Enhanced Morphological Visualization and Diagnostic Reliability of Entamoeba histolytica Using 0.1% Methylene Blue-Glycerol Vital Stain

Abstract

Microscopic identification of Entamoeba histolytica in traditional saline wet mounts is frequently compromised by poor refractive contrast and rapid specimen desiccation. This study evaluated 0.1% Methylene Blue-Glycerol as a specialized vital stain designed to enhance morphological visualization and extend the diagnostic window in resource-limited settings. A comparative analysis was conducted on 100 Entamoeba-positive fecal specimens. Each sample was evaluated via 0.85% saline wet mount and 0.1% Methylene Blue-Glycerol. Morphological quality was quantified using a 5-point Likert scale targeting Nuclear Definition, Cytoplasmic Detail, and Contrast Ratio. Statistical significance was determined using the Wilcoxon Signed-Rank Test, while inter-observer reliability among three independent microscopists was assessed using Fleiss’ Kappa. The Methylene Blue-Glycerol method yielded a statistically significant improvement over saline across all parameters. Nuclear definition increased by 148.3%, while the contrast ratio improved by 191.7%. Cytoplasmic detail rose by 87.2%, significantly improving the detection of erythrophagocytosis. Specimen longevity extended from a mean of 12 minutes in saline to over 120 minutes in Methylene Blue-Glycerol. Inter-observer reliability was "Almost Perfect" with an overall Fleiss’ Kappa of 0.84. The 0.1% Methylene Blue-Glycerol reagent provides a superior, low-cost alternative for amebiasis screening. By utilizing the cationic affinity of Methylene Blue for chromatin and the optical clearing properties of glycerol, this method standardizes morphological identification and offers a reliable bridge between traditional microscopy and costly molecular diagnostics.