Co-morbidity and health outcomes in three Auckland hospitals.

Aims: To establish the burden of co-morbid disease using the Charlson Index among hospital inpatients and its relationship to key health outcomes.
Methods: An initial screen was carried out on 1575 medical records selected by systematic list sample from admissions for 1995 in three public hospitals in the Auckland region. In the course of the administration of the instrument, screeners were required to record the occurrence of co-morbid disease using the Charlson Index.
Results: A third of patients had co-morbid disease, of which chronic pulmonary disease and congestive heart failure were the most frequently recorded. While the Charlson Index was associated with age of patient, length of stay, inpatient mortality, and adverse event status, the simple presence or absence of co-morbidity was as an effective predictor as the extended index. Co-morbidity was more likely to be recorded for Maori, for patients from deprived areas, and for circulatory or respiratory diagnoses. Specific co-morbid conditions were predictive of health outcomes.
Conclusions: Levels of co-morbid disease established for patients using the Charlson Index in three Auckland public hospitals are similar to those recorded internationally. Co-morbidity is predictive of key health outcomes that are of clinical and managerial significance. Controlling for co-morbidity will be important in making comparisons of the quality of care.