The value of transcutaneous method of bilirubin measurement in newborn population with the risk of ABO hemolytic disease.

OBJECTIVE OF THE STUDY. To evaluate the correlation between total serum bilirubin (TSB) and transcutaneous bilirubin (TcB) levels in newborn infants at risk of ABO hemolytic disease. MATERIAL AND METHODS. During a prospective study, 130 full-term (>or=37 weeks of gestation) newborn infants with diagnosed ABO blood group incompatibility were examined. TSB level was measured at the age of 6 hours; further measurements were performed at 24, 48, and 72 hours following the first measurement. Blood samples were collected from the peripheral veins. In clinical laboratory, total serum bilirubin level was measured using Jendrassik-Grof method. TcB level in the forehead was measured using a noninvasive bilirubinometer BiliCheck (SpectRX Inc, Norcross, GA) according to the manufacturer's instructions within +/-30 min after getting a blood sample. RESULTS. During the study, 387 double tests were performed to measure TSB and TcB levels. TSB level (114.83 [62.85] micromol/L) closely correlated with TcB level (111.51 [61.31] micromol/L) (r=0.92, P<0.001). The strongest correlation was reported at the age of 54 hours (r=0.873, P<0.001), the weakest - at the age of 6 hours (r=0.729, P<0.001). TSB and TcB levels showed a strong correlation; the difference between these values was significant (95% CI, 0.70; 5.93; P<0.05). The greatest difference between TSB and TcB levels was detected at the age of 6 hours (5.58 [17.46] micromol/L, 95% CI, 2.55; 8.61; P<0.001). No significant difference was reported at the age of 30, 54, and 78 hours. Using linear regression analysis, it was established that correlation of TSB and TcB was described by equation y=14.13+0.903x. Transcutaneously measured bilirubin level underestimated serum bilirubin level. When at the age of 6 hours TcB level is >or=98 micromol/L, ABO hemolytic disease in newborns may be diagnosed with 100% sensitivity and 98% specificity; positive predictive value was 62% and negative predictive value was 100%. While a newborn's age increases, TcB sensitivity and specificity for diagnosing ABO hemolytic disease decrease. CONCLUSION. While evaluating bilirubin level transcutaneously according to nomograms of serum bilirubin level, the results should be considered with caution, especially for newborns with a risk of ABO hemolytic disease. The hour-specific nomograms of transcutaneous bilirubin level should be used to evaluate hyperbilirubinemia using only a noninvasive method.