Visual estimates of serum bilirubin levels use the phenomenon of cephalocaudal progression of jaundice. Kramer correlated the presence of dermal icterus with a serum bilirubin levels and found a cephalocaudal progression that continues as the concentration of serum bilirubin is increasing and remains the same when the level becomes stabilized. Jaundice to the level of the shoulders correlates to 5-7 mg/dL, to the level of the umbilicus to 7-10 mg/dL, below the umbilicus to 10-12 mg/dL, and below the knees to >15 mg/dL. The cephalocaudal progression is only seen when the bilirubin is rising. When the bilirubin begins to fall, the dermal icterus fades gradually in all affected skin areas at the same time. The reason why this occurs is not known.

REf:
Kramer, LI. 1969. Advancement of dermal icterus in the jaundiced newborn. Am J Dis Child, 118, 454-8.