2.2. Results of Phase I
2.2.1. Reliability
Bland-Altman plots for agreement between any pair of two raters (Fig. 2) illustrated that the raters were very consistent on all but two scenarios. For two patient care units to have the same composite score on quality of care in the scenarios, the difference between units on one measure (hospital-acquired pressure ulcer rate or total fall rate) must be offset by an equivalent difference in the opposite direction on the other measure. Rater median scores were plotted to demonstrate the inverse relationship (see Supplemental Data File 2 for the plots). Average slope of the lines in the plots was 1.12 indicating the experts had given almost equal weights to the two measures.
2.2.2. Proposed Overall Composite Nursing Care Quality Index
We then used a generalized penalty analysis to determine the overall Pressure Ulcer and Fall Rate Quality Composite Index, which is the Pressure Ulcer and Fall Rate Quality Composite Index=100PURcFR, where PUR and FR stand for unit hospi- tal-acquired pressure ulcer rate and total fall rate respectively and c is the parameter. We used 100 to make the Pressure Ulcer and Fall Rate Quality Composite Index score intuitive because every unit starts with a Pressure Ulcer and Fall Rate Quality Composite Index score of 100 and then quality is reduced based on the unit hospital- acquired pressure ulcer rate and total fall rate. The c parameter is estimated to equal 1.12 based on the reliability study of experts’ ratings, however we use c equal to 1 for simplicity. Because a higher value of total fall rate represents a lower level of quality, c is a positive parameter and is the relative penalty for total fall rate. Therefore, the final formula is Pressure Ulcer and Fall Rate Quality Composite Index = 100 PUR FR. For every one percent hospital- acquired pressure ulcer rate, the Pressure Ulcer and Fall Rate Quality Composite Index is reduced by one point. Then, for every one fall per 1000 patient days, the Pressure Ulcer and Fall Rate Quality Composite Index also is reduced by one point. Higher Pressure Ulcer and Fall Rate Quality Composite Index values represent higher unit nursing quality. The highest possible Pressure Ulcer and Fall Rate Quality Composite Index score is 100. Scores could be negative in theory, but not likely in practice.