Evaluating pressure ulcer occurrence in long-term care: pitfalls in interpreting administrative data.

Administrative databases for long-term care frequently collect information on fixed dates of the calendar year, rather than for entire episodes of care. Patients discharged or dying prior to an evaluation date are lost to follow-up. We used one such database, the VA Patient Assessment File, to examine pressure ulcer occurrence in long-term care. Clinical studies have established that most pressure ulcers develop during the first several weeks following admission. In these data, however, pressure ulcer development was less common in patients assessed within 2 months following admission, as compared to those examined at 3 to 6 months. This finding appears to be related to the selective discharge of patients, which makes these patient populations noncomparable. These results highlight that care must be exercised when interpreting results obtained from such administrative data.