Valoración del uso del índice ictérico como parámetro para la gestión de la determinación de la bilirrubina total

Introduction

As too many laboratory tests may not represent significant improvements, their efficient use should be considered. Bilirubin is a classical biochemical marker of hepatic alterations, and the icteric index is an indirect measure for the semi-quantitative determination of jaundice.

Objectives

To evaluate the use of the icteric index in the identification of patients with serum bilirubin concentrations with values higher or lower than 1.20 mg/dL, as well as to assess the determination of bilirubin, and to evaluate the savings that the application of this algorithm would represent.

Material and methods

A retrospective study was performed to determine the relationship between icteric index and total bilirubin. A regression analysis was also performed. The diagnostic efficiency of the index was studied using a Receiver Operating Characteristic curve to determine the cut-off value that would allow to distinguish bilirubin values higher and lower than 1.20 mg/dL. The sensitivity and specificity, positive predictive value and negative predictive value were also calculated.

Results and discussion

The statistical analysis showed a high correlation between both variables. The study of diagnostic efficacy showed that to use an icteric index equal to 2 as a cut-off point yields a high negative predictive value, sensitivity and specificity.

Conclusions

Icteric index values are well correlated with bilirubin, which allows filtering for hyperbilirubinaemia. Therefore, 89.72% of bilirubin requests would not be needed. With those samples with icteric index ≤ 1 subsequently being reported as < 1.20 mg/dL, thus representing a savings to the laboratory.