The variation in observed mortality rates across hospitals was wide, ranging from 4.3 to 15.8%. Based on the locally derived model, mean predicted risks of death ranged from 3.6 to 15.8%. At a hospital level, the mean predicted risk of death explained 87% of the variance in observed hospital mortality rates (ie, R2 = 0.87). As a result, the variation in SMRs was less than the variation in observed mortality. SMRs ranged from 0.85 to 1.21 (Fig 3). The correlation between SMRs and mean ICU length of stay (LOS) and mean hospital LOS were not significant (R = 0.07, p = 0.72; and R = 0.06, p = 0.75; respectively).
Only one hospital had an SMR that was lower (p < 0.01) than 1.0, while three hospitals had SMRs that were greater (p < 0.01) than 1.0. However, none of the four hospitals that were statistical outliers with respect to SMRs were outliers during each of the 4 study years when years 1 to 4 were examined individually this purchase antibiotics online. Although the lack of consistency across each year may be due in part to smaller sample sizes, hospital SMRs across years exhibited some degree of variability, particularly for hospitals with smaller patient volumes. For example, the range of SMRs across years 1 to 4 was > 0.30 for six hospitals. In addition, variation in hospital SMRs was greater in year 1 than in subsequent years. For example, the difference between the highest SMR (1.64) and lowest (0.83) was 0.81 in year 1 and 0.42, 0.44, and 0.48 in years 2, 3, and 4, respectively, while interquartile differences were 0.19, 0.17, 0.15, and 0.11 in years 1, 2, 3, and 4, respectively.
SMRs tended to be lower in the five major teaching hospitals than in other hospitals (mean SMRs 0.95 ± 0.07 vs 1.04 ± 0.10, respectively; p = 0.09).
Observed mortality rates were similar over the 4-year period of data collection (11.4%, 11.4%, 11.4%, and 11.1% in years 1, 2, 3, and 4, respectively; p = 0.45). However, mean predicted mortality tended to increase (10.8%, 11.1%, 11.6%, and 11.7% in years 1 to 4, respectively; p < 0.001), resulting in a decline in the overall SMR (1.06, 1.02, 0.98, and 0.95 in years 1 to 4, respectively).
Figure 3. Variation in SMRs (ie, observed/predicted hospital mortality) across hospitals. Error bars indicate 99% confidence intervals. SMRs > 1.0 indicate higher than expected mortality, while SMRs < 1.0 indicate lower than expected mortality. Major teaching hospitals are denoted by the black squares.