All specimens were analyzed with the Vitros 5,1 FS analyzer for TBIL and NBIL. The TBIL assay is a diazo method that measures the sum of Bu, Bc, and [delta]-bilirubin.
Hb interference with the NBIL method was negligible (Fig.
In 92 blood specimens from neonates 1-14 days old, mean values for TBIL and NBIL were 102.8 mg/L and 105.5 mg/L, respectively; the regression equation was
We tried to identify the cause of the difference between the Vitros TBIL and the NBIL values.
For the high-DTB solution, the Vitros TBIL value was 14% lower than that of the reference method, whereas the NBIL value was higher by ~19%.
 Nonstandard abbreviations: BSA, bovine serum albumin; UBIL, unconjugated bilirubin; CAP, College of American Pathologists; TBIL, Vitros total bilirubin method; NB, Neonatal Bilirubin (Survey); C, Chemistry (Survey); DTB, ditaurobilirubin; NBIL, Vitros neonatal bilirubin method (sum of Bu + Bc); Bu, unconjugated bilirubin; and Bc, conjugated bilirubin.