Capillary and venous bilirubin values. Are they really different?
G. I. Leslie, J. B. Philips 3rd and G. Cassady
Department of Pediatrics, University of Alabama, Birmingham.
We measured total serum bilirubin values in paired capillary and venous
samples from 79 untreated jaundiced newborn infants (group 1) and in 29
infants who were receiving phototherapy (group 2). While bilirubin values
from the two sites correlated significantly for both groups, capillary
samples underestimated venous bilirubin values when the latter exceeded 170
mumol/L (10 mg/dL) (mean and 95% confidence limits: group 1, -15.1 mumol/L
[-0.9 mg/dL] and -24.7 to -5.5 mumol/L [-1 to -0.3 mg/dL]; group 2, -10.3
mumol/L [-0.6 mg/dL] and -17.1 to -3.4 mumol/L [-1 to -0.2 mg/dL]).
Furthermore, capillary samples underestimated venous bilirubin levels by
more than 17 mumol/L (1 mg/dL) in eight of 16 group 1 patients and five of
18 group 2 patients when venous bilirubin values exceeded 170 mumol/L (10
mg/dL). Lower capillary values at higher bilirubin levels might be due to
the influence of environmental light. As clinical treatment decisions may
be made on the basis of differences in serum bilirubin level of about 17
mumol/L (1 mg/dL) and as capillary samples may underestimate venous
bilirubin levels by a similar amount, it may be prudent to measure venous
rather than capillary bilirubin levels when the total serum bilirubin level
exceeds 170 mumol/L (10 mg/dL).
