Construct validity of the Quebec Back Pain Disability Scale: a factor analytic and Rasch study
Bibliographic record
Abstract
BACKGROUND: Studies on structural validity of the Quebec Back Pain Disability Scale (QBPDS) showed uncertain unidimensionality. AIM: The aim of this study was to investigate dimensionality and internal construct validity of the QBPDS, using advanced psychometric methods. DESIGN: The design of this study is a secondary analysis of data from a cross-sectional observational study. SETTING: The setting was an outpatient rehabilitation hospital. POPULATION: Analyzed subjects consisted of 201 patients with chronic low back pain (40% men; mean age 48±12 years). METHODS: Confirmatory (CFA) and then Exploratory Factor Analysis (EFA), and Rasch analysis were used. RESULTS: CFA could not provide a satisfactory one-factor solution. Thus, according to a preliminary parallel analysis, two factor structures were examined: 1) a single-factor solution, that showed good model fit according to Goodness of Fit Index and Comparative Fit Index, acceptable fit according to Root Mean Square Error of Approximation, and poor fit according to Standardized Root Mean Square of Residuals; and 2) a bi-factor solution, both showing a good fit in all 4 indices. The Explained Common Variance Index was 0.87. Thus, it was considered appropriate to apply Rasch analysis to our QBPDS data. Four items underfit the Rasch model and showed (two by two) local dependency. Removing these 4 misfitting items resulted in an acceptable fit to the Rasch model of the 16 remaining items. CONCLUSIONS: All results pointed towards an essential unidimensionality of the QBPDS. Thus, we suggest to provisionally use the full QBPDS and its global score, pending further research on scale's construct validity. If the suboptimal performance of 4 items would be confirmed, the deletion of some of them could improve the metric quality of the scale. CLINICAL REHABILITATION IMPACT: This study fills an evidence gap on important measurement properties of the QBPDS (namely, dimensionality and internal construct validity), thus representing a useful step towards the definition of the more suitable outcome measures for research and clinical practice in nonspecific chronic LBP.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.010 | 0.027 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.004 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".