[Refractometric measurement of total serum protein, comparison of refractometry and biuret test (author's transl)]

Study on the Refractometric Determination of Total Protein in Serum, Comparison of the Refractometric and Biuret Method. Total protein concentration in serum was determined by the aid of the Abbé-refractometer and the biuret method. Both methods showed a good precision and accuracy. The investigation was carried out in 241 sera with normal bilirubin (up to 1 mg/100 ml), cholesterol (up to 200 mg/100 ml) and urea (up to 23,0 mg/100 ml) concentration, in 43 sera with increased (10,6-26,6 mg/100 ml) bilirubin concentration, in 129 sera with increased (200-520 mg/100 ml) cholesterol concentration and in 43 sera with increased (23,0-155,3 mg/100 ml) urea concentration. The comparison of the refractometric values with the values obtained by the biuret method in the 241 sera with normal bilirubin, cholesterol and urea concentration (correlation coefficient = 0,971) showed a close correlation and in the 43 sera with increased bilirubin concentration (correlation coefficient = 0,958) an acceptable correlation. However no close correlations were observed in the 129 sera with increased cholesterol concentration and in the 43 sera with increased urea concentration. The correlation lines diverged proportional with the increase of cholesterol and urea concentration from the expected correlation lines.