Table I.

Studies systematically reviewed to determine if sCOMP is elevated in patients with radiographically diagnosed knee OA

Authors	Level of evidence (CEBM)	Quality index score (%)	Study design	OA group inclusion criteria	No. control patients	No. OA patients	Dependent variables measured
Cibere et al. (2009)14, *	2b	81.25%	Exploratory cohort	Aged 40–79 years; pain, aching, or discomfort in or around the knee on most days of the month at any time in the past; any pain, aching, or discomfort in or around the knee in the past 12 months	16	Pre- ROA = 105 ROA = 80† Total = 185	C2C; C1, 2C; CPII; CS846; NTX-I; CTX-II; HA; sCOMP; WOMAC
Clark et al. (2007)4	2b	81.25%	Retrospective cohort	Caucasian, knee OA K/L ≥ 2	148	K/L 2 = 109 K/L 3,4 = 34 Total = 143	sCOMP
Fernandeset al. (2007)3, ‡	4	68.75%	Case control	Aged 40–70 years, mechanical pain in one or both knees for minimum 3 months, and knee crepitus upon clinical evaluation	86	SOA = 75** Pain = 11 NOA = 18** Total = 104	WOMAC; VAS and sCOMP
Jordan et al. (2003)23	2b	87.5%	Retrospective cohort	Radiographs and serum COMP samples in database	302	K/L 2 = 313 K/L 3 = 110 K/L 4 = 44 Total = 467	sCOMP
Mundermann et al. (2009)33	4	43.75%	Case control	Definite osteophyte presence in the medial or lateral tibiofemoral compartment; a narrowest point inter-bone distance of the medial compartment less than the lateral compartment; pain in and around at least one knee for most of the days in the past months; at least some difficulty with two or more items in the WOMAC physical function scale	41	K/L 1 = 11 K/L 2 = 7 K/L 3 = 12 K/L 4 = 12 Total = 42	Gait analysis; ambulatory load and sCOMP
Senolt et al. (2004)11	4	25%	Case control	Undergoing arthrocentesis, no history of renal disease of diabetes mellitus and had normal levels of creatinine	38	K/L 1 = 2 K/L 2 = 18 K/L 3 = 14 K/L 4 = 4 Total = 38	sCOMP and Pentosidine
Wakitani et al. (2007)12,††	4	25%	Case control	Patients undergoing knee surgery	24	K/L 1 = 7 K/L 2 = 4 K/L 3 = 6 K/L 4 = 7 Total = 24	Articular cartilage assessment, keratan sulfate, CS6, CS846, HA and sCOMP and synovial COMP

^*Pre-ROA = pre-radiographic OA (K/L < 2); ROA = radiographic OA (K/L ≥ 2); C2C = Type II collagen cleavage neopeptide; C1, 2C = Types I and II collagen cleavage neoepitope; CS846 = cartilage proteoglycan aggrecan turnover epitope; NTX-I = N-telopeptide of type I collagen; CTX-II = C-telopeptide of type II collagen; HA = hyaluronan acid; WOMAC = Western Ontario McMaster University Index.

^†Only the ROA group was used for this review.

^‡SOA (symptomatic OA) = K/L grades 2, 3, 4; NOA (non-symptomatic OA) = K/L 2 or higher; Pain = K/L 0 or 1; VAS = visual analog scale.

^**Only the SOA and NOA groups were used for this review.

^††C6S = chondroitin 6 sulfate.