TOTAL AND FREE PROTEIN S IN NEPHROTIC SYNDROME

25 consecutive patients (15M, 10F ; mean age 30 years) with nephrotic syndrome (NS) of different grade were studied. Control group consisted in 18 healthy adult volunteers. Total protein S antigen (TPS:Ag) and free protein S antigen (FPS:Ag) after precipitation of C4-BP-bound protein S by PEG 3-5 % final concentration were measured by Laurell's technique. PS:Ag was also searched in concentrated urine of 9 patients by ELISA method, more sensitive than the Laurell's technique. In the same plasma samples we measured C4-BP, Protein C Ag and AT III biological activity (all reagents from D.Stago). Serum albumin level, proteinuria, proteinuria selectivity index, triglycerides, cholesterol levels were recorded. TPS:Ag was found elevated in NS (1.30±0.3 U/ml) in comparison with control group (1.09±0.32 U/ml) and the difference was statistically significant (p<0.05). The mean values of FPS:Ag observed in patients and controls were not statistically different, but if we consider 95 % confidence limits (0.99-1-35 U/ml), 16 pts had normal or elevated FPS:Ag level, whereas 9 had decreased FPS:Ag level. A positive correlation was found between TPS:Ag and FPS:Ag in control group (r=0.66 ; p< 0.001) and in patients with NS (r=0.4l, p<0.05). C4-BP was significantly (p<0.01) increased in nephrotic patients ( 1.37 ± 0.36 U/ml) in comparison with control group (1.04±0.27 U/ml). A negative correlation was found between FPS:Ag and C4-BP levels in control group (r = −0.57, P< 0.01) but not in nephrotic patients. A positive correlation was found between FPS:Ag and albumin level and between FPS:Ag and cholesterol level. No correlation was found between TPS:Ag or FPS:Ag and proteinuria, proteinuria selectivity index, AT III and protein C levels. Traces of PS were found in urine (0. to 2.5 U/day) in 9 patients tested. 2/25 pts suffered thromboembolic events : one had a very low level of FPS:Ag in addition to a decreased level of AT III. The other one had normal FPS:Ag and AT III level but a borderline Protein C level. In conclusion. An acquired FPS:Ag deficiency was observed in 9/25 pts with NS despite an increased level of TPS:Ag. In this small series of patients the acquired FPS deficiency does not seem to be related either to an urinary loss of FPS or to an increased binding to C4-BP, as suggested by some authors.