Validity and reliability of the Serbian version of Patient-Reported Impact of Spasticity Measure in multiple sclerosis

The Patient-Reported Impact of Spasticity Measure (PRISM) has been developed recently to assess the impact of spasticity on quality of life after spinal cord injury. Although PRISM may also be useful in patients with multiple sclerosis (MS), its psychometric properties in MS have not been established and PRISM is currently available only in English. The aims of this cross-sectional study were to translate PRISM into the Serbian language (PRISMSR) and examine its validity (construct, convergent, divergent) and reliability (internal consistency, test-retest reliability) in 48 patients with spasticity because of MS diagnosed at least 1 year earlier and in remission at least 3 months. PRISMSR was administered twice 3 days apart. The validity of seven PRISMSR subscales was examined against the Modified Ashworth Scale (MAS), the Numerical Rating Scale (NRS) for spasticity, sex, and education. Internal consistency was assessed with Cronbach α and test-retest reliability with intraclass correlation coefficient for agreement (ICC2,1). During the forward-backward translation, only one PRISM item required minor cultural adaption. Almost all PRISMSR scores correlated significantly with MAS and NRS scores (r=0.29-0.51, 0.001≤P≤0.043). They were all significantly higher for MAS≥2 group versus the MAS<2 group (0.003≤P≤0.035) and for the NRS≥7 group versus the NRS<7 group (0.001≤P≤0.042), except for the Social Embarrassment subscale (P=0.083). The PRISMSR scores were not significantly different between sexes (P≥0.104) or those with high school versus college degree (P≥0.139). Both Cronbach α (0.78-0.93) and test-retest ICC2,1 (0.82-0.90) were high. The original PRISM may be translated successfully into other languages. PRISMSR shows adequate validity and reliability for assessing the impact of spasticity on quality of life in patients with MS.