Laboratory Evaluation of the Jaundiced Infant of 35 or More Weeks’ Gestation

Jaundice in first 24 hMeasure TcB and/or TSB
Jaundice appears excessive for infant’s ageMeasure TcB and/or TSB
Infant receiving phototherapy or TSB rising rapidly (ie, crossing percentiles [Fig 2]) and unexplained by history and physical examinationBlood type and Coombs’ test, if not obtained with cord blood
Complete blood count and smear
Measure direct or conjugated bilirubin
It is an option to perform reticulocyte count, G6PD, and ETCOc, if available
Repeat TSB in 4–24 h depending on infant’s age and TSB level
TSB concentration approaching exchange levels or not responding to phototherapyPerform reticulocyte count, G6PD, albumin, ETCOc, if available
Elevated direct (or conjugated) bilirubin levelDo urinalysis and urine culture. Evaluate for sepsis if indicated by history and physical examination
Jaundice present at or beyond age 3 wk, or sick infantTotal and direct (or conjugated) bilirubin level
If direct bilirubin elevated, evaluate for causes of cholestasis
Check results of newborn thyroid and galactosemia screen, and evaluate infant for signs or symptoms of hypothyroidism