Platelet distribution width, platelet count, and plateletcrit in diabetic retinopathy A systematic review and meta-analysis of PRISMA guidelines

Background: Screening and diagnosis of diabetic retinopathy (DR) mainly depends on fundus examination, which is not an intuitive and simple screening or diagnostic method. Recently, the relationship between platelet parameters and DR has become a hot topic. Whether platelet parameters have clinical value in DR is controversial. Methods: Literature was retrieved by formal search of electronic databases (PubMed, Embase, Cochrane library, Scopus, and CNKI) and by hand searching of reference lists of related articles from the beginning of building database to December 2017. Review manager 5.3 was utilized to deal with statistical data. This study was registered at International Prospective Register of Systematic Reviews (number: CRD42018093773). Results: This study included 1720 DR patients, 1477 type 2 diabetic mellitus (T2DM) without DR patients and 1456 health controls in 21 eligible studies. We found there was significant increase of platelet distribution width (PDW) level in the comparison of DR versus Control group (standard mean difference [SMD] [95% confidence interval [CI]]= 1.04 [0.68, 1.40]) and DR versus T2DM without DR group (SMD [95% CI]= 0.68 [0.40, 0.95]). For platelet count (PLT), it showed obvious decrease in the comparison of DR versus T2DM without DR group (SMD [95% CI]= -0.26 [-0.49, -0.03]) and no difference in comparison of DR versus Control (SMD [95% CI]= -0.26 [-0.51, -0.00]). Subgroup analysis showed that significant result of PDW level appeared in China and Turkey in all comparisons, while similar results of PLT only in China. In addition, PDW level was different in various DR-subtypes, obvious high level in proliferation DR. Conclusions: We concluded that the guiding significance of PDW and PLT in diagnosis and monitor of DR, and especially, application of PDW to PDR management may have potential sense.