Crossing the Divide: Piloting Integrated Care to Reduce Amputations Among Rural Patients With Diabetic Foot Ulcers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Crossing the Divide: Piloting Integrated Care to Reduce Amputations Among Rural Patients With Diabetic Foot Ulcers (NCT05203471), a non-randomized na study. The primary outcome is Proportion of Patients Receiving Guideline-concordant Vascular and Infectious Disease Care Processes.

2. Clinical Question

3. Trial Design

This is a completed, nonrandomized pilot study of an integrated care model for rural patients with diabetic foot ulcers. The registry lists the study model as sequential and masking as none. Patients in the historical group received care before the intervention launched; integrated-care patients received care after launch. The record specifies that only patients who provided informed consent and enrolled were treated with the integrated care model.

The sequential arrangement means that the groups were observed in different periods rather than assigned at random at the same time. Changes in care or patient characteristics over time could therefore affect comparisons. The registry explicitly cautions that the arms are not a like-for-like control comparison. The record does not report a randomized allocation process or masking.

The registry lists enrollment as 131 and the study status as completed. It names University of Wisconsin, Madison as the sponsor. The record lists phase as NA. The study start date is 2023-02-16, and the primary completion date is 2025-05-01.

Healthcare workers employed in participating clinics are also described as a study group. They are distinct from the patient groups used in the primary outcome contrast. The record does not report how patients or clinics were selected, how many were included in each patient group, or the analysis populations. Further details about recruitment and retention 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

Reasons for not completing this period:

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.

Population: Study relevant baseline data not collected from Healthcare Workers per protocol.

6. Primary Endpoint

The registry lists the primary outcome as Proportion of Patients Receiving Guideline-concordant Vascular and Infectious Disease Care Processes, measured over up to 3 months.

The primary endpoint is the proportion of integrated-care patients receiving guideline-concordant vascular and infectious disease care within up to 3 months of enrollment, contrasted with the proportion of historical patients receiving such care within up to 3 months of participant enrollment. The registry defines the measure as the integrated-care proportion minus the historical-patient proportion.

This endpoint measures care processes, not amputation or another patient health outcome. A process measure can describe whether specified clinical activities occurred according to guidelines. It can help characterize how a care model was delivered, but by itself it does not establish that those processes changed patient outcomes.

The registry record does not provide the operational definition of guideline concordance, the specific vascular or infectious disease processes counted, or the endpoint results. It also does not report how patients with incomplete follow-up or missing process information were handled. Those details matter for understanding exactly how the proportions were formed and how broadly they can be interpreted.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a proportion measure?

General statistical explanation: a proportion describes the share of an analysis group meeting a specified condition. For this study, the condition is receipt of guideline-concordant vascular and infectious disease care within the defined follow-up period. Interpreting a proportion requires knowing both which participants count as meeting the condition and which participants form its denominator. The operational criteria and group-specific denominators are not reported in the registry record.

What does the stated contrast mean?

The registry defines the primary contrast as the integrated-care proportion minus the historical-patient proportion. General statistical explanation: subtracting one proportion from another expresses an absolute difference on the proportion scale. A positive value would indicate a higher observed proportion in the integrated-care group, while a negative value would indicate a lower observed proportion. This direction describes the arithmetic of the contrast, not a causal interpretation. The registry record does not report the observed value.

Why does the design affect interpretation?

General statistical explanation: random allocation can help balance measured and unmeasured characteristics between groups, on average. This study was not randomized. Its sequential model compares patients treated before the intervention launched with patients treated after launch. As a result, intervention exposure is linked to calendar period. Any concurrent changes in care, patient mix, or documentation could be difficult to distinguish from changes associated with the integrated care model. The registry record cautions that the arms are not a like-for-like control comparison; it does not report an adjustment strategy to address this concern.

What would an uncertainty interval add?

General statistical explanation: a confidence interval describes the range of values reasonably compatible with the data under a specified statistical model. It conveys precision as well as the direction and magnitude of an estimate. A narrow interval indicates greater precision than a wide interval, but an interval does not remove bias from a nonrandomized design. No confidence interval or primary-outcome estimate is reported in the registry record.

What does the analysis record establish?

The registry lists zero analyses. It does not report a statistical analysis plan, a method for estimating the primary contrast, covariate adjustment, handling of repeated observations, missing-data procedures, or analysis populations. These elements should not be inferred from the endpoint description alone. Without them, readers cannot determine how the planned comparison would be estimated or what assumptions would support an inferential result.

How should the planning illustration be understood?

General statistical explanation: sample-size planning asks how much information a future study might need to detect a chosen effect under stated assumptions. The registry's planning illustration is described as based on the observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation; its target effect is a stated fraction of the observed effect. The record says non-time-to-event calculations represent participants per arm, while time-to-event calculations represent total events. These are planning assumptions, not observed power and not evidence that the pilot was designed with those assumptions. The registry does not report the trial's own sample-size justification. The primary outcome is a count-of-participants measure, but the observed effect needed to interpret a planning illustration is not reported in the record.

General statistical explanation: assumptions matter because planning results depend on the effect size and analysis model chosen. A planning calculation does not demonstrate that a study had a particular probability of detecting an effect after the data are observed. Nor does it replace an estimate and uncertainty interval from the actual analysis. The registry record does not report a primary-outcome analysis from which to assess the observed contrast.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Historical Controls", "Integrated Care")
n      <- c(81, 27)
events <- c(14, 6)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Historical Controls  81  14  17.3  9.8  27.3  10.6  26.9  10.6  27.0
ARM  Integrated Care  27  6  22.2  8.6  42.3  10.6  40.8  10.7  41.0

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures and identifies the proportion receiving guideline-concordant vascular and infectious disease care processes as the primary outcome. It also lists the proportion of patients undergoing amputation as a secondary outcome. The registry record does not report a multiplicity plan, such as whether or how interpretation would account for examining multiple outcomes. No outcome-specific results or statistical tests are reported.

Missing-data methods are not reported in the registry record. The record does not explain whether missing care-process documentation, incomplete follow-up, or withdrawal affected inclusion in the primary analysis. It also does not state whether missing observations were excluded, imputed, or handled in another way. These choices can affect estimated proportions and their denominators, so the absence of this information limits assessment of the endpoint.

Analysis populations are likewise not reported in the registry record. Although the description says that integrated-care patients provided informed consent and enrolled, it does not specify which enrolled patients were included in the primary analysis or how eligibility and follow-up were handled for historical patients. The record also does not describe how healthcare workers relate to the patient outcome analyses.

The registry lists zero analyses and does not report a statistical analysis plan. It is therefore not possible to identify a prespecified testing hierarchy, adjustment approach, or analysis population from the posted record. These omissions do not show that particular procedures were or were not used; they mean that those procedures are not reported in the registry record.

12. 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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: deep space abscess (3.7%), myocardial infarction (3.7%).

The registry reports adverse-event information separately for Historical Controls, Integrated Care, and Healthcare Workers. For integrated care, it lists 27 participants at risk, 2 participants with serious adverse events, 27 at risk for other adverse events, and 4 participants with other adverse events. For historical controls, the record lists zero at risk for both categories and zero affected; for healthcare workers, it also lists zero at risk and zero affected. These entries should be read as registry-reported counts, not as comparative rates.

The registry lists deep space abscess and Myocardial Infarction among the top serious-event terms, each at 3.7%. It does not provide additional event-level descriptions or explain the term-specific denominator in the available record. The record also lists deaths as 3 for historical controls, 1 for integrated care, and 0 for healthcare workers. It does not report further detail about cause, timing, or relationship to the intervention.

These safety entries do not support a like-for-like comparison between the patient groups: allocation was nonrandomized and sequential, and the record lists zero participants at risk in the historical and healthcare-worker adverse-event fields. The registry record does not explain those zero-at-risk entries. No conclusion about comparative safety should be drawn from these counts alone.

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

The record describes a pilot that compares care-process proportions between integrated-care patients and historical patients. It provides the endpoint definition, the order of the contrast, the sequential nonrandomized design, and some registry-listed safety counts. It does not report the primary endpoint estimate, an uncertainty interval, or a p-value. Consequently, the posted results do not establish whether the care-process proportions differed or how precisely any difference was estimated.

The endpoint concerns guideline-concordant vascular and infectious disease care, not amputation. Although the registry lists the proportion of patients undergoing amputation as a secondary outcome, it does not report that outcome's result. The study title and background description do not establish the study findings. The registry's description of prior work and the motivation for a future trial should not be interpreted as results from this pilot.

Even a reported difference in care processes would need to be interpreted in light of the study design. Patients were compared across periods rather than randomized concurrently, and the registry cautions that the arms are not a like-for-like control comparison. A contrast could reflect the intervention, differences between patients or clinics, other changes over time, or a combination of factors. The record does not report methods that would allow those possibilities to be assessed.

The stated purpose includes improving recruitment and retention strategies and generating preliminary evidence for a future statewide efficacy trial. That is a pilot-study role. The registry record does not report whether recruitment or retention goals were achieved, or present results that establish efficacy. The record therefore supports describing the study question and limitations, but not a conclusion about clinical benefit or harm.

14. Why This Trial Matters Statistically

This study addresses an important statistical challenge in evaluating care models in rural settings: the intervention is introduced within participating care systems, and the comparison uses patients observed before launch. Such sequential comparisons can be practical for a pilot, but intervention status is entangled with time. Statistical estimates from this design can be informative descriptively while remaining vulnerable to differences between periods.

The primary endpoint focuses on care processes. This can help characterize whether recommended vascular and infectious disease care was delivered, which is relevant to understanding implementation. But the process endpoint is not the same as a patient outcome such as amputation. The registry lists amputation as a secondary outcome, but its result is not reported. Keeping process outcomes distinct from clinical outcomes is necessary when interpreting what a study measures.

The pilot framing also matters. The registry says pilot data will inform recruitment and retention strategies and provide preliminary evidence for a future statewide efficacy trial. A pilot can help identify questions for a subsequent study, while not necessarily providing a definitive effect estimate. The registry record does not report results for the primary endpoint, so the available information cannot quantify preliminary evidence about the care-process contrast.

Finally, transparent reporting of group denominators, endpoint definitions, missing-data procedures, and analysis methods would be important for judging the precision and robustness of any comparison. These details are not reported in the registry record. Their absence limits statistical interpretation, especially given the nonrandomized sequential design and the explicit warning that the arms are not like-for-like.

15. 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.

The most consequential limitation stated in the registry is that allocation was nonrandomized and the arms are not a like-for-like control comparison. Historical patients were cared for before the integrated care model launched, while integrated-care patients were treated after launch. Differences between periods may therefore complicate attribution of any observed contrast to the model.

The registry does not report group-specific patient counts, primary-outcome denominators, or the operational criteria for guideline-concordant care. Although enrollment is listed as 131, this does not show how many patients contributed to each endpoint group. Missing-data handling, follow-up completeness, and analysis populations are also not reported in the registry record.

No primary-outcome estimate, confidence interval, or p-value is reported, and the registry lists zero analyses. The statistical analysis plan, covariate adjustment, and multiplicity approach are not reported. As a result, the precision and robustness of the planned comparison cannot be evaluated from the record.

The registry lists safety counts, but the historical and healthcare-worker groups have zero participants at risk in the adverse-event fields. The record does not explain these entries, so they cannot be treated as evidence that no events occurred in comparable groups. The record also does not give further context for the listed deaths or serious adverse-event terms.

Finally, the registry describes a pilot whose aims include informing a future statewide efficacy trial. Recruitment and retention results are not reported, and the posted information does not establish the primary endpoint result or an amputation result.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Crossing the Divide: Piloting Integrated Care to Reduce Amputations Among Rural Patients With Diabetic Foot Ulcers — NCT05203471.
• Registry record last updated 2026-04-27; status last verified 2026-04.
• Results first posted 2026-04-27.
• 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.

19. Record Summary

NCT05203471 is a completed, nonrandomized, sequential pilot of an integrated care model for rural patients with diabetic foot ulcers. It compares guideline-concordant vascular and infectious disease care processes among integrated-care patients after launch with historical patients treated before launch. The primary contrast is defined as the integrated-care proportion minus the historical-patient proportion within up to 3 months.

The registry lists enrollment as 131, masking as none, and University of Wisconsin, Madison as sponsor. The record also describes a healthcare-worker group and lists amputation as a secondary outcome. It cautions that the patient arms are not a like-for-like control comparison.

The registry lists zero analyses and does not report a numerical primary-outcome result, confidence interval, or p-value. Group-specific endpoint denominators, missing-data methods, and analysis populations are not reported in the registry record. The record's pilot purpose includes informing recruitment and retention strategies and a future statewide efficacy trial.