Background

Most health promotion trials in cancer screening offer limited evidence of external validity. We assessed internal and external validity in a nationwide, population-based trial of an intervention to promote regular mammography screening.

Methods

Beginning in September 2000, study candidates age 52 years and older (n = 23 000) were randomly selected from the National Registry of Women Veterans and sent an eligibility survey. Consistent with intention-to-treat principles for effectiveness trials, we randomly assigned eligible respondents and nonrespondents to one of five groups. We mailed baseline surveys to groups 1–3 followed by intervention materials of varying personalization to groups 1 and 2. We delayed mailing baseline surveys to two additional control groups to coincide with the mailing of postintervention follow-up surveys to groups 1–3 at year 1 (group 4) and year 2 (group 5). Mammography rates were determined from self-report and Veterans Health Administration records. To assess internal validity, we compared groups on participation and factors associated with mammography screening at each stage. To assess external validity, we compared groups 3, 4, and 5 on mammography rates at the most recent follow-up to detect any cueing effects of prior surveys and at the respective baselines to uncover any secular trends. We also compared nonparticipants with participants on factors associated with mammography screening at the trial’s end.

Results

We established study eligibility for 21 340 (92.8%) of the study candidates. Groups 1–3 were similar throughout the trial in participation and correlates of mammography screening. No statistically significant survey cueing effects or differences between nonparticipants and participants across groups were observed. Mammography screening rates over the 30 months preceding the respective baselines were lower in group 5 (82.3% by self-report) than in groups 1–4 (85.1%, P = .024, group 5 vs groups 1–4 combined), suggesting a decline over time similar to that reported for US women in general.

Conclusion

This systematic assessment provides evidence of the trial’s internal and external validity and illustrates an approach to evaluating validity that is readily adaptable to future trials of behavioral interventions.

Background

Few health promotion trials have evaluated strategies to increase regular mammography screening. We conducted a randomized controlled trial of two theory-based interventions in a population-based, nationally representative sample of women veterans.

Methods

Study candidates 52 years and older were randomly sampled from the National Registry of Women Veterans and randomly assigned to three groups. Groups 1 and 2 received interventions that varied in the extent of personalization (tailored and targeted vs targeted-only, respectively); group 3 was a survey-only control group. Postintervention follow-up surveys were mailed to all women after 1 and 2 years. Outcome measures were self-reported mammography coverage (completion of one postintervention mammogram) and compliance (completion of two postintervention mammograms). In decreasingly conservative analyses (intention-to-treat [ITT], modified intention-to-treat [MITT], and per-protocol [PP]), we examined crude coverage and compliance estimates and adjusted for covariates and variable follow-up time across study groups using Cox proportional hazards regression. For the PP analyses, we also used logistic regression.

Results

None of the among-group differences in the crude incidence estimates for mammography coverage was statistically significant in ITT, MITT, or PP analyses. Crude estimates of compliance differed at statistically significant levels in the PP analyses and at levels approaching statistical significance in the ITT and MITT analyses. Absolute differences favoring the intervention over the control groups were 1%–3% for ITT analysis, 1%–5% for MITT analysis, and 2%–6% for the PP analysis. Results from Cox modeling showed no statistically significant effect of the interventions on coverage or compliance in the ITT, MITT, or PP analyses, although hazard rate ratios (HRRs) for coverage were consistently slightly higher in the intervention groups than the control group (range for HRRs = 1.05–1.09). A PP analysis using logistic regression produced odds ratios (ORs) that were consistently higher than the corresponding hazard rate ratios for both coverage and compliance (range for ORs = 1.15–1.29).

Conclusions

In none of our primary analyses did the tailored and targeted intervention result in higher mammography rates than the targeted-only intervention, and there was limited support for either intervention being more effective than the baseline survey alone. We found that adjustment for variable follow-up time produced more conservative (less favorable) intervention effect estimates.

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Pharmacists are key members of the healthcare team, especially in minority and urban communities. This study was developed to assess pharmacists' ability and willingness to counsel the public on prostate cancer in the community pharmacy setting. A mail survey was sent to all 192 community pharmacies in Washington, DC, and Prince George's County, Maryland. A total of 90 pharmacists responded to the questionnaire, providing a 46.9% response rate. One third of the pharmacists indicated a willingness to participate in a prostate cancer training program. Perceived benefits and perceived barriers were each measured through five questionnaire items using Likert-style statements with responses ranging from "strongly agree" to "strongly disagree." The most significant predictor of perceived benefits of providing prostate cancer information was gender; male pharmacists perceived greater benefits for providing prostate cancer information than female pharmacists. Similarly, black pharmacists perceived greater benefits of providing prostate cancer information to their patients than non-black pharmacists. Also, pharmacists in stores that offered disease state management programs had a significantly lower perceived benefit of providing prostate cancer information. These findings indicate that gender and race may play a role in health promotion in health disparities. There were no significant barriers to providing prostate cancer information. Thus, many pharmacists are willing to participate in health education on prostate cancer.