Effectiveness Trial for Evaluating IAHA for PFPS: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effectiveness Trial for Evaluating IAHA for PFPS (NCT01811654), a randomized na study. The primary outcome is Change in Visual Analog Scale (VAS) Score.

2. Clinical Question

The trial asks whether adding intra-articular hyaluronan to standard care is associated with a different change in activity-related pain for people with symptomatic patellofemoral pain syndrome (PFPS). The registry describes the condition as chronic and identifies change in Visual Analog Scale (VAS) score as the primary outcome, assessed from baseline to 3 month follow-up. Higher VAS scores indicate greater pain.

This is a question about the incremental difference between treatment strategies, not about the effect of injections in isolation. Both groups receive standard care, while the intervention group also receives injections. Because the registry lists no masking, the comparison is described as unmasked. The posted results do not provide an estimated difference in change, its uncertainty, or a test result, so the clinical question cannot be answered from the reported outcome data.

3. Trial Design

The registry describes a randomized, parallel-group trial. Participants were assigned to standard care or standard care plus intra-articular hyaluronan (Euflexxa). The registry classifies the injection intervention as a device. Masking is listed as none, so the trial is described as unmasked. The registry lists the phase as NA.

Standard care could consist of physical therapy, activity modification (relative rest), and/or oral analgesic therapy. A specific physical therapy protocol was to be implemented. The intervention group was to receive standard care as well as three consecutive weekly injections. The description also says oral analgesics in that group would be used at the lowest dose and for the shortest time possible to treat PFPS symptoms. The record does not provide further detail on adherence, treatment changes, or how each component of standard care was delivered.

The registry lists enrollment as 30. The number enrolled in each randomized group, the allocation ratio, and the number analyzed for the primary outcome are not reported in the registry record. The primary completion date is 2016-12-07, and the overall status is completed. The registry lists the study start as 2013-04 and identifies NYU Langone Health as the sponsor.

The primary outcome is change in VAS score, described at baseline and 3 month follow-up. A PFPS Severity Scale (PSS) score is listed as a secondary outcome. The record identifies two outcome measures but does not give an analysis for either. It also does not report details of sequence generation, concealment of treatment assignment, adherence assessment, or the timing of the secondary outcome. Those design details 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

Analysis population for the primary outcome, as defined in the registry: Both " Overall Number of Participants Analyzed" and "Participant Flow" are now consistent

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 Visual Analog Scale (VAS) Score, measured over At baseline and 3 month follow-up.

The primary endpoint is change in activity-related pain measured with a visual analog scale. The registry describes a 100mm scale and records the measurement in millimeters. It states that no pain is categorized as 0-4 mm, mild pain as 5-44 mm, moderate pain as 45-74 mm, and severe pain as 75-100 mm. Higher scores indicate a higher level of pain. The planned measurement occasions are baseline and 3 month follow-up.

Change from baseline is used to represent how the pain score moves over the follow-up period, rather than relying only on a follow-up score. The registry description specifies a comparison of the groups' mean change. In general, a continuous score can retain gradations of response that would be lost if it were reduced to broad categories; the registry's pain categories give context to the scale, while the stated primary analysis concerns mean change.

The endpoint description names a 2-sample t-test for comparing the group means. The registry record does not report the groups' mean changes, a between-group estimate, a confidence interval, a p-value, or an analysis population count. Therefore, the measurement and intended comparison are described, but the magnitude and precision of the primary endpoint result are not available in the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a mean-based comparison of a continuous outcome. The primary outcome is change in VAS score, measured in millimeters, from baseline to 3 month follow-up. The stated analysis compares mean changes between two treatment groups using a 2-sample t-test. No analysis result is reported in the registry record.

What does a 2-sample t-test compare?

In general, a 2-sample t-test evaluates whether the observed difference between two group means is compatible with a null hypothesis of equal means, given the variability in the observations and the assumptions of the test. In this trial's stated analysis, the quantity being compared is mean change from baseline, not simply the mean follow-up score. The test is intended to address whether the groups differ in average change. The registry description characterizes the null hypothesis in words, but does not provide the calculated test statistic or p-value.

In general, the test's interpretation depends on how the outcome is distributed and how variability is estimated. A standard t-test is commonly used for a continuous outcome when the sampling distribution of the estimated mean difference is adequately approximated by the test assumptions. The registry record does not report diagnostic checks, details of variance handling, or an alternative analysis. Those methods cannot be inferred from the named test alone.

What would a confidence interval add?

In general, a confidence interval expresses the uncertainty around an estimated group contrast. Its endpoints show a range of values compatible with the data under the analysis procedure, rather than establishing a single exact effect. Reading the interval alongside the estimate helps distinguish a relatively precise estimate from one with substantial uncertainty. No confidence interval for the primary outcome is reported in the registry record, so the precision of any treatment contrast cannot be assessed from the posted results.

A p-value and a confidence interval answer related but different questions. In general, a p-value summarizes how unusual the observed data, or more extreme data, would be under a specified null model. It does not measure the probability that the null hypothesis is true, and it does not describe the size or practical importance of a difference. A confidence interval provides information about plausible effect values and precision, while an effect estimate gives the contrast on the outcome scale. The registry record reports none of these primary analysis quantities.

Why use change from baseline?

In general, a change score expresses the difference between a participant's later measurement and their baseline measurement. Comparing average changes between randomized groups focuses on the difference in how scores move over the stated follow-up interval. This is the approach named in the registry description. The record does not report how individual missing measurements were handled or whether any baseline adjustment beyond calculating change was used.

Change scores have a direct interpretation in the scale's units, but their variability depends on both baseline and follow-up measurements and their relationship. In general, the precision of a mean-change comparison depends on the amount of variation in those changes and the number of observations analyzed. The record does not report group-specific outcome variation or analyzed counts for the primary endpoint, so precision cannot be reconstructed.

How should planning illustrations be read?

In general, sample-size planning uses assumptions about an effect to be detected, variability, a significance level, allocation, and a statistical model. A planning calculation is a hypothetical design exercise; it is not a result from the trial. The registry's stated illustration assumptions describe a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. These assumptions describe planning illustrations, not the trial's own design.

Such planning values should not be called observed power. In general, observed power is not a substitute for reporting the effect estimate and its uncertainty. A trial's observed estimate and confidence interval are more directly useful for understanding what the data support. The registry record does not provide the primary outcome effect or its uncertainty, and does not report the trial's sample-size justification or statistical planning procedure. Accordingly, the planning assumptions should not be read as evidence about the original design or as a measure of the strength of the trial result.

The record identifies no primary outcome analyses in its posted analysis information. It therefore does not allow a reader to check the stated t-test against the actual analysis, assess model assumptions, or determine whether the comparison was adjusted for any other factors. Those details are not reported in the registry record. The methods that can be described are limited to the stated mean-change comparison and its named test.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists the VAS change as the primary outcome and the PFPS Severity Scale (PSS) score as a secondary outcome. It identifies two outcome measures, but does not report analyses for them. The timing and detailed scoring of the secondary outcome are not reported in the registry record. The record does not describe a multiplicity adjustment, a hierarchy of hypotheses, or how interpretation would account for testing more than one outcome. It would therefore be inappropriate to assume that any particular correction or testing strategy was used.

In general, multiplicity arises when several outcomes, time points, subgroups, or statistical comparisons are considered. Testing multiple hypotheses can increase the chance of at least one apparently unusual result under a collection of null hypotheses. Prespecifying a primary outcome and an analysis strategy can help readers distinguish the main question from secondary or exploratory questions. The registry identifies a primary outcome, but the statistical plan and any multiplicity procedure are not reported in the registry record.

Missing-data handling is also not described. The record does not state how many participants had VAS measurements at baseline or 3 month follow-up, whether any measurements were missing, or how missing observations were handled. It does not report sensitivity analyses for missing outcomes. In general, the implications of missing data depend on how much is missing and why; neither can be assessed from the posted results.

The population note says that the entries for “Overall Number of Participants Analyzed” and “Participant Flow” are now consistent. It does not provide, in the outcome information, a primary-outcome analysis count or details of an intention-to-treat or per-protocol population. The population used for the reported primary analysis is therefore not reported in the registry record. These gaps limit assessment of both the analysis population and the robustness of any outcome inference.

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.

The registry lists serious adverse event counts, other adverse event counts, and deaths for each treatment group. For Standard Care, the serious-event risk group is 14 and the serious events recorded are 0; the other-event risk group is 14 and the other events recorded are 0. For Intra-Articular Hyaluronic Acid-Euflexxa, the corresponding risk group is 16 for serious events with 0 recorded, and 16 for other events with 0 recorded. Deaths are recorded as 0 in each group.

These entries describe what the registry reports for the listed categories; they do not establish that no adverse events of any kind occurred outside the recorded definitions or observation process. The registry record does not report additional detail on event definitions, surveillance duration, severity grading, attribution, or completeness of collection. The absence of reported event counts should therefore be read as a limitation of the available safety summary, not as a comprehensive account of all possible harms.

In general, adverse-event counts are interpreted in relation to the people at risk, how long they were followed, and the way events were sought and classified. The record supplies risk-group counts but does not describe follow-up exposure for safety or the collection procedures. These safety entries do not provide evidence about the primary pain outcome, and they should not be used to infer an efficacy result.

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

The registry record gives a defined clinical comparison: standard care alone versus standard care with intra-articular hyaluronan, with change in activity-related VAS pain as the primary outcome. It also specifies the scale, its direction, and the intended comparison of average change. These details clarify what the trial was designed to examine at the level of its stated outcome.

However, the posted results do not report the primary outcome analysis. There is no reported group mean change, estimated between-group contrast, confidence interval, or p-value. Without those results, the record does not establish the magnitude or direction of any difference in activity-related pain change, nor how precisely any difference was estimated. It also does not provide an analysis of the secondary PSS outcome.

The trial's registry enrollment figure is not a substitute for the number analyzed or for outcome data. Likewise, recorded zero counts for the specified adverse-event categories do not answer the primary efficacy question. Safety and pain outcomes are different types of evidence, and the safety counts have their own limitations because event collection and follow-up details are not reported.

In general, a randomized comparison can support an estimate of the contrast between assigned strategies when its results and analysis are reported. Interpreting that estimate also requires attention to uncertainty, missing data, adherence, and the population analyzed. The registry describes randomization and a parallel design, but does not report many of those analytic details. It is therefore possible to describe the intended comparison, but not to assess the actual primary result or the robustness of an effect estimate from the registry record.

The record should not be read as demonstrating that the added injections changed pain, nor as demonstrating that they did not. Those conclusions would require outcome findings that are not reported in the registry record. The appropriate statistical reading is limited: the study question and measurement strategy are documented, while the principal estimate and its precision are unavailable.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of how a practical treatment question can be framed as an incremental comparison. Both groups receive standard care, while the intervention group also receives intra-articular hyaluronan. The contrast therefore concerns the addition of injections to the stated care strategy, rather than comparing injections with no care. That distinction is essential when interpreting the treatment effect a trial is intended to estimate.

The primary outcome is a continuous measure of activity-related pain, and the registry specifies a mean change comparison. A continuous endpoint preserves variation in the measured score and yields an estimate in millimeters that can be interpreted on the scale. The scale's pain categories offer descriptive context, but the stated primary test compares mean changes. This illustrates why outcome definition, units, time point, and analysis target should be considered together.

The record also illustrates the importance of reporting results, not only design. A randomized allocation and a named statistical test do not reveal the observed treatment contrast. Without the estimate and its uncertainty, readers cannot distinguish a small, precise difference from a larger but uncertain one, or assess whether the data are compatible with effects in different directions. The missing outcome analysis prevents the central statistical question from being answered from the registry record.

Finally, the listed adverse-event counts and the planning assumptions serve different purposes. Safety counts describe reported events within specified categories, while planning illustrations are hypothetical calculations under assumptions. Neither substitutes for a reported primary outcome estimate. Keeping these forms of information separate is a basic part of sound trial interpretation.

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 of the available registry information is that the primary outcome results are not reported. Although the registry defines change in VAS score and names a 2-sample t-test, it provides no group means, mean-change contrast, confidence interval, or p-value. The magnitude, direction, and precision of the primary result cannot be assessed.

Other outcome reporting is also limited. The PSS score is listed as a secondary outcome, but its measurement timing, analysis, and results are not reported in the registry record. The record identifies two outcome measures and does not describe a multiplicity strategy. It also does not report the analysis population count for the primary endpoint or how missing outcome measurements were handled.

Several design and implementation details are not reported, including the allocation ratio, sequence generation, allocation concealment, adherence, and details of follow-up assessment. The registry lists no masking, but does not describe how outcome assessment was conducted. Because the intervention involves injections and the trial is unmasked, expectations or care behavior could potentially differ between groups; the record does not provide information with which to evaluate this possibility.

The safety summary reports zero events in the listed categories but does not describe event definitions, ascertainment procedures, or safety follow-up duration. The registry's enrollment figure does not by itself show how many participants contributed to each outcome. These limitations are specific to the information reported for this trial and constrain interpretation of both efficacy and safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effectiveness Trial for Evaluating IAHA for PFPS — NCT01811654.
• Registry record last updated 2020-02-26; status last verified 2020-02.
• Results first posted 2020-02-13.
• 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

The registry describes a completed randomized, parallel-group, unmasked trial sponsored by NYU Langone Health. It lists enrollment as 30, the study start as 2013-04, and the primary completion date as 2016-12-07. The comparison is standard care versus standard care plus three consecutive weekly intra-articular hyaluronan (Euflexxa) injections.

The primary outcome is change in activity-related VAS pain from baseline to 3 month follow-up, with mean change compared using a 2-sample t-test. A PFPS Severity Scale score is listed as a secondary outcome. The registry record does not report analyses or results for these outcomes, including an effect estimate or its uncertainty. Safety entries record zero serious adverse events, zero other adverse events, and zero deaths in each listed group; further event-collection details are not reported.