Disease Activity in Psoriatic Arthritis: Comparison of the Discriminative Capacity and Construct Validity of Six Composite Indices in a Real World

Table 2

Descriptive statistics of all composite disease activity indices.

	DAS28-CRP	DAS28-ESR	SDAI	CPDAI	DAPSA	PASDAS
Lowest value	0.99	0.70	0.40	0.00	0.40	0.34
Highest value	6.22	5.54	88.10	12.00	89.10	7.18
Arithmetic mean	3.17	2.73	19.69	6.16	20.62	3.93
95% CI for the mean	2.93 to 3.41	2.51 to 2.95	17.12 to 22.26	5.57 to 6.76	17.96 to 23.28	3.66 to 4.20
Median	3.59	3.13	21.00	5.00	22.05	4.21
95% CI for the median	2.37 to 4.00	1.87 to 3.52	10.84 to 25.53	4.00 to 7.00	11.51 to 26.73	3.39 to 4.88
Variance	2.55	2.19	291.69	15.81	311.37	3.19
Standard deviation	1.59	1.48	17.07	3.97	17.64	1.78
Relative standard deviation	0.50 (50.32%)	0.54 (54.18%)	0.86 (86.72%)	0.64 (64.47%)	0.85 (85.55%)	0.45 (45.46%)
Standard error of the mean	0.12	0.11	1.30	0.30	1.34	0.13
Coefficient of skewness	0.04 (𝑃=0.8220)	0.04 (𝑃=0.8131)	0.84 (𝑃<0.0001)	0.26 (𝑃=0.1502)	0.79 (𝑃=0.0001)	−0.16 (𝑃=0.3548)
Coefficient of kurtosis	−1.46 (𝑃<0.0001)	−1.54 (𝑃<0.0001)	0.86 (𝑃=0.0509)	−1.44 (𝑃<0.0001)	0.71 (𝑃=0.0887)	−1.42 (𝑃<0.0001)
Kolmogorov-Smirnov test for normal distribution	reject Normality (𝑃=0.0020)	reject Normality (𝑃=0.0007)	reject Normality (𝑃<0.0001)	reject Normality (𝑃<0.0001)	reject Normality (𝑃=0.0001)	reject Normality (𝑃=0.0014)

ESR: erythrocyte sedimentation rate; CRP: C-reactive protein; DAS28: 28-Disease Activity Score; SDAI: Simplified Disease Activity Index; CPDAI: Composite Psoriatic Disease Activity Index; DAPSA: disease activity in psoriatic arthritis; PASDAS: Psoriatic Arthritis Disease Activity Score.