To provide a valid, continuous reference interval, including a 10th percentile cut-off, for Hammersmith Infant Neurological Examination (HINE) scores based on 3- to 7-month-old term infants with weight appropriate for gestational age.

In a prospective study, we examined 168 Norwegian infants at one timepoint with HINE at 3-7 months of age. In 134 of these infants Ages and Stages Questionnaire was completed by their parents at 2 years of age to ensure typical motor development. We calculated a reference interval for HINE scores with the 10th percentile as cut-off for age-dependent optimal scores.

The best fitting mean model for HINE total score was 78.1358 + 9659.231∗1/age in weeks²-5104.174∗natural logarithm(age in weeks)/age in weeks², which explained 49.8% of the variance. The HINE total score 10th percentile cut-off corresponded to 52.1 points at age 12 weeks, 55.6 points at 16 weeks, 59.0 points at 20 weeks, 61.8 points at 24 weeks, and 63.8 points at 28 weeks. We found an excellent intraclass correlation coefficient of 0.953 (0.931-0.968) between 2 examiners. The infants had a typical motor development at 2 years follow-up.

We have presented a valid, continuous reference interval and a 10th percentile cut-off for HINE scores for infants age 3-7 months.