Background Manual measurement of head circumference (HC) is used to quantify head growth in preterm infants. Laser shape digitizers offer semi-automatic HC measuring and additional information on head volume (HV). Reliability and accuracy in obtaining HC and HV in neonates has not been investigated yet.

Aims

1. To determine intraobserver and interobserver variability of HC and HV measurements in neonates with a 3D digital capture system.

2. To compare the method with manual HC measurements.

Methods Standard weekly HC measurements on a neonatal unit were conducted manually and digitally with STARScanner laser shape digitizer (Vorum Research Corp., Vancouver, BC) over 12 months. Method comparison was performed using Passing-Bablok-Regression (PBR), Cusum test and Bland-Altman (BA) analyses. Multiple scan examinations by different trained observers were performed to obtain intraobserver/interobserver data.

Results

1. Intraobserver coefficient of variation was low for HC (0.1–0.9%) and HV (0.54–1.1%). BA (mean percentage of difference M _d ; 95% CI) of interobserver data showed interchangeability for HC (M _d –0.005; CI-0.39–0.39) and HV (M _d 1.51; CI –1.17–4.1).

2. 2. Method comparison data was acquired from 446 measurements in 258 infants (HC 318±19.5mm). Overall agreement was good (M _d –0.82; CI –4.89–3.24), PBR showed no significant systematic or proportional differences (a=1.03, CI 0.99–1.06; b= –7.06 CI –17.7–3.01). There was no significant deviation from linearity (p=0.62).

Conclusions Infant head shape capturing with the examined device is reliable, accurate and save. It offers additional information on HV. Possible benefits of HV in quantifying head growth in preterm infants need to be further investigated.