of sexual behaviors.25
Poor recall, although plausible, may be more likely among younger adolescents whose sexual behavior is sporadic or episodic rather than older adolescents or young adults who have a greater frequency and regularity of sexual intercourse. Singly, or more likely, a combination of limitations may partly account for the observed discrepancy between young adults' positive STD status and self-reported abstinence.