Table 1.

Characteristics of included studies for COMP

Author	Group	N	Age (years)	Female (n)	BMI (kg/m2)	Region	K-L 0~4 of patients (n)	ELISA manufacture information	Type of ELISA
Clark1999	Control	148	60 ± 20	144		USA	K-L 0 = 148, K-L2 = 109 K-L 3,4 = 34	In-house method	Competitive
	OA	143	60 ± 20
Das Gupta E2017	Control	30	62.5 ± 12	15	25.01 ± 6.31	Malaysia	K-L 2 = 30 K-L 3 = 23 K-L 4 = 7	R&D Systems	Solid-phase sandwich
	OA	60	57.5 ± 9	46	26.72 ± 5.35
Fernandes2007	Control	40	53.8 ± 8.5	24		Brazil	K-L 0,1 = 40 K-L 2–4 = 75	AnaMar Medical (Uppsala, Sweden)	Sandwich
	OA	75	56.6 ± 7.6	51
Jordan JM2003	Control	302	63.3 ± 10.8	258	31.5 ± 7.4	USA	K-L 0 = 302, K-L 2 = 313, K-L 3 = 110, K-L 4 = 44	AnaMar Medical (Lund, Sweden)	Sandwich
	OA	467	60.6 ± 9.6	190	28.9 ± 6.1
Li2012	Control	35	53 ± 12.53	19	21.8 ± 4.9	China	K-L 1 = 28, K-L 2 = 36, K-L 3 = 27, K-L 4 = 24	AnaMar Medical AB (Lund, Sweden)	Sandwich
	OA	115	55 ± 13.32	60	22.3 ± 5.7
Mündermann A2009	Control	41	57.5 ± 7	20	25.7 ± 4.2	USA	K-L 1 = 11, K-L 2 = 7, K-L 3 = 12, K-L 4 = 12	AnaMar Medical AB (Lund, Sweden)	Sandwich
	OA	42	60.7 ± 8.6	22	27.0 ± 3.8
Author	Group	N	Age (years)	Female (n)	BMI (kg/m2)	Region	K-L 0~4 of patients (n)	ELISA manufacture information	Type of ELISA
Senolt L2005	Control	38	58.3 ± 9.1	23		Czech Republic	K-L 1 = 2, K-L 2 = 18 K-L 3 = 14, K-L 4 = 4	In-house method	Sandwich
	OA	38	64.1 ± 10.1	25
Sowers MF2009	Control	36	47.5 ± 2.6	36	29.7 ± 6.2	France	K-L 0,1 = 36 K-L 2 = 16 K-L 3,4 = 20	AnaMar Medical (COMPTM ELISA kit)	A two-site ELISA
	OA	36	47.5 ± 2.6	36	39.15 ± 8.22
Wakitani2007	Control	24	20–54	8		Japan	K-L 1 = 7, K-L 2 = 4 K-L 3 = 6, K-L 4 = 7	Kamiya Biomedical Company, Seattle, WA, USA	Sandwich
	OA	24	40–80	20

COMP cartilage oligomeric matrix protein, K-L Kellgren-Lawrence classification, ELISA enzyme-linked immunosorbent assay