THE RELIABILITY OF NEONATAL HEAD CIRCUMFERENCE MEASUREMENT

Interobserver reliability in head circumference measurement was assessed in a cohort of 1105 low birthweight (less-than-or-equal-to 2000 g) infants enrolled in a study of brain hemorrhage. In 927 (83.9%) subjects, head circumference was measured both by a pediatric resident or admitting pediatrician, and by a trained ultrasound technologist. The Pearson correlation coefficient for these two sets of measurements was 0.934 (p < 0.01), and the intraclass correlation coefficient was 0.933. By contrast, analysis of differences revealed that the limits of agreement were from -1.99 to 2.03 cm, indicating that 5% of measurements differed by 2 cm or more. Using clinicians' measurements as the gold standard, ultrasound technologists detected abnormal head circumferences with a sensitivity of 91.2%, a specificity of 97.2%, and a positive predictive value of 88.0%. For clinical purposes this level of reliability may be acceptable, but in research studies this degree of misclassification would lead to attenuation of the odds ratio.