Diagnostic accuracy of transcutaneous bilirubinometer devices compared with the total serum bilirubin measurement in preterm (≤35 weeks) very low birth weight neonates during the neonatal period up to 7 days of life

Introduction: Hyperbilirubinaemia is the commonest morbidity in preterm neonates, most of whom are of very low birthweight (VLBW ≤1500g) babies. Repeated blood sampling in preterm VLBW neonates not only causes pain but may lead to sepsis and anaemia. Transcutaneous measurement of bilirubin by a device called transcutaneous bilirubinometer (TcB) is an effective alternative tool to predict neonatal hyperbilirubinaemia in late preterm and term neonates, most of whom have birthweights >2000g.

Objectives: To evaluate diagnostic accuracy of TcB devices in comparison to total serum bilirubin (TSB) measurements in VLBW neonates.

Method: We evaluated 128 preterm neonates with gestational ages ranging from 28 to 35 weeks and birthweights ≤1500g till 7 days of post-natal age. A total of 1003 TcB readings were taken, along with concurrent heel prick capillary samples, for laboratory measurement of TSB. For TcB, Drager JM-103 transcutaneous bilirubinometer was used and for TSB, Microlab’s Easybil instrument was used. Coefficient of correlation (r) and Bland-Altman plot were calculated to check correlation between TSB and TcB.

Results:Total number of neonates was divided into 2 groups: i) ≤1000g and ii) 1001-1500g. Paired readings of TSB and TcB were taken before and after starting phototherapy. All the paired readings were analysed for correlation between TcB and TSB. Correlation co-efficient (r) value for group i) was 0.87 and for group ii) was 0.89 (p<0.0001). Before and after starting phototherapy, readings were analysed separately to see the effect of phototherapy on correlation between TcB and TSB. Correlation co-efficient (r) values for paired readings before starting phototherapy were 0.97 & 0.90 respectively for both groups and for paired readings after starting phototherapy were 0.81 & 0.83 respectively for both groups.

Conclusions: TcB measurements correlate significantly with TSB levels in early preterm neonates with VLBW. Phototherapy does not affect the correlation significantly.