Assessment of risk of neurodevelopmental sequelae in preterm infants: a comparison of the Neurodevelopmental Risk Exam and Neurobiologic Risk Score methods

Abstract

Premature infants are at risk of adverse neurodevelopmental outcomes, yet methods for the early assessment of risk are limited. Two instruments, the Neurobiologic Risk Score (NBRS) and the Neurodevelopmental Risk Exam (NRE), have been shown to have moderate correlation with developmental outcomes. The correlation between these two instruments is unknown, and their predictive value in the contemporary neonatal intensive care unit is uncertain. The objective of the study was to compare the NBRS and NRE methods for assessing risk of neurodevelopmental sequelae in infants less than 32 weeks' gestational age. The subjects were 219 neonates less than 32 weeks' gestational age who were discharged from the neonatal intensive care unit between November 2001 and December 2006 (being born between May 2001 and November 2006, and with examination dates between 30th October 2001 and December 2006) who had undergone both the NBRS and the NRE. The NBRS includes seven categories: episodes of acidosis, infection, seizures, intraventricular haemorrhage, periventricular leukomalacia, hypoglycaemia and mechanical ventilation. The NRE includes five categories: sensory and behavioural responses, axial tone, extremity tone, deep tendon reflexes and primitive reflexes. Both the NBRS and NRE independently generate a summary score that correlates with low, intermediate or high risk of neurodevelopmental sequelae. The subjects had a mean birth weight of 1110 g and a mean gestational age of 27.8 weeks. Risk scores for the two instruments were distributed as follows: NBRS ( n = 214), 161 (75.2%) low, 29 (13.6%) intermediate and 24 (11.2%) high; NRE ( n = 201), 197 (98%) low, 4 (2%) intermediate and 0 (0%) high. The Spearman rank correlation coefficient between the two examinations was 0.43, with the ventilation and pH categories of the NBRS having the highest individual correlations with the overall NRE score (0.35 and 0.37 respectively). The correlation between the NBRS and the NRE suggests that a combination of the two screening methods may increase the predictive value of developmental screening for premature infants.