Laboratory Test Use and Values in the Last Year of Life-a Matched Cohort Design.

Background: As individuals approach death, they experience declines in their cognitive, physical, motor, sensory, physiologic, and psychosocial functions. In this exploratory study we examined individuals' physiologic changes in the last year of life by examining laboratory tests commonly used in clinical practice. Methods: Using health administrative datasets, we conducted an observational matched cohort study to assess laboratory test use and values over a decedent's last 12 months and a matched observation window for non-decedents. Laboratory tests included tests for electrolytes: potassium and sodium; complete blood count: hemoglobin and leukocytes; diabetes: hemoglobin A1c; and kidney or liver function: albumin-serum, alanine aminotransferase, and creatinine. Results: We identified 376,463 decedents, 367,474 (97.6%) of whom were matched to non-decedents (similar age and sex). For each test, the proportion of non-decedents who received the test was stable over the 12-month observation period. A higher proportion of decedents had a laboratory test than non-decedents for all but the diabetes test. As decedents neared death, there was a gradual increase in test use until their final month of life, when test use dramatically increased. Across all laboratory tests, test values remained similar for non-decedents over the 12-month observation period. However, for decedents, there were differences in the magnitude and direction of the test values over the 12 months. Conclusion: Our findings indicate distinct changes in decedents' laboratory test use and values over their last 12 months. Future work should explore whether laboratory tests could predict survival or improve the performance of mortality prediction models.