Urea and Creatinine Concentration in the Blood;a Statistical Study.

The relationship between the accumulation of urea and creatinine in the blood has held considerable interest since Myers 1 reported evidence which tended to show that in nephritis urea increased in the blood before creatinine did. It seemed probable that data obtained in a clinic where most of the patients were undergoing treatment for chronic diseases might show some relationships between these compounds which would be of value. Results obtained over a period of eight years were therefore tabulated and studied. All cases where analyses of both compounds in the same sample of blood were available were utilized. Such studies were not made on all patients, but blood was obtained from most of those in whom the presence of renal insufficiency was suspected. During the greater part of the period creatinine determinations were done on all specimens where a urea nitrogen concentration greater than 20 mg. per 100 cc. was found, but were generally omitted when the concentration was lower than this figure. During the earlier part of the period both substances were determined in most specimens submitted. The method of Folin and Wu 2 was used for the creatinine determination. During the last two years an unpublished method of Folin and Sumner was used for determining the urea nitrogen; before that time the technique recommended by Van Slyke and Cullen 3 was followed.