VARIATIONS IN STANDARDIZED HOSPITAL MORTALITY-RATES FOR 6 COMMON MEDICAL DIAGNOSES - IMPLICATIONS FOR PROFILING HOSPITAL QUALITY

OBJECTIVES. The authors determined whether standardized hospital morta lity rates varied for six common medical diagnoses. METHODS. The retro spective cohort study included 89,851 patients aged 18 years and older discharged from 30 hospitals in a large metropolitan area in 1991 to 1993 with a principal diagnosis of acute myocardial infarction, conges tive heart failure, pneumonia, stroke, obstructive lung disease, or ga strointestinal hemorrhage. For each hospital, standardized mortality r atios (observed/predicted mortality) were determined using validated r isk-adjustment models that were based on clinical data elements abstra cted from patients' hospital records. Hospitals also were categorized into quintiles on the basis of standardized mortality ratios. Correlat ions between standardized mortality ratios and agreement between quint ile rankings were determined for each pair of diagnoses. RESULTS. Corr elations between hospital-standardized mortality ratios for individual diagnoses were generally weak. For the 15 possible pairs of diagnoses , Pearson coefficients ranged from -0.10 to 0.43; only six were 0.30 o r greater. Agreement between hospital quintile rankings was also gener ally low, with weighted kappa values ranging from -0.12 to 0.42. Three of 15 kappa values were less than 0 (ie, agreement lower than chance) , and only four exceeded 0.20, the threshold for ''fair'' agreement. A lthough simulated analyses found that random variation and relatively low hospital volumes accounted for some of the difference in standardi zed mortality ratios for diagnoses, a large proportion of the differen ce remained unexplained. CONCLUSIONS. Standardized hospital mortality rates varied for six diagnoses that likely are managed by similar prac titioners. Although variability may be decreased by restricting analys es to hospitals with large volumes, the findings indicate that for man y hospitals, diagnosis-specific mortality rates may be an inconsistent measure of hospital quality, even when data are aggregated for multip le years.