Validity and internal consistency of the Helsinki Serratus Palsy Index for patients with serratus palsy.

Abstract

To our knowledge, no validated scales exist as yet for measuring quality of life and functioning level in patients with serratus palsy. This cross-sectional survey study examined whether a broadly validated Western Ontario Rotator Cuff Index (WORC) could be partially adapted for patients with serratus palsy. The relevancy of WORC, 21 items, along with 4 additional new items, was tested by 95 patients with serratus palsy and a panel of 9 medical experts. Its content validity was measured by a content validity index (CVI), a content validity ratio (CVR), and a modified κ. The internal consistency of 11 retained items was assessed with the Cronbach α. Its construct validity was assessed by exploratory factor analysis. Of the 25 items, 11 were considered relevant (CVI ≥0.78) for serratus palsy by the panelists, with overall test CVI (S-CVI) of 0.86. The internal consistency of these 11 items was excellent, with a Cronbach α of 0.94. The exploratory factor analysis accompanied by a parallel analysis confirmed the unidimensionality of a new test. All except 2 items of WORC that were considered relevant by the panelists were also marked with scores of >5 by the patients on an 11-point scale of relevancy. Adapted from the WORC, the new 11-item Helsinki Serratus Palsy Index scale was internally consistent and face and content valid for serratus palsy patients.