[A negative interference effect of pathologic levels of bilirubin on the determination of serum creatinine].

BACKGROUND: Negative interference of bilirubin with assessment of creatinine concentration is generally known from the biochemical aspect. The objective of the presented work was to find the bilirubin level and creatinine concentration where this phenomenon has actually a clinical impact. METHODS AND RESULTS: In 200 samples selected at random the bilirubin and creatinine levels were examined by the classical Jaffé method and a method where the effect of bilirubin is suppressed. After dividing the group into 8 sub-groups by bilirubin and creatinine concentrations it was revealed that the interference plays a statistically significant role (p < 0.01) already at total bilirubin concentrations above 70 mumol.l-1. In abnormal creatinine levels the interference is manifested only at bilirubin concentrations above 150 mumol.l-1 (p < 0.001). The degree of interference in the whole group is directly proportional to the bilirubin level (r = 0.5497, p < 0.001). CONCLUSIONS: At bilirubin levels above 70 to 150 mumol.l-1 its interference with assessment of the creatinine concentration can be so significant that it must be taken into account when evaluating the patient's renal function.