Agreement between oral contraceptive users and prescribers: implications for case-control studies

A comparison of self-reported oral contraceptive use and automated pharmacy data in perimenopausal and early postmenopausal women

PURPOSE

Oral contraceptive (OC) use can occur throughout a woman's reproductive life span with the potential for long-term impacts on health. To assess potential measurement error in prior OC use, this study compared level of agreement between self-reported prior OC use and pharmacy dispensing data in perimenopausal and/or early postmenopausal women.

METHODS

The study's 1399 women (ages, 45-59 years) were participants in a population-based case-control study of the association between OC use and fracture risk. Episodes of lifetime self-reported OC use (in months) were collected, by telephone interview, for January 1, 2008 through November 25, 2012. Pharmacy fills, back to 1980, were collected from automated data. Agreement was measured using the prevalence-adjusted and bias-adjusted kappa index.

RESULTS

The number of women with OC pharmacy fills was 11% to 45% higher than those who reported OC use during each time period. Between-measures agreement was better for more recent use. Prevalence-adjusted and bias-adjusted kappa index values ranged from 0.88 (95% confidence interval, 0.85-0.90) within 5 years from the reference date to 0.65 (95% confidence interval, 0.59-0.71) within 15 to 20 years.

CONCLUSIONS

For studies designed to assess the long-term effects of OC use, the current results are reassuring in noting moderate agreement between self-reported OC use and pharmacy data for up to 15 to 20 years before the interview.

Agreement between patient-reported and provider-reported choice of contraceptive method among family planning patients in New York City: implications for public health

National data on choice of contraceptive method and subsequent use are critical for monitoring progress toward meeting public health goals in reducing unintended pregnancy in the US. Yet few studies have focused on the reliability of clinically-reported or patient-reported measures of choice of contraceptive method for the range of available contraceptive methods. Among 1,844 women receiving reproductive health care at two federally funded centers in New York City, choice of contraceptive method at the end of the visit from two data sources was compared, ie, patient self-report, and provider-report as recorded in the clinical-administrative database. Agreement between the two data sources was assessed for the sample. Sociodemographic predictors of agreement were assessed using logistic regression. Agreement between the data sources was also assessed on a method-by-method basis using positive specific agreement. Participants were predominantly Latina (69%), foreign-born (76%), and low-income (99% with incomes <200% federal poverty level). Agreement of patient-reported and provider-reported contraceptive choice was highest for hormonal methods (positive specific agreement 94.0%) and intrauterine devices (89.9%), and lowest for condoms (53.5%). In the logistic regression model, agreement was lower among teens aged 16–19 years compared with women aged 25+ years (odds ratio 0.74; 95% confidence interval 0.55–0.99). Because teens are more likely to rely on condoms, the logistic regression model was repeated, adjusting for provider report of condom choice; after adjustment, no sociodemographic differences in agreement were observed. National data sources or studies relying on provider-reported method choice to derive estimates of contraceptive prevalence may overestimate choice of condoms. Our findings raise the question of whether condom choice can be accurately assessed by a single open-ended measure of choice of contraceptive method.

Comparison of prospective daily diaries and retrospective recall to measure oral contraceptive adherence

BACKGROUND

The purpose of this study was to determine if retrospective recall of oral contraceptive (OC) adherence provides data that are similar to data collected via daily diaries over the same time period. Factors associated with inconsistent agreement between prospective and retrospective measurements of adherence also were explored.

STUDY DESIGN

A total of 185 women participated in a longitudinal, prospective cohort of OC users, and 113 of these women provided complete information on OC adherence during follow-ups. Concordance beyond chance was assessed using weighted kappa statistics, and logistic regression was used to identify factors associated with inconsistent reporting of adherence.

RESULTS

There was substantial agreement between prospective and retrospective adherence information (weighted kappa=0.64; 95% CI: 0.52-0.77). Participants with a high school education or less and those who had problems with feeling sad while using OCs had increased odds of inconsistent reporting of adherence (OR=4.38, 95% CI: 1.41-13.61 and OR=3.52, 95% CI: 1.25-9.94, respectively).

CONCLUSION

While prospective data collection via diaries may improve accuracy, the added expense and burden on study participants may not be necessary. However, the use of retrospective recall may not be appropriate for all study populations.

How well do women recall past contraceptive use? A pilot study

BACKGROUND AND METHODOLOGY

Many women use a variety of contraceptive methods during their reproductive lives. Investigating this exposure is one of the most frequently performed epidemiological investigations. Accurate recall of methods used, as well as validating this information, can be difficult. A pilot study compared recalled contraceptive use over 5 years with that documented in the case notes of 30 women.

RESULTS

47% of episodes of method use were accurately recalled to the month of starting method use; this figure rose to 94% when episodes with disagreement within +/-12 months were also considered. Similarly, 44% and 91% of episodes were accurately recalled to the month and within +/-12 months of stopping method use, respectively. Accuracy of recall for duration of use followed a similar pattern. 7% of users were unable to distinguish between use of a combined pill and a progestogen-only pill and one-third of women using an intrauterine contraceptive were unable to distinguish an intrauterine device (IUD) from the intrauterine system (IUS).

DISCUSSION AND CONCLUSIONS

Almost all women can recall accurately which contraceptive methods they have used in the past year but are less accurate in respect of exact starting and stopping dates. Some women confuse the combined pill with the progestogen-only pill and others confuse the IUD and the IUS. The findings need to be replicated in other settings and with populations of less well-educated women.

Oral contraceptives and risk of gestational trophoblastic disease

Clinical reports suggested that the use of oral contraceptives (OC) after a molar pregnancy may increase the risk of persistent throphoblastic disease. However, few epidemiologic studies have analyzed the effect of OC use on the risk of developing gestational trophoblastic disease (GTD). To give further information, we have analyzed data from a case-control study on risk factors for GTD. Cases were 268 women with a histologically confirmed diagnosis of complete or partial mole referred to the participating Trophoblastic Disease Centers. A total of 268 subjects were interviewed; 79 cases were classified as partial and 159 as complete mole. Controls were randomly selected women who gave birth to healthy infants at term on randomly selected days in the same network of hospitals in which cases had been identified. A total of 104 cases and 130 controls reported ever OC use, and the corresponding odds ratio (OR) was 1.5 (95% CI, 1.1-2.1). The risk of GTD increases with duration of OC use: the OR was 1.7 (95% CI 1.2-2.6) for ever-users reporting >or=12 months of use. No consistent pattern of risk was observed with time since last OC use. We have analyzed separately the association between OC use and risk of complete and partial moles: no statistically significant difference emerged, but the OR for partial moles was higher (OR 3.0, 95% CI 1.6-8.4) than for complete mole (OR 1.0, 95% CI 1.8). In conclusion, we observed a weak association between OC use and GTD; such a weak association could be explained by factors other than causality.

Comparison of a traditional questionnaire with an icon/calendar-based questionnaire to assess occupational history

BACKGROUND

Self-reported work histories are an essential tool for estimating exposure in many occupational epidemiologic studies. However, the transience of some occupations such as farm work can hamper recall, resulting in inaccurate reporting. To address this problem, we have developed an icon/calendar-based questionnaire. This study compares work histories collected via this questionnaire to those collected via a traditional questionnaire.

METHODS

Eighty-nine farmworkers and non-farmworkers were interviewed twice, 8-10 months apart, about their lifetime employment. In the first interview, subjects were asked to recount their entire work history, starting from the interview date and moving backwards in time ("traditional questionnaire"). In the second interview, subjects were first asked about important life events, which were recorded with icons on a calendar. They were then asked to recount their work history, which was recorded, job-by-job, on the calendar with icons ("icon-calendar questionnaire").

RESULTS

Number of jobs and amount of work time accounted for since first employment were significantly greater using the icon-calendar questionnaire than the traditional questionnaire, the disparity increasing with time from the date of interview. The ratio of number of jobs in the traditional questionnaire to number of jobs in the icon-calendar questionnaire decreased from 100.0% in the most recent time period to 0.0% in the earliest time period. While the percentage of time explained by employment remained relatively constant across time periods in the icon-calendar questionnaire, ranging from 86.3 to 98.9%, it rapidly decreased with time in the traditional questionnaire, from 77.9% in the most recent time period to 0.0% in the earliest time period.

CONCLUSIONS

The icon-calendar questionnaire was more effective than the traditional questionnaire for obtaining complex work histories during interviews, producing a more complete picture of a person's work history.

Oral contraceptive use and risk of gestational trophoblastic tumors

BACKGROUND

Gestational trophoblastic disease refers to a spectrum of rare benign and malignant gynecologic disorders whose pathogenesis is not well understood. Recent studies from China and the United States have raised the hypothesis that long-term use of oral contraceptives before conception may increase the risk of gestational trophoblastic tumors. A multicenter case-control study of gestational trophoblastic tumors was undertaken to test this hypothesis.

METHODS

Telephone interviews were conducted with 235 case patients, including 50 with gestational choriocarcinoma, and 413 control subjects matched on recentness of pregnancy, age at pregnancy, and area of residence. Relative risks (odds ratios) were computed by conditional logistic regression. Reported P values are two-sided.

RESULTS

The relative risk estimate for ever having used oral contraceptives before the index pregnancy was 1.9 (95% confidence interval [CI] = 1.2-3.0), and the risk increased with duration of use (P for trend = .05). The estimate was highest for women who used oral contraceptives during the cycle in which they became pregnant (relative risk = 4.0; 95% CI=1.6-10), but there was no consistent pattern according to the time interval since last use. Separate analyses of choriocarcinoma and persistent mole yielded similar results, i.e., the relative risk estimates for oral contraceptive use were 2.2 (95% CI=0.8-6.4) and 1.8 (95% CI=1.0-3.0), respectively. Control for the number of sexual partners, which was independently associated with risk (P for trend = .05), did not materially change the results.

CONCLUSIONS

This study, the largest to date, indicates that long duration of oral contraceptive use before conception increases the risk of gestational trophoblastic tumors. These findings may provide clues to the pathogenesis of this rare disease. Changes in use of oral contraceptives are not warranted, however, because the incidence attributable to oral contraceptive use is very low.