Transcutaneous bilirubin (TcB) measurement being a non-invasive method is feasible for mass screening of at risk neonates. Several studies have reported the utility of TcB as a surrogate of Total Serum Bilirubin (TSB) [6]. TcB nomograms have been published from several countries [7-9], but for Indian population, only one published study is available [10]. The present study was carried out with the objectives of developing TcB nomogram and to assess predictive ability of these nomograms.

This was a prospective longitudinal study carried out at Neonatal unit of Department of Pediatrics, Medical College Vadodara, Gujarat over period of 6 months from December, 2013 to June, 2014. The study was approved by scientific review committee and Institutional ethics committee and waiver of consent was granted.

TcB estimations were done by using Dragger JM – 103, a hand held bilirubinometer that measures TcB levels by using multiwavelength spectral reflectance analysis. All TcB measurements were taken at forehead and we took average of five repeat measurements. All readings were taken with same device by resident doctors, according to the manufacturer’s instructions. TcB readings were taken every 6±1 hourly interval starting from 0 hour of life upto 96 hours. After 96 hours of life, whenever possible, we continued to take TcB readings, to know normal change in bilirubin values. The need for phototherapy and management of hyperbilirubinemia was ascertained by treating consultant based on unit protocols and evidence-based practice guidelines of NNF [4]. TSB estimation was done on clinical demand, when TcB values were within 2 mg/dL or 80% of age specific threshold for starting phototherapy (as per nomograms of Bhutani, et al. [5]) or when value of TcB was >13 mg/dL.

Statistical analysis: Baseline and outcome data were recorded in a predesigned performa and master chart was prepared in Microsoft Excel sheet. The data was entered into a custom-designed interface in STATA-IC-13 software and checked for completion, consistency and accuracy. TcB readings were clubbed in 6-hour epochs starting at 0 hour of age. Percentile for each epoch and rate of rise in TcB level in different percentiles were obtained by using same software.

There were 1,782 neonates who were assessed for eligibility; 1,075 neonates were finally included in the study, of which 65 neonates who required phototherapy, were not included for construction of nomogram (Fig. 1).

Fig. 1 Study flow.

Of 1010 neonates, gender distribution was almost equal, 28% had weight <2500 grams, 3.9% had gestational age of < 37 weeks and 6.1 % were SGA. All were exclusively breast fed and 969 (95.9%) mothers had received oxytocin during labour.

Fig. 2 Age-specific nomogram of neonates up to 96 hours.

A total of 12,922 TcB measurements were available in first 96 hours, nomogram of which is shown in Fig. 2. To follow the normal pattern of bilirubin, 15685 reading were available till 168 hours. Nomogram for this is shown in Fig. 3.

Fig. 3 Age-specific nomogram of neonates up to 168 hours.

TABLE I TcB Percentiles

TcB percentile values are depicted in Table I. The mean value of TcB at 0 to 1 hour of age obtained was 1.6 mg/dL. Peak value obtained was 11.6 mg/dL at 90 hours of age. The rate of rise (ROR) of TcB percentiles is shown in Table II. The mean value of ROR observed in first 12 hours of life was 0.2 mg/dL, 0.17 mg/dL at 12 to 24 hours of life, 0.14 mg/dL and 0.12 mg/dL at 24-36 hours and 36 to 48 hours of life, respectively.

TABLE II Transcutaneous Biliruben Rate of Rise Percentiles for Normal Neonates (N=1010)

Present study provides normative data with various percentile values of TcB and its rate of rise in term healthy and late preterm Indian neonates. The neonates who required phototherapy had consistently higher readings of TcB and ROR.

Nomograms using TcB have been developed by various countries for their population, but only a single study from India by Mishra, et al. [10]. The ROR observed in the study of Mishra, et al. [10] is somewhat higher in first 48 hours compared to our study. This may be because there were more pre-term neonates in their study group compared to the present study. Maisels, et al. [7] provide nomograms from a predominantly white population from North America from a convenient sample of day time TcB measurements after six hours of life. The overall TcB observations including all percentiles are lower compared to our data. This can be due to almost all newborns in our study were exclusively breastfed and due to racial and ethnic variations. A systemic review by De Luca, et al. [11] had compared four TcB nomogram developed in North America (mixed population) [7], European [8], Hispanic [12] and Thai population [9]. The analysis revealed significant differences in values of bilirubin across various populations. Significant differences were observed in TcB values at different percentiles at different hours of life, different rate of rise and peak values of TcB. Nomogram have been also reported from Canada [13,14], Brazil [15], China [16] and Israel [17] for healthy term and late pre-term neonates. The Israel [17] study included only clinically jaundiced neonates. The Brazilian [15] study included only term neonates. Nomogram developed by De Luca, et al. [8] had also included neonates who required phototherapy. Few of the authors have given separate nomogram according to gestational age [7]. The major limitation of almost all studies is that they are not population-based and represent data from single center.

There were few limitations of this study. It is not a population-based study; however, with increasing number of institutional deliveries, our sample of healthy neonates by and large is representative of normal neonatal population. For developing country-wide nomogram, a multicenter trial should be conducted. The nomogram should be validated for predictive ability with a separate cohort of neonates.

Contributors: PT: conceived and designed the study; HC: was involved in data collection; PT, VD, HC: did analysis and interpretation of data; PT, HC: drafted the manuscript. All authors have approved the final version of manuscript.

Funding: None; Competing interest: None stated.