Table 1.

Test results were classified as normal/abnormal using the reference ranges from each center.

Center	ESR, mm/h	CRP, mg/l	RF, IU/ml	ACPA, U/ml
1	< 25	< 5	< 40	< 20
2	2–37 in 1st hour	< 5	< 30	0–10
4	< 10	< 5	< 40	< 20
6	< 8 in 1st hour, < 18 in 2nd hour	< 5	< 14	< 10
8 (2 sites)	0–9	< 5	0–13	0–6
		< 8	0–14	0–10
13	Female 2–20 Male 2–15	< 10	< 16	< 7
14	Male: yrs divided by 2 Female: yrs + 10 divided by 2	< 5	1–20	< 25
18	1–20	< 10	< 25	< 25
20	< 15	< 5	< 50	< 50
21	< 28	< 5	< 20	< 26
22	< 30	< 5	< 20	< 10
23	< 37	< 10	16	< 8
24	< 37	< 10	16	< 8
25	1–15	< 10	< 40	< 7
30	< 37	< 10	16	< 8
31	0–29	< 8	< 10	< 15.6
32	Male 0–22 Female 0–29	≤ 8	< 10	< 15.6
33	0–29	< 8	< 14	< 20
34	< 20	< 8	< 14	< 16
40	< 20 women < 14 men	< 5	1–20	< 251
41	Women: (age + 10)/2 Men: age/2	≤ 8	≤ 35	< 7, negative; > 10 positive

ESR: erythrocyte sedimentation rate; CRP: C-reactive protein; RF: rheumatoid factor; ACPA: anticitrullinated protein antibodies.