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.