Neonatal age indicator (AGE_NEONATE) indicates admissions during the first 28 days after birth. It is only reported for patients less than 1 year old (AGE=0). AGE_NEONATE is calculated from age in days (AGEDAY) and should be used in conjunction with AGE.

AGE_NEONATE is missing (.)

• if AGE is one year or more
• if AGEDAY is missing (.), invalid (.A), inconsistent (.C), or not present on the HCUP files

Beginning with 2012 data, the data element AGEDAY is replaced by the neonatal age indicator (AGE_NEONATE) on the NIS.