Mean platelet volume and mortality risk in a national incident hemodialysis cohort.

Background: Higher mean platelet volume (MPV) is an indicator of larger, reactive platelets, and has been associated with a higher risk of thrombosis and cardiovascular events in the general population. Hemodialysis patients have a higher risk for cardiovascular death and predisposition to platelet dysfunction (thrombosis and bleeding diathesis), but the relationship between MPV and mortality in this population is unknown.

Methods: Among a 5-year cohort (1/2007-12/2011) of 149,118 incident hemodialysis patients from a large national dialysis organization, we examined the association between MPV and all-cause mortality. In primary analyses, we granularly analyzed MPV across five categories: 7.2-7.5, >7.5-9.5, >9.5-11.5, >11.5-13.5, and >13.5-15.0fL. In secondary analyses, we examined MPV categorized as low, normal, and high based on thresholds in the general population: 7.2-7.5, >7.5-11.5, and >11.5fL, respectively. Associations between baseline and time-dependent MPV with mortality were estimated using traditional and time-dependent Cox models in order to determine long-term and short-term exposure-mortality associations, respectively, using three adjustment levels: unadjusted, case-mix, and case-mix+laboratory models.

Results: In primary analyses, higher baseline and time-dependent MPV levels were associated with incrementally higher death risk in case-mix+laboratory analyses (reference: >9.5-11.5fL). In secondary analyses, high baseline and time-dependent MPV levels were associated with higher mortality, whereas low MPV was associated with lower death risk across all multivariable models (reference: normal MPV).

Conclusions: Hemodialysis patients with higher MPV have heightened mortality risk. Further studies are needed to determine the pathophysiologic basis for the higher risk, and if modification of MPV ameliorates mortality in this population.