[How reliable are assays with the ictometer? Comparative studies with direct measurement of billirubin and a diazo technique (author's transl)].

Comparison of measurements of a diazo technique with those of a direct assessment of bilirubin with the photo-ictometer type II (Hirtz & Co., Cologne). Comparative analysis of total bilirubin-concentration in 172 non-hemolytic sera of neonates and in dilution series with and without contamination by hemoglobin and/or lipid-suspension gave the following results and conclusions drawn from them: 1. In non-contaminated sera the relation between the two techniques is linear, well correlated, parallel and with little divergence. 2. In contrast to the ictometer the diazo technique used underrates the bilirubin content in hemolytic sera. 3. In contrast to the diazo technique the ictometer underrates the bilirubin content in strongly turbid sera. 4. The precision of the ictometer is superior in series and from day to day to the already good precision of the diazo technique. 5. The standard built- in after calibration has to be checked daily and adjusted during the first working hour of the ictometer on several occasions. 6. In order to aboid major systematic faults each apparatus should be compared with a safely calibrated technique. 7. The very simple and rapidly serviced apparatus is suitable for the assay of total bilirubin in sera of the newborn. For older neonates and after exchanges transfusions the results should not be trusted.