Abstract
PurposeTo assess score agreement between the Atroshi-Lyrén 6-item symptoms scale and the Boston 11-item symptom severity scale and compare their responsiveness in patients with carpal tunnel syndrome before and after carpal tunnel release surgery.MethodsThis prospective cohort study included 3 cohorts that completed the A-L and Boston scales (conventional score 1–5) on the same occasion: a preoperative and short-term postoperative cohort (212 patients), a mid-term postoperative cohort (101 patients), and a long-term postoperative cohort (124 patients). Agreement was assessed with Lin’s concordance correlation coefficient and Passing-Bablok regression analysis. Analyses using item response theory were conducted on responses from the preoperative/short-term postoperative cohort including testing of item infit/outfit. Reliability was assessed with Cronbach alpha. Overall and sex-specific effect sizes were calculated using Cohen’s d.ResultsLin’s CCCs were high (0.81–0.91). Passing-Bablok analysis showed constant and proportional differences in all cohorts except preoperative to short-term postoperative change. Both scales showed high reliability (alpha, 0.88–0.93). The IRT-based analyses showed infit/outfit values within the desired range. With IRT-based scoring, the A-L scale had significantly higher responsiveness than the Boston scale, overall (d, 2.02 vs 1.59), in women (d, 2.22 vs 1.77) and in men (d, 1.74 vs 1.36).ConclusionThe Atroshi-Lyrén 6-item symptoms scale and the Boston 11-item symptom severity scale show good agreement but are not equivalent in measuring CTS-related symptoms severity. When using IRT-based scoring, the Atroshi-Lyrén scale demonstrated significantly higher responsiveness.
Highlights
In patients with carpal tunnel syndrome (CTS), change in symptom severity is usually the most important treatment outcome and often used as primary endpoint in randomized clinical trials of treatment effectiveness [1,2,3,4]
In our previous research we investigated the Boston scale using modern measurement methodology based on item response theory (IRT) in a stepwise process that resulted in removal of 4 items that did not fit well in the scale and merging of 2
We developed a 6-item symptoms scale that demonstrated good internal consistency, test–retest reliability and validity in a comparison with the Boston scale and it did not exhibit differential item functioning with regard to gender [10]
Summary
In patients with carpal tunnel syndrome (CTS), change in symptom severity is usually the most important treatment outcome and often used as primary endpoint in randomized clinical trials of treatment effectiveness [1,2,3,4]. The Atroshi-Lyrén (A-L) 6-item CTS symptoms scale has been translated to various languages and used in clinical studies [12,13,14]. It is not known whether the scores of the Boston and the A-L scales are equivalent to enable direct score comparisons across studies that have used either scale. The purpose of this study was to assess the score agreement between the A-L 6-item CTS symptoms scale and the Boston 11-item symptom severity scale in patients with CTS before and after carpal tunnel release (CTR) surgery and compare their responsiveness. Since the A-L scale was developed using IRT, we hypothesized that the A-L scale would demonstrate higher responsiveness than the Boston scale
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