Objective: To translate the Non-Motor Symptoms Questionnaire (NMSQ) and the Non-Motor Symptoms Scale (NMSS) into Swedish, and test their linguistic validity and user-friendliness.

Background: Non-motor symptoms (NMS) are common but under recognized among people with Parkinson’sdisease (PwPD). The NMSQ and NMSS were developed to ease NMS detection and assessment. The NMSQ is a patient-reported checklist regarding the presence of 30 NMS. The NMSS is a clinician-administered interview based rating scale regarding the frequency and severity of 30 NMS. Both are widely used, but Swedish versions have been lacking.

Methods: The English NMSQ and NMSS were translated into Swedish in two stages. First, Swedish translations were produced by a professional translator and 3 bilingual PD-clinicians. Second, translations were reviewed by 3 independent PD-clinicians, resulting in minor revisions. The subsequent Swedish versions were then field-tested by 4 PD-clinicians on 5 PwPD each (n=20; 15 men; mean age and PD duration 67.6 and 9 years; HY stages II-IV). Evaluations included user burden (completion time), content relevance, and easiness to understand and use.

Results: PwPD completed the NMSQ in a mean (range) of 4.8 (2-8) minutes. NMSQ content was considered relevant by 19 PwPD; 19 found instructions easy to understand and 17 found items easy to understand and respond to. The NMSS was completed in 13 (8-25) minutes. All 4 clinicians considered NMSS contents as relevant and instructions easy to understand; 1 considered items easy to rate. Two clinicians reported NMSS items as easy to understand for PwPD, and 1 clinician reported items as easy to answer for PwPD. Two clinicians considered theNMSS “very much” or “moderately”, and 2 considered it “a little” useful for clinical research. One clinician considered the NMSS “moderately”, and 3 considered it “a little” useful for clinical practice, but none would use it themselves. Translators, reviewers and field-test clinicians highlighted ambiguities with the NMSS not related to the translation.

Conclusions: The NMSQ and NMSS were translated into Swedish and the linguistic validity of both translations was supported. There was also support for the user-friendliness of the NMSQ, but not for the NMSS. Issues detected with the NMSS do not appear to be specific for the Swedish version. Further evaluations of the NMSS in larger samples are needed.