Table 2

Construct (Cronbach α test) and external validity of the different clinical and ultrasonographic scoring systems evaluated in 76 patients with active rheumatoid arthritis

Scoring system	Construct validity (Cronbach α test)	External validity (vs CRP: coefficient of correlation)
Joint count^*
20 Clinical	0.76	0.28
20 US B mode	0.76	0.28
20 US power Doppler	0.81	0.37
28 Clinical	0.78	0.35
28 US B mode	0.87	0.35
28 US power Doppler	0.86	0.43
38 Clinical	0.78	0.35
38 US B mode	0.86	0.30
38 US power Doppler	0.85	0.39
Joint score^*
20 Clinical	0.86	0.29
20 US B mode	0.83	0.28
20 US power Doppler	0.82	0.34
28 Clinical	0.85	0.31
28 US B mode	0.89	0.39
28 US power Doppler	0.84	0.38
38 Clinical	0.88	0.31
38 US B mode	0.88	0.34
38 US power Doppler	0.85	0.37

↵* See Patients and methods section for the definition of count versus score and for the description of the evaluated joints.
CRP, C reactive protein; US, ultrasound.