Abstract
Neutral α-glucosidase (NAG) activity in human seminal plasma is an important indicator for epididymis functionality. In the present study, the classic World Health Organization (WHO) method has been adapted to enhance assay robustness. Changes include modified enzyme reaction buffer composition and usage of an alternative enzyme inhibitor for background correction (glucose instead of castanospermine). Both methods have been tested in parallel on 144 semen samples, obtained from 94 patients/donors and 50 vasectomized men (negative control), respectively. Passing-Bablok regression analysis demonstrated equal assay performance. In terms of assay validation, analytical specificity, detection limit, measuring range, precision, and cut-off values have been calculated. These data confirm that the adapted method is a reliable, improved tool for NAG analysis in human semen.
Highlights
Semen D-glucosidase activity can be subdivided into a neutral and an acid fraction [1]
Enzyme activity is normal when azoospermia results from sperm maturation arrest, an obstruction located between the epididymis and the rete testis, or in the rete testis
Neutral D-glucosidase is a sensitive marker for detection of epididymis-related problems [2]
Summary
Semen D-glucosidase activity can be subdivided into a neutral (epididymis-related) and an acid (prostate-derived) fraction [1]. D-glucosidase (NAG) activity in seminal plasma is a reliable parameter for epididymal function. Alternative markers, such as glycerophosphocholine and L-carnitine, are available but NAG activity appears to be more specific and sensitive [2]. Seminal plasma of azoospermic males with bilateral obstruction between the epididymis and the ejaculatory duct contains very low D-glucosidase [3]. Enzyme activity is normal when azoospermia results from sperm maturation arrest, an obstruction located between the epididymis and the rete testis, or in the rete testis. NAG assessment in seminal plasma of normally virilized men with azoospermia allows differentiation between the major causes of this condition [4,5]
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