Objective: To validate a new writer’s cramp impairment scale (WCIS) and compare it with an existing writer’s cramp rating scale (WCRS)

Background: Writer’s cramp (WC) is characterized by cramping and abnormal posturing of the hand while writing. WC causes significant disability, and studies on WC have been hampered by the lack of objective, validated rating scales. The WCRS has been helpful, but limited in capturing all aspects of motor impairment with WC, affecting its reliability. The face validity of the WCIS and WCRS have not been determined.

Methods: Eight patients with WC and 8 age- and handedness-matched healthy volunteers (HV) were videotaped while performing standardized writing tasks. A standard video protocol was followed for each participant. For patients receiving botulinum toxin (BTX) treatment, patients had to wait at least 3 months and also had to have the effects of the BTX worn off before participating. Each subject was rated by 4 blinded raters two times, separated by a one-week interval. The ratings were performed using WCIS and WCRS based on the standard videos. Intraclass correlation coefficient(ICC) was used for inter-rater and intra-rater reliability analysis Coefficient of variation (CV) for each subject was calculated using the 8 measures (2 ratings/rater). Two-sample t-test was used to examine the difference in WCIS and WCRS between WC and HV.

Results: Reliability analysis indicated intra-rater ICCs were 0.892 (95% CI: 0.800-0.955) and 0.810 (95% CI: 0.659-0.918) for WCIS and WCRS, respectively. Inter-rater ICCs were 0.698 (95% CI: 0.489-0.863) and 0.395 (95% CI: 0.149-0.673) for WCIS and WCRS, respectively. The coefficient of variation for WCIS, was smaller for the WCIS than for WCRS in all subjects. The means of scores were significantly lower in HV compared to WC across all 4 raters using WCIS, while significance was found in only 2 out of 4 raters using WCRS.

Conclusions: These results suggest higher reliability for WCIS than for WCRS based on both intra and inter-rater ICC. WCIS better distinguished WC patients from HV. The WCIS is a lengthy scale, and the importance of individual components of the scale will need to be assessed.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-new-scale-to-measure-impairment-in-patients-with-writers-cramp/