Practice Guidelines Grading Systems: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Practice Guidelines Grading Systems (NCT00940290), a randomized na study. The primary outcome is Change in Behavior in Physicians Attitude Towards a Decision to Give a Medication.

2. Clinical Question

The trial addresses whether the way evidence and recommendations are graded can influence a clinician’s response to a common clinical scenario. The outcome is an attitude or stated decision measured after reading the case and recommendation; it is not a measure of prescribing in routine practice. The registry describes a one-day timeframe.

The central comparison is among the four grading approaches, rather than between a medication and a placebo or between clinical treatments. The result therefore speaks to responses to differently graded recommendations in this experimental setting. It does not by itself establish how physicians would behave when making decisions for patients in ordinary care, or whether any resulting decision would change patient outcomes.

3. Trial Design

The registry describes a randomized, parallel-group trial with no masking. It lists four arms: GRADE System, SIGN Grading System, NICE Grading System, and CEBM-Oxford. Each arm received a clinical recommendation built and graded using its named system. The registry lists enrollment as 216 and identifies the condition as Decision Making. The study status is completed.

The primary outcome was a continuous measure: mean change in centimeters in physicians’ attitude toward a decision to give a medication. Physicians read a fictitious case of a child with acute diarrhea and answered whether they would recommend racecadotril. A zero to 10 visual-analog scale and a Likert scale were used, with the visual-analog scale described as ranging from definitely no to definitely yes. The registry says that before-after changes and differences among groups were measured on the 10 centimeters scale.

The timeframe for the outcome is one day. The registry lists the study start as 2009-08 and primary completion as 2009-10. It identifies Instituto Tecnologico y de Estudios Superiores de Monterey as the sponsor. The phase is listed as NA, which is consistent with the record presenting this as a study of decision making rather than a drug-development phase.

Further details of random sequence generation, allocation concealment, the exact process for presenting recommendations, and participant flow are not reported in the registry record. Masking is listed as none. The record reports one primary outcome measure and one analysis, and no secondary outcomes are posted. These details limit how fully the conduct and analysis can be reconstructed from the registry alone.

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: Participants were not eligible for randomization if they refuse to participate in the trial or if they reported less than six months of clinical practice (residents). After randomization they were allocated to one of the four study groups. A survey was applied and no wash out was observed or desertions.

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 Change in Behavior in Physicians Attitude Towards a Decision to Give a Medication, measured over One day.

The primary endpoint measures change in physicians’ stated attitude toward recommending medication after they read a fictitious clinical case and a recommendation presented under one of the grading systems. The response was recorded on a visual-analog scale, with the stated decision ranging from definitely no to definitely yes. The reported unit is mean change in centimeters, and the timeframe is one day.

This kind of endpoint can capture a clinician’s immediate response to how evidence and recommendations are framed. Comparing change across randomized groups can help assess whether the grading approach is associated with different stated responses under the study conditions. A continuous measure also retains gradations in response rather than reducing each answer to a simple yes-or-no category.

The endpoint is not actual prescribing behavior. It records a response to a fictitious scenario, not a documented treatment decision for a patient. Nor does the registry establish that the stated decision predicts subsequent clinical practice. The case involved acute diarrhea in a child and asked about racecadotril, so interpretation should remain tied to this scenario and the measurement used. The registry does not report further details about how the visual-analog and Likert responses were combined or how any discrepancy between them was handled.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The outcome is continuous and is reported as a mean change in centimeters. A mean summarizes the average direction and magnitude of responses in an arm, while individual clinicians may have responded differently. The mean alone does not describe the spread of individual responses. The registry gives confidence intervals but does not report a standard deviation or another measure of within-arm dispersion.

What does a confidence interval convey?

In general, a confidence interval expresses the precision of an estimate under the assumptions of the method used to construct it. A narrower interval indicates greater precision than a wider interval, all else being equal. It does not show the range containing most individual participants’ responses, and it does not guarantee that the true value lies within the reported limits. Here, the intervals are reported for the mean changes in each arm. They help show uncertainty around those arm-specific estimates, but they are not themselves the between-group test.

The arm-specific intervals have different relationships to zero: the GRADE interval lies above zero, while the SIGN, NICE, and CEBM-Oxford intervals each include zero. Zero represents no mean change on the measure. This comparison can describe whether an arm’s interval is compatible with no mean change under its calculation, but it cannot replace the randomized comparison across arms. In particular, the fact that one interval excludes zero and another includes zero does not, by itself, prove that the two arm means differ.

What does the Kruskal-Wallis test assess?

In general, the Kruskal-Wallis test is a rank-based method for comparing responses across independent groups. It assesses whether the groups appear to come from the same distribution, using the relative ordering of observations rather than relying on a comparison of means alone. It is often useful when a normal-distribution model for the outcome is not considered suitable. The registry names this test for the comparison among the four grading-system arms and reports p = 0.007.

The reported test is omnibus. A result from an omnibus test does not reveal which particular groups account for the overall pattern. To make pairwise claims, investigators generally need specific follow-up comparisons, with appropriate attention to multiplicity. Such comparisons are not reported in the registry record. The test also does not directly quantify the size of any pairwise difference in centimeters.

How should the p-value be read?

In general, a p-value measures how incompatible the observed data, or data more extreme, are with a specified null model, assuming that model and the analysis assumptions hold. It is not the probability that the null model is true, and it is not a measure of the size or importance of an effect. The registry gives p = 0.007 for the reported four-group analysis. The record does not report a prespecified significance threshold or a fuller statistical analysis plan, so those details should not be inferred.

The rank-based test and the arm-specific mean changes summarize different features of the data. Means retain the outcome’s centimeter scale and are easy to interpret as average changes. A rank-based test evaluates an overall distributional comparison and may respond to patterns beyond differences in means. Because the registry does not report the individual observations or further distributional summaries, the test cannot be independently reconstructed from the posted arm means and confidence intervals alone.

What can and cannot be recalculated?

Unadjusted comparisons may sometimes be recalculated from posted summary statistics, but such calculations depend on the information available and the assumptions used. The registry record lists a continuous-endpoint comparison as not estimable for a two-arm comparison. It does not provide a separate recalculated pairwise result to compare with the sponsor’s four-group analysis. The sponsor’s reported Kruskal-Wallis result is therefore the available inferential result; the arm means and confidence intervals are descriptive estimates, not a substitute for that test.

In general, a confidence interval’s width reflects both the amount of information and the variability of the outcome, as well as the method used. Greater variability can reduce precision, and the number of observations can also affect precision. The registry provides arm counts and confidence limits, but not all of the information required to verify the interval calculations or assess their assumptions. A reader should distinguish the posted estimates from any unreported modeling choices.

10. Analyses Reported by the Sponsor

The registry reports the sponsor’s analysis as a Kruskal-Wallis test across GRADE, SIGN, NICE, and CEBM-Oxford, with p = 0.007. It also posts mean changes and confidence intervals for each arm. These summaries serve different purposes: the arm results describe estimated average changes, while the reported test provides an overall rank-based comparison among the groups.

The record does not report a recalculated two-arm comparison for this continuous outcome; it identifies such a comparison as not estimable. Consequently, there is no separate recalculated pairwise estimate or p-value to set against the sponsor’s result. The arm-level means and confidence intervals should not be presented as though they were a recalculation of the sponsor’s omnibus test.

No discrepancy is flagged between a sponsor analysis and a recalculation. The registry’s reported analysis is therefore the available inferential result. It supports an overall difference in response distributions under the reported test, but does not identify which pair of grading systems differs. The record does not report pairwise follow-up analyses, adjustment for multiple comparisons, or additional details of the sponsor’s statistical plan.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and one analysis, and reports no secondary outcomes. It does not report whether additional outcomes or analyses were planned but not posted, or whether the reported analysis was prespecified. A listed count of outcomes alone does not establish that no other analyses were considered during the study.

The sponsor reports one Kruskal-Wallis comparison spanning the four randomized groups. This is an omnibus test, not a full set of pairwise tests. The registry does not report follow-up comparisons between individual grading systems or whether any such comparisons were adjusted for multiplicity. Without those details, the overall p-value should not be used to claim that a specific pair of arms differs.

The record gives the number of participants in each arm, but does not report participant flow, exclusions from analysis, or the analysis population definition. It does not state whether all randomized participants were included in the primary analysis, how incomplete responses were handled, or whether any participants had missing endpoint data. These items are not reported in the registry record, so the degree to which the analysis followed an intention-to-treat principle cannot be assessed.

The record also does not report an imputation method, a sensitivity analysis for missing data, or reasons for missing observations. Missingness can affect an estimate when the participants with observed data differ from those without observed data. Without information about completeness and handling, the potential impact cannot be evaluated. The posted results should therefore be interpreted as the reported analysis rather than as evidence that missing data were absent.

Randomization can support a fair comparison when allocation and analysis are conducted appropriately, but details of sequence generation and allocation concealment are not reported. Masking is listed as none. The registry does not describe safeguards against influence from knowing the grading system or the procedure for handling any deviations. These reporting gaps leave uncertainty about implementation and analysis, even though the broad randomized parallel design is stated.

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

The result indicates that physicians’ measured responses differed across the four grading-system groups in the reported overall analysis. The posted mean changes show a larger positive change in the GRADE arm than in the other arms, and the confidence intervals describe uncertainty around those arm-specific estimates. Together, these findings concern responses to the particular fictitious case and recommendation used in the trial.

The result does not establish which specific grading systems differ from one another. The Kruskal-Wallis p-value is an overall test, and pairwise findings are not reported. Nor does the result show that a grading system changes real-world prescribing, improves the quality of decisions, or benefits patients. The measured endpoint was a stated attitude toward recommending racecadotril, not a clinical outcome or observed prescription.

It also does not show that the observed pattern would persist over time. The registry gives a one-day timeframe and does not report follow-up on later decisions. Generalization beyond physicians responding to this case is uncertain because participant characteristics and recruitment details are not reported in the registry record.

The study is informative as a test of whether the presentation and grading of a recommendation can be associated with an immediate measured response in a randomized setting. Its interpretation should remain limited to that question. The result is not a treatment comparison, and it should not be read as a recommendation about racecadotril or any other medication. It neither establishes clinical effectiveness nor offers medical advice.

13. Why This Trial Matters Statistically

This trial raises a methodological question relevant to guideline development: whether the system used to grade evidence and recommendations can influence clinicians’ stated decisions. Random assignment to different grading presentations provides a framework for comparing responses while holding the clinical scenario broadly in view. The outcome focuses on the decision process rather than a therapeutic effect.

Statistically, the record illustrates why descriptive estimates and an overall hypothesis test should be interpreted together but not treated as interchangeable. The mean changes communicate the scale and direction of average responses in each arm. The Kruskal-Wallis result supplies an overall rank-based comparison. Neither alone answers every question: the means do not establish pairwise differences, and the omnibus test does not specify which arms account for the overall pattern.

The confidence intervals are also useful for showing uncertainty in the arm estimates. Their relationship to zero addresses whether each estimated mean change is compatible with no change under the interval calculation, not whether the arms differ from one another. This distinction is important whenever several groups are compared.

The trial’s limits are equally instructive. An immediate stated response to a fictitious case may be useful for studying presentation effects, but it is not the same as observed clinical behavior. Missing reporting on participant characteristics, allocation procedures, analysis populations, and follow-up prevents a fuller assessment of precision, bias, and generalizability. The record thus supports a focused statistical reading: an overall difference in measured responses was reported, while the exact pairwise pattern and its relevance to routine care remain unresolved.

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 primary endpoint is a stated response to a fictitious clinical case, rather than observed prescribing or patient health. The record does not report whether responses to the visual-analog scale and Likert scale were analyzed separately or how the final endpoint was derived from them. This makes the measurement process less reproducible from the registry description alone.

Participant characteristics, recruitment procedures, and clinical settings are not reported in the registry record. It is therefore difficult to assess whether the participants resemble physicians who make comparable decisions in routine practice. The record also does not describe whether the four recommendation presentations differed only by grading system or whether other presentation features varied.

Although randomization and a parallel design are reported, the method of sequence generation and allocation concealment is not. Masking is listed as none, and the record does not explain whether participants or outcome assessors could influence measurement through awareness of the grading system. The possible effect of these factors cannot be established from the registry description.

The registry does not define the analysis population, report participant flow, or explain handling of missing endpoint data. It also does not report pairwise comparisons after the omnibus test, a multiplicity procedure, or a detailed statistical plan. These gaps restrict independent evaluation of the reported analysis and make it inappropriate to infer which specific systems differ from one another.

Finally, the short, one-day timeframe limits conclusions about persistence. The outcome represents an immediate response to a particular case about acute diarrhea in a child. The findings do not establish whether the response would carry over to other clinical scenarios, lead to actual medication use, or affect patient outcomes.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Practice Guidelines Grading Systems — NCT00940290.
• Registry record last updated 2010-01-20; status last verified 2009-11.
• Results first posted 2010-01-13.
• 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

NCT00940290 is a completed randomized, parallel-group trial with no masking. It compared four systems for grading clinical recommendations: GRADE, SIGN, NICE, and CEBM-Oxford. The registry lists enrollment as 216 and identifies Decision Making as the condition.

The primary outcome was mean change in centimeters in physicians’ stated attitude toward recommending racecadotril after reading a fictitious case of a child with acute diarrhea. The outcome timeframe was one day. The reported group comparison used the Kruskal-Wallis method and gave p = 0.007.

The posted results describe an overall difference among the groups, but do not report pairwise comparisons. The endpoint measures a response to a scenario, not prescribing in routine care or a patient outcome. Details about participant flow, missing data, analysis populations, and several aspects of trial conduct are not reported in the registry record.