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Osteoarthritis NA Registry Results NCT00740376

Uniglide™ Mobile Bearing Unicondylar Knee System vs the Uniglide™ Fixed Bearing Unicondylar Knee System: Complete Statistical Analysis

This analysis examines a randomized comparison of mobile-bearing and fixed-bearing Uniglide unicondylar knee systems for osteoarthritis. The registry reports endpoint counts but no posted statistical analyses, and the arm counts and endpoint counts do not reconcile clearly.

Trial start: 2008-08  ·  Enrollment: 37  ·  Sponsor: Corin
Scope of this record

This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.

1. Trial at a Glance

This page covers the registry results for Uniglide™ Mobile Bearing Unicondylar Knee System vs the Uniglide™ Fixed Bearing Unicondylar Knee System (NCT00740376), a randomized na study. The primary outcome is The Number of Implants Which Achieve Composite Clinical Success (CCS) at Month 24..

37
Enrollment
NA
2
Arms
In the primary outcome
n/a
Effect
No re-analysis shown
n/a
95% CI
See limitations
FeatureRegistry value
ClinicalTrials.gov identifierNCT00740376
PhaseNA
ConditionOsteoarthritis
AllocationRandomized
Design modelParallel
MaskingDouble
Enrollment37
Arms in the primary outcome2
Lead sponsorCorin
Results postedYes

2. Clinical Question

Population

People with osteoarthritis undergoing unicondylar knee implantation. The registry lists 37 participants enrolled, but the eligibility criteria and detailed characteristics of the analyzed population are not reported in the registry record.

Intervention

The Uniglide Mobile Bearing Unicondylar Knee System (MBK), identified as the investigational device in the registry summary.

Comparator

The Uniglide Fixed Bearing Unicondylar Knee System (FBK), identified in the registry summary as the control device currently cleared.

Primary question

At month 24 postoperative, how many implants in each group met the Composite Clinical Success criteria? The registry describes the study purpose as assessing whether MBK is not inferior to FBK, but the posted results do not include an inferential comparison or a non-inferiority estimate.

The registry describes a prospective, comparative, randomized, double-blind, multicenter study with a parallel-group design. The main outcome combines clinical status, radiographic findings, and implant-related procedures into a single success classification. In that sense, the question is broader than whether a participant achieved a particular score: success also depends on avoiding specified imaging findings and avoiding removal, replacement, or revision of any component within the stated period.

The endpoint is reported as a count of implants meeting the criteria at month 24, rather than as a posted comparison of group-level success rates. The reported MBK and FBK counts are 17 and 15, respectively, while their accompanying arm counts are 19 and 12. The registry does not explain how those figures relate to one another. Without a clear denominator and a comparative estimate, the posted counts alone do not establish the size or precision of a difference between the groups.

3. Trial Design

The registry describes a prospective, randomized, double-blind, multicenter, parallel-group device study. It compares the Uniglide Mobile Bearing Unicondylar Knee System (MBK) with the Uniglide Fixed Bearing Unicondylar Knee System (FBK) in the setting of osteoarthritis. The stated purpose was to evaluate whether the investigational MBK system was not inferior to the FBK control system on Composite Clinical Success at month 24 postoperative. The registry lists the trial phase as not applicable.

The enrollment figure is 37. The record lists the study start as 2008-08, primary completion as 2014-05, and overall status as terminated. A reason for termination is not reported in the registry record. Nor is a detailed account of recruitment, participant flow, follow-up completion, or the timing of the termination reported in the registry record. These omissions limit the ability to understand how the planned study course compared with what was completed.

The posted primary outcome is a count of implants achieving Composite Clinical Success at month 24. The registry also lists six secondary outcomes: American Knee Society Score totals and component scores; Hospital for Special Surgery totals and component scores; Knee Injury and Osteoarthritis Outcome Score domains; survival using Kaplan-Meier curves; implants with device-related complications; and implants with radiographic findings at month 24 postoperative. The record does not post analyses for those secondary outcomes.

The reported endpoint counts and arm counts are not readily reconciled: MBK is listed with an arm count of 19 and a success count of 17, while FBK is listed with an arm count of 12 and a success count of 15. The registry does not explain the discrepancy or identify which participants contributed to each figure. This makes a direct reconstruction of group success proportions inappropriate from the posted figures alone. Further details about randomization procedures, masking procedures, the intended analysis population, and the statistical 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.

Overall Study

StageUniglide Mobile Bearing Unicondylar Knee System (MBK)Uniglide Fixed Bearing Unicondylar Knee System (FBK)
STARTED2215
COMPLETED1912
NOT COMPLETED33

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.

CharacteristicUnitUniglide Mobile Bearing Unicondylar Knee System (MBK)Uniglide Fixed Bearing Unicondylar Knee System (FBK)Total
Participants analysed221537
Age, Continuousyears60.42 (48 to 71)57.48 (43 to 77)58.95 (43 to 77)
Sex: Female, Male: FemaleImplants18725
Sex: Female, Male: MaleImplants81422
Region of Enrollment: United StatesImplants262147

6. Primary Endpoint

The registry lists the primary outcome as The Number of Implants Which Achieve Composite Clinical Success (CCS) at Month 24., measured over Month 24 postoperative.

ElementRegistry entry
Result typeCount Of Units
Measure of spreadnot applicable
UnitImplants
Endpoint classificationnot reduced to a single comparison

The primary endpoint is the number of implants achieving Composite Clinical Success (CCS) at month 24 postoperative. The registry defines CCS using clinical, radiographic, and procedural criteria. The clinical component requires a Hospital for Special Surgery (HSS) score of at least 70. For a preoperative HSS score between 60 and 69, success requires a postoperative HSS score of at least 70 together with a minimum 10-point improvement.

The radiographic component requires no radiographic failure. The listed failure conditions include radiolucent lines greater than 1 mm in greater than 50% of zones around any component, progressive radiolucencies, implant subsidence greater than 2 mm, and changes in angular orientation greater than 2 degrees consistent with aseptic loosening. The procedural component requires no removal, replacement, or revision of any component, including the bearing, on or before day 730 following initial surgery. Planned removal, replacement, or revision also counts against success.

A composite endpoint is used to represent several dimensions of outcome in one classification. General statistical context: this can make a result sensitive to any component criterion, while obscuring which component most often determines success or failure. The registry does not report component-level primary endpoint results, a breakdown of failures by criterion, or the operational details used to assess each criterion. The endpoint therefore describes a combined status at a specified follow-up point, rather than the separate contribution of each clinical, imaging, or procedural feature.

7. Why No Re-analysis Is Shown

Reported as posted, not recalculated. Values missing or not estimable for a two-arm comparison (count other endpoint). A result is recalculated only when the posted data support a clean two-arm comparison, so no result is shown beyond what the sponsor posted.

8. Statistical Interpretation

Clinical Biostats interpretation

The registry identifies CCS at month 24 as the primary outcome and describes the intended question as non-inferiority of MBK compared with FBK. The posted outcome figures are counts: 17 for MBK and 15 for FBK. The accompanying arm counts are 19 for MBK and 12 for FBK. Those counts do not align in a way the registry explains, including the FBK success count being greater than its listed arm count. The record does not provide a clarified denominator, participant-level data, or an explanation for the inconsistency. Consequently, the counts should be treated as posted registry figures, not as a basis for deriving group success rates.

No inferential comparison is posted. In particular, the registry does not report a risk difference, relative measure, confidence interval, p-value, or non-inferiority margin for the primary endpoint. There is therefore no posted estimate of the between-group effect and no measure of its statistical precision. The record also lists no posted analyses, so the endpoint counts cannot be interpreted as the result of a reported sponsor analysis. A sponsor analysis is not available in the registry record to resolve the unclear counts.

General statistical context: non-inferiority is not established merely because a study fails to show a statistically significant difference. It normally depends on a prespecified margin and an estimate with uncertainty that can be judged against that margin. Neither the margin nor an inferential result is reported in the registry record. The stated non-inferiority objective therefore describes the study's purpose, not a conclusion supported by the posted results.

The enrollment figure is 37, but the record does not explain how that figure relates to the endpoint arm counts. The reported primary outcome counts should not be combined with the enrollment number to infer missing outcomes, exclusions, or follow-up status. Those details are not reported in the registry record. Similarly, the registry's terminated status does not by itself explain why the study ended or whether termination affected the analysis; a reason is not reported.

The listed secondary outcomes cover scores, survival, device-related complications, and radiographic findings. Although these are relevant outcome domains for interpreting a device comparison, the registry does not post numerical analyses for them. Thus, the posted record cannot show whether those outcomes were similar or different between groups, how precisely they were estimated, or whether their findings were consistent with the primary endpoint.

Planning illustrations associated with the posted material are not observed trial results and are not evidence of power achieved. The stated planning assumptions use a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. For time-to-event outcomes, the illustration reports total events; for other outcomes, it reports participants per arm. The trial's own sample-size justification is not reported in the registry record. No numerical planning result should be read as a feature of the enrolled trial or as an observed-power calculation.

Overall, the posted record supports a description of the trial design, intended endpoint, and several outcome counts. It does not support a precise comparative conclusion about CCS or a conclusion that the non-inferiority objective was met. The central interpretive issue is not simply uncertainty around an effect estimate: an interpretable comparative estimate and a reconciled endpoint denominator are not posted.

9. Statistical Methods Explained

General statistical context: a randomized parallel-group study assigns participants to one of the comparison groups and then evaluates outcomes across those groups. Randomization is intended to make the groups comparable on average with respect to factors that could affect outcomes. The registry describes this study as randomized and parallel, but the sequence-generation method, allocation concealment procedures, and implementation details are not reported in the registry record. The record also calls the study double blind, but does not explain who was masked or how masking was maintained. These details matter when assessing the risk of selection, performance, and assessment bias.

What does a count endpoint tell us?

The primary measure is a count of implants meeting a composite success definition at month 24 postoperative. A count is a direct tally, but a comparison between groups ordinarily needs both the number meeting the outcome and the number assessed in each group. These denominators identify the population to which the counts refer and allow an effect estimate to be calculated. Here, the registry lists counts of 17 and 15, alongside arm counts of 19 and 12, without explaining the relationship. The mismatch prevents a reliable reconstruction of group proportions or a comparative effect from those figures.

General statistical context: for a binary outcome such as success or failure, analysts may compare proportions, differences in proportions, or other measures. Each comparison answers a somewhat different question. A confidence interval expresses the range of effect values compatible with the observed data under the analysis assumptions; its width reflects precision. The registry record does not post a comparative estimate or confidence interval for CCS, so the magnitude and precision of any group difference cannot be assessed from the record.

Why does the non-inferiority objective need a margin?

General statistical context: a non-inferiority analysis asks whether an intervention is not worse than a comparator by more than a prespecified amount. That amount, the non-inferiority margin, defines what difference would be considered unacceptable for the study question. The estimate and its uncertainty are then compared with that margin using an analysis specified in advance. A non-significant superiority test is not a substitute for this assessment. The registry describes a non-inferiority objective but does not report the margin, the analysis method, or an inferential result. Therefore, the objective cannot be evaluated from the posted endpoint counts alone.

What role do the composite criteria play?

General statistical context: a composite endpoint groups multiple events or criteria into a single outcome. This can capture a wider picture of status, but the composite may be driven more by one component than by another. In this study, the definition includes HSS performance, radiographic criteria, and absence of removal, replacement, or revision. A count of overall CCS successes does not reveal which criterion was most influential. The registry does not report separate component results or the distribution of reasons for not achieving CCS.

How should the planning illustrations be read?

The posted planning assumptions describe a two-sided significance level of 0.05, equal allocation, and a normal approximation. The target effect is framed as a stated fraction of the observed effect. For time-to-event calculations, the illustration concerns total events using the Schoenfeld approach; for other outcomes, it concerns participants per arm. These assumptions describe a planning exercise, not the design justification documented by the trial sponsor. The sponsor's own sample-size justification is not reported in the registry record, and the planning illustration is not observed power. It should not be interpreted as evidence that the completed study had a particular probability of detecting an effect.

General statistical context: power is a design quantity tied to an assumed effect, variability, analysis, and sample size. It is not a measure of how likely a result is true after data have been observed. Planning calculations can show how sample-size requirements change under different assumptions, but they cannot repair missing denominators or replace an analysis of the trial data. No planning calculation can establish non-inferiority in the absence of a reported margin and comparative estimate.

What can be inferred from the listed secondary outcomes?

The registry lists six secondary outcomes spanning knee scores, survival, device-related complications, and radiographic findings. Naming an outcome indicates that it was specified for collection or evaluation, but does not establish that a result was analyzed or posted. The record lists 0 posted analyses. No numerical comparisons, uncertainty estimates, or analysis descriptions for those secondary outcomes are reported in the registry record. General statistical context: secondary outcomes can add context, but interpretation depends on prespecified methods, complete reporting, and attention to the number of comparisons. Without posted analyses and a statistical plan, their evidential contribution cannot be assessed.

Several design and analysis details that would help interpret the results are not reported in the registry record. These include the planned analysis population, methods for missing outcome data, handling of protocol deviations, covariate adjustment, and any interim analyses. The record also does not describe whether analyses were intended to follow an intention-to-treat or per-protocol principle. These omissions are especially relevant to a non-inferiority question because choices about analysis population and missingness can affect the interpretation of the comparison. No particular method should be assumed in their absence.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists six secondary outcomes in addition to the primary CCS endpoint. These include knee score domains, survival, device-related complications, and radiographic findings. The record lists 0 posted analyses and does not report results for those secondary outcomes. It also does not report a multiplicity strategy, such as a hierarchy of hypotheses or an adjustment to account for multiple comparisons. General statistical context: when several outcomes or repeated tests are examined, the chance of observing at least one apparently unusual result can increase. Prespecified methods help distinguish primary evidence from exploratory findings. No such strategy can be inferred from the outcome list.

Missing-data methods and analysis populations are not reported in the registry record. The record does not state how participants without month 24 assessments were handled, whether any implants were excluded, or how follow-up status was determined. It also does not identify an intention-to-treat or per-protocol analysis population. These are important omissions for interpreting the endpoint counts, particularly because the listed MBK and FBK success counts do not reconcile with their accompanying arm counts.

The registry does not report an interim-analysis plan, stopping rules, or details about analysis timing. The overall status is terminated, but a reason for termination is not reported in the registry record. Without these details, it is not possible to determine whether early ending, incomplete follow-up, or analysis choices affected the posted endpoint information. No assumption about the direction or size of any such effect is warranted.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

ArmParticipants with serious adverse eventsParticipants at riskPercentage
Uniglide Mobile Bearing Unicondylar Knee System (MBK)62227.3%
Uniglide Fixed Bearing Unicondylar Knee System (FBK)71546.7%
Participants with at least one serious adverse event
Serious adverse events by armUniglide Mobile Bearing Unico…27.3%Uniglide Fixed Bearing Unicon…46.7%% of participants with at least one serious adverse event

Deaths

ArmDeaths (participants affected of at risk)
Uniglide Mobile Bearing Unicondylar Knee System (MBK)0 of 22
Uniglide Fixed Bearing Unicondylar Knee System (FBK)0 of 15

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

ArmParticipants affected of at risk
Uniglide Mobile Bearing Unicondylar Knee System (MBK)20 of 22
Uniglide Fixed Bearing Unicondylar Knee System (FBK)14 of 15

Most frequent serious adverse event terms

Event termOrgan systemUniglide Mobile Bearing Unicondylar Knee System (MBK)Uniglide Fixed Bearing Unicondylar Knee System (FBK)
Contralateral TKRSurgical and medical procedures2 of 220 of 15
Myocardial infarctionCardiac disorders0 of 222 of 15
Chronic lymphocytic leukaemia anemiaBlood and lymphatic system disorders1 of 220 of 15
Chronic lymphocytic leukaemia progressionNeoplasms benign, malignant and unspecified (incl cysts and polyps)1 of 220 of 15
PneumoniaRespiratory, thoracic and mediastinal disorders1 of 220 of 15
Contralateral hip arthrotomy for loose body removalSurgical and medical procedures1 of 220 of 15
Contralateral UKRSurgical and medical procedures1 of 220 of 5
Closed reduction percutaneous screw fixation of ipsilateral subcapital femoral neck fractureSurgical and medical procedures1 of 220 of 15
Revision for meniscal bearing dislocationSurgical and medical procedures1 of 220 of 15
Revision for periprosthetic fractureSurgical and medical procedures1 of 220 of 15

Most frequent non-serious adverse event terms

Event termOrgan systemUniglide Mobile Bearing Unicondylar Knee System (MBK)Uniglide Fixed Bearing Unicondylar Knee System (FBK)
NauseaGastrointestinal disorders7 of 227 of 15
ConstipationGastrointestinal disorders3 of 224 of 15
Muscle spasmMusculoskeletal and connective tissue disorders4 of 222 of 15
Nausea and vomitingGastrointestinal disorders4 of 221 of 15
Acute post-op blood loss anemiaInjury, poisoning and procedural complications3 of 221 of 15
ItchingSkin and subcutaneous tissue disorders2 of 222 of 15
Knee pain (operative side)Musculoskeletal and connective tissue disorders2 of 222 of 15
Post-fall knee pain (operative side)Injury, poisoning and procedural complications3 of 221 of 15
InsomniaGeneral disorders0 of 224 of 15
Pes anserine bursitis (operative side)Musculoskeletal and connective tissue disorders2 of 221 of 15

Serious events with the highest arm-level rate: myocardial infarction (13.3%), contralateral tkr (9.1%), carpal tunnel release surgery (6.7%), contralateral knee hematoma drainage (6.7%), contralateral knee traumatic wound dehiscence (6.7%).

Do not overextend the safety comparison. Serious-adverse-event counts are safety observations, not efficacy outcomes, and should not be combined with the primary result into a single benefit-risk number.

The registry reports serious adverse event figures for both groups. For MBK, 22 are listed as at risk and 6 as affected; for FBK, 15 are listed as at risk and 7 as affected. The reported figures for other, non-serious adverse events are 20 affected among 22 at risk for MBK and 14 affected among 15 at risk for FBK. Deaths are listed as 0 in each group. These are registry counts, and no comparative safety analysis or uncertainty estimate is reported.

The listed serious adverse event terms include myocardial infarction (13.3%), contralateral TKR (9.1%), carpal tunnel release surgery (6.7%), contralateral knee hematoma drainage (6.7%), contralateral knee traumatic wound dehiscence (6.7%), and gastrointestinal polyp removal (6.7%). The registry record does not explain the denominators behind these percentages or provide enough detail to compare event risks across groups. The terms should therefore be read as reported event categories, not as evidence that an event was caused by either device.

General statistical context: adverse event counts depend on how events are defined, collected, and followed over time. A count of affected participants is not necessarily the same as a count of all events, since one participant may experience more than one event. Exposure time, attribution, severity criteria, and completeness of follow-up are not described in the posted safety figures. The counts alone do not establish a comparative safety profile.

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

The registry record establishes that a prospective, randomized, double-blind, multicenter, parallel-group comparison of two Uniglide unicondylar knee systems was registered, with CCS at month 24 as the primary outcome. It also reports endpoint counts and group-level adverse event figures. The listed primary endpoint counts are 17 for MBK and 15 for FBK, with accompanying arm counts of 19 and 12. Because the record does not explain this mismatch, those figures cannot be reliably translated into comparative success rates.

The record does not establish that MBK was non-inferior to FBK. It reports no non-inferiority margin, effect estimate, confidence interval, p-value, or sponsor analysis for the primary outcome. The study purpose is not itself a result. Nor does the absence of a posted inferential analysis show that there was no difference; it means the registry record does not provide the analysis needed to assess the question.

The safety figures document reported counts of serious and other adverse events, but they are not accompanied by a comparative statistical analysis or details about exposure and follow-up. They do not by themselves show whether one device has greater or lesser risk, and event listings should not be treated as causal conclusions. Secondary outcomes are listed, but numerical results are not reported in the registry record.

General statistical context: a conclusion about a treatment comparison depends on the quality and completeness of the data, the prespecified estimand and analysis, and the precision of the estimate. Here, the unresolved relationship between endpoint counts and arm counts is a direct obstacle to interpretation. The record is informative about the study question and its intended outcome framework, but insufficient to determine the comparative clinical result or the certainty around it.

13. Why This Trial Matters Statistically

This trial is statistically notable because its stated aim is non-inferiority, while the registry record does not report the elements needed to evaluate that aim. A non-inferiority question requires more than a pair of endpoint counts: interpretation depends on a prespecified margin, a defined analysis population, and a comparative estimate with uncertainty. The margin and analysis are not reported in the registry record. This illustrates why a registry statement of study purpose should be distinguished from evidence that the purpose was achieved.

The primary outcome combines clinical score, radiographic status, and implant-related procedures. Such a composite can make a multidimensional endpoint easier to summarize, but the overall count does not reveal which criterion shaped the result. The absence of component-level results limits the ability to understand how the composite outcome behaved. The registry also lists several secondary outcome areas, but no analyses are posted for them.

The listed success counts and arm counts are difficult to reconcile, and the record offers no explanation. That issue is consequential: a transparent denominator is necessary to interpret a count as a group outcome and to calculate a comparison. The enrollment figure alone cannot resolve the mismatch, because participant flow and analysis populations are not reported.

Finally, the terminated status is recorded without a reason. It should not be taken as evidence of a particular outcome or problem, but it underscores the importance of complete reporting about study completion, follow-up, and analyses. The registry record therefore demonstrates how design information can be available while the comparative evidence needed for a clear statistical conclusion remains unavailable.

14. Limitations

The main limitation of the posted record is the lack of a clear relationship between the primary endpoint counts and the accompanying arm counts. MBK is listed with 17 successes and an arm count of 19; FBK is listed with 15 successes and an arm count of 12. The record does not explain the discrepancy. Without clarified denominators and participant flow, these figures cannot support a dependable comparison of success proportions.

The registry does not report a non-inferiority margin, statistical analysis plan, comparative effect estimate, confidence interval, or p-value. It lists 0 posted analyses. The stated study objective therefore cannot be evaluated statistically from the posted results. The record also does not report the sponsor's sample-size justification or the reason the study was terminated.

Further details about baseline characteristics, eligibility criteria, randomization implementation, masking procedures, analysis populations, missing data, protocol deviations, and follow-up completeness are not reported in the registry record. These details would help assess whether the endpoint groups are comparable and whether the month 24 outcomes represent the enrolled population. The record does not provide component-level CCS results, so it is not possible to identify how clinical scores, imaging, and revision-related criteria contributed to the reported counts.

Although safety counts and several serious adverse event terms are listed, follow-up duration, event attribution, event-level detail, and comparative safety analyses are not reported. Secondary outcomes are identified but their numerical results are absent. These limitations are specific to the information available in this trial's registry record and prevent a comprehensive assessment of efficacy, non-inferiority, and safety.

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17. Sources

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18. Record Summary

The registry describes a prospective, randomized, double-blind, multicenter, parallel-group comparison of the Uniglide Mobile Bearing and Fixed Bearing Unicondylar Knee Systems for osteoarthritis. It lists 37 participants enrolled, study start 2008-08, primary completion 2014-05, and status terminated. A reason for termination is not reported in the registry record.

The primary outcome is the count of implants meeting Composite Clinical Success criteria at month 24 postoperative. The registry lists counts of 17 for MBK and 15 for FBK, alongside arm counts of 19 and 12, with no explanation for the mismatch. Six secondary outcomes are listed, but the record lists 0 posted analyses. It reports adverse event counts, but no comparative statistical safety analysis.

The registry states a non-inferiority objective, but does not report a margin, comparative estimate, confidence interval, or analysis supporting a conclusion on that objective. The posted record describes the design and outcome framework but does not provide enough clarified comparative results to determine the primary statistical finding.

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