The Validity, Reliability and Interpretability of Thai-version of Chronic Urticaria Quality of Life Questionnaire: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Validity, Reliability and Interpretability of Thai-version of Chronic Urticaria Quality of Life Questionnaire (NCT02285023), a registered phase not stated study. The primary outcome is Cross-Cultural Validity of Thai-version CU-Q2oL.

2. Clinical Question

The central statistical question is about measurement: whether questionnaire items group into domains in a way that supports use of the Thai version as a culturally adapted instrument. The registry also lists secondary aims concerning reliability, score change for responders and non-responders, and area under the curve in the responder group. It does not give enough detail to establish how response status was defined, how participants were assigned to those groups, or what numerical results were observed. Consequently, the record describes the questions and methods more fully than it reports the findings needed to answer them.

3. Trial Design

This is a completed questionnaire-validation study sponsored by Mahidol University. Its registry title identifies the work as an evaluation of the validity, reliability and interpretability of the Thai-version CU-Q2oL. The study began in 2014-11, reached primary completion in 2015-02, and lists enrollment of 166 participants. The intervention is classified as “OTHER” and named CU-Q2oL; the record describes assessment activities rather than assignment to competing treatments.

The listed assessment included the Urticaria Activity Score (UAS7), DLQI and CU-Q2oL questionnaires. The primary outcome concerns cross-cultural validity, with a 4 week timeframe. Secondary outcomes address mean total and domain scores in relation to reliability, change in Thai CU-Q2oL scores from baseline for responders and non-responders, and area under the curve for Thai CUQ2oL scores in the responder group. The registry lists 4 outcome measures and 2 analyses, but does not give the detailed analysis populations or numerical findings for these outcomes.

The record does not describe a randomized treatment comparison or a separate control arm. Allocation is not stated, and the registry indicates that the arms are not a like-for-like control comparison. The study should therefore be read as an assessment of a measurement instrument, not as a trial estimating the effect of a treatment against a control. Further details on recruitment, eligibility, questionnaire administration, visit schedule beyond the stated primary timeframe, and sample-size justification are not reported in the registry record. The completed status indicates that the study is recorded as complete; it does not, by itself, provide evidence about the magnitude or precision of the questionnaire's measurement properties.

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

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.

Population: Patients diagnosed as chronic idiopathic urticarial were enrolled.

6. Primary Endpoint

The registry lists the primary outcome as Cross-Cultural Validity of Thai-version CU-Q2oL, measured over 4 week.

The primary endpoint is cross-cultural validity of the Thai-version CU-Q2oL. The registry defines this as the degree to which performance of the Thai questionnaire items can adequately reflect performance of the original CU-Q2oL items. It labels the outcome unit as Percentage and the parameter as NUMBER, while its description focuses on exploratory factor analysis and item-to-domain structure. No primary endpoint value is reported in the registry record, so the listed unit cannot be used to infer a numerical finding.

The described analysis uses principal component analysis with varimax rotation to examine how items cluster into scales. The stated rule retains domains with an eigenvalue >= 1, and classifies an item into a domain when its loading is >= 0.5. These criteria make the intended assessment more specific: the analysis is looking for a structured grouping of questionnaire items, rather than simply asking whether participants completed the instrument.

In general, factor-based methods can help evaluate whether the pattern of item responses supports the proposed domains of a questionnaire. That is relevant to cross-cultural adaptation because a translated instrument may not preserve the original item groupings automatically. Such analysis can contribute evidence about structure, but it does not alone establish every aspect of validity, reliability or interpretability. The registry does not report the retained domains, item loadings, or a summary result, so the endpoint's method is described without a result that can be interpreted from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary method described is exploratory factor analysis, implemented using principal component analysis with varimax rotation. The purpose is to examine whether questionnaire items form domains or scales. The registry specifies an eigenvalue >= 1 as the criterion for retaining a domain and an item loading >= 0.5 as the rule for assigning an item to a domain. It does not report the resulting domains or loadings.

What does factor analysis examine?

General explanation: factor-based methods assess patterns of association among measured items. Items that vary together may be represented as belonging to a shared underlying domain. For a quality-of-life questionnaire, this can help assess whether groups of questions behave like coherent parts of the instrument. In a cross-cultural adaptation, this is useful because translation and cultural context can affect how respondents interpret items and how item responses relate to one another. Evidence about item grouping is one part of evaluating whether an adapted instrument retains a meaningful structure.

The registry calls the analysis exploratory. In general, an exploratory approach investigates the structure present in the data rather than testing only a fully prespecified structure. The record does not describe any confirmatory analysis or state that a particular factor structure was fixed in advance. It also does not report the number of domains retained, how much variation the components represented, or the item-level results. Those omissions prevent assessment of whether the structure was simple, stable, or consistent with the intended questionnaire domains.

What do principal components and rotation contribute?

General explanation: principal component analysis constructs components from the observed item responses, with the aim of representing patterns in those responses. A rotation can make the resulting pattern easier to interpret by clarifying which items are more strongly associated with which components. Varimax is an orthogonal rotation: in general, it seeks a simpler pattern while keeping the rotated components uncorrelated in the mathematical representation. That choice is part of the analytic approach; it does not itself establish that the domains are valid or that they should be treated as unrelated in the underlying clinical concept.

The stated eigenvalue rule sets a threshold for retaining domains. In general, an eigenvalue reflects how much of the observed information is represented by a component under the analysis. A threshold is a decision rule, not an observed outcome. The rule does not tell the reader how many domains were retained; that depends on the actual analysis results, which are not reported in the registry record.

The loading criterion of >= 0.5 identifies the stated threshold for assigning an item to a domain. In general, a loading expresses the strength of the relationship between an item and a component in the fitted structure. A threshold can make assignment rules explicit, but an item may load on more than one domain or may not meet the stated rule for any domain. The record does not indicate whether cross-loadings were assessed, how ambiguous items were handled, or how many items met the criterion. Those details are important when judging the interpretability of a proposed scale structure.

Why do reliability and interpretability need separate evidence?

The secondary outcome descriptions name reliability and interpretability as areas of interest. General explanation: reliability concerns the consistency or repeatability of measurement under specified conditions, while interpretability concerns what a score or change in score means. These concepts require defined measures and analysis procedures. The registry mentions mean total and domain scores in relation to reliability, but does not state the reliability statistic, retest interval, acceptable threshold, or numerical result. It also lists score change from baseline for responders and non-responders, but does not define the response groups or report the changes.

Area under the curve is listed for Thai CUQ2oL scores in the responder group. General explanation: an area-under-the-curve analysis can describe how well a measure distinguishes between groups defined by an external status or reference. Its interpretation depends on how the groups and reference status are defined, which score is evaluated, and how uncertainty is reported. Those details and the resulting estimate are not reported in the registry record. The outcome title alone cannot establish the instrument's discriminative performance.

Overall, the methods description contains useful operational thresholds for the primary structural analysis, but the evidence needed to evaluate the analysis is absent: results, uncertainty, analytic sample sizes, missing-response handling, and details of the secondary methods are not reported in the registry record. In general, a confidence interval, when reported, describes the range of values compatible with the data and analysis under its assumptions; no confidence intervals for the primary or secondary outcomes are reported.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 4 outcome measures and 2 analyses. The primary outcome addresses cross-cultural validity, while the secondary outcome descriptions cover reliability, score change from baseline in responder and non-responder groups, and area under the curve in the responder group. Because several measurement questions are named, interpretation can depend on whether outcomes were prespecified as primary or secondary and whether any adjustment or hierarchy was used to address multiplicity.

Multiplicity refers, in general, to the increased chance of observing apparently noteworthy results when multiple outcomes or analyses are examined. It does not imply that a reported finding is invalid; it means that the analysis plan and reporting should make clear how the set of tests was handled. The registry does not describe a multiplicity adjustment, a testing hierarchy, or how the 2 analyses relate to the listed outcomes. Such details are not reported in the registry record, so readers cannot determine whether or how multiplicity was addressed.

Missing-data methods are also not described. The record does not state how incomplete questionnaire items, missing visits, or unavailable outcome measurements were handled, whether any imputation was used, or whether complete-case analyses were conducted. The analysis populations and numbers contributing to each endpoint are not reported in the registry record. Enrollment of 166 does not show that all enrolled participants contributed to every analysis.

The record does not state whether all participants were included according to a defined analysis population, nor does it report exclusions after enrollment. Definitions for responder and non-responder groups are not given. Without those definitions and the corresponding participant counts, the secondary comparisons cannot be reconstructed or assessed for possible selection effects. A sample-size justification and a detailed statistical analysis plan are not reported in the registry record. These gaps limit assessment of both the planned analysis and the robustness of any findings, quite apart from the absence of numerical outcome results.

11. Safety Results

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

Other (non-serious) adverse events

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

The registry lists a serious-adverse-event count of 0 among 166 at risk in the Chronic Idiopathic Urticaria group. It also lists 0 other adverse events among 166 at risk in that group. These are the posted event counts and denominators for the recorded safety categories.

A count of 0 in the registry is not proof that no adverse experience occurred under every definition or during every period of observation. Interpretation depends on what events were collected, the observation window, how events were classified, and whether reporting was complete. Those details are not reported in the registry record. The record also does not provide serious-event terms, so it does not identify specific events or explain the event-collection process.

The deaths field is not reported in the registry record; it should not be read as a count of 0. The safety figures are descriptive and do not establish a comparative safety effect, since the study is not described as a randomized treatment comparison and no like-for-like control group is specified. They should be read as the event counts recorded for this study, with the limits of the available reporting in mind.

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

The record describes a study of the Thai-version CU-Q2oL as a measurement instrument for people with chronic urticaria. It identifies cross-cultural validity as the primary question and reports the method used to examine item-to-domain structure. That is useful information about the intended evaluation: the study sought evidence on whether the Thai items represented the original questionnaire's item performance through an appropriate domain structure.

However, the registry does not report the primary endpoint value, retained domains, or item loadings. Without these results, it is not possible to assess whether the stated criteria were met or how the Thai questionnaire performed in this analysis. The secondary outcome descriptions likewise do not include numerical results, and the registry does not provide the details needed to interpret the reliability, score-change, or area-under-the-curve analyses. The listed enrollment of 166 does not fill these reporting gaps or indicate the precision of any estimate.

The study's measurement focus also sets limits on what can be concluded. It is not described as a randomized comparison of treatments, and the record does not identify a like-for-like control arm. It therefore does not estimate the effect of a treatment on chronic urticaria or establish that using the questionnaire changes patient outcomes. The study's stated purpose and assessment activities concern questionnaire validity, reliability and interpretability.

In general, evidence about questionnaire structure can contribute to the evaluation of a culturally adapted measure, but no single analysis establishes every desirable measurement property. Conclusions would also depend on the actual results, the population and analysis details, and the reporting of uncertainty. Those elements are not fully reported in the registry record. The appropriately bounded reading is that the registry documents a completed measurement-validation study and its primary analytic approach, while leaving the numerical evidence needed to judge its findings unavailable.

13. Why This Trial Matters Statistically

Questionnaires are measurement instruments: before interpreting their scores, researchers need evidence that the items represent the intended concepts in the population and language of use. This study is statistically important because its stated focus is the cross-cultural evaluation of a Thai version of CU-Q2oL, rather than a comparison of treatments. Its primary method seeks to assess whether questionnaire items organize into domains using a stated analysis and explicit item-assignment criteria.

That focus highlights a distinction central to clinical research. An outcome measure can be used in a study only if its scores are interpretable for the intended purpose and setting. Translation alone does not establish that an adapted instrument preserves its item structure. Examining item groupings is one way to investigate that issue; reliability and interpretability are related but distinct properties and call for their own evidence. The registry's secondary outcome titles show that these dimensions were included among the study questions.

The record also illustrates why methods and results must be read separately. It specifies principal component analysis with varimax rotation, a domain-retention criterion and an item-loading threshold. These details clarify the planned analytic logic, but without factor results, uncertainty, and analysis-population information, the reader cannot judge how well the observed data supported that logic. Numerical results are essential for moving from an analysis description to an evidence-based conclusion.

Finally, the study should not be read as an efficacy trial. It evaluates a questionnaire and does not describe a randomized, like-for-like comparison of clinical interventions. Keeping that distinction clear prevents measurement evidence from being mistaken for evidence about treatment outcomes. The registry record gives a meaningful account of the statistical question, but its limited results reporting restricts what can be concluded about the Thai CU-Q2oL's performance.

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 most important limitation for interpreting this record is the absence of numerical outcome results. No primary cross-cultural validity value, domain structure, or item loadings are reported. The secondary outcomes are named but do not have reported estimates. As a result, the reader cannot assess the magnitude or precision of the measurement findings from the registry record.

Methodological details needed to evaluate the primary analysis are also missing. The record does not report the number of retained domains, item-level patterns, treatment of cross-loadings or items that did not meet the stated loading criterion, or any uncertainty measures. The analysis sample size for the primary endpoint is not reported in the registry record. The stated enrollment of 166 cannot be assumed to equal the number with usable data in each analysis.

The secondary outcomes need further definition for interpretation. Definitions of responders and non-responders, the reference used to classify response, reliability statistics, and details of the area-under-the-curve analysis are not reported in the registry record. Nor does the record describe how missing questionnaire data were handled or whether any adjustment for multiple outcomes or analyses was used.

The registry does not provide eligibility criteria, detailed recruitment procedures, a sample-size justification, or a full statistical analysis plan. It also does not describe a separate control group or a randomized allocation, so the study cannot be interpreted as a controlled treatment comparison. These limitations are specific to the information available in the registry record; they do not establish that the omitted procedures were not performed, only that their details and results are not reported there.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Validity, Reliability and Interpretability of Thai-version of Chronic Urticaria Quality of Life Questionnaire — NCT02285023.
• Registry record last updated 2019-02-08; status last verified 2018-09.
• Results first posted 2019-02-08.
• 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

NCT02285023 is a completed study sponsored by Mahidol University titled “The Validity, Reliability and Interpretability of Thai-version of Chronic Urticaria Quality of Life Questionnaire.” The registry lists chronic urticaria as the condition, enrollment of 166, a start date of 2014-11, and primary completion in 2015-02.

The primary outcome is cross-cultural validity of the Thai-version CU-Q2oL, with a 4 week timeframe. The record describes exploratory factor analysis using principal component analysis with varimax rotation, an eigenvalue >= 1 criterion for retaining domains, and an item loading >= 0.5 criterion for assigning items to domains. Secondary outcomes concern reliability, score change by responder status, and area under the curve for responder-group scores.

Numerical results for these outcomes, analysis populations, missing-data methods, and a sample-size justification are not reported in the registry record. The posted safety counts are 0 serious adverse events and 0 other adverse events among 166 at risk in the Chronic Idiopathic Urticaria group; deaths are not reported.