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

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

	N	Mean	SD	Median	25th percentile	75th percentile	Correlation with H&Y^a	Correlation with UPDRS-III^a	Correlation with BDI^a	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

^aSpearman’s rank correlation
** P < 0.001; * P < 0.01
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

ISSN: 1477-7525