Date Published: April 24, 2012
Publisher: Informa Healthcare
Author(s): Maria Cöster, Magnus K Karlsson, Jan-Åke Nilsson, Åke Carlsson.
A questionnaire was introduced by the New Zealand Arthroplasty Registry for use when evaluating the outcome of total ankle replacement surgery. We evaluated the reliability, validity, and responsiveness of the modified Swedish version of the questionnaire (SEFAS) in patients with osteoarthritis or inflammatory arthritis before and/or after their ankle was replaced or fused.
The questionnaire was translated into Swedish and cross-culturally adapted according to a standardized procedure. It was sent to 135 patients with ankle arthritis who were scheduled for or had undergone surgery, together with the foot and ankle outcome score (FAOS), the short form 36 (SF-36) score, and the EuroQol (EQ-5D) score. Construct validity was evaluated with Spearman’s correlation coefficient when comparing SEFAS with FAOS, SF-36, and EQ-5D, content validity by calculating floor and ceiling effects, test-retest reliability with intraclass correlation coefficient (ICC), internal consistency with Cronbach’s alpha (n = 62), agreement by Bland-Altman plot, and responsiveness by effect size and standardized response mean (n = 37).
For construct validity, we correlated SEFAS with the other scores and 70% or more of our predefined hypotheses concerning correlations could be confirmed. There were no floor or ceiling effects. ICC was 0.92 (CI 95%: 0.88–0.95), Cronbach’s alpha 0.96, effect size was 1.44, and the standardized response mean was 1.00.
SEFAS is a self-reported foot and ankle score with good validity, reliability and responsiveness, indicating that the score can be used to evaluate patients with osteoarthritis or inflammatory arthritis of the ankle and outcome of surgery.
The construct validity analyses, including the Spearman correlation coefficients, are presented in Table 1. SEFAS mainly measures pain and function, and as expected we found the highest correlations between SEFAS and the subscales in FAOS and SF-36 that measure similar constructs. 70% or more of our predefined hypotheses could be confirmed. We also found higher correlations with FAOS pain and ADL than with SF-36 BP and PF, as expected. Concerning discriminant validity, the correlation between SEFAS and SF-36 GH, SF-36 RP, and the summary scale in SF-36 mental health were low. The correlations coefficients between the pain-specific questions in SEFAS and the FAOS subscale pain and SF-36 BP were 0.81 and 0.75, respectively. The correlation coefficients between the function-specific questions in SEFAS and FAOS subscale ADL and SF-36 BF were 0.68 and 0.50, respectively.
This study shows that the SEFAS self-reported foot and ankle score has good validity, reliability, and responsiveness, which could be used to evaluate osteoarthritis or inflammatory arthritis of the ankle both before and after surgical intervention. For evaluation of overall validity of an outcome instrument, several clinimetric properties should be of sufficient quality (Bremander et al. 2003, Terwee et al. 2007). We found that these properties of the SEFAS were comparable with those of the ankle specific-score FAOS. The FAOS is a widely used foot and ankle-specific score that has been translated to several languages (Goksel Karatepe et al. 2009), but to our knowledge has only been validated for ankle ligament reconstructions (Roos et al. 2001). The correlation between SEFAS and the FAOS subscale for sport and recreation was low, as the FAOS may better capture sports-specific deficits while the SEFAS reflects everyday activity. There was also lower correlation with the FAOS symptoms subscale, which includes various unspecific phenomena.