Promoting regular mammography screening II. Results from a randomized controlled trial in US women veterans.
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.
Vernon
Sally W
SW
Division of Health Promotion and Behavioral Sciences, University of Texas-Houston School of Public Health, 7000 Fannin, Ste 2560, Houston, TX 77030, USA. sally.w.vernon@uth.tmc.edu
del Junco
Deborah J
DJ
Tiro
Jasmin A
JA
Coan
Sharon P
SP
Perz
Catherine A
CA
Bastian
Lori A
LA
Rakowski
William
W
Chan
Wen
W
Lairson
David R
DR
McQueen
Amy
A
Fernandez
Maria E
ME
Warrick
Cynthia
C
Halder
Arada
A
DiClemente
Carlo
C
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001943:Breast Neoplasms / Q000401:mortality / Q000517:prevention & control*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008327:Mammography / Q000706:statistics & numerical data; D008403:Mass Screening / Q000379:methods* / Q000706:statistics & numerical data; D008875:Middle Aged; D010349:Patient Compliance; D018579:Patient Selection; D016016:Proportional Hazards Models; D012042:Registries; D015203:Reproducibility of Results; D012107:Research Design; D014481:United States / Q000453:epidemiology; D014728:Veterans / Q000706:statistics & numerical data*