Probabilistic linkage of computerized ambulance and inpatient hospital discharge records: a potential tool for evaluation of emergency medical services.

STUDY OBJECTIVES: Emergency medical services (EMS) is an important part of the health care system. The effect of EMS on morbidity, mortality, and costs of illness is difficult to evaluate because hospital information is not available in out-of-hospital databases. We used probabilistic linkage to create such a database from ambulance and inpatient data and demonstrate the potential for linkage to facilitate evaluation of EMS responses resulting in hospital admission. METHODS: Statewide ambulance and inpatient hospital discharge records were available for 1994 through 1996. Ambulance records indicating admission to the emergency department or hospital (165,649 records) were linked to inpatient hospital records indicating emergency admission (146,292 records) by using probabilistic linkage. Out-of-hospital data (dispatch code, treatments rendered, and ages), linkage rates, and inpatient data (discharge status, charges, length of stay, and payer category) were analyzed. RESULTS: We linked 24,299 (14.7%) ambulance events to inpatient hospital discharges. If we had used exact linkage methods, we would have only linked 14,621 record pairs, a loss of nearly 40%. Linkage rates were relatively constant between years (approximately 15%) but differed by ambulance dispatch codes. Out-of-hospital dispatch codes with high linkage rates included breathing problems (22.6%), chest pain (21.5%), diabetic problems (16.9%), drowning incidents (14.9%), falls (19.2%), strokes (32.8%), and unconsciousness or fainting episodes (16.1%). Linkage to the hospital record provided access to hospital outcome data. Inpatient mortality was 6.8%. Survivors were discharged home (60.7%), transferred to other acute-care facilities (3.6%) or intermediate-care facilities (23.3%), or discharged with home health care provision (4.9%). The median length of stay was 3 days, and median charges were $6,620; total inpatient charges were $286,737,067. CONCLUSION: Probabilistic linkage enables ambulance and hospital discharge records to be linked together and potentially increases our ability to critically evaluate EMS by providing access to hospital-based outcomes. Such evaluation will be further improved by linking to ED, other outpatient, and other public health data sources.

Shoulder belts in motor vehicle crashes: a statewide analysis of restraint efficacy.

The purpose of our study was to evaluate the impact of shoulder belt use on motor vehicle crash ejection, morbidity and mortality. We analyzed motor vehicle crash records linked to hospital inpatient data for front seat occupants of passenger cars in Utah between 1994 and 1996 (n = 103,035). Stochastic simulations were used to adjust for possible seatbelt misclassification. There were 276 (0.3%) occupants coded as using only a shoulder belt. The adjusted odds of ejection for shoulder only belted occupants was higher compared to lap-shoulder belted (odds ratio (OR) = 18.9; 95% confidence interval (CI) = 15.1, 25.1) and lap only belted occupants (OR = 4.3; 95% Cl = 2.9, 7.7). There was no difference in the odds of ejection for an occupant using a shoulder belt only and an occupant using no seatbelt (OR = 1.1; 95% CI = 1.0, 1.3). Occupants using a shoulder belt only were more likely to sustain a fatal or hospitalizing injury than lap-shoulder belted (OR = 2.3; 95% Cl = 1.9, 3.0), and lap only belted occupants (OR = 1.8; 95% CI = 1.3, 2.7), while controlling for other covariates. Occupants using only a shoulder belt had the same odds of a fatal or hospitalizing injury as unbelted occupants (OR = 1.1; 95% Cl = 0.9, 1.4). Average hospital inpatient length of stay, charges and injury severity scores were similar for all restraint types. These results stress the need for the use of a lap belt in conjunction with the shoulder belt.

Motor vehicle crash characteristics and medical outcomes among older drivers in Utah, 1992-1995.

STUDY OBJECTIVE: We sought to compare the characteristics and medical outcomes of motor vehicle crashes for drivers 70 years and older with those of drivers between the ages of 30 and 39 years. METHODS: We probabilistically linked statewide motor vehicle crash and hospital discharge data between the years of 1992 and 1995 for the state of Utah. We calculated the odds of older drivers exhibiting certain motor vehicle crash characteristics compared with younger drivers. Adjusting for nighttime crash, high-speed crash, and seatbelt use, we calculated the odds of an older driver being killed or hospitalized compared with those of a younger driver. RESULTS: During the study years, there were 14,466 drivers older than 69 years and 68,706 drivers between the ages of 30 and 39 years involved in motor vehicle crashes in Utah. Older drivers were less likely to have crashes involving drug or alcohol use (odds ratio [OR] 0.1; 95% confidence interval [CI] 0.1 to 0.2) and less likely to have crashes at high speed (OR 0.6; 95% CI 0.6 to 0.7). Although older drivers were no more likely to have a crash involving a right-hand turn (OR 1.0; 95% CI 0.9 to 1.1) than younger drivers, they were over twice as likely to have a crash involving a left-hand turn (OR 2.3; 95% CI 2.2 to 2.5). Also, older drivers were more likely to be killed or hospitalized than younger drivers (OR, 3.5; P <.001). Among belted drivers, an older driver was nearly 7 times more likely to be killed or hospitalized than a younger driver (OR 6. 9; 95% CI 5.4 to 8.9). CONCLUSION: Older drivers do have distinctive motor vehicle crash patterns. Interventions must be taken to reduce the number of left-hand turn crashes involving older drivers. In addition, further research is needed to design, implement, and evaluate countermeasures that may enable older drivers to continue driving while keeping public safety in the forefront.

Pre-hospital emergency medical services: a population based study of pediatric utilization.

OBJECTIVES: To examine emergency medical services (EMS) usage by children in one state. METHODS: Dispatch of an EMS vehicle in response to a call in the US is referred to as a "run". Runs for Utah for 1991-92 were linked to corresponding hospital records. Abbreviated injury severity scores (AISs) were assigned using ICDMAP-90 software. RESULTS: For the two year period there were at least 15 EMS runs per 100 children per year, with incomplete reporting from rural areas. EMS response and scene times were similar for all age groups, but interventions were less frequent for children under 5 years of age. When the principal AIS region of injury was the head, neck, or face, cervical immobilization was less frequent for children less than 5 years of age (54%) than for older children (76%) and immobilization was associated with improved outcome, using the crude measure of lower hospital charges. There was a similar association between splinting of upper extremity fractures and reduced hospital charges. Both associations did not appear to be due to differences in injury severity. CONCLUSIONS: The majority of EMS use by children is for trauma. Children less than 5 years of age are less likely to have an EMS intervention than older children. Whether the lower frequency of interventions is due to the lack of properly sized equipment on the vehicle, or to other factors, is undetermined.