A Frailty Index Based on Common Laboratory Tests in Comparison With a Clinical Frailty Index for Older Adults in Long-Term Care Facilities

Introduction: Easily employed measures of frailty are needed in the evaluation of elderly people. Recently, a frailty index (FI) based on deficits in commonly used laboratory tests (the FI-LAB) has been proposed. To address the usefulness of the FI-LAB in long-term care (LTC) settings, we studied institutionalized participants in the Canadian Study of Health and Aging first clinical examination database. Our objectives were to compare the FI-LAB with a clinical FI LTC (FI-Clinical-LTC) focused on common health deficits seen in LTC and to assay its relationship with mortality. Methods: In this secondary analysis, Canadian Study of Health and Aging first clinical examination participants who, at baseline, were LTC residents, and who consented to having blood drawn for 21 commonly employed laboratory tests (eg, complete blood count, electrolytes, renal, thyroid, and liver function) were studied. A 23-item FI-LAB was constructed based on the 21 laboratory tests, plus measures of systolic and diastolic blood pressure. The FI-Clinical-LTC was constructed from data obtained during the clinical evaluation and the FI-LAB was constructed from laboratory data plus systolic and diastolic blood pressure measurements. A combined FI (FI-Combined) included all items from each index. Predictive validity was tested using Cox proportional hazards analysis and overall utility was evaluated using the Akaike Information Criterion and the Wald statistic. Results: The mean FI-Clinical-LTC was 0.32 ± 0.14, the FI-LAB was 0.26 ± 0.11 and the FI-Combined was 0.30 ± 0.11. There was a strong linear relationship (Pearson correlation coefficient = 0.95) between the FI-LAB and the FI-Clinical-LTC, with a significant slope of 0.18 (P value of <.0001). Strong relationships with mortality were demonstrated through Kaplan-Meier curves and Cox regressions, with the FI-Clinical-LTC having a hazard ratio of 1.03, FI-LAB ratio of 1.02, and FI-combined ratio of 1.04 for each 0.01 increment in the corresponding FI in age and sex adjusted models. Conclusions: An FI based on routinely collected laboratory data can identify LTC residents at increased risk of death. This approach may be a useful screening tool in this setting.