Reliability of self-reported contraceptive use and sexual behaviors among adolescent girls.

Self-report data on contraceptive use and sexual behavior are used to identify adolescents at risk for unintended pregnancy and sexually transmitted diseases (STDs) and to evaluate programs aimed at preventing these outcomes. The most efficient, feasible and commonly used approach to studying sexual behaviors is self-reported recall of those behaviors over some time frame. Errors in self-report can bias prevalence estimates of high-risk behaviors and thus lead to misclassification of individuals at risk, thereby hampering prevention efforts. Important intervention components may be overlooked or overemphasized in situations where measurement error leads to biased estimates of relationships between variables (Catania, Chitwood, Gibson & Coates, 1990). Thus, minimizing error related to the measurement of contraceptive and sexual behaviors is of interest to both adolescent health service providers and researchers.

Many questions related to adolescents' self-reported sexual behaviors and contraceptive use remain unanswered. For example, it is unclear what time intervals adolescents can recall in a reliable fashion (e.g., 3-month period, 6-month period) and whether using partner-specific assessments decreases bias in reporting of sexual and contraceptive behaviors over a given time interval.

Measurement error related to self-reports may stem from respondents themselves or measurement instruments used. Respondent variables that influence the task of providing information include those related to memory and recall (Catania, 1999). The length of the recall period may influence the consistency and accuracy of respondents' reports (Catania et al., 1990). Adolescents may base short-term reports on counts of recent events, but they may use estimation to recall over longer periods of time (McFarlane & St. Lawrence, 1999). Although research consistently documents that reliability of reported sexual behaviors decreases with increasing duration of recall period (Catania et al., 1990; Kauth, St. Lawrence, & Kelly, 1991), few studies have explicitly compared reliability of teenagers' self-reports using short and longer-term recall periods (for an exception, see McFarlane & St. Lawrence, 1999).

The frequency of behaviors being assessed may also influence the consistency and accuracy of adolescents' reports. A study with 12- to 19-year-olds (McFarlane & St. Lawrence, 1999) showed that estimates of yearly behavior based on 2-week, 2-month, or 12-month recall periods produced discrepant conclusions about adolescents' sexual activity. In this study, discrepancies between recall periods were larger with estimates of relatively frequent behaviors, such as condom-protected sexual intercourse, than with infrequent behaviors, such as unprotected oral and anal sex.

Complex patterns of sexual activity may also influence adolescents' ability to recall behavior. For example, individuals in monogamous relationships with a routine pattern of sexual activity may give highly reliable estimates, but adolescents with more complex sexual patterns (e.g., multiple sexual partners and contraceptive use patterns that vary between partners) may have more difficulty in providing overall behavioral estimates. It is assumed that partner-by-partner estimates simplify respondents' task and thus improve the consistency and accuracy of reports, but few studies have examined consistency between adolescents' partner-based estimates and temporal estimates of sexual and contraceptive behavior (Catania et al., 1990).

Another respondent variable that may influence self-reports of sexual activity relates to self-presentation. Fear of reprisal, social desirability, and other personal factors may bias adolescents' reports of sexual behavior. Young people who fear reprisal may under-report sexual activity, or others who want to project an adult image may overestimate sexual activity. Adolescents who seek approval of health care providers may over-report their contraceptive use (Catania, 1999; McFarlane & St. Lawrence, 1999; Shew et al., 1997). Sex and ethnic affiliation may influence self-presentation since sexual norms and values can vary between genders and ethnic groups. Data from a nationwide sample of sexually experienced teens (Upchurch, Lillard, Aneshensel, & Fang, 2002) showed that girls were less inconsistent than boys in reports of their sexual behaviors; however, patterns of response inconsistency did not differ between teens from different racial and ethnic groups. Several studies suggest that self-presentation bias can be minimized under conditions that allow more privacy than face-to-face interviewing typically permits, such as self-administered questionnaires and computer-assisted surveys (Romer et al., 1997; Turner, Lessler, & Devore, 1992; Turner et al., 1998).

Instrument variables, including question order, question structure and terminology, may also influence the task of providing information about sexual behavior. It is commonly assumed that more sensitive questions should be asked later in a survey; respondents become gradually desensitized to more intimate items. Another consideration in ordering questions is that respondents may lose interest in answering questions over the course of time, leading to greater measurement error at the end of long surveys. Self-administered questionnaires and computer-assisted surveys that allow respondents to pace themselves, as well as interview methods tailored to individuals' sexual histories, may be less susceptible to order effects than traditional interview methods (Catania et al., 1990; Hearn, O'Sullivan, & Dudley, 2003). Survey instruments that provide detailed explanations of sexual terms and frame sexual questions using non-judgmental and developmentally appropriate wording may also help minimize self-report bias (Catania et al., 1990; Hearn et al., 2003; Romer et al., 1997). Pretesting an instrument with members of a target population--in which the focus is on respondents' perceptions of the questions and the tasks of survey completion--provides valuable information on appropriate survey length, acceptability of question order and structure, and understanding of sexual terms employed (Romer et al., 1997).

The current study was undertaken to develop evaluation measures for Prime Time, a multi-component intervention study to increase the consistency of contraceptive use and reduce sexual risk behaviors among sexually active adolescent girls (Sieving et al., 2003). The overall goal of the current study was to examine the reliability of responses to questions about sexual behavior and contraceptive use using two frames: a temporal referent and a partner-specific referent. The current study addressed two core research questions:

1. How reliable are adolescent girls' self-reports of contraceptive use using partner-referent questions and time-referent questions within the same survey? To address this question, we compared measures of contraceptive use based on adolescents' partner-specific reports with their reports of contraceptive use over the past 3 months and their reports of contraceptive use over the past 6 months. We also compared reliability of 3- and 6-month time referent questions. Given that adolescent sexual behavior can be episodic, we assumed that self-reports using longer recall period, and thus a more comprehensive picture of adolescent sexual experience, may be justified if such reports were highly reliable.

2. What is the test-retest reliability of self-reported contraceptive use and sexual behaviors as measured twice over a 1- to 2-week period? To address this question, we analyzed the consistency of responses over time for both partner-referent and time-referent measures.

METHOD

Design and Participants

Data for this study were from a sample of 13- to 18-year-old girls seeking reproductive health care services at six school- and community-based adolescent clinics in the Minneapolis-St. Paul metropolitan area. Clinic staff identified 274 potential participants based on study eligibility criteria (e.g., ages 13-18, seeking reproductive health services, English-speaking). Research staff invited all girls who met eligibility criteria to participate in the study. Girls were informed about the study and were told that participation would involve completing one or two paper-and-pencil surveys that included questions about their first sexual experience, along with their recent sexual behavior and contraceptive use patterns. In accordance with Minnesota's 1971 Medical Bill for Minors Act, which gives youth under the age of 18 the right to seek confidential reproductive services, girls who agreed to participate in the study (n = 225; 82% of girls invited) provided their own written consent for study participation. After providing written consent for study participation, participants completed a paper-and-pencil survey (T1 survey) which took an average of 20 minutes to complete. Participants were paid $10 to complete the T1 survey. Of 225 study participants, 196 (87.1%) reported having had consensual vaginal intercourse in the previous 6 months on the T1 survey. These 196 participants comprise the baseline sample for this study.

All participants who reported having vaginal sex in the past 6 months were classified as sexually active and invited to return to the clinic in 1 to 2 weeks to complete a second identical survey (T2 survey). Girls were offered $20 to complete the T2 survey. Of 196 eligible participants, 156 (79.6%) completed the T2 survey. Of those completing T2 surveys, three participants (1.9%) included information on new sexual partners between surveys, and one participant (0.6%) reported not having sex in the past six months on the T2 survey; data from these youth were excluded from follow-up analyses. The remaining 152 participants comprise the follow-up sample for this study. For this sample, the mean interval between T1 and T2 surveys was 9.5 days.

All study protocols were reviewed and approved by the Institutional Review Board at the University of Minnesota.

Instrument and Measures

T1 and T2 survey instruments included identical questions about timing of sexual intercourse, sexual partners and sexual relationships, and contraceptive use. Some of the questions were derived specifically for this study, and others were derived from previous studies of youth sexual behavior and contraceptive use (Brindis, Peterson, Card & Eisen, 1996; Sieving et al., 1997; Sieving et al., 2001). Questions were asked in sequential survey sections referring to the last 3 months, the last 6 months, and recent sexual partners (up to 3 partners). The T1 survey included additional questions about participants' age, ethnic background, lifetime pregnancy history, education and current living situation. Survey instruments are available from the corresponding author upon request.

To maximize the reliability and validity of self-report measures, we incorporated several methodologic recommendations (Catania et al., 1990) into instrument development. First, we wrote survey questions using a combination of standard and familiar sexual terms. For example, throughout the instrument "sex" was defined as "a male's penis inside your vagina." Participants were asked to exclude experiences of rape, sexual assault, and same-sex intercourse in answering survey questions. "Sex partner" was consistently defined as "male you had sex with"; for example, with questions related to last male sex partner, participants were asked to "think about the last male you had sex with (his penis in your vagina)." "Birth control" was defined by a list of contraceptive methods including condoms, spermicidal foam or film, diaphragm, oral contraceptive pills (OCPs; "birth control pills"), depot medroxyprogesterone acetate (DMPA; Depo-Provera; "the Depo-Provera shot"), and levonorgestrel implants ("Norplant"). The majority of survey questions about contraception focused specifically on OCR DMPA, and condom use because these methods are commonly used by adolescents and are considered effective in reducing pregnancy risk. Second, anchor dates were used for reporting periods in order to improve recall of behavior. Third, the instrument was pilot tested with 2 focus groups of adolescent girls (n = 16 teens). Focus group respondents indicated that they understood survey terminology and that both the content of questions and the mode of survey administration were acceptable to girls their age.

Time-Referent Items. In an initial section of the survey, participants answered a series of questions about number of sexual partners, level of condom use, duration of OCP use and duration of DMPA use referring to the preceding 6 months. In the next survey section, participants were asked the same series of questions referring to the preceding 3 months. The following is an example of the format used in these sections: "In the last 3 months, how often did you use condoms when you had sex?" (response options: Never, Less than half the time, About half the time, More than half the time, Always).

Partner-Referent Items. After completing survey sections using temporal references, participants were asked a third series of questions referring to specific sexual partners. Participants were asked to respond to questions for each of up to 3 most recent male sexual partners over the past 6 months. For each partner, participants were asked questions about first and most recent sexual intercourse, partner age, characteristics of the relationship, interval between first sex and first contraceptive use, dual method contraceptive use practices, level of alcohol or other drug use in combination with sex, and reasons for not using contraception. The partner-specific questions included a 6-month contraceptive calendar that asked participants to indicate, by month, whether they had sex with this partner, whether they used OCPs or DMPA, and the level of condom use with this partner. Participants' monthly reports of condom use were grouped into one of 3 categories: "E" responses = always used condoms; "M" and "S" responses = sometimes used condoms; No response = never used condoms.

For purposes of comparing partner-referent and time-referent reports, we created composite measures of contraceptive use based on calendar reports. Initially, we completed month-by-month counts of various forms of contraceptive use (e.g., DMPA, OCP, condom use) using calendar reports. For condom use counts, numeric values were assigned according to above-mentioned categories (1 = always used condoms; 0.5 = sometimes used condoms; 0 = never used condoms). For a count of "any birth control method," numeric values were assigned to each month (1 = used hormonal method or always used condoms; 0.5 = did not use hormonal method and sometimes used condoms; 0 = did not use hormonal method and did not use condoms). For each form of contraceptive use, monthly counts were summed; a proportion was created by dividing this sum by the number of months the participant reported having vaginal intercourse. To compare with time-referent reports, proportions were grouped into 5 categories: Never used this method of contraception, Used this method less than half the time (proportions with values of 0.1-0.3), Used this method about half the time (proportions with values of 0.4-0.6), Used this method more than half the time (proportions with values of 0.7-0.99), Always used this method (proportions = 1.0).

For participants who completed contraceptive calendars for 2 or 3 sexual partners (32.7% of follow-up sample), the partner-specific condom use measure and "any birth control use" measure combined information from partners in months when the participant reported having intercourse with more than one partner. For example, if a participant reported having sex with Partner A and Partner B in the month of January, always using condoms with Partner A and never using condoms with Partner B in that month, we classified January as a "sometimes" condom use month (the average of "always" condom use with Partner A and "never" condom use with Partner B).

Procedure

We administered all surveys in clinic settings, with participants completing the T1 survey at the time of their clinic appointments. To maximize the validity and reliability of participants' self-reports (Catania et al., 1990; Weinhardt et al., 1998), trained research staff introduced the survey to each participant using a standardized, nonjudgmental explanation of the purpose of the survey. Research staff reviewed definitions of "sex" and "birth control," anchor dates, item reporting periods, and sexual partner calendars with each participant prior to administering the survey. Participants were assured that their survey responses would remain confidential, that they could choose not to answer questions that made them uncomfortable, and that participation would in no way affect their clinical care. To maximize privacy during survey administration, participants completed surveys in private rooms outside of public waiting areas.

We followed identical procedures during administration of the T2 survey. For the T2 survey, research staff specifically instructed participants not to report on behaviors or new relationships that had occurred since the administration of the first survey.

Data Analysis

To address Research Question 1, we examined within-survey consistency between categorical time-referent measures and partner-referent measures of contraceptive use. We used T2 survey data from the follow-up sample for these analyses, so results for the within-survey and between-survey analyses are comparable. We restricted these analyses to participants who reported 3 or fewer sex partners in the past 6 months. Parallel analyses were completed comparing partner-referent measures to 3-month referent measures and to 6-month referent measures. We used a weighted kappa statistic to assess within-survey reliability (Rosner, 1990). Compared to an unweighted kappa statistic, a weighted kappa statistic allows for some error in grouping into categories. A kappa value of 0.0 suggests that the amount of agreement between categorical measures is what would be expected by chance alone; a kappa value of 1.0 suggests perfect agreement between categorical measures. Using established guidelines (Landis & Koch, 1977), we interpreted kappa values of 0.01-0.20 to indicate slight agreement between measures; kappa values of 0.21-0.40 to indicate fair agreement; kappa values of 0.41-0.60 to indicate moderate agreement; kappa values of 0.61-0.80 to indicate substantial agreement; and kappa values of 0.81-0.99 to indicate almost perfect agreement between measures.

To address Research Question 2, we examined consistency of contraceptive use and sexual behavior measures as reported at two points over a 1- to 2-week interval. T1 and T2 survey data from the follow-up sample were used for these analyses. We examined consistency over time of both temporal and partner-referent measures. For categorical measures, we assessed consistency using an unweighted kappa statistic, because comparison categories were identical across surveys. For continuous measures, we assessed consistency using Pearson's correlation coefficient and a percent matching statistic (Rosner, 1990). Percent matching refers to the percentage of participants whose T1 survey responses match exactly with their T2 survey responses. Since this measure takes only identical responses into account, it is a more conservative measure of reliability than a correlation coefficient, which takes into account similar response patterns across surveys (Rosner, 1990).

RESULTS

Description of Samples

Descriptive characteristics of baseline and follow-up samples are listed in Table 1. Chi-square analyses (not shown) were used to compare participants who did and did not return for T2 surveys on these descriptive statistics. As compared to participants who only completed baseline surveys, a significantly lower percentage of the follow-up sample reported having dropped out of school. There were no other statistically significant differences in demographic characteristics or lifetime sexual history measures between these two groups of participants.

The median age at which follow-up sample participants first had vaginal intercourse was 15.0 years. Approximately 81.5% of this sample reported that they or their partner used some form of contraception at first intercourse. Almost 35% of this sample reported having one lifetime vaginal sex partner, and 37.5% reported having four or more lifetime sexual partners.

Recent patterns of sexual relationships and contraceptive use among the follow-up sample are listed in Table 2. Approximately one third of this sample (32.5%) reported having more than one sexual partner over the past 6 months. In terms of timing of first sexual intercourse in a relationship, one quarter of this sample (24.7%) was either dating for less than a week or not in a dating relationship when they first had vaginal intercourse with their most recent sexual partner. Only 26.3% of this sample reported using a condom every time they had sex in the past six months. Approximately one third of this sample (33.5%) reported using OCPs during the past 6 months. Patterns of OCP use suggest substantial risk for pregnancy and STDs. Of OCP users, one third (33.3%) missed pills on more than one occasion in the past 6 months, and fewer than 1 in 5 (16.65%) always used condoms while taking OCPs. Of this sample, 11.8% used DMPA over the previous 6-month period. Participants using DMPA were less likely than other participants to use barrier contraception. Around 55.5% of DMPA users reported never using condoms while on DMPA, compared to 21.1% of the full sample.

Within-Survey Comparisons

Data from T2 surveys of the follow-up sample were used to examine consistency between time- and partner-referent measures of contraceptive use. Partner-referent measures were compared to both 3-month and 6-month time-referent measures. As listed in Table 3, weighted kappa statistics indicate substantial to high levels of agreement between time- and partner-referent reports. Discrepancies between time- and partner-referent measures are somewhat greater for questions about condom use than for questions about hormonal contraceptive use.

For each method, the consistency of respondents' recall was similar using 3- and 6-month reference points. For example, the consistency between time- and partner-referent measures of OCP use over a 3-month recall period was k = 0.86; consistency of these measures over a 6-month period was k = 0.84. Thus, a 6-month recall period did not appear to create more inconsistency between time- and partner-referent reports than a 3-month recall period.

Test-Retest Comparisons

In a second set of reliability analyses, data from the follow-up sample were used to examine consistency between T1 and T2 survey responses to questions regarding recent sexual activity and contraceptive use.

Consistency of Time-Referent Items. As listed in Table 4, participants' responses to time-referent measures were generally consistent across T1 and T2 surveys. High levels of consistency were seen with both 3- and 6-month measures. For example, kappa statistics associated with duration of OCP use were 0.85 and 0.88 for 3- and 6-month questions, respectively, indicating that participants were likely to report the same duration of OCP use when asked about use on two occasions 1 to 2 weeks apart.

Two exceptions to the pattern of high-level consistency across time are shown in Table 4. First, participants' estimates of the frequency of their sexual intercourse over the past 3 or 6 months were not consistent. Although the Pearson's correlation coefficients indicate strong associations between baseline and follow-up reports (e.g., girls who report having sex relatively frequently at baseline will also report high frequency at follow-up), the low percent matching suggests girls' frequency point estimate varied between surveys. Second, reports of number of occasions in which OCPs were missed over the past 6 months were only moderately consistent over time. Thus, memory of missing pills appears to be less consistent using a 6-month, compared to a 3-month, retrospective reporting period.

Consistency of Partner-Referent Items. We conducted a separate analysis to assess consistency of partner-referent measures over time. This analysis used data from participants' contraceptive calendars; it included 148 participants from the follow-up sample who completed partner-specific calendars on both T1 and T2 surveys. Results indicated substantial agreement between baseline and follow-up calendar reports. A T1-T2 comparison of month-by-month calendar reports revealed highly consistent reports of whether dyads had sex, used condoms, and were protected by OCPs or DMPA in each of six months included in the calendar. Specifically, unweighted kappa statistics for monthly profiles, including information on whether participant had sex, used condoms, and used hormonal methods during that month, ranged from 0.75 to 0.82. The unweighted kappa statistic estimating consistency of overall calendar reports between TI and T2 was 0.89.

DISCUSSION

This study demonstrates the reliability of self-reported measures of sexual behavior and contraceptive use among adolescent girls who have had vaginal intercourse in the past 6 months. Several findings are notable. Related to Research Question 1, the consistency between time-referent and partner-referent methods of measuring contraceptive use was substantial. An interesting pattern emerged from this comparison: the consistency between time-referent estimates and partner-referent estimates was lower with condom use than with hormonal contraceptive use. Thus, time-referent reports were less likely to match partner-referent reports when measuring contraceptive behaviors that are partner-dependent (e.g., condom use) than when measuring behaviors that are partner-independent (e.g., OCP use, DMPA). Although earlier research suggests that partner-by-partner estimates may enhance respondents' recall ability (Catania et al., 1990), findings from this study suggest that partner-specific reporting methods may be useful in assessing contraceptive use behaviors that depend on a male partner (Grimley, Prochaska, Velicer, & Prochaska, 1995).

Regarding Research Question 2, test-retest consistency of contraceptive use and sexual behavior measures was high. Test-retest results indicated that adolescent girls respond to questions in these domains in a consistent fashion over a 1- to 2-week interval. Both partner- and time-referent measures produced stable estimates of behavior over time. For time-referent measures, high levels of consistency were evident with both 3- and 6-month measures. One exception was participants' exact responses to questions about frequency of intercourse, which varied over time. It is not surprising that participants did not report the exact same frequency of intercourse across surveys, nor is it necessarily of programmatic or clinical significance. Higher reliability may be obtained by asking participants to choose from meaningful response categories (e.g., once, less than once a month, I-3 times per month, more than 3 times per month) rather than to provide an exact number.

A discrepancy occurred in one pair of temporal stability estimates. Although the percent matching statistic associated with the measure of sexual partners in the past 3 months (86%) indicated relatively high levels of test-retest consistency, the Pearson's correlation coefficient is lower (r = 0.69). Due to the restricted range of item responses in this sample (e.g., at T2, 91% reported 1 or 2 sexual partners in past 3 months), the correlation coefficient may have underestimated the temporal stability of this measure (Howell, 1987; Sieving et al., 2001).

Findings from this study expand our understanding of the range of sexual behaviors that urban adolescent girls are able to report with high reliability. Previous studies with 12- to 14-year-old girls (Hearn et al., 2003) and 15to 18-year-old girls (Hornberger, Rosenthal, Biro, & Stanberry, 1995) suggest that adolescent girls are highly reliable in reporting age at first sexual and romantic milestone experiences (e.g., age first in love, age first touched a penis, age at first intercourse). Measuring recent sexual experience, Shew et al. (1997) found that 13- to 21-yearold girls' self-reports of condom use with up to 2 most recent male sexual partners was highly consistent with their verbal reports to clinicians. In addition to consistent reports of recent condom use, our findings suggest that sexually experienced 13- to 18-year-old girls can provide reliable reports of number of sexual partners and duration of hormonal contraceptive use in the past 6 months.

Our findings regarding consistency of participants' recall over recent time periods extend those of McFarlane and St. Lawrence (1999), who found that 12- to 19-year-olds provided consistent estimates of sexual behavior over time using a 2-month recall period. Comparing reliability of 3- and 6-month reports, our findings suggest that 13- to 18-year-old girls report contraceptive use patterns with equal consistency over these retrospective recall periods, with the exception of higher consistency in reports of missed OCPs in the past 3 months than in the past 6 months. Thus, a 6-month referent may be more likely than a 3-month referent to capture behaviors that are episodic in nature, and therefore may provide a more accurate picture of sexually active adolescents' behavior over time (McFarlane & St. Lawrence, 1999).

This study has several limitations. Although a 1- to 2-week period between T1 and T2 surveys minimizes the likelihood of retest response inconsistencies due to actual changes in sexual and contraceptive behaviors, this retest interval may inflate reliability estimates due to memory of responses from T1 surveys. A 1- to 2-week interval has been used with other psychometric studies of self-reported behavior among adolescents (Brener et al., 2002; Romer et al., 1997; Williams, Toomey, McGovern, Wagenaar, & Perry, 1995).

Second, although this study tests the reliability of self-reported contraceptive use and sexual behaviors among sexually active adolescent girls, we do not examine the validity of these self-reports. Without the availability of a gold standard, it is impossible to conclude whether any of the three measurement methods produces valid indicators of sexual behavior or contraceptive use (Carmines & Zeller, 1979). This study's measures should be used with an awareness of previous research suggesting that adolescent girls may over-report OCP use (Potter, Oakley, Leon-Wong, & Canamar, 1996) as well as condom use with casual sexual partners (Jeannin, Konings, Dubois-Arber, Landert, & Van Melle, 1998). To establish validity of adolescent girls' retrospective self-reports, further research is needed comparing daily self-monitoring data to retrospective reports of sexual behaviors and contraceptive use. Third, for practical reasons, response options to categorize condom use differed in time-referent and partner-referent sections of the survey. Although we created a measure to compare these items, the statistical tests of reliability between time- and partner-referent measures may have been attenuated because of the differences in response options. Fourth, this study was conducted with a sample of sexually active adolescent girls seeking reproductive care in urban clinic settings. Thus, findings may not be generalizable to other populations. Additional studies need to be conducted to assess the reliability of these measures with normative and high-risk populations living in rural, suburban and urban settings.

In summary, survey items and data collection methods used in this study appeared to be understandable and acceptable to the target group of sexually active adolescent girls. With the exception of frequency of intercourse, girls were able to recall their sexual and contraceptive behaviors over as long as a 6-month interval in a consistent fashion. Although recall of condom use differs somewhat using time- and partner-referent reporting methods, our data suggest that sexually active adolescent girls respond reliably to both referents.

Table 1. Demographic & Lifetime Sexual History Descriptors, Baseline
(n = 196) and Follow-Up (n = 152) Samples

                                     Baseline Sample   Follow-up Sample

Current age
  13-14 years old                       6    (3.1%)        6    (4.0%)
  15-16 years old                      64   (32.6%)       47   (30.9%)
  17-18 years old                     126   (64.3%)       99   (65.1%)
School status (1)
  In middle/high school               155   (79.1%)      123   (80.9%)
  Completed high school               128   (14.3%)       22   (14.5%)
  Dropped out of school                 7    (3.6%)        2    (1.3%)
  Unknown                               6    (3.1%)        5    (3.3%)
Reasons for clinic visit
  Pelvic exam                          89   (45.4%)       69   (45.3%)
  Contraception                       128   (65.3%)       94   (61.8%)
  STD test                             69   (35.2%)       54   (35.5%)
  Pregnancy test                        8    (4.1%)        7    (4.6%)
  Other/Unknown                        16    (8.2%)       13    (8.6%)
Race/ethnic background (2)
  Caucasian                           161   (82.1%)      122   (80.3%)
  African American                     25   (12.8%)       23   (15.1%)
  Hispanic/Latina                      12    (6.1%)       11    (7.2%)
  American Indian                      10    (5.1%)        7    (4.6%)
  Asian                                 8    (4.1%)        7    (4.6%)
  Other                                 7    (3.6%)        5    (3.3%)
Age at first vaginal intercourse
  [less than or equal to] 14 year s    67   (34.2%)       51   (33.5%)
  15-16 years                          94   (48.0%)       74   (48.7%)
  17-18 years                          34   (17.3%)       27   (17.8%)
  Unknown                               1    (0.5%)        0    (0.0%)
Contraceptive use at first sex
  Yes                                 155   (79.1%)      123   (81.5%)
  No                                   41   (20.9%)       28   (18.5%)
Lifetime vaginal sex partners
  1                                    62   (31.6%)       53   (34.9%)
  2                                    36   (18.4%)       26   (17.1%)
  3                                    18    (9.2%)       14    (9.2%)
  4 or more                            78   (39.8%)       57   (37.5%)
  Unknown                               2    (1.0%)        2    (1.3%)

(1) Significantly different frequency distribution
([[chi square].sub.3df] = 10.07; p = 0.02) between participants who
completed baseline surveys only and follow-up sample.

(2) Column totals > 100%, since participants were asked to mark all
applicable race/ethnic groups.

Table 2. Recent Patterns of Sexual Activity and
Contraceptive Use, Follow-Up Sample (n = 152)

Number of vaginal sex partners, past six months
  1                                               67.5%
  2                                               17.2%
  3                                                7.3%
  4 or more                                        8.0%
Relationship with most recent sexual
    partner at the time of first sex
  Dating for > 1 month                            46.6%
  Dating for 1 week-1 month                       28.7%
  Dating for < 1 week                             11.4%
  Not in a dating relationship                    13.3%
Closest relationship with most recent
    sexual partner
  Living together                                  4.0%
  Planning to get married                         17.2%
  Monogamous dating relationship                  54.3%
  Dating each other and other people              12.6%
  Not in a dating relationship                    10.6%
  Other                                            1.3%
Consistency of contraceptive use, past
    six months
  Always used                                     55.9%
  More than half the time                         17.8%
  Half the time or less                           17.8%
  Never used                                       8.5%
Consistency of condom use, past six months
  Always used                                     26.3%
  More than half the time                         18.4%
  Half the time or less                           34.2%
  Never used                                      21.1%
Duration of OCP use, past six months
  4-6 months                                      28.9%
  3 months or less                                 6.6%
  Did not use OCPs                                64.5%
Number of times missed OCPs, past six
    months (among n = 54 reporting OCP use)
  Never                                           24.1%
  One time                                        42.6%
  More than one time                              33.3%
Combined condom and OCP use, past six months
    (among n = 54 reporting OCP use)
  Always                                         16.65%
  More than half the time                        16.65%
  Half the time or less                           38.9%
  Never                                           27.8%
Duration of DMPA use, past six months
  More than 3 months (2 shots)                     9.2%
  3 months or less (1 shot)                        2.6%
  Did not use DMPA                                88.2%
Combined condom and DMPA use, past six months
    (among n = 18 reporting DMPA use)
  Always                                          16.7%
  Half the time or less                           27.8%
  Never                                           55.5%

Table 3. Consistency between Partner-Referent and Time-Referent
Measures, Follow-Up Sample (1)

                                       Past 3 months   Past 6 months
                                       (n = 134) (2)   (n = 137) (3)

Duration (# months) OCP use                 0.86            0.84
Duration (#months) DMPA use                 0.94            0.93
Level of condom use (4,5)                   0.66            0.74
Level of any birth control use (4,6)        0.68            0.69

(1) Consistency between measures estimated using weighted kappa
statistic (all measures were categorical).

(2) Follow-up sample (n = 152) minus participants who did not report
sex in past 3 months on partner-specific survey items (n = 7) and
participants who reported having more than 3 sexual partners in past
6 months (n = 11).

(3) Follow-up sample (n = 152) minus participants who did not report
having sex in past 6 months on partner-specific survey items (n = 4)
and participants who reported having more than 3 sexual partners in
past 6 months (n = 11).

(4) Level of use classified into five categories ranging from 1
(Never) to 5 (Always).

(5) Partner-referent measure of condom use is a proportion based on
calendar counts of number of months using condoms divided by number
of months sexually active. When a participant reported 2 partners in
a month, condom use for that month was estimated by averaging reports
of condom use with each partner.

(6) Partner-referent measure a proportion based on calendar counts
of number of months using birth control divided by number of months
sexually active. When a participant reported 2 partners in a month,
birth control use for that month was estimated using reported
hormonal use in that month and an average of reported condom use with
each partner.

Table 4. Test-Retest Consistency of Time-Referent Measures,
Follow-Up Sample (n = 152)

                                  Past 3 months     Past 6 months

Continuous Measures (1)
  Number of sexual partners      0.86 (r = 0.69)   0.82 (r = 0.82)
  Frequency of intercourse       0.53 (r = 0.96)   0.48 (r = 0.86)
Categorical Measures (2)
  Duration (# months) OCP use         0.85              0.88
  Number of times missed OCPs         0.75              0.60
  Duration (# months) DMPA use        0.90              0.87
  Delayed DMPA injection              1.0               1.0
  Level of condom use (3)             0.85              0.80
  Level of any birth control
    use (3)                           0.77              0.82

(1) Consistency estimated using percent matching and Pearson's
correlation coefficient (r).

(2) Consistency estimated using unweighted kappa statistic.

(3) Level of use classified into five categories ranging from 1
(Never) to 5 (Always).

This study was supported by grant #U48/CCU513331, the National Teen Pregnancy Prevention Research Center, from the Centers for Disease Control and Prevention.

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Manuscript accepted October 5, 2004

R. Sieving, W. Hellerstedt, C. McNeely, R. Fee, J. Snyder, and M. Resnick

University of Minnesota

Address correspondence to Renee Sieving, Ph.D., RNC, University of Minnesota School of Nursing, 5-160 Weaver-Densford Hall, 308 Harvard Street S.E., Minneapolis, MN, 55455; e-mail: [e-mail].