Table 3

Sensitivity and specificity of clinical and ultrasound variables for the prediction of RA

	Sensitivity	Specificity	Positive LR	Negative LR	PPV	NPV	AUC
MCP joints
MCP clinical involvement	97	69	3	0.05	76	95	0.828
MCP clinical symmetry	65.5	97	19	0.36	95	74	0.810
MCP GS ≥1 involvement	100	38	2	0	62	100	0.690
MCP GS ≥1 symmetry	93	76	4	0.09	79	92	0.845
MCP GS ≥2 involvement	90	48	2	0.21	63	82	0.690
MCP GS ≥2 symmetry	86	79	4	0.17	81	85	0.828
MCP GS count ≥8	45	100		0.55	100	64	0.724
MCP PD ≥1 involvement	97	55	2	0.06	68	94	0.759
MCP PD ≥1 symmetry	83	79	4	0.22	80	82	0.810
MCP PD ≥2 involvement	90	66	3	0.16	72	86	0.776
MCP PD ≥2 symmetry	83	83	5	0.21	83	83	0.828
PIP joints
PIP clinical involvement	62	76	3	0.50	72	67	0.690
PIP clinical symmetry	41	93	6	0.63	86	61	0.672
PIP GS ≥1 involvement	79	62	2	0.33	68	75	0.707
PIP GS ≥1 symmetry	48	79	2	0.65	70	61	0.638
PIP GS ≥2 involvement	79	66	2	0.32	70	76	0.724
PIP GS ≥2 symmetry	48	90	5	0.58	82	63	0.690
PIP PD ≥1 involvement	76	69	2	0.35	71	74	0.724
PIP PD ≥1 symmetry	45	90	4	0.62	81	62	0.672
PIP PD ≥2 involvement	66	76	3	0.46	73	69	0.707
PIP PD ≥2 symmetry	38	97	11	0.64	92	61	0.672
Wrist joints
Wrist clinical involvement	69	86	5	0.36	83	74	0.776
Wrist clinical symmetry	48	93	7	0.56	88	64	0.707
Wrist GS ≥1 involvement	97	41	2	0.08	62	92	0.690
Wrist GS ≥1 symmetry	86	62	2	0.22	69	82	0.741
Wrist GS ≥2 involvement	79	69	3	0.30	72	77	0.741
Wrist GS ≥2 symmetry	52	93	7	0.52	88	66	0.724
Wrist PD ≥1 involvement	93	48	2	0.14	64	88	0.707
Wrist PD ≥1 symmetry	83	66	2	0.26	71	79	0.741
Wrist PD ≥2 involvement	90	48	2	0.21	63	82	0.690
Wrist PD ≥2 symmetry	69	72	2	0.43	71	70	0.707
MTP joints
MTP clinical involvement	17	100		0.83	100	55	0.586
MTP clinical symmetry	10	100		0.90	100	53	0.552
MTP GS ≥1 involvement	69	55	2	0.56	61	64	0.621
MTP GS ≥1 symmetry	55	79	3	0.56	73	64	0.672
MTP GS ≥2 involvement	59	72	2	0.57	68	64	0.655
MTP GS ≥2 symmetry	41	83	2	0.71	71	56	0.621
MTP PD ≥1 involvement	52	90	5	0.54	83	65	0.707
MTP PD ≥1 symmetry	35	100		0.66	100	60	0.672
MTP PD ≥2 involvement	38	100		0.62	100	62	0.690
MTP PD ≥2 symmetry	24	100		0.76	100	57	0.621
Other variables
Leiden score ≥8	62	93	9	0.41	90	71	0.776
1987 ACR criteria (4/7 clinical)	79	90	8	0.23	89	81	0.845
ACR criteria 4/7 GS	93	65.5	3	0.10	73	91	0.793
ACR criteria 4/7 PD	86	76	4	0.18	78	85	0.810
X-ray hand/foot erosion	3.5	100		0.97	100	45	0.517
US hand/foot erosion	38	93	5.5	0.67	85	60	0.655
ACPA positive	48	100		0.52	100	66	0.741
ACPA positive or MTP PD ≥2 Involvement or MCP GS count ≥8	76	100		0.24	100	81	0.879
PD10 index ≥10	79	93	11.5	0.22	92	82	0.862

ACPA, anti-cyclic citrullinated peptide antibody; ACR, American College of Rheumatology; AUC, area under the receiver operating characteristic curve; GS, ultrasound greyscale; LR, likelihood ratio; metacarpophalangeal joint (MCP) GS ≥1 involvement, MCP joint involvement with an ultrasound greyscale grade of at least 1; MCP joint GS count ≥8, at least eight MCP joints with GS involvement of grade ≥1; NPV, negative predictive value; PD, ultrasound power Doppler; PD10 index, summed power Doppler grades of MCP 2–3 joints, wrists and metatarsophalangeal (MTP) 2–3 joints; PIP, proximal interphalangeal joint; PPV, positive predictive value; RA, rheumatoid arthritis; US, ultrasound.