Handgrip Strength Index: A Novel Parameter Which Quantifies Clinical Weakness in People on Haemodialysis

Abstract

Objective: The muscle strength in people on haemodialysis is associated with nutritional status, quality of life, functional independence, and survival. Handgrip Strength (HGS) is simple to measure, but clinical interpretation is limited by the lack of reference ranges for a haemodialysis population. This study aims to define a novel parameter, HGS index, which quantifies degree of clinical weakness specific to a haemodialysis population and to test if this predicts survival.

Methods: In a cross-sectional single center study HGS was measured in stable participants on haemodialysis. HGS in the well-nourished subgroup, was used to develop a predictive equation for "expected" HGS according to demographic variables. This then was compared to observed HGS resulting in HGS index (%), an individualized parameter indicating weakness due to clinical variables while accounting for demographic contributors to strength. The association between HGS index and survival was explored in all participants.

Results: Among 427 well-nourished individuals on haemodialysis, HGS was strongly associated with demographic variables and predicted in males by the equation: HGS (kg) = 0.38∗height (cm) - 0.31∗age (years) - 18, and in females by the equation: HGS (kg) = 0.25∗height (cm) - 0.11∗age (years) - 16. Among 547 participants (22% with protein energy wasting), lower HGS index was associated with diabetes (P = .004), lower body mass index (BMI) (P = .005), lower albumin (P = .033), and longer dialysis vintage (P = .007). Over a mean observation period of 2.8 years, quintile of HGS index was strongly associated with survival (P = .023), and in a Cox proportional hazards model, the independent predictors of mortality were age, albumin, BMI and HGS index.

Conclusion: HGS index, defined as observed relative to expected HGS, is an individualized measure of clinical weakness. It is a novel parameter which independently predicts survival. HGS index improves the detection of clinically relevant muscle weakness in people on haemodialysis, opening up the possibility of earlier, individualized interventions, and improving outcomes in this vulnerable group.

Keywords: equation; haemodialysis; handgrip; nutritional status; renal.