Background. Standardized assessment of patients' activity limitations in acute care settings can provide valuable information. Existing measures have not been widely implemented. Objectives. The aim of this study was to provide evidence for validity of scores on Activity Measure for Post-Acute Care (AM-PAC) "6-Clicks" measures of basic mobility and daily activity in acute care. Design. A retrospective measurement study was conducted. Methods. The study used a database from one health system

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... aining "6-Clicks" scores from first and last physical therapist and occupational therapist visits for 84,446 patients. Validity was analyzed by examining differences in "6-Clicks" scores across categories of patient characteristics; the ability of "6-Clicks" scores to predict patients' having more than one therapy visit; correlation of "6-Clicks" scores with Functional Independence Measure (FIM) scores; and internal responsiveness over the episode of care. Internal consistency reliability also was determined. Results. The "6-Clicks" scores differed across patients' age, preadmission living situation, and number of therapy visits. The areas under receiver operating characteristic curves derived using "6-Clicks" scores at the first visit to predict patients receiving more than one visit were 0.703 and 0.652 using basic mobility and daily activity scores, respectively. The "6-Clicks" scores at the final visit were correlated with scores on subscales of the FIM completed on admission to inpatient rehabilitation facilities (rϭ.65 and .69). Standardized response means were 1.06 and 0.95 and minimal detectable changes with 90% confidence level (MDC 90 ) were 4.72 and 5.49 for basic mobility and daily activity scores, respectively. Internal consistency reliability of basic mobility and daily activity scores was .96 and .91, respectively. Limitations. Using clinical databases for research purposes has limitations, including missing data, misclassifications, and selection bias. Rater reliability is not known. Conclusions. This study provides evidence for the validity of "6-Clicks" scores for assessing patients' activity limitations in acute care settings.