Sodium thiosulfate 5% is a crucial in vitro diagnostic agent that plays an important role in various staining kits. Thanks to its function as a reducing agent, it can effectively remove excess silver ions in staining kits based on silver impregnation techniques. These kits include the GROCOTT staining kit for fungal spore detection, the WARTHIN-STARRY staining kit for Helicobacter pylori and spirochaetes, the BODIAN staining kit and the BIELSCHOWSKY staining kit. In all these applications, sodium thiosulfate improves the specificity of the staining and the contrast of the target structures, leading to more precise and higher quality results. In the MOVAT Pentachrome multicolor staining kit, it helps stabilize the staining by reducing excess color particles, resulting in clear and detailed imaging.