Does information on novel identified autoantibodies contribute to predicting the progression from undifferentiated arthritis to rheumatoid arthritis: a study on anti-CarP antibodies as an example

Table 2 Proportion of 2010-UA and 1987-UA patients progressing to RA within 1 year within groups of similar ACPA and RF status

		RA	No RA	% RA/% non-RA development (pre-test risks)^a	OR (95% CI)	PPV (95% CI)	NPV (95% CI)
1987-UA patients (n = 1352)
ACPA–RF– (n = 929)	anti-CarP+	23	42	21/79	2.1 (1.3–3.7)	35 (25–48)	80 (77–82)
ACPA–RF– (n = 929)	anti-CarP–	176	688	21/79	2.1 (1.3–3.7)	35 (25–48)	80 (77–82)
ACPA+RF– (n = 64)	anti-CarP+	16	10	50/50	2.2 (0.8–6.1)	62 (43–78)	58 (42–72)
ACPA+RF– (n = 64)	anti-CarP–	16	22	50/50	2.2 (0.8–6.1)	62 (43–78)	58 (42–72)
ACPA–RF+ (n = 140)	anti-CarP+	8	9	39/61	1.4 (0.5–4.0)	47 (26–69)	62 (53–70)
ACPA–RF+ (n = 140)	anti-CarP–	47	76	39/61	1.4 (0.5–4.0)	47 (26–69)	62 (53–70)
ACPA+RF+ (n = 219)	anti-CarP+	107	42	71/29	1.2 (0.6–2.2)	72 (64–78)	31 (22–43)
ACPA+RF+ (n = 219)	anti-CarP–	48	22	71/29	1.2 (0.6–2.2)	72 (64–78)	31 (22–43)
2010-UA patients (n = 838)
ACPA–RF– (n = 755)	anti-CarP+	1	48	4/96	0.5 (0.1–3.5)	2 (0–11)	96 (94–97)
ACPA–RF– (n = 755)	anti-CarP–	30	676	4/96	0.5 (0.1–3.5)	2 (0–11)	96 (94–97)
ACPA+RF– (n = 15)	anti-CarP+	1	2	13/87	5.5 (0.2–129)	33 (6–79)	92 (65–99)
ACPA+RF– (n = 15)	anti-CarP–	1	11	13/87	5.5 (0.2–129)	33 (6–79)	92 (65–99)
ACPA–RF+ (n = 35)	anti-CarP+	0	4	17/83	Undefined	0 (0–49)	81 (64–91)
ACPA–RF+ (n = 35)	anti-CarP–	6	25	17/83	Undefined	0 (0–49)	81 (64–91)
ACPA+RF+ (n = 33)	anti-CarP+	9	12	42/58	1.1 (0.2–4.4)	43 (24–63)	58 (32–81)
ACPA+RF+ (n = 33)	anti-CarP–	5	7	42/58	1.1 (0.2–4.4)	43 (24–63)	58 (32–81)

Patients were stratified according to the presence of different autoantibody combinations (ACPA–RF–, ACPA+RF–, ACPA–RF+, and ACPA+RF+); within these groups the predictive value of the presence of anticarbamylated protein (anti-CarP) antibodies for progression to rheumatoid arthritis (RA) was determined, both within 2010-undifferentiated arthritis (UA) and 1987-UA patients
ACPA, anticitrullinated protein antibodies; CI, confidence interval; NPV, negative predictive value; OR, odds ratio; PPV, positive predictive value; RF, rheumatoid factor
^a Observed risk of RA development within ACPA and RF strata (pre-test risks), without information on anti-CarP status

ISSN: 1478-6362