Optimal Care of Complicated Appendicitis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Optimal Care of Complicated Appendicitis (NCT03159754), a non-randomized phase 4 study. The primary outcome is Overall Cost of Care.

2. Clinical Question

The clinical question concerns children with complicated appendicitis and compares immediate surgery, surgery several weeks after diagnosis, and treatment without appendectomy. These are the three approaches described in the study summary. The main registered question was economic: which approach was most cost-effective. The record identifies total health care cost from the time of admission as the intended primary measure, with an original intention to gather cost data for 2 years per person following admission.

The primary question cannot be answered from the posted primary-outcome information. The registry states that the institutions potentially involved did not provide access to cost data, and that no cost data for any participants could be procured. It also lists secondary outcomes related to complications, treatment burden, health care use, quality of life, and recurrent appendicitis, but the record does not present their results. Those outcomes therefore cannot fill the gap in the primary economic comparison.

The study was non-randomized. This matters because the observed differences between arms, if available, could reflect differences in the participants or care circumstances that led to each approach, as well as differences associated with the approach itself. The registry does not report the basis for treatment selection or the characteristics needed to assess how similar the groups were. The study question is clear, but the posted record does not provide an analyzed cost comparison or enough information to interpret the arms as causal alternatives.

3. Trial Design

This was a completed, Phase 4, parallel study sponsored by the University of Michigan. The registry lists an enrollment of 40 and dates the study from 2017-06-29 to primary completion on 2020-03-26. Allocation was non-randomized, and masking was none. These design features are important when interpreting any comparison between the three care approaches.

The arms were Early Appendectomy, Interval Appendectomy, and No Appendectomy. The listed interventions include early appendectomy, interval appendectomy, and antibiotics. The arm descriptions themselves are blank in the registry record, so details about what participants received, including treatment timing and treatment protocols, are not reported in the registry record. The record also does not explain how participants came to receive one approach rather than another.

A non-randomized, parallel design can describe outcomes in groups receiving different care approaches, but it does not ensure that the groups were comparable at the outset. In a randomized trial, assignment by chance is intended to balance measured and unmeasured factors on average. That protection is not available. Without information about treatment selection and baseline characteristics, observed differences cannot automatically be attributed to the care approach.

The primary outcome was Overall Cost of Care, with total health care cost from admission intended as the measure. Although the original intention was to collect cost data for 2 years per person following admission, the record states that no cost data were obtained, so the outcome could not be analyzed for any length of time. The listed secondary outcomes include complications, parents away from work, duration of antibiotic therapy, length of stay, percutaneous drainage procedures, radiographic imaging studies, quality of life measured with PedsQL, and recurrent appendicitis. The registry lists nine secondary outcome measures, but does not give their results in this record.

The registry marks the study completed, but completion does not mean that every planned outcome was measured or analyzed. The record lists zero analyses. It does not report a detailed statistical analysis plan, a sample-size justification, interim analyses, or analysis populations. Consequently, the posted design information supports a description of the study structure, but not an assessment of how any treatment comparison was statistically conducted.

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

Analysis population for the primary outcome, as defined in the registry: No cost data for any participants was able to be procured. Thus this outcome could not be achieved or analyzed in any fashion.

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 Overall Cost of Care, measured over The original intention was to gather cost data for 2 years per person following admission. As no cost data was able to be procured, there is no time frame to which it applies..

The intended primary endpoint was overall cost of care. The registry describes it as total health care cost starting from the time of admission. The original intention was to gather costs for 2 years per person following admission. A cost endpoint is relevant to a study whose stated purpose is to determine which of several care approaches is most cost-effective: it can describe the resource expenditure associated with care, while the other listed outcomes cover clinical events, care use, and quality of life.

That rationale describes the planned role of the endpoint, not an observed result. The registry record says institutions potentially involved were unwilling to provide access to cost data. It also states that no cost data for any participants could be procured. As a result, the primary outcome could not be achieved or analyzed in any fashion. The record therefore supplies no estimated overall cost, no uncertainty interval around a cost estimate, and no analyzed time period for this endpoint. The original 2-year intention does not become an analyzed follow-up window because the cost data were unavailable.

Cost-effectiveness is broader than simply naming a cost measure. In general, an economic comparison needs the relevant cost information and an outcome basis on which to judge value. Here, the registered primary outcome was total cost, while the study summary stated the broader cost-effectiveness objective. The registry record does not report a completed economic analysis or a cost-effectiveness result. The secondary outcomes listed in the record may relate to clinical outcomes or resource use, but their results are not reported and cannot substitute for the missing cost data.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

There is little reported analysis methodology to describe for this study. The registry lists a non-randomized parallel design, no masking, and zero analyses. It does not report the statistical methods used for the primary or secondary outcomes, the analysis populations, a missing-data method, or a prespecified multiplicity strategy. The explanations below are general statistical context, not claims about methods used in this study.

What does non-randomized allocation mean for comparisons?

In general, random assignment helps make comparison groups similar with respect to both measured and unmeasured factors, on average. With non-randomized allocation, group membership may be associated with participant characteristics, clinical circumstances, or decisions about care. A difference in outcomes could therefore reflect these factors, the care approach, or both. Statistical adjustment can sometimes address measured differences, but it cannot automatically eliminate bias from unmeasured or inadequately recorded factors. The registry record does not report the allocation process, baseline characteristics, or an adjustment method, so the extent to which comparability was assessed is not reported in the registry record.

What would an estimate and confidence interval show?

In general, an estimate summarizes the observed difference or association in a sample. A confidence interval shows the range of values compatible with the data under the assumptions of the analysis; a wider interval indicates less precision. It does not by itself correct for selection bias or prove that an observed association is causal. Because the primary cost data were not obtained, there is no posted primary cost estimate or confidence interval to interpret. The registry record does not report estimates or intervals for the listed secondary outcomes either.

Why does the absence of cost data matter?

For an economic endpoint, data collection is part of the analysis chain. Costs must be available for the relevant participants and time period before investigators can summarize or compare spending. Here, the record says no cost data for any participant could be procured, and that the intended endpoint could not be analyzed for any length of time. This means the problem is not simply that an estimate is imprecise. No cost estimate is reported. Statistical methods cannot recover the unobserved cost values without additional information and assumptions, and the registry does not report such information or a model-based substitute.

How should the planning illustrations be read?

The page includes calculated sample-size illustrations, which should be read as planning scenarios rather than as findings about what happened in the study. In general, a sample-size calculation asks how much information might be needed to detect a specified effect under specified assumptions. The assumptions listed for these illustrations are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect is set as a stated fraction of the observed effect. For time-to-event tables the figures refer to total events, while other tables refer to participants per arm.

These conditions do not describe the actual non-randomized allocation across the three study arms. The record does not report that the investigators used these assumptions to plan the trial, and the illustrations are not observed power. In general, observed power is not a substitute for interpreting an estimate and its uncertainty; moreover, a planning exercise based on an observed effect does not establish that an effect is real or clinically important. Since the posted primary outcome has no cost estimate, any illustration based on an effect should not be mistaken for a cost finding.

What is over-dispersion, in general?

For count outcomes, a statistical model may assume a particular amount of variability. Over-dispersion means the observed variability is greater than the model assumes. If it is ignored, standard errors may be too small and confidence intervals or significance tests may appear more certain than warranted. This is a general issue in count-data analysis; the registry record does not report whether count models were used or whether over-dispersion was assessed.

What can be inferred from event counts?

Counts describe how many events or affected participants were recorded in a group, given the way the registry presents the figures. They do not automatically account for different group sizes, follow-up duration, baseline risk, or participant differences. A rate requires a clearly defined denominator and observation period, while a comparative effect estimate requires an analysis that specifies the outcome and comparison. The registry's adverse-event section reports group counts at risk and affected, but the record does not provide a comparative model or an adjustment strategy. The serious-event figures should therefore be treated descriptively.

Finally, a statistical test or confidence interval would answer a question only within the scope of its analysis and assumptions. With non-randomized allocation, missing cost information, and no analyses listed, there is no reported primary comparison to test. General statistical concepts can explain what an analysis might communicate, but they cannot supply the absent measurements or methods.

10. Multiplicity, Missing Data and Analysis Populations

The record lists a primary cost outcome and nine secondary outcome measures. These secondary measures cover complications, parents away from work, antibiotic duration, length of stay, drainage procedures, imaging, quality of life measured with PedsQL, and recurrent appendicitis. The registry does not report a multiplicity plan. It is therefore not reported in the registry record whether the investigators adjusted for multiple comparisons, designated a hierarchy among secondary outcomes, or treated the secondary analyses as exploratory.

Multiplicity is a general concern when many outcomes or comparisons are examined: the more opportunities there are to identify an apparently notable result, the more important it is to understand which questions were prespecified and how uncertainty was handled. This is a general explanation, not a statement that a particular error occurred in this study. The registry lists zero analyses and provides no results for the secondary measures here, so there is no set of posted outcome tests on which to assess multiplicity.

Missing-data information is limited. For the primary cost outcome, the record specifically says that no cost data for any participants could be obtained. This is a failure to obtain the endpoint data, not a reported pattern of partial cost observations that can be characterized by group. The record does not describe missingness, exclusions, or imputation for the secondary outcomes. Analysis populations, including any intention-to-treat or per-protocol population, are not reported in the registry record.

These omissions matter because an analysis population and missing-data approach define which participants contribute to an estimate and under what assumptions. No such approach should be inferred from the study's completed status or its enrollment figure. In the absence of reported analyses, the posted record cannot show how missing observations were handled or whether analysis decisions changed the interpretation.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: recurrence of appendicitis (16.7%), admission for c-diff (4.2%), testicular swelling-hydrocele (4.2%), ed admission - fever and abdominal pain (4.2%).

The registry's adverse-event section reports serious-event counts for Early Appendectomy, Interval Appendectomy, and No Appendectomy, alongside the number at risk in each group. It lists serious events affecting 3 among 24 at risk in Early Appendectomy, 2 among 12 at risk in Interval Appendectomy, and 0 among 4 at risk in No Appendectomy. Deaths are listed as 0 for each group. These are the posted descriptive figures, not adjusted comparisons.

The record also lists serious-event terms with percentages: Recurrence of Appendicitis, 16.7%; Admission for C-Diff, 4.2%; Testicular Swelling-hydrocele, 4.2%; and ED Admission - Fever and Abdominal Pain, 4.2%. The registry information does not explain the denominators for these terms, so the percentages should be quoted as listed rather than interpreted as directly comparable group-specific risks.

In general, event counts alone do not establish that one approach caused more or fewer events. The groups are non-randomized and unequal in size, and the record does not report follow-up details or adjusted safety analyses. The counts are useful as a description of what the registry posted, but they do not support a firm ranking of safety across the approaches.

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

The record documents a study asking which of three approaches to complicated appendicitis in children is most cost-effective. Its primary outcome was intended to measure total health care cost from admission. The most important result for interpreting that question is that the cost data were not obtained. Thus, the posted record does not answer which approach had lower or higher costs, nor does it establish which approach was most cost-effective.

This absence should not be confused with a finding of no difference. A study can produce an estimate near zero, with uncertainty around it, or it can fail to produce an estimate at all. Here, the registry states that no cost data for any participants could be procured and that the outcome could not be analyzed in any fashion. The record therefore provides neither a primary cost estimate nor a statistical comparison of costs.

The registry's secondary outcome list identifies other questions that the study intended to examine, including complications, time away from work for parents, antibiotic duration, length of stay, drainage procedures, imaging, quality of life, and recurrent appendicitis. The record does not report results for those outcomes in the information. Their listing alone cannot be taken as evidence of a benefit, harm, or equivalence.

The posted serious adverse-event figures are descriptive counts, with zero deaths listed in each arm. Because the study was non-randomized and the arms differed in size, these counts should not be treated as evidence that one approach is safer. Nor does a count of zero in a group prove that an event cannot occur. The record does not provide a comparative safety analysis or the information needed to assess differences in participants and follow-up.

More generally, a completed registry record can be informative about the question, design, and data availability even when it cannot provide a definitive comparison. In this case it shows the intended three-way comparison and the failure to obtain the primary cost outcome. It does not show that the interventions are equivalent, does not identify a preferred approach, and does not establish causal effects on clinical outcomes. Those conclusions would require analyzable results and an interpretation that accounts for the non-randomized design.

13. Why This Trial Matters Statistically

This study is statistically instructive because its main question and its available data do not align. The study sought to compare the cost-effectiveness of three approaches, but the registered primary measure was overall cost of care and the registry says no cost data could be obtained. That distinction matters: a clear question and a completed study do not guarantee that the outcome needed to answer the question is available.

The record also illustrates why design labels matter. A parallel study can have distinct treatment groups without having randomized assignment. Here, allocation was non-randomized, so the groups should not be assumed to be comparable. This is particularly important when interpreting descriptive adverse-event figures. Group counts can summarize what was posted, but they do not by themselves separate treatment effects from differences in who received each approach or the circumstances of their care.

A further lesson is to distinguish outcome registration from outcome reporting. The registry lists a primary cost measure and several secondary outcomes, but the presence of an outcome in the record is not evidence that it was measured successfully or analyzed. In this study, the primary cost measure could not be analyzed, and the record lists zero analyses. Readers should not fill those gaps by inferring results from the outcome names or from the study's completed status.

Finally, planning calculations and outcome analyses answer different questions. The sample-size illustrations are planning scenarios under specified assumptions, not evidence of the trial's statistical power or of a treatment effect. They cannot replace the missing cost observations or correct the limitations of non-randomized allocation. Together, these points show why careful reading of registry records requires attention to the design, actual data availability, analysis reporting, and the distinction between descriptive counts and causal conclusions.

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.

The principal limitation is that the primary endpoint was not available for analysis. Although the original intention was to collect cost data for 2 years per person following admission, the registry states that no cost data were procured from any participants because institutions potentially involved were unwilling to provide access. There is therefore no reported cost estimate or economic comparison, and no applicable analyzed time frame for the primary endpoint.

Interpretation of the care groups is limited by non-randomized allocation. The registry does not report how the approach was selected, relevant baseline characteristics, or an adjustment method. It is not possible from this record to assess whether the groups were similar or to separate treatment effects from selection differences. The arm descriptions are blank, and the record does not provide detailed treatment protocols.

The record lists nine secondary outcome measures but reports zero analyses and does not present their results. It does not report analysis populations, methods for missing secondary-outcome data, a multiplicity strategy, interim analyses, or a detailed statistical plan. These details are not reported in the registry record, so they should not be inferred.

The adverse-event information is descriptive, and its group sizes are unequal. The registry does not provide a comparative safety model or adjustment details. It also does not explain the denominators for the listed serious-event term percentages in the information. These limits prevent the figures from supporting a reliable ranking of the approaches.

Finally, the enrollment figure and completed status do not establish that planned analyses were possible or adequately powered. The record does not report the investigators' sample-size justification. Any planning illustrations elsewhere on the page are not the trial's own design rationale and should not be interpreted as observed power.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Optimal Care of Complicated Appendicitis — NCT03159754.
• Registry record last updated 2023-11-28; status last verified 2023-11.
• Results first posted 2023-11-28.
• 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

The registry record describes a completed, Phase 4, non-randomized parallel study sponsored by the University of Michigan, with no masking and an enrollment of 40. The study compared three approaches to complicated appendicitis in children: Early Appendectomy, Interval Appendectomy, and No Appendectomy. Its stated objective was to determine which approach was most cost-effective.

The primary outcome was intended to measure overall health care cost from admission, originally over 2 years per person. The registry reports that no cost data were obtained, so the primary outcome could not be analyzed. Nine secondary outcome measures are listed, but the record reports zero analyses and does not provide their results. The adverse-event section lists group counts and zero deaths in each group; these figures are descriptive and do not establish comparative safety. Because allocation was non-randomized and key outcome and analysis details are unavailable, the record does not identify a preferred approach or support a causal comparison.