Osmotic gradient ektacytometry – a novel diagnostic approach for neuroacanthocytosis syndromes

Introduction: The unique red blood cell (RBC) properties that characterize the rare neuroacanthocytosis syndromes (NAS) have prompted the exploration of osmotic gradient ektacytometry (Osmoscan) as a diagnostic tool for these disorders. In this exploratory study, we assessed if Osmoscans can discriminate NAS from other neurodegenerative diseases. Methods: A comprehensive assessment was conducted using Osmoscan on a diverse group of patients, including healthy controls (n = 9), neuroacanthocytosis syndrome patients (n = 6, 2 VPS13A and 4 XK disease), Parkinson’s disease patients (n = 6), Huntington’s disease patients (n = 5), and amyotrophic lateral sclerosis patients (n = 4). Concurrently, we collected and analyzed RBC indices and patients’ characteristics. Results: Statistically significant changes were observed in NAS patients compared to healthy controls and other conditions, specifically in osmolality at minimal elongation index (O_min), maximal elongation index (EI_max), the osmolality at half maximal elongation index in the hyperosmotic part of the curve (O_hyper), and the width of the curve close to the osmolality at maximal elongation index (O_max-width). Discussion: This study represents an initial exploration of RBC properties from NAS patients using osmotic gradient ektacytometry. While specific parameters exhibited differences, only O_hyper and O_max-width yielded 100% specificity for other neurodegenerative diseases. Moreover, unique correlations between Osmoscan parameters and RBC indices in NAS versus controls were identified, such as osmolality at maximal elongation index (O_max) vs. mean cellular hemoglobin content (MCH) and minimal elongation index (EI_min) vs. red blood cell distribution width (RDW). Given the limited sample size, further studies are essential to establish diagnostic guidelines based on these findings.