Association between platelet indices and non-alcoholic fatty liver disease: a systematic review and meta-analysis

Background: Platelet indices have the potential for the evaluation of the activity of non-alcoholic fatty liver disease (NAFLD), but their associations are under hard debate. This meta-analysis aims to assess whether platelet count (PC), mean platelet volume (MPV) and platelet distribution width (PDW) are associated with NAFLD and its progression. Methods: A literature search was conducted using electronic databases to find publications up to July 2022, where the relationship between PC, MPV, PDW and NAFLD was evaluated. Random-effects models were applied to pool effect estimates that were presented as standardized mean differences (SMD) with 95% confidence interval (CI). Results: Nineteen studies involving 3592 NAFLD patients and 1194 healthy individuals were included. The pooled results showed that NAFLD patients had a lower PC (SMD=-0.66, 95% CI =-1.22 to -0.09, P=0.023) but a higher MPV (SMD=0.89, 95% CI=0.26-1.51, P=0.005) and PDW (SMD=0.55, 95% CI=0.11-0.99, P=0.014) compared to healthy controls. Patients with non-alcoholic steatohepatitis (NASH) exhibited a lower PC (SMD=-0.86, 95% CI=-1.20 to -0.52, P<0.001) and a higher MPV (SMD=0.71, 95% CI=0.40-1.02, P<0.001) than non-NASH individuals. A meta-regression analysis demonstrated that MPV was significantly positively correlated with aspartate aminotransferase (P=0.008), the total cholesterol (P=0.003), triglyceride (P=0.006) and low-density lipoprotein cholesterol (P=0.007), but was significantly negatively correlated with high-density lipoprotein cholesterol (P=0.010). Conclusion: This meta-analysis revealed that NAFLD patients presented a reduced PC but an increased MPV and PDW, and the changes might be associated with NAFLD severity. A higher MPV is associated with lipid metabolic disorders in NAFLD.