Accred Qual Assur (2000) 5 : 54–57 Q Springer-Verlag 2000 PRACTITIONER’S REPORT Diler Aslan Filiz Kuralay Tijen Tanyalcin Orcan Tanyalcin A practical analytical quality report on the effect of carotenemia on neonatal bilirubin levels Received: 20 April 1999 Accepted: 24 September 1999 T. Tanyalcin (Y) Ege University School of Medicine, Department of Biochemistry, Bornova, TR-35100 Izmir, Turkey e-mail: ibot6unimedya.net.tr Fax: c 90-232-4630910 D. Aslan Pamukkale University School of Medicine, Department of Biochemistry, Denizli, Turkey F. Kuralay Dokuz Eylul University School of Medicine, Department of Biochemistry, Balcova, Izmir, Turkey O. Tanyalcin Tanyalcin Tip Laboratuvari, 1359 sk No: 4/3 Alsancak, Izmir, Turkey Abstract The effect of haematocrit and b-carotene levels on the serum total bilirubin measurement in two analytical methods was studied as an example of the impact of practi- cal analytical quality in medical de- cision making. The precision char- acteristics of the two methods were very similar. Based upon the signif- icant difference in the correlation coefficient in a method comparison study before and after 20% trim- ming of the data, an interference effect study was performed. Hae- moglobin (expressed as haemato- crit) and b-carotene were the sub- stances studied to explain the ob- served differences. The bilirubin test results from the Wako bilirubi- nometer were easily affected (np19; X(S): 13.83B2.43; tp–6.17; Pp0.000) and more elevated than in the Vitros dry chemistry systems (np18; X(S): 12.72B2.21; tp–2.48; Pp0.017), due to the presence of b-carotene ( 1 200 mg/dl). Key words Analytical interference 7 Analytical quality 7 Analytical quality indicator Introduction Serum total bilirubin measurement is one of the labora- tory tests most commonly performed on newborn in- fants since jaundice in neonates frequently occurs dur- ing the first few days following birth. Whatever the cause of hyperbilirubinemia, the decision to perform photo therapy or a blood transfusion should be based on accurately performed measurements of total biliru- bin concentrations in newborns. The under- and over- estimation of total bilirubin concentrations could lead to a failure to provide essential therapy or unnecessary clinical intervention in some cases [1]. The apparent inter-laboratory variability of bilirubin quantification may reflect differences in the type of measurement be- ing reported, such as total bilirubin or “neonatal total bilirubin”. The accurate determination of serum biliru- bin concentrations is important for the care of new- borns. High performance liquid chromatography (HPLC) provides accurate determination of serum bili- rubin, however it is expensive and time-consuming for a routine clinical laboratory to perform. So most labo- ratories with a heavy routine workload rely on auto- mated analysis for rapid bilirubin determinations in multiple samples [2, 3]. Here we compare the results for neonatal bilirubin determination in serum of newborns as measured using a Wako neonatal bilirubinometer (SE 101 DII Model Osaka Japan) with results from the Vitros DT 60 dry chemistry system (Johnson & John-