PAS diastase

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In histology, PAS diastase is stain to ellucidate gastric duodenal metaplasia in duodenal adenomas.^[1] More generally, PAS diastase is a histological stain often used as a negative control for glycogen. Diastase is an enzyme that breaks down glycogen and PAS is a stain that typically gives a magenta colour in the presence of glycogen. When the two are used together a light pink colour replaces the deep magenta. Differences in the intensities of the two stains (PAS and PAS-D) can be attributed to different glycogen concentrations and can be used to semiquantify glycogen in samples.