Measurement Properties of the SF-MPQ-2 Neuropathic Qualities Subscale in Persons with CRPS: Validity, Responsiveness, and Rasch Analysis

Abstract

Objectives:The purpose of this study was to conduct classical psychometric evaluation and Rasch analysis on the Neuropathic Qualities subscale from the Short Form McGill Pain Questionnaire-2 utilizing scores from persons with complex regional pain syndrome to consider reliability and person separation, validity (including unidimensionality), and responsiveness in this population. Methods: Secondary analysis of longitudinal data from persons with acute complex regional pain syndrome was utilized for analysis of the psychometric properties and fit to the Rasch model of the Neuropathic Qualities subscale. We followed an iterative process of Rasch analysis to evaluate and address data fitting challenges. Results: Repeated measures from n=59 persons meeting the Budapest criteria were used for analysis. Both item-total correlations and unidimensionality analyses supported theoretical construct validity; all convergent construct validity hypotheses were also supported. Responsiveness was demonstrated comparing baseline and one-year data at d= 0.92, with a standardized response mean of 0.97. Data were able to fit the Rasch model but all Neuropathic Qualities items had disordered thresholds requiring rescoring. Additionally, local dependency and differential item function were addressed by 'bundling', suggesting no further item reduction would be possible. Conclusions: This study provided preliminary support for the validity and responsiveness of the Neuropathic Qualities subscale in persons with complex regional pain syndrome. Rasch analysis further endorses use of the Neuropathic Qualities subscale as a 'stand-alone' measure for neuropathic features, but with substantial background data transformations. Replication with larger samples is recommended to increase confidence in these findings.

Reproducibility: reliability and agreement parameters of the Revised Short McGill Pain Questionnaire Version-2 for use in patients with musculoskeletal shoulder pain

“…Cross sectional reliability was established for the SF-MPQ-2 total and subscale scores with satisfactory coefficients supporting internal consistency that are similar to previous estimates among mixed-MSK [23] (total, 0.93; subscale, 0.84-0.92), CRPS [20] (total, 0.95; neuropathic subscale, 0.83), knee OA [22] (total, 0.88; subscale 0.75-0.81) and acute back pain [21] (total, 0.93; subscale, 0.77-0.84) patient populations. Inter-item correlations were also adequate.…”

“…For instance, participants with pain emerging from neuropathic sources will be more inclined to respond adequately to the neuropathic subscale, thereby reducing the likelihood of floor effects. This has been observed with the use of the SF-MPQ-2 among complex regional pain syndrome (CPRS) patients [20]. This implies that floor effects on the SF-MPQ-2 domains may not always represent redundancy, but rather, may suggest that an item does not describe the patient's pain experience [25].…”

“…Since then, multiple studies have utilized the SF-MPQ-2 as a primary outcome for pain assessment in clinical trials; its measurement properties have been examined in different populations including cancer pain [16], surgical pain [17], visceral pain [18], and neuropathic pain [19]. Among MSK conditions, studies have reported measurement evidence for patients with complex regional pain syndrome [20], back pain [21], knee osteoarthritis (OA) [22], and mixed MSK populations [23,24]. Although the SF-MPQ-2 is becoming increasingly popular, our recent review [25][26][27] reported on evidence with design flaws including inadequate description of Intraclass correlation coefficient (ICC) models, insufficient justification of retest interval, and a lack of attention to absolute reliability parameters.…”

Recommendations for a first Core Outcome Measurement set for complex regional PAin syndrome Clinical sTudies (COMPACT)

“…A number of questionnaire outcome measures were considered to capture this aspect of pain (see Table 1) however, the six SF-MPQ-2 neuropathic items capture the essential qualities with minimum patient burden. A preliminary Rasch analysis supported the use of this sub-scale as a ‘stand-alone’ assessment [42] however, this needs to be repeated in a larger, mixed population.…”

Patient satisfaction with virtual evaluation, diagnosis, and treatment of CRPS

“…Further, the strong effect size ( d = 2.2) exceeded that reported using a well-validated condition-specific measure (ES = 1.99) in an observational cohort followed for 1 year after symptom onset. 20 It is important to note that the relationship between overall recovery and response to CRPS treatment is influenced by the nature and severity of the precipitating injury and that treating CRPS does not guarantee resolution of symptoms due to the initial insult.…”