International study on the psychometric attributes of the Non-Motor Symptoms Scale in Parkinson disease

Nov 11, 2009Neurology

International study of how well the scale measures non-movement symptoms in Parkinson’s disease

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Abstract

Four hundred eleven patients with Parkinson disease had a mean Non-Motor Symptoms Scale score of 57.1 points.

The Non-Motor Symptoms Scale (NMSS) demonstrated satisfactory reproducibility with an intraclass correlation coefficient of 0.90 for the total score.
Cronbach alpha coefficients for NMSS domains ranged from 0.44 to 0.85, indicating variable internal consistency.
The NMSS total score correlated significantly with the SCOPA-Autonomic, Parkinson's Disease Questionnaire-39, and EuroQol-5 dimensions, with correlation coefficients ranging from 0.57 to 0.70.
Women and patients with longer disease duration, higher Hoehn and Yahr stages, and greater Clinical Impression of Severity Index severity levels had higher NMSS total scores.
The scale showed no floor or ceiling effects, supporting its comprehensive assessment capabilities.

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BACKGROUND: Nonmotor symptoms (NMS) have a great impact on patients with Parkinson disease (PD). The Non-Motor Symptoms Scale (NMSS) is an instrument specifically designed for the comprehensive assessment of NMS in patients with PD. NMSS psychometric properties have been tested in this study.

METHODS: Data were collected in 12 centers across 10 countries in America, Asia, and Europe. In addition to the NMSS, the following measures were applied: Scales for Outcomes in Parkinson's Disease (SCOPA)-Motor, SCOPA-Psychiatric Complications (SCOPA-PC), SCOPA-Cognition, Hoehn and Yahr Staging (HY), Clinical Impression of Severity Index for Parkinson's Disease (CISI-PD), SCOPA-Autonomic, Parkinson's Disease Sleep Scale (PDSS), Parkinson's Disease Questionnaire-39 items (PDQ-39), and EuroQol-5 dimensions (EQ-5D). NMSS acceptability, reliability, validity, and precision were analyzed.

RESULTS: Four hundred eleven patients with PD, 61.3% men, were recruited. The mean age was 64.5 +/- 9.9 years, and mean disease duration was 8.1 +/- 5.7 years. The NMSS score was 57.1 +/- 44.0 points. The scale was free of floor or ceiling effects. For domains, the Cronbach alpha coefficient ranged from 0.44 to 0.85. The intraclass correlation coefficient (0.90 for the total score, 0.67-0.91 for domains) and Lin concordance coefficient (0.88) suggested satisfactory reproducibility. The NMSS total score correlated significantly with SCOPA-Autonomic, PDQ-39, and EQ-5D (r(S) = 0.57-0.70). Association was close between NMSS domains and the corresponding SCOPA-Autonomic domains (r(S) = 0.51-0.65) and also with scales measuring related constructs (PDSS, SCOPA-PC) (all p < 0.0001). The NMSS total score was higher for women (p < 0.02) and for increasing disease duration, HY, and CISI-PD severity level (p < 0.001). The SEM was 13.91 for total score and 1.71 to 4.73 for domains.

CONCLUSION: The Non-Motor Symptoms Scale is an acceptable, reproducible, valid, and precise assessment instrument for nonmotor symptoms in Parkinson disease.

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International study on the psychometric attributes of the Non-Motor Symptoms Scale in Parkinson disease

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