How good are the National Health Interview Survey injury estimates? A comparison of injury rates from the National Health Interview Survey and two medical records based surveys

The National Health Interview Survey (NHIS) provides national estimates on the cause and circumstance of injuries and demographic and health characteristics of the injured person which are not recorded on medical records. However, whether the injury estimates are comparable to those from medical records is unknown. Injury estimates from the NHIS and two nationally representative medical records surveys were compared by demographic and injury characteristics to identify where estimates vary.

Three nationally representative surveys were used to estimate injury: NHIS 2005-2007, National Hospital Ambulatory Medical Care Survey, Emergency Department (NHAMCS-ED) 2006 and National Hospital Discharge Survey (NHDS) 2006. Ratios of injury rates from NHIS were compared to NHAMCS-ED and NHDS by selected characteristics.

The NHIS reported rate of injury episodes treated in the ED was 0.6 times the NHAMCS-ED reported initial visit rate. The NHIS reported rate of injury episodes requiring hospitalization was 1.2 times the NHDS injury hospital discharge rate. The NHIS estimated fracture rates were slightly higher than the analogous estimates reported from NHAMCS-ED and similar to estimates reported from NHDS.

For more severe injuries, such as those requiring hospitalization, the NHIS provides comparable estimates to medical records based surveys. For less severe injuries, such as those seen in the ED, the NHIS may underestimate the rate of injury. Rate differences could be due to issues in injury enumeration (e.g. misclassification, recall) and population coverage. The NHIS provides details not recorded on medical records which are useful for injury prevention and control but may underestimate less severe injuries.