Most women become sexually active during adolescence, and earlier age at first sexual intercourse is associated with increased STI risk. The US Preventive Services Task Force recommends screening women younger than 25 years for C trachomatis
and N gonorrhoeae,13,26
and the Centers for Disease Control and Prevention suggests annual screening for C trachomatis
for sexually active women within 1 year of first coitus and screening for N gonorrhoeae
for women at increased risk until age 26 years.12
However, neither group has made evidence-based recommendations on the most appropriate starting age and the most appropriate frequency of screening.14
To our knowledge, this research provides the first data on the timing of the initial and subsequent STIs following the onset of sexual activity in a high-risk sample of urban young women. Half of the study participants became infected within 2 years of first sexual intercourse, with C trachomatis
infection detected earlier than N gonorrhoeae
and T vaginalis
.001).Repeated STIs were common, and the time to reinfections usually was very short, especially for C trachomatis
. This is consistent with the results of previous studies supporting relatively early rescreening following an initial STI, especially if the index infection is due to C trachomatis
However, continuing surveillance may be necessary because of the continuing high risk of infection even if the first rescreening test result is negative.
The findings highlight the importance of early STI screening in urban adolescent women, especially considering the minimal harm of screening.28
For example, our data show that 25% of young women will have their first STI within 1 year after first intercourse (). Therefore, if screening starts within 1 year of first intercourse, a great majority (75%) of young women will have the benefit of screening before acquiring their first STI. Alternatively, our data can be used to support the beginning ages of screening in the absence of information about prior sexual activity. For example, 25% of first infections with C trachomatis
, N gonorrhoeae
, and T vaginalis
occur at ages 15, 17, and 17 years, respectively (). Therefore, beginning screening at age 15 years would bring benefit to more than 75% of the young women before acquiring the first infection. Similarly, our data can be used to guide screening frequency. If we wish to screen at a time when no more than 25% of reinfections have occurred with C trachomatis
, N gonorrhoeae
, and Tvaginalis
, our screening intervals would be 3.6, 6, and 4.8 months, respectively (). If the 10th percentile is used, more aggressive screening for these organisms (in 2.4 months) would be needed. Similar rescreening intervals have been suggested for an urban adult population.29
Despite the current guidelines’ dependence on clinical determination of sexual activity, the interval between first sexual intercourse and first STI test was especially prolonged for those with earliest onset of first intercourse. For example, the median delay of the first STI test was almost 5 years after the first coitus for those young women who reported first intercourse at age 10 years. A wide range of factors may have contributed to delayed screening, including vague language of the guidelines, patients’ deferral of appointments, and misperception among some providers that STI risk begins at later ages. Statutory requirement to report underage sexual activities may also discourage risk assessment. Regardless, these data are consistent with findings that physicians fail to obtain sexual history from a large proportion of adolescent patients.30,31
An important implication of these findings is the need for renewed emphasis on training, skills, and incentives to conduct such screenings by those who care for adolescent patients. Quality assurance standards such as the Health Plan Employer Data and Information Set (http://www.ncqa.org/tabid/892/Default.aspx
) can serve as important reminders for screening for sexual activity among young women, although the Health Plan Employer Data and Information Set does not define sexual activity. Within the context of standards for preventive health care for young women, perhaps a more specific and achievable national health objective would be obtaining initial STI screening tests within 12 months of young women’s first sexual intercourse, as our data suggest.
Intervals between first sexual intercourse and first STI appear to be different for the 3 organisms, which to our knowledge, has not been prospectively demonstrated among adolescent women. This differential time to infection could at least in part be explained by the organisms’ respective prevalence rates among the partner population. Previous studies show that young age is associated with increased risk of C trachomatis
infection, while older age is associated with increased risk of T vaginalis
Cervicovaginal tissue immaturity, cervical ectopy, or immunologic naivete are proposed as explanations for age-related differences in C trachomatis
However, the same ordering of STI was seen for each sexual intercourse onset cohort (data not shown). While the issue is beyond the scope of the current article, there may be a need for a closer examination of the transmission risks of these organisms. Whatever the explanation, these data lend more credence to current emphasis on early C trachomatis
screening among young women.
Our study focuses on a sample of urban adolescents at elevated STI risk, characterized by early age at first coitus, multiple sexual partners, and high STI rates. The results may not be readily generalizeable to suburban and rural youths or urban residents of higher socioeconomic status. However, considering that inner-city residents of lower socioeconomic status bear much of the disease burden of STI, such a focus is justified. The research points to the need for future studies to examine the STI time patterns in other groups. Second, the use of STI tests obtained from electronic medical records raises the possibility that some tests were obtained for diagnostic evaluations rather than for routine screening. To the extent that this is true, it would lead to an underestimate of the STI incidence before the study period. Therefore, the actual occurrence of the first STI events following the onset of sex could be sooner than what we reported, thus justifying an even earlier starting age of screening. In this sense, our data represent a potentially more conservative timeline of STI testing events in adolescent women.
Timely screening and treatment of STIs in women, particularly C trachomatis
, decrease the risk of complications resultingfromuntreatedinfection.35
To achieve such a goal, STI screening should begin within a year after first intercourse. Furthermore, because of ongoing high risk for subsequent infection, our study suggests the need for follow-up screening as frequently as every 3 to 4 months. We recognize the many financial and practical barriers to such intensive programs. Nevertheless, screening and treatment efforts based on evidence-based estimates of onset and level of risk will be the mainstay of prevention of STI complications.