Ratio of Urea Nitrogen to Total Non-Protein Nitrogen in the Blood in Pregnancy.

Abstract

In normal whole blood the urea nitrogen usually accounts for about 50% of the total non-protein nitrogen, although the variations found in this ratio (35-55) scarcely justify the practice occasionally seen in hospital laboratories by which the concentration of urea nitrogen is calculated from the non-protein nitrogen or vice versa. The fact seems well established that in the blood of patients with nitrogen retention of considerable magnitude the relative concentration of urea nitrogen may be increased as high as 75% of the non-protein nitrogen. On the other hand, the finding of a lowered ratio to non-protein nitrogen which has been noted by certain investigators to occur in the blood of pregnant women has not received universal confirmation, for while certain observations would indicate that this lowered ratio is found in the blood in normal pregnancy, others have found this relative decrease in the urea fraction only in abnormal cases. The records of still other observations would indicate that the ratio of urea to non-protein nitrogen is the same in the blood of non-pregnant and of pregnant subjects.