Promoting Successful Weight Loss in Primary Care in Louisiana: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Promoting Successful Weight Loss in Primary Care in Louisiana (NCT02561221), a randomized na study. The primary outcome is Body Weight (Percent Change).

2. Clinical Question

The trial’s stated aim was to develop and test a patient-centered, pragmatic, scalable obesity-treatment program delivered within primary care. Its primary question concerns whether the program was associated with a different mean change in body weight than the usual-care approach over the stated follow-up period. The endpoint is expressed as percent change from baseline, rather than as an absolute weight value.

The registry record identifies the primary outcome measure and its analysis scale, but does not report the estimated change in either group, the between-group contrast, or its confidence interval. The direction and magnitude of the observed result therefore cannot be assessed from the registry record. The record also does not report participant eligibility criteria or details of how the underserved population was defined.

3. Trial Design

This was a completed, randomized, parallel-group trial of a behavioral intervention in primary care. The design is identified as cluster-randomized, so clinics, rather than individual patients, were the units assigned to the study groups. The brief summary describes half of the clinics as receiving the behavioral intervention and half as receiving usual care. The registry lists enrollment as 803.

The intervention was called Lifestyle Counseling. Patients in that group attended weekly sessions during the first six months, including 16 in-person sessions, and monthly sessions for the remaining 18 months. A trained health coach embedded in the primary-care clinic delivered the intervention. In the usual-care group, patients continued their usual interactions with Primary Care Practitioners and received newsletters covering topics such as sleep, brain and memory health, goal setting, and smoking cessation. The record does not describe all details of the intervention or usual-care delivery.

The primary outcome was body-weight percent change from baseline to Month 24. The record describes the measure as body weight measured in light indoor clothes and specifies a least-squares mean with a 95% confidence interval. Secondary outcomes listed include waist circumference, systolic blood pressure, fasting plasma glucose, total cholesterol, and several PROMIS-29 measures.

The recorded start was 2016-04, primary completion was 2019-09-06, and status is COMPLETED. The phase is listed as NA. Further details about the randomization procedure, clinic counts, allocation concealment, and follow-up procedures are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Body Weight (Percent Change), measured over Percent (%) Change from Baseline to Month 24.

The primary endpoint is body-weight percent change from baseline to Month 24. The registry describes body weight as measured in light indoor clothes and specifies a least-squares mean as the summary measure, with a 95% confidence interval. The endpoint therefore concerns change relative to each participant’s baseline weight, summarized at the group level using the sponsor’s stated model-based estimate.

Percent change can express change in relation to the starting measurement, rather than only in the original measurement units. This can be useful when participants begin at different body weights, although the registry record does not explain why this endpoint or analysis scale was chosen. A least-squares mean is generally a model-based average; its interpretation depends on the model and any adjustments used. The model specification and adjustment variables are not reported in the registry record.

A confidence interval communicates the uncertainty around an estimate under the assumptions of the analysis. It is not a guarantee that the true effect lies within the interval, and its width is relevant to how precisely the estimate is known. Here, the registry record states that a 95% confidence interval was used but does not report the endpoint estimates or interval limits. Consequently, the observed magnitude, direction, and precision of the primary result cannot be described from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary outcome as a least-squares mean with a 95% confidence interval. These terms identify a type of summary and an uncertainty measure, but they do not reveal the full analysis method. The model, its covariates, the handling of repeated observations, and the treatment of missing outcome measurements are not reported in the registry record.

What does a least-squares mean represent?

In general, a least-squares mean is a model-based estimate of a group average. It can differ from a raw average because the model may account for specified features of the data. For example, a model can adjust for prespecified variables or reflect the structure of observations. The interpretation relies on knowing which terms were included and how the model was fitted. Those details are not reported in the registry record, so the adjustment and exact interpretation of the reported estimand cannot be further described.

What does a confidence interval communicate?

In general, a confidence interval describes uncertainty around an estimate under the statistical model and its assumptions. A narrower interval indicates greater precision than a wider interval for the same type of estimate, but precision is not the same as importance. A confidence interval also should not be read as a probability statement about a fixed effect after the data have been observed. The registry specifies a 95% confidence interval for the primary measure, but the estimate and interval endpoints are not reported in the registry record.

Why does cluster randomization matter?

Clinics were the units of randomization. Patients cared for at the same clinic can share staff, workflows, local practices, and other features, so their outcomes may be correlated. General statistical principle: this within-clinic correlation means that patient observations do not necessarily contribute as much independent information as the same number of observations drawn from unrelated settings. A suitable analysis needs to account for the clustering when estimating uncertainty. The registry record states that a simple individual-level re-analysis would be misleading and that only the sponsor’s own analysis is shown. It does not report the specific model or its treatment of clustering.

Cluster randomization also affects how the design should be interpreted. The intervention was delivered within primary-care clinics, and assignment at clinic level is consistent with evaluating a clinic-delivered program. However, the registry information does not provide clinic counts, the number of patients by clinic, or measures of within-clinic similarity. These missing design details limit independent assessment of the effective information available for estimating the intervention contrast.

What is the role of the planning illustration?

The registry’s sample-size assumptions describe a planning illustration computed from the observed effect, using a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. These are planning assumptions, not evidence about the trial’s achieved precision. Sample sizes calculated from such assumptions are planning illustrations, never observed power. The record does not report the illustration’s numerical sample-size values in the information available for this description. Nor does it report that these assumptions were the trial’s original design assumptions.

General statistical principle: power is a property of a design under specified assumptions about the true effect, variability, analysis, and threshold for statistical significance. After a trial is complete, a post hoc calculation based on an observed effect does not establish the probability that the study would have detected a meaningful effect. Interpretation should instead focus on the estimated effect and its uncertainty, along with the design and analysis assumptions. Those primary-result estimates are not reported in the registry record.

How should comparisons be read?

The primary endpoint concerns a comparison of group-level body-weight change. A difference between group estimates, if reported, would describe the contrast under the sponsor’s analysis; its uncertainty would be assessed using the relevant interval or test. A within-group change alone would not answer the randomized comparison, because change over time can reflect factors shared across groups as well as the intervention. The registry record does not report either group’s primary estimate or the between-group contrast.

The record identifies randomization, a parallel design, and no masking. It does not describe blinding of outcome assessment, allocation concealment, model diagnostics, or sensitivity analyses. These details can inform assessment of bias and robustness, but should not be inferred from the design label alone. The lack of these details does not establish that such procedures were absent; it means they are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 24 outcome measures, including the primary body-weight measure and secondary clinical and patient-reported outcomes. It lists no analyses. The record does not report which secondary outcomes were analyzed, how many comparisons were planned, whether outcome measures were grouped into families, or whether any multiplicity adjustment was used. Without that information, the statistical approach to multiple outcomes cannot be assessed.

General statistical principle: when many outcomes or comparisons are examined, the chance of observing at least one apparently unusual result can increase if each is assessed independently using the same threshold. Prespecification and appropriate multiplicity procedures can help make interpretation more transparent. This general issue does not establish that the reported results are false or that an adjustment was required in this trial; the registry record does not describe the analysis plan or report the analysis results.

Missing-data methods are also not reported in the registry record. It does not state how many primary outcome measurements were unavailable, how missing values were handled, or whether sensitivity analyses assessed the effect of missing observations. The planned follow-up endpoint is Month 24, but the registry summary does not describe retention or measurement completion at that time.

The analysis population is not reported in the registry record. In particular, the record does not specify whether the primary analysis included all randomized participants, participants with observed outcomes, or another defined population. No assumptions about missingness or adherence should be inferred in the absence of these details. These omissions limit assessment of how well the analysis preserves the randomized comparison and how sensitive the findings might be to incomplete follow-up.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hysterectomy (1.1%), hypertensive event (0.9%), atrial fibrillation (0.9%), malignant neoplasm (0.9%), respiratory system infection (0.7%).

The registry safety fields report serious adverse events affecting 48 of 452 people at risk in Lifestyle Counseling and 35 of 351 people at risk in Usual Care. Other adverse events affected 35 of 452 people at risk in Lifestyle Counseling and 46 of 351 people at risk in Usual Care. The record lists 2 deaths in Lifestyle Counseling and 1 in Usual Care. These are descriptive counts; the registry information does not report comparative statistical tests or establish that events were caused by the intervention.

The record lists the following serious adverse-event terms and percentages: Hysterectomy, 1.1%; Hypertensive Event, 0.9%; Atrial Fibrillation, 0.9%; Malignant Neoplasm, 0.9%; Respiratory System Infection, 0.7%; and Mid- or Post-Surgical Complication, 0.7%. These listed terms do not constitute a complete account of all safety outcomes. The registry record does not describe the event definitions, observation period for these counts, severity grading, or how relatedness to the intervention was assessed.

Counts of affected people should not be interpreted as a measure of causal risk without considering follow-up, ascertainment, and the trial design. The figures also should not be added together: the record does not state whether a person could experience more than one event or appear in more than one category. The registry record does not report a safety analysis adjusted for clinic clustering.

12. What the Result Does, and Does Not, Mean

The record establishes that a randomized, cluster-based trial compared a primary-care lifestyle-counseling program with usual care, and that body-weight percent change from baseline to Month 24 was the primary endpoint. It also describes the intervention schedule, some features of usual care, and several secondary outcome measures. These registry entries clarify what the trial set out to evaluate.

The registry information does not report the primary endpoint estimates or a between-group comparison. It therefore does not show whether the groups differed in body-weight change, how large any difference was, or how precisely it was estimated. The stated use of a least-squares mean and 95% confidence interval is not enough to answer those questions without the numerical result and analysis details. The same caution applies to the listed secondary outcomes: their presence in the record is not evidence of a particular result.

General statistical principle: an estimate should be interpreted alongside its uncertainty and the design that generated it. For a cluster-randomized trial, the clinic-level assignment and possible similarity among patients at the same clinic matter to the analysis. The registry record itself warns that a simple individual-level re-analysis would be misleading, and identifies the sponsor’s analysis as the relevant one. Its numerical results are not reported in the registry information.

The safety counts describe recorded events in the groups, but do not by themselves establish causation or comparative safety. The record does not provide the context needed to judge event relatedness, follow-up completeness, or inferential comparisons. Accordingly, these registry entries support a limited description of trial structure and recorded outcomes, not a claim about treatment effectiveness or a recommendation for care.

13. Why This Trial Matters Statistically

This trial raises an important statistical issue because the intervention was delivered through primary-care clinics and the trial is identified as cluster-randomized. The assignment unit matters: outcomes from patients in the same clinic may be correlated, so analyses need to reflect the clinic structure. The registry record explicitly cautions that a simple individual-level re-analysis would be misleading. That warning is central to interpreting any estimate from this study.

The primary outcome also illustrates the difference between naming an endpoint and reporting evidence about it. The record specifies body-weight percent change from baseline to Month 24 and a least-squares mean with a 95% confidence interval. Those details identify the intended summary, but without the estimates and interval limits, neither effect magnitude nor precision can be judged. A clear endpoint definition is useful, but it cannot replace the numerical findings.

The trial’s pragmatic, scalable primary-care aim makes implementation context part of the statistical question. The intervention involved a health coach embedded in primary care, while the comparator involved usual practitioner interactions and newsletters. Evaluating a program delivered through clinics requires attention to how clinic-level assignment, clinic differences, and patient outcomes are represented in the analysis. The registry record does not describe enough model detail to assess those choices independently.

Finally, the record lists multiple outcome measures but no analyses. This makes transparency about outcome selection, multiplicity, missing data, and analysis populations especially relevant to interpreting results. The absence of these details in the registry record should be distinguished from evidence that a procedure was not used. Taken together, the trial’s design highlights why the unit of randomization, the analysis model, and complete reporting of estimates and uncertainty all matter in clinical biostatistics.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several limitations specific to this trial cannot be resolved from the registry record. The primary outcome is named and its summary measure is specified, but the numerical least-squares means, between-group estimate, and confidence interval are not reported. Without those results, the primary comparison cannot be described in terms of direction, magnitude, or precision.

The study is cluster-randomized, and the record warns that a simple individual-level re-analysis would be misleading. Yet the information available does not report the number of clinics, participants by clinic, the model used to account for clustering, or the model’s adjustment variables. Those details are important for understanding how clinic-level assignment informed the estimated uncertainty.

The registry record also does not report eligibility criteria, analysis-population definitions, missing-outcome counts, missing-data methods, or sensitivity analyses. It does not describe the prespecified statistical plan, multiplicity handling, allocation concealment, or outcome-assessment procedures. These omissions prevent independent assessment of several potential sources of uncertainty and bias. Their absence from the registry information does not show that the procedures were not used.

The intervention description gives a broad schedule and delivery setting, but does not provide a complete account of intervention fidelity, participant adherence, or variation in clinic implementation. The description of usual care is also limited. The record’s safety fields list affected people and deaths but do not specify the event observation period, relatedness assessment, or comparative analysis. These limitations call for caution in interpreting the available information; they do not establish that the trial was poorly conducted.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Promoting Successful Weight Loss in Primary Care in Louisiana — NCT02561221.
• Registry record last updated 2023-08-01; status last verified 2023-07.
• Results first posted 2020-12-10.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT02561221, Promoting Successful Weight Loss in Primary Care in Louisiana, is recorded as a completed, randomized, parallel, cluster-based trial sponsored by Pennington Biomedical Research Center. The recorded start was 2016-04, primary completion was 2019-09-06, and enrollment was 803. The phase is listed as NA.

The trial compared Lifestyle Counseling, delivered by a trained health coach in primary care, with usual care that included usual practitioner interactions and newsletters. The primary outcome was body-weight percent change from baseline to Month 24, summarized as a least-squares mean with a 95% confidence interval.

The registry record does not report the primary outcome estimates, the between-group result, or the confidence interval limits. It lists secondary outcomes and safety counts, but does not report analysis details for multiplicity, missing data, or analysis populations. The record cautions that an individual-level re-analysis would be misleading because of the cluster-randomized design.