Jul 6, 2010 - Serum concentrations of creatinine and of the three low molecular weight (LMW) proteins cystatin C, factor D of the complement system and ...
Acta Med Scand 1985; 218: 499-503
Serum Concentration of Cystatin C, Factor D and b-Microglobulin as a Measure of Glomerular Filtration Rate A. GRUBB, 0. SIMONSEN, G. STURFELT, L. TRUEDSSON and H. THYSELL From the Department of Clinical Chemistry, Malmo General Hospital, Malmo, and Departments of Nephrology and Immunology, Uniwrsiry Hospital, Lund, Sweden
ABSTRACT. Grubb A, Simonsen 0, Sturfelt G, medsson L, Thysell H. (Department of Clinical Chemistry, Malmo General Hospital, Malmo, and Departments of Nephrology and Immunology, University Hospital, Lund, Sweden.) Serum concentration of cystatin C, factor D and B2-microglobulinas a measure of glomerular filtration rate. Acta Med Scand 1985; 218: 4-503.
Serum concentrations of creatinine and of the three low molecular weight (LMW) proteins cystatin C, factor D of the complement system and µglobulin were measured in 135 consecutive patients, whose glomerular filtration rates (GFR) were determined by CrEDTA. In the total patient series, the reciprocals of S-creatinine and S-cystatin C were numerically and, in males, significantly more closely correlated to GFR than the reciprocals of S-factor D. The reciprocals of µglobulin showed a weaker correlation to GFR than those of the other three substances. The calculated glomerular elimination rates of creatinine, cystatin C and factor D were normally distributed, in contrast to those of p2microglobulin. According to data presented so far, cystatin C seems to be the LMW protein of first choice when GFR is to be estimated by measuring the plasma concentration of a LMW protein. Key words: flz-microglobulin, creatinine, Cr-EDlX clearance, cystatin C , factor D.
Serum concentrations of various low molecular weight (LMW) proteins reflect more or less precisely the glomerular filtration rate (GFR) (1-8). In earlier studies (9) serum levels of factor D in the complement system and of cystatin C (IO)-an inhibitor of cystein protease-were found to be as good, in some patients even better, estimators of GFR as Screatinine. This study was performed to compare the serum levels of these two LMW proteins as a measure of GFR in a larger series of patients. PATIENTS Serum samples were collected from 135 consecutive patients (67 females and 68 males, 7-77 (median 42) years old) referred to the Department of Clinical Physiology, University Hospital, Lund, for determination of GFR. Fifty patients had primary glomerulonephritis, 9 glomerulonephritis secondary to systemic diseases, 21 rheumatoid disorders, 4 diabetic nephropathy, 6 lithium nephropathy, 13 various urological disorders, 16 various malignancies and 16 various known or unknown renal disorders.
METHODS GFR was determined by "Cr-EDTA (11) and S-creatinine as described by Heinegbd and Tidestrom (12). The serum samples were frozen at -20°C until analysed. Cystatin C and pz-microglobulin were determined by enzyme amplified single radial immunodiffusion (13) and factor D by an enzyme amplified electroimmunoassay (14). Factor D concentration was expressed in per cent of the concentration in a normal plasma pool used as standard.
Abbreviations: GFR = glomerular filtration rate, LMW = low molecular weight.
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LMW proteins and GFR
Acta Med Scand 1985; 218 Number of patients
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Fig. 2. Distribution of the calculated glomerular elimination rates of ,&-microglobulin, factor D, cystatin C and S-creatinine.
Statistics Correlations were calculated by the method of least squares. Differences between correlation coefficients were calculated according to Hotelling (15). Student's t-test was used in the comparison between patient groups.
RESULTS In the total patient series the reciprocals of S-creatinine and S-cystatin C were numerically more closely correlated to GFR (r=0.75 and r=0.77, respectively) than those of S-factor D (r=0.69) (Fig. 1). When males and females were studied separately, the differences in r-values became significant (creatinine-factor D p
