Deficiency and urinary losses of factor XII in adult nephrotic syndrome.

Factor XII was measured in the plasma and urine of 16 adult patients with nephrotic syndrome and 10 normal volunteers using a monospecific antibody to human factor XII. In addition plasma factor XII procoagulant activity was determined in both groups. Plasma immunoreactive factor XII level was significantly lower in the nephrotic group than the control group. This was associated with a significant reduction of plasma factor XII procoagulant activity. To examine the effect of albumin concentration on factor XII procoagulant activity purified human serum albumin was added in the in vitro system. Manipulation of albumin concentration failed to alter plasma factor XII activity. Considerable amounts of factor XII were recovered in the urine of all but one of the tested nephrotic patients while none were found in the urine of the control group. Plasma factor XII concentration was within normal limits in the single patient whose urine contained no detectable factor XII. Moreover, there was a significant negative correlation between plasma and urinary factor XII concentrations (r = -0.79; p less than 0.01). In addition, plasma factor XII concentration showed a significant correlation with serum albumin concentration (r = 0.63; p less than 0.05). It thus appears that renal losses of this plasma protein contribute to its low plasma concentration in our patients.