Pancreaticobiliary Reflux in Patients Without Cholelithiasis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pancreaticobiliary Reflux in Patients Without Cholelithiasis (NCT00890201), a registered phase not stated study. The primary outcome is Amylase and Lipase Values in Gallbladder Bile.

2. Clinical Question

3. Trial Design

The record describes a clinical investigation of pancreaticobiliary reflux in patients with and without gallstones. Its title emphasizes patients without cholelithiasis, while the official title frames the question as whether reflux in patients with and without cholelithiasis is a normal phenomenon. The registry lists a total enrollment of 197 and the status as completed. The listed sponsor is Cirujanos la Serena. The study dates recorded are 2009-01 for start and 2009-07 for primary completion.

The study procedure combines gallbladder bile sampling with intraoperative cholangiography. The arms are defined by gallbladder condition and surgical context rather than by a randomized intervention. The normal-gallbladder group is described as patients without gallstones on preoperative ultrasonography, with postoperative biopsy also mentioned. These patients were submitted to elective gastroesophageal surgery. The gallstone group is described as patients submitted to elective cholecystectomy for gallbladders with stones evidenced by preoperative ultrasound. The record also describes normal pancreaticobiliary junction findings and preoperative serum amylase and lipase levels as criteria relevant to the gallstone group.

Allocation is not stated, and the registry explicitly cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. That matters because group membership is tied to disease status and the reason for surgery. The available record does not describe a method for making the groups comparable or an adjusted analysis that accounts for differences between them.

The primary measure is a continuous outcome: mean amylase and lipase in gallbladder bile. The record gives a timeframe of 24 hours and specifies standard deviation as the dispersion measure. It lists five outcome measures and zero analyses in the outcome-analysis record. The number included in the primary analysis was determined by eligibility, with some participants excluded according to protocol exclusion criteria; exact group-specific analysis counts are not reported in the registry record. Detailed procedures, full eligibility rules, and a statistical analysis plan 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.

Before assignment: Patients submitted to elective cholecystectomy for symptomatic gallstone disease, older than 16 years of age and patients submitted to elective gastrectomy for gastric cancer harboring normal gallbladders (without gallstones), were included in this trial. Patients within any other clinical situation were excluded

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The number of participants analyzed was determined by the number of participants that matched the inclusion criteria. As posted elsewhere some participants were excluded from this analysis based in the exclusion criteria of the protocol.

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 Amylase and Lipase Values in Gallbladder Bile, measured over 24 hours.

The primary endpoint concerns amylase and lipase measured in gallbladder bile. These enzymes are reported as continuous values in mg/dl, with the primary outcome described as a mean and standard deviation. The stated timeframe is 24 hours. The registry description says normal values of lipase and amylase in gallbladder bile should be zero. The endpoint is therefore intended to characterize whether these enzymes are present in bile and how their measured levels vary across the two gallbladder groups.

In general, a continuous endpoint retains information about the magnitude of measured values rather than reducing each observation to a yes-or-no classification. A group mean describes the central value, while a standard deviation describes how spread out participant-level values are around that mean. These statistics can help readers assess both the average enzyme level and the variability within each group. They do not, by themselves, show whether an observed difference is compatible with chance or whether groups are comparable on other characteristics.

The registry record does not report the group means, standard deviations, participant counts analyzed, or an inferential comparison for the primary endpoint. It also does not specify whether amylase and lipase were treated as separate co-primary measures or combined in a prespecified way. Consequently, the endpoint definition conveys what the investigators intended to measure, but the posted record does not permit interpretation of the observed enzyme levels or their precision.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical information in the registry record is limited. It identifies the primary outcome as a mean of continuous measurements and names standard deviation as the dispersion statistic. It does not report the analysis procedure used to compare the groups, the estimates, or measures of inferential uncertainty. General explanations of these statistical ideas can clarify what such information would mean, but they cannot substitute for results that are not reported in the registry record.

What does a mean describe?

In general, a mean is a measure of the central level of a continuous outcome. For this study, it would describe the average bile amylase or lipase value among participants included in an analysis group. A mean does not describe every participant’s measurement, and it can be influenced by unusually high or low values. The registry identifies the mean as the parameter of interest, but does not report its value for either group.

A comparison of group means can describe the average difference between groups if the estimates and their uncertainty are reported. The numerical contrast alone does not establish that the groups are otherwise comparable. In this study, gallstone status is tied to different clinical and surgical pathways, and allocation is not stated. In general, that context matters because group differences could reflect other characteristics as well as gallstone status. The registry does not report an adjustment strategy to address that possibility.

Why report standard deviation?

In general, standard deviation describes the spread of individual measurements around a group mean. A small standard deviation indicates that measurements tend to cluster more closely around the mean, while a larger standard deviation indicates greater variability. It is not the same as the standard error, which describes the precision of an estimated mean, and it is not a confidence interval. The registry names standard deviation but does not provide group-specific values. Readers therefore cannot assess the observed variation in bile enzyme measurements.

Variation is important for interpreting the mean because participants may have heterogeneous enzyme values even when the average is near the stated reference expectation. The distribution of measurements can also affect which statistical methods are appropriate. General methods may rely on assumptions about the outcome distribution; when data are highly skewed or contain influential values, an untransformed mean and a method based on an unsuitable distribution can give a misleading summary or uncertainty estimate. The registry does not report distributional checks or alternative analyses.

What would a confidence interval add?

In general, a confidence interval expresses uncertainty around an estimated quantity under a specified statistical model and sampling procedure. For a group mean, it would show the precision of that estimate; for a contrast between groups, it would show the precision of the estimated difference. A confidence interval is not a guarantee that the true value lies in the interval, and its interpretation depends on the method and assumptions used. No confidence intervals are reported in the registry record, so the precision of the primary endpoint and any group contrast cannot be assessed.

A test result and an effect estimate answer related but different questions. A test assesses compatibility of the observed data with a specified null hypothesis under its assumptions. An effect estimate describes the size and direction of the observed contrast, while an interval conveys uncertainty around it. A small p-value would not by itself establish clinical importance or remove concerns about group comparability; conversely, an imprecise result would not prove that groups are equivalent. The registry does not report a p-value, a hypothesis test, or a prespecified analysis strategy.

What do the planning assumptions mean?

The record describes sample-size planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation. The illustrations frame the target as detecting a stated fraction of the observed effect. For outcomes other than time-to-event outcomes, the planning quantity is participants per arm; time-to-event calculations use a total event count with the Schoenfeld method. These are planning illustrations, not evidence about the amount of power achieved in the completed study. They do not describe the trial’s original design justification, and the registry record does not report that justification.

In general, such calculations depend on assumptions about the target effect, variability, allocation, and analysis. A normal approximation is a simplifying model for the sampling distribution of an estimate; its adequacy depends on the data and design. If data are unusually skewed, strongly affected by outliers, or otherwise inconsistent with the model, the resulting planning quantities may not reflect actual operating characteristics. The record does not provide enough outcome information to assess those assumptions for the observed measurements.

Why does group structure matter?

The study groups are based on gallbladder condition and distinct clinical settings, rather than a randomized allocation described in the registry. In general, randomization helps balance measured and unmeasured characteristics on average, while a nonrandomized comparison may retain confounding. An unadjusted difference in means would summarize the observed groups, but could not isolate the association of gallstones with bile enzyme levels from all other group differences. The registry does not report whether an adjusted model was used, which covariates might have been included, or how model assumptions were assessed.

Multiplicity is another general concern when several outcomes are examined. Conducting multiple tests can increase the chance that at least one result appears noteworthy by chance, depending on the testing strategy. The registry lists five outcome measures, but does not report a multiplicity plan or analysis results. It is not possible to determine whether outcomes were tested separately, whether any adjustment was applied, or whether all planned outcomes were reported.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures, including the primary measure of amylase and lipase values in gallbladder bile and secondary outcomes concerning amylase and lipase values in normal gallbladders and gallbladders with cholelithiasis, operative cholangiography, and preoperative serum values. It also lists zero analyses. The posted record does not provide outcome estimates or inferential results for these measures.

When a study examines several outcomes, multiplicity can affect how test results should be interpreted. In general, conducting multiple statistical tests can increase the chance of at least one apparently positive finding under a set of null hypotheses. Researchers may address this through a prespecified hierarchy, adjustment procedure, or clear distinction between primary and exploratory analyses. The multiplicity approach is not reported in the registry record. The record also does not say whether amylase and lipase were analyzed as separate primary measures or under a joint endpoint strategy.

Missing-data handling is not reported in the registry record. The primary outcome description states that the number analyzed depended on meeting inclusion criteria and that some participants were excluded according to protocol exclusion criteria. The number analyzed in each group, the number with missing bile measurements, and reasons for exclusion or missingness are not reported. These details are important because the analyzed sample can differ from the enrolled group, and conclusions may depend on which participants contribute measurements.

The registry does not report whether analyses followed a prespecified analysis population, whether any imputation was used, or whether sensitivity analyses assessed the effect of exclusions or missing measurements. Full inclusion and exclusion criteria are not reported in the registry record. Therefore, neither the completeness of the primary endpoint data nor the sensitivity of any findings to analysis-population choices can be evaluated from the posted results.

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

The study addresses a biologically focused measurement question: whether amylase and lipase are present in gallbladder bile among patients with normal gallbladders and patients with gallstones. The registry states that normal bile values for these enzymes should be zero and identifies the mean enzyme values as the primary outcome. This description explains the intended use of the endpoint, but it does not supply the observed values needed to characterize either group.

The record therefore does not establish whether measured bile enzyme levels were zero, above zero, or different between groups. It does not report an estimated group contrast, a confidence interval, or a test result. No conclusion about the frequency or magnitude of pancreaticobiliary reflux can be drawn from the endpoint description alone. The background summary records the authors’ belief that reflux might be a normal phenomenon in patients with and without gallstones, while also suggesting that reflux in patients with cholelithiasis might be associated with biliary tree and sphincter of Oddi dysmotility. These are stated hypotheses and context, not a reported finding from the primary analysis.

Even if a group difference were reported, a nonrandomized comparison would require careful interpretation. The registry does not state that participants were randomly allocated, and the groups are recruited through different clinical and surgical contexts. A difference could reflect gallstone status, other differences between the groups, or a combination. Without reported adjustment and uncertainty estimates, the contribution of each possibility could not be separated.

The record’s completed status and enrollment count do not fill the results gap. The number analyzed depends on eligibility and protocol exclusions, and exact analysis counts are not reported in the registry record. The posted information consequently supports description of the research question and intended measurement, but not a claim about the observed result, its precision, or its broader implications. It also does not establish that reflux is normal or abnormal, or that it has a particular clinical consequence.

12. Why This Trial Matters Statistically

This study is statistically interesting because it frames pancreaticobiliary reflux as a question that can be examined through measurable enzyme values in gallbladder bile. Rather than defining the issue only by a clinical label, the primary endpoint focuses on continuous measurements of amylase and lipase. That design makes the choice of summary statistics important: the mean describes the central level, while standard deviation describes the spread of measurements. Both are useful for understanding a continuous outcome, but neither is reported as a result in the registry record.

The comparison also illustrates a central interpretive challenge in clinical research. The groups are defined by gallbladder status and clinical setting, with one group undergoing elective gastroesophageal surgery and the other elective cholecystectomy. Allocation is not stated, and the registry cautions that the arms are not a like-for-like control comparison. A contrast between these groups would therefore require attention to the possibility that other differences contribute to the observed measurements. Statistical adjustment can sometimes address measured differences, but no such analysis is reported in the registry record.

The outcome description supplies a reference expectation of zero for normal bile values. That gives the measurement question an interpretable anchor, but a comparison with a reference value and a comparison between groups are not identical statistical questions. Each requires clear estimates and uncertainty. Since the group means, dispersion, and inferential results are not reported, readers cannot judge how much information the measurements contain or how precisely the question was answered.

The record also shows why enrollment is not interchangeable with an analysis count. Eligibility and protocol exclusions determine how many participants contribute to the primary outcome, yet the group-specific analysis counts are not reported. The combination of a defined endpoint, unequal clinical contexts, and incomplete reporting makes this trial a useful case for distinguishing a research question from the evidence needed to answer it.

13. 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 trial-specific limitation in the posted record is the absence of primary outcome results. Although the endpoint and measurement scale are described, group means, standard deviations, analysis counts, and an inferential comparison are not reported in the registry record. The result’s direction, magnitude, and precision therefore cannot be evaluated.

The group comparison is not randomized according to the registry, and allocation is not stated. The normal-gallbladder and gallstone groups are drawn from different surgical contexts. The registry itself cautions that the arms are not a like-for-like control comparison. Baseline characteristics, any method for adjusting group differences, and any adjusted estimates are not reported in the registry record, limiting causal interpretation of a potential contrast.

The registry states that the number analyzed was based on inclusion criteria and that some participants were excluded under protocol exclusion criteria. It does not report the analyzed count for each group, the detailed exclusion criteria, or the number and reasons for missing measurements. As a result, it is not possible to assess how the analyzed participants relate to the enrolled group or whether exclusions could affect the result.

The record lists five outcome measures but does not describe a multiplicity strategy, a statistical analysis plan, or the handling of missing data. The full eligibility description is not available in the recorded arm text, and the primary analysis method is not reported. These limitations concern the detail available in the registry record; they do not establish that such procedures were absent from the investigators’ work.

14. Related Tutorials

15. Related Statistical Calculators

16. Sources

• ClinicalTrials.gov: Pancreaticobiliary Reflux in Patients Without Cholelithiasis — NCT00890201.
• Registry record last updated 2010-12-17; status last verified 2010-09.
• Results first posted 2009-10-20.
• 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.

17. Record Summary

The registry record describes a completed study of pancreaticobiliary reflux in patients with and without gallstones, sponsored by Cirujanos la Serena. Enrollment is listed as 197. The study compares a normal-gallbladder group recruited through elective gastroesophageal surgery with a gallstone group undergoing elective cholecystectomy. The listed procedure is gallbladder bile sampling and intraoperative cholangiography.

The primary outcome is mean amylase and lipase values in gallbladder bile, measured in mg/dl, with standard deviation and a timeframe of 24 hours. The stated normal values should be zero. The registry lists five outcome measures and zero analyses. It also notes that analysis counts were determined by eligibility and that some participants were excluded under protocol criteria.

Allocation is not stated, and the registry cautions that the groups are not a like-for-like control comparison. Primary outcome results, analysis counts by group, inferential methods, missing-data handling, and multiplicity procedures are not reported in the registry record. The posted information describes the research question and design, but does not show the measured outcome pattern.