Presence of Autoantibodies in Erosive Hand Osteoarthritis and Association with Clinical Presentation

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Figure 1.
A. Autoantibodies in patients with HOA of HOSTAS, EHOA, and ECHO cohorts, and clinical features of HOSTAS. ELISA were performed to detect anti-CarP antibody, ACPA, and RF in sera of 196 HC and 580 HOA patients (510 HOSTAS, 23 EHOA, and 47 ECHO). B. The HOSTAS group was subdivided in erosive and nonerosive HOA. The mean plus 2-times the SD in HC was established as the cutoff for the anti-CarP antibody and RF. For ACPA, a cutoff of 25 AU/ml was used. The dotted line represents the cutoff. The number of samples tested in each group and the prevalence, corrected for the response on nonmodified FCS or CCP2-arginine, is shown below the graphs. Mann-Whitney U test for level and Pearson’s chi-square test for prevalence were performed in erosive versus nonerosive OA. HOA: hand osteoarthritis; EHOA: erosive HOA; anti-CarP: anticarbamylated protein antibody, ACPA: anticitrullinated protein antibodies, RF: rheumatoid factor, HC: healthy controls; AU: arbitrary units; FCS: fetal calf serum; CCP: cyclic citrullinated peptide.

Table 1.

Baseline characteristics of cohorts.

Patient Characteristics	HOSTAS, n = 510	EHOA, n = 23	ECHO, n = 47	Healthy Controls, n = 196
Age, yrs, mean ± SD	61.0 ± 8.6	57.1 ± 7.0	63.4 ± 9.2	44.1 ± 13.9
Women, %	85.7	73.9	89.4	51.0
BMI, kg/m², mean ± SD	27.1 ± 4.7, n = 496	26.3 ± 4.7	27.4 ± 4.5, n = 45	23.7 ± 3.0, n = 195
Ever smoker, % (former/current)	64.9 (323/498)	65.2	33.3 (15/45)	34.9 (68/195)
Fulfilling ACR criteria^a, %	90.0	100	100	–

↵a American College of Rheumatology classification criteria for hand OA. BMI: body mass index; OA: osteoarthritis; EHOA: erosive hand OA.

Table 2.

Other clinical features of HOSTAS cohort.

Variables	anti-CarP+, n = 36	anti-CarP−, n = 471	p	RF+, n = 30	RF−, n = 477	p
Sum-score KL (0–120)^a	17.5 (9.5–30.75)	18.0 (8.0–29.0)	0.74	13.5 (8.75–30.5)	18.0 (8.0–30.5)	0.59
Sum-score OARSI osteophytes (0–58)^a	9.5 (6.0–19.0)	10.0 (4.0–18.0)	0.64	8.0 (4.75–16.25)	10.0 (4.5–18.0)	0.74
Sum-score OARSI joint space narrowing (0–58)^a	5.5 (3.0–16.75)	7.0 (3.0–17.0)	0.72	6.5 (2.75–18.0)	7.0 (3.0–17.0)	0.98
CRP raised (> 5.0 mg/l)^b, % (n/total)	11.5 (3/26)	10.4 (34/326)	0.86	7.7 (2/26)	10.7 (35/326)	0.63

Values are median (IQR) unless otherwise specified.
↵a For 3 patients, no hand radiographs were available; Mann-Whitney U test was performed.
↵b Only 352 patients had their CRP levels measured within 22 days from baseline; Pearson’s chi-square test was performed. Anti-CarP: anticarbamylated protein antibodies; RF: rheumatoid factor; KL: Kellgren-Lawrence arthritis grading scale; OARSI: Osteoarthritis Research Society International; CRP: C-reactive protein; IQR: interquartile range.