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Table 6 Descriptive statistics for PDQ-39-SI and PDQ-8-SI at baseline and follow up

From: Evaluation of PDQ-8 and its relationship with PDQ-39 in China: a three-year longitudinal study

  N Mean SD Median 25th percentile 75th percentile Correlation with H&Ya Correlation with UPDRS-IIIa Correlation with BDIa Average ICC 95% CI
Baseline 283           
PDQ-39-SI   20.2 14.6 17.3 9.0 27.6 0.53** 0.50** 0.67**   
PDQ-8-SI   21.3 16.8 18.8 9.4 31.3 0.48** 0.47** 0.64** 0.96** 0.95–0.97
Difference   −1.1 −2.2 −1.5 −0.4 −3.7      
Follow-up year 1 101           
PDQ-39-SI   17.5 13.3 14.1 8.3 24 0.35** 0.40** 0.68**   
PDQ-8-SI   17.5 14.9 15.6 6.3 21.9 0.29** 0.34** 0.69** 0.96** 0.95–0.98
Difference   0 −1.6 −1.5 2 2.1      
Follow-up year 2 81           
PDQ-39-SI   19.7 16 14.7 9.0 26.3 0.38** 0.43** 0.66**   
PDQ-8-SI   19.9 17.5 15.6 6.3 28.1 0.32** 0.43** 0.69** 0.98** 0.97–0.99
Difference   −0.2 −1.5 −0.9 2.7 −1.8      
  1. aSpearman’s rank correlation
  2. ** P < 0.001; * P < 0.01
  3. Abbreviations: BDI Beck Depression Inventory, H&Y stage Hoehn and Yahr stage, ICC intraclass correlation coefficient, PDQ-8 8-item Parkinson’s disease Questionnaire, PDQ-8-SI PDQ-8 summary index, PDQ-39 39-item Parkinson’s disease Questionnaire, PDQ-39-SI PDQ-39 summary index, SD standard deviation, UPDRS-III Unified Parkinson’s Disease Rating Scale part III