Table 3

Measurement properties of spinal mobility with radiographic damage set as the “gold standard”

	Gold standard defined as mSASSS >0						Gold standard defined as mSASSS >3						Gold standard defined as mSASSS >6
	AUC	Cut off point	Sens	Spec	LR+	LR−	AUC	Cut off point	Sens	Spec	LR+	LR−	AUC	Cut off point	Sens	Spec	LR+	LR−
BASMI, Bath Ankylosing Spondylitis Metrology Index; cut off point, value with the optimal sensitivity and specificity according to a receiver operator characteristic (ROC) analysis; AUC, area under the curve; sens, sensitivity; spec = specificity; LR+, likelihood ratio of a positive test; LR−, likelihood ratio of a negative test.
Chest expansion (cm)	0.75	⩽4.9	0.68	0.75	2.7	0.4	0.79	⩽4.2	0.69	0.81	3.7	0.4	0.84	⩽4.1	0.75	0.82	4.1	0.4
Finger to floor distance (cm)	0.72	>12.0	0.63	0.78	2.9	0.5	0.71	>12.0	0.68	0.72	2.5	0.4	0.74	>11.8	0.78	0.71	2.7	0.5
Occiput to wall distance (cm)	0.71	>1.5	0.59	0.80	2.9	0.5	0.77	>2.4	0.68	0.84	4.2	0.4	0.81	>2.4	0.75	0.80	3.7	0.5
Tragus to wall distance (cm)	0.72	>12.5	0.59	0.76	2.4	0.5	0.77	>12.6	0.67	0.78	3.0	0.4	0.81	>14.1	0.62	0.86	4.5	0.5
Modified Schober (cm)	0.73	⩽2.3	0.47	0.92	5.7	0.6	0.76	⩽2.4	0.58	0.90	5.8	0.5	0.83	⩽1.9	0.57	0.96	15.6	0.6
Cervical rotation (degrees)	0.71	⩽68.0	0.63	0.73	2.4	0.5	0.72	⩽54.0	0.46	0.92	5.7	0.6	0.75	⩽54.0	0.51	0.89	4.6	0.5
Lateral spinal flexion (cm)	0.81	⩽13.9	0.84	0.74	3.2	0.2	0.86	⩽11.3	0.76	0.81	4.0	0.3	0.88	⩽9.4	0.74	0.86	5.2	0.2
Intermalleolar distance (cm)	0.68	⩽102.0	0.52	0.83	3.0	0.6	0.65	⩽102.0	0.53	0.73	2.0	0.7	0.71	⩽104.0	0.63	0.70	2.1	0.6
BASMI	0.85	>3.0	0.75	0.84	4.8	0.3	0.86	>3.2	0.78	0.79	3.7	0.3	0.89	>3.6	0.80	0.84	5.1	0.3