Randomized Controlled Trial for a
Diabetes Self-Management Program

RESEARCH QUESTION

What the Trial Set Out to Test

This randomized controlled trial example follows a primary care research team that is testing a structured self-management program for adults with type 2 diabetes against usual care. The primary question is whether average glycated hemoglobin (HbA1c) differs between the two groups at six months, and the team wants the analysis fixed in writing before the database is unblinded.

The question is stated as an estimand: the effect of being offered the program, whether or not participants keep attending it. Some participants will stop attending or miss later visits, so the plan states in advance how those participants enter the analysis, and that choice cannot be revisited once the data are seen.

STUDY DESIGN AND DATA

Two Arms, Scheduled Visits and Some Missing Data

A two-arm trial with about 240 adults, randomized one to one and stratified by clinic site. The dataset holds the randomization record with clinic site, age, diabetes duration, and HbA1c at baseline, three months and six months. Visits are scheduled in the protocol, so the measurement times are the same for everyone. HbA1c is measured at each visit whether or not a participant still attends the program; missing values come only from participants who withdraw from the study or miss a visit.

METHOD AND ASSUMPTIONS

Why Adjust for Baseline, and What Must Hold

A first draft of many plans compares final values in participants who completed every visit, which discards randomized participants and answers a different question from the one posed. This plan analyzes everyone as randomized, with a mixed model for repeated measures that uses all available visits, adjusts for the baseline HbA1c and the randomization stratum, and estimates the treatment difference at six months. With a single follow-up visit, this model reduces to the familiar covariance-adjusted comparison of final values; here it carries that adjustment across all scheduled visits, and baseline is a legitimate covariate because it is measured before randomization.

The covariance of repeated measures within a participant is modeled explicitly, not assumed independent, and the choice is reported. The primary analysis assumes missing visits are missing at random given the observed data, which cannot be verified, so a tipping-point analysis asks how different the missing outcomes would have to be to change the conclusion. A per-protocol analysis is listed as supplementary and labeled as such.

OUTPUT AND INTERPRETATION

How the Results Are Read

The output has the adjusted mean difference in HbA1c at six months with its 95% confidence interval, the adjusted group means over time, and a participant flow diagram. The interval is read against the smallest difference the team considers clinically worthwhile, set before the data were seen, so that precision and relevance are discussed together and not only whether the interval excludes zero.

Sensitivity analyses report the tipping-point result, a comparison of covariance structures, and the supplementary per-protocol estimate with an explanation of why it can be biased. Secondary outcomes are labeled as such and not treated as confirmatory. The write-up states what the estimates support and the limits of a trial of this size.

REPORTING

What the Researcher Received

A written report structured to the CONSORT statement for randomized trials, with the flow diagram and statistical wording for the analysis section, matched to the output, for the team to check and incorporate in the target journal's format. The trial design, clinical interpretation and conclusions remain with the research team.