Serum levels of YKL-40 and C reactive protein in patients with hip osteoarthritis and healthy subjects: a cross sectional study.
BACKGROUND
YKL-40 is a 40 kDa glycoprotein secreted by chondrocytes and synoviocytes. It has been suggested that it is a surrogate marker of synovial inflammation and joint destruction in rheumatoid arthritis (RA) and osteoarthritis (OA) and related to C reactive protein (CRP) serum levels in RA.


OBJECTIVE
To study serum levels of YKL-40 in patients with hip OA and its relation with CRP.


METHODS
YKL-40 and CRP were assayed in serum samples from 45 patients (24 women, 21 men, mean age 65) with symptomatic OA of the hip and 33 healthy controls. YKL-40 was assayed by immunoassay and CRP by ultrasensitive immunonephelometry. OA severity was assessed by the measurement of joint space width with a computer analysis system of digitised hip radiographs. Statistical analysis was performed to determine correlations between serum markers and radiological joint space width.


RESULTS
The mean (standard error) YKL-40 level was 90.3 (8.2) ng/ml in patients with hip OA and 66.9 (8.2) ng/ml in controls (p=0.03). The mean CRP level was 2.93 (3.03) mg/l in OA and 1.40 (1.61) mg/l in controls (p=0.006). The serum levels of YKL-40 and CRP increased with age and were significantly correlated (Spearman test: r(s)=0.42, p=0.005) in patients but not in controls. Neither YKL-40 nor CRP correlated with radiographic joint space width.


CONCLUSIONS
Serum YKL-40 was significantly increased in patients with hip OA. The correlation between YKL-40 and CRP suggests that YKL-40 may be a marker of joint inflammation in OA. Longitudinal studies are required to assess the usefulness of YKL-40 in the monitoring of patients with hip OA.
Conrozier
T
T
Department of Rheumatology, Centre Hospitalier Lyon-Sud, Pierre-Bénite, France. th.conrozier@wanadoo,fr
Carlier
M C
MC
Mathieu
P
P
Colson
F
F
Debard
A L
AL
Richard
S
S
Favret
H
H
Bienvenu
J
J
Vignon
E
E
D054392:Adipokines; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers; D002097:C-Reactive Protein / Q000032:analysis*; D016022:Case-Control Studies; D000071451:Chitinase-3-Like Protein 1; D003430:Cross-Sectional Studies; D005260:Female; D006023:Glycoproteins / Q000097:blood*; D006621:Hip Joint / Q000000981:diagnostic imaging; D006801:Humans; D007118:Immunoassay; D037102:Lectins; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry; D015207:Osteoarthritis, Hip / Q000097:blood* / Q000000981:diagnostic imaging; D011859:Radiography; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric
D054392:Adipokines; D015415:Biomarkers; C084533:CHI3L1 protein, human; D000071451:Chitinase-3-Like Protein 1; D006023:Glycoproteins; D037102:Lectins; D002097:C-Reactive Protein