Measuring levels of comorbidity in drug user* emergency patients treated in Ontario hospitals.

We examined the nature and extent of health problems in drug user patients initially treated in emergency departments and who were subsequently admitted to all hospitals in Ontario, using data from the Hospital Medical Records Institute (HMRI). The modified standardized morbidity ratio (modified SMR) is introduced to improve the measurement and visual display of reduced morbidity as well as excess morbidity. During 1985-86, about 75% of drug user patients entered hospital through the emergency department. There were 5077 emergency patients with primary drug use-related diagnoses and 9827 with secondary drug use-related diagnoses. Cases with poisoning diagnosis made up over 80% of all drug use cases treated in emergency departments. Cases with non-dependent abuse of drugs accounted for 8-12% of emergency drug user patients, whereas those with drug dependence accounted for about 3% of emergency drug user patients. These patients had more than three times the comorbidity experience of all hospital patients. They had excess comorbidity due to mental disorders, infectious and parasitic disorders, and injury and poisoning diagnoses. However, they had reduced comorbidity due to complications of pregnancy, childbirth, and the puerperium and from congenital anomalies and conditions originating in the perinatal period. Cocaine patients were more likely to have infectious parasitic diseases and diseases of the skin and subcutaneous tissue, while amphetamine patients were more likely to have diseases of the digestive system and of the musculo-skeletal system and connective tissue.