4.3. Limitations
Although our sample included a large number of hospitals and units, NDNQI hospitals electively join the database, are a select sample, and are not representative of the overall population of U.S. hospitals. NDNQI is under-representative of small hospitals. Although about half of U.S. hospitals are under 100 beds, only one quarter of NDNQI hospitals are of that size. We limited our attention to seven unit types. Further some NDNQI units do not collect both hospital-acquired pressure ulcer rate and total fall rate, so those units were not included in the study. Therefore, results may not be generalizable to other hospitals and units.
As a caution, smaller units should be cautious about applying the Pressure Ulcer and Fall Rate Quality Composite Index over a short period of time. For statistical stability there should be at least 30 patients surveyed for hospital-acquired pressure ulcers in a quarter before considering the Pressure Ulcer and Fall Rate Quality Composite Index. Due to the small number of critical access units in the study, the results regarding critical access units especially should be used with caution.