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Table 2 Correlation matrix for criterion validity

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

  Correlation with PDQ-8-SIa
PDQ-39-SI 0.93**
Age of onset −0.19**
Duration of disease 0.31**
Education −0.19*
H&Y stage 0.48**
UPDRS-III 0.47**
LEDD 0.32**
BDI 0.67**
MMSE −0.20**
  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, LEDD Levodopa equivalent daily dose, MMSE Mini–Mental Status Examination, 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, UPDRS-III Unified Parkinson’s Disease Rating Scale part III