RESUMO
We recently described a direct spectrophotometric method for unconjugated bilirubin, with caffeine reagent (Clin Chem 1986;32:1389-93). Because this method is independent of the protein matrix we used it for the preparation of bilirubin standards (Clin Chem 1987;33:1817-21). Now, in this paper, we utilize the caffeine reagent in setting up a bilirubin method for serum from neonates. This resulted in a two-wavelength (465 and 528 nm) equation, which fully corrects for HbO2 interferences. In combination with a bilirubin standard, this equation may be transformed into a simple relative formula for use with this simple dilution method. We studied this two-wavelength method with 55 neonates' sera, comparing results with those by both the diazo method of Doumas et al. (Clin Chem 1985;31:1779-89) and the borate method of Hertz et al. (Scand J Clin Lab Invest 1974;33:215-30). We found that this new method is independent of hemolysis and of the matrix of the sera. Therefore, it is very suitable for use in neonatology.
Assuntos
Bilirrubina/sangue , Cafeína , Espectrofotometria , Hemólise , Humanos , Indicadores e Reagentes , Recém-Nascido , Icterícia Neonatal/sangue , Oxiemoglobinas/sangue , Controle de Qualidade , Análise de RegressãoAssuntos
Bilirrubina/sangue , Padrões de Referência , Ácido Ascórbico , Humanos , Concentração de Íons de Hidrogênio , Luz , Métodos , Albumina SéricaRESUMO
The molar absorptivity of unconjugated bilirubin in caffeine reagent is independent of the protein matrix. This finding, together with the simplicity of a dilution step for direct spectrophotometry, will improve the calibration methods of bilirubin and make them more nearly accurate. This is encouraging for the development of a new method for bilirubin determination in neonates; moreover, the caffeine reagent has a clearing influence on the turbidity of human sera. These findings should also be important for standardization, especially because the method of Jendrassik and Gróf is also protein-independent. Therefore, the introduction of one reliable, inexpensive, "universal" standard of bilirubin in bovine serum albumin will be of importance for both methods.