ABSTRACT
Determination of serum BETA[2]-microglobulin concentration, an invasive procedure, has been advocated for monitoring patients' response to treatment in rheumatoid arthritis. The object of this study was to find out if serum BETA[2]-microglobulin concentration correlated with urinary excretions of type 1 collagen cross-linked N-telopeptides [NTx] and deoxypyridinoline [Pyrilinks-D] in rheumatoid arthritis [RA]. Using chemiluminiscent assay, serum BETA[2]-microglobulin concentrations were estimated in 25 female patients with active RA, 25 female with inactive disease, and 25 age-matched healthy female controls. Concentrations of NTx and Pyrilinks-D were also determined by immunoabsorbent assays in spot urine samples from these subject groups. The serum concentration of BETA[2]-microglobulin 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]. Similarly, in patients with active RA, the spot urinary concentrations of NTx [123.08 +/- 25.53 nmol BCE/mmol creatinine] and Pyrilinks-D [15.08 +/- 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 patients with active RA, serum concentration of BETA[2]-microglobulin correlated positively with spot urinary NTx concentrations [r=0.9910, P=0.0001], and Pyrilinks-D concentration [r=0.6177, P=0.001]. In patients with active RA, the spot urinary concentrations of NTx and Pyrilinks-D correlated positively with serum BETA[2]-microglobulin. Therefore, the estimations of these urinary markers may take the place of serum BETA[2]-microglobulin estimation in monitoring the patient's response to treatment in rheumatoid arthritis