Evaluation of hemoglobin interference in capillary heel-stick samples collected for determination of neonatal bilirubin.
OBJECTIVE
In this study, we determined the assay performance criteria necessary to produce acceptable results for >or=98% of neonate bilirubin samples collected by capillary heel-stick.


METHODS
We determined serum free hemoglobin levels in 151 heel-stick serum samples to determine the hemolysis level. We then tested the effect of hemolysis on total bilirubin levels determined by four commercially available assays.


RESULTS
The mean level of serum free hemoglobin was 1.62 g/L. Of the serum total bilirubin assays tested, the Total Bilirubin Special (Roche Diagnostics) and the TBILI (Roche Diagnostics) reagents did not show significant interference at the concentrations of free hemoglobin observed in >or=98% of heel-stick samples. The Vitros Bu/Bc slide (Ortho-Clinical Diagnostics) showed significant interference only at normal bilirubin concentrations; while the Bilirubin DPD reagent (Amresco Inc.) showed significant interference starting at hemoglobin concentrations of 1.0 g/L.


CONCLUSIONS
Bilirubin assays that are not sensitive to approximately 6 g/L free hemoglobin should provide accurate results for most samples obtained via capillary heel-stick. Of the four assays tested, the Bilirubin DPD reagent (Amresco Inc.) was the most susceptible to the presence of free hemoglobin and will result in a higher rejection rate of neonate capillary heel-stick samples.
Algeciras-Schimnich
Alicia
A
Department of Laboratory Medicine and Pathology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
Cook
Walter J
WJ
Milz
Thomas C
TC
Saenger
Amy K
AK
Karon
Brad S
BS
D001663:Bilirubin / Q000097:blood*; D001800:Blood Specimen Collection / Q000295:instrumentation* / Q000592:standards; D006365:Heel / Q000098:blood supply*; D006454:Hemoglobins / Q000032:analysis*; D006461:Hemolysis; D006801:Humans; D006949:Hyperlipidemias / Q000097:blood; D007231:Infant, Newborn; D015203:Reproducibility of Results