[Evaluation of glomerular filtration rate in plasma cell dyscrasias--which test for ambulatory practice?]

To select the best mathematical formula for ambulatory monitoring of glomerular filtration rate (GFR) in patients with plasma cell dyscrasias (PCD's) we evaluated GFR in 32 pts (22 M + 10 F; mean age 66.1 +/- 9.6) with newly recognized PCD's with the following routine GFR tests: creatinine concentration in serum (Crs); 24 hr's standard creatinine clearance (Crcl) as a reference test; calculation of GFR from Baracskay (BGFR) and Cockcroft-Gault (C-GGFR) formulas. There were: 16 pts without monoclonal proteinuria MP(-) and 16 pts with monoclonal proteinuria MP(+) (0.44-40.3; mean 9.54 g/day). The abnormal values for Crs were defined as > 1.5 mg/dl; for Crcl as < 80.0 ml/min. Only 41% (13/32) of pts had abnormal values of Crs and 84% (27/32) had abnormal values of Crcl. In the group of pts without monoclonal proteinuria MP(-) statistical significance between 24-hr's creatinine clearance and GFR calculated by Cockcroft-Gault as well as Baracskay formulas was not stated. In the group of pts with monoclonal proteinuria MP(+) statistical significance was not stated only between 24-hr's creatinine clearance and GFR calculated by Cockcroft-Gault formula. That was no statistical significance in GFR evaluated with this methods between patients with kappa and lambda monoclonal proteinuria. We concluded, that for ambulatory monitoring of pts with PCD's MP(+) only Cockcroft-Gault formula is recommended. On the other hand pts MP(-) might be monitored using Barasckay as well as Cockcroft-Gault formulas. Because Csr over estimated values of Crcl in both groups of pts, the other serum marker of GFR should be investigated.