SERUM BETA-2-MICROGLOBULIN CONCENTRATION CORRELATES WITH URINARY CONCENTRATIONS OF TYPE-1 COLLAGEN CROSS-LINKED N-TELOPEPTIDES AND DEOXYPYRIDINOLINE IN RHEUMATOID-ARTHRITIS

Background: Determination of serum beta(2)-microglobulin concentration , an invasive procedure, has been advocated for monitoring patients' r esponse to treatment in rheumatoid arthritis. The object of this study was to find out if serum beta(2)-microglobulin concentration correlat ed with urinary excretions of type 1 collagen crosslinked N-telopeptid es (NTx) and deoxypyridinoline (Pyrilinks-D) in rheumatoid arthritis ( RA). Subjects and Methods: Using chemiluminiscent assay, serum beta(2) -microglobulin concentrations were estimated in 25 female patients wit h active RA, 25 female with inactive disease, and 25 age-matched healt hy female controls. Concentrations of NTx and Pyrilinks-D were also de termined by immunoabsorbent assays in spot urine samples from these su bject groups. Results: The serum concentration of beta(2)-microglobuli n in patients with RA (7.45+/-2.10 mg/L) was significantly higher (P<0 .001) than the concentrations in patients with inactive disease (3.33/-0.76 mg/L), or than in normal healthy controls (2.74+/-0.52 mg/L). S imilarly, in patients with active RA, the spot urinary concentrations of NTx (123.08+/-25.53 nmol BCE/mmol creatinine) and Pyrilinks-D (15.0 8+/-3.29 nmol/mmol creatinine) were significantly higher (P<0.01) than those in patients with inactive disease (58.42+/-12.65 nmol BCE/mmol creatinine and 10.10+/-2.43 nmol/mmol creatinine, respectively). In pa tients with active RA, serum concentration of beta(2)-microglobulin co rrelated positively with spot urinary NTx concentrations (r=0.9910, P= 0.0001), and Pyrilinks-D concentration (r=0.6177, P=0.001). Conclusion : In patients with active RA, the spot urinary concentrations of NTx a nd Pyrilinks-D correlated positively with serum beta(2)-microglobulin. Therefore, the estimations of these urinary markers may take the plac e of serum beta(2)-microglobulin estimation in monitoring the patient' s response to treatment in rheumatoid arthritis.