Inter-observer variability in scoring of white matter injury on brain magnetic resonance imaging in moderate-to-late preterm infants.

Background: Punctate white matter injury on brain magnetic resonance imaging (MRI) is described in very preterm infants (< 32 weeks' gestation) and is predictive of poorer developmental outcomes. The reliability of scoring and the incidence and evolution of white matter injury in moderate-late preterm infants is unknown.

Objective: To assess inter-observer variability in white matter injury using a published scoring system (UCSF system), and to describe changes over time in moderate-late preterm infants.

Materials and methods: Infants born between 32 + 0 and 36 + 6 weeks' gestation in the Auckland region underwent MRI scans as soon as clinically feasible after birth and again at term-equivalent age. De-identified scans were scored independently by two observers. White matter injury was graded as minimal (< 3 lesions measuring < 2 mm), moderate (> 3 lesions or lesions > 2 mm), or severe (> 5% hemispheric involvement). Scores were compared between reviewers using weighted and unweighted kappa statistics interpreted using Cohen's criteria. Incidences were compared between scans using generalised estimating equations.

Results: Scans of 101 infants were assessed. Inter-observer agreement was near perfect for the presence of white matter injury (k = 0.88 and 0.81 for the first and second scan respectively), and for the severity of white matter injury was near perfect at the first scan (k = 0.85) and substantial at the second scan (k = 0.80). The incidence of white matter injury detected by the two observers decreased between the first and second scans (30% to 22% and 29% to 19%), and severity also decreased.

Conclusions: This scoring system can be reliably applied in moderate-late preterm infants. White matter injury is common in moderate-late preterm infants but may be underestimated when MRI is performed close to term-equivalent age.