A Systematic Review of Studies Performing the Hypo-Osmotic Swelling Test to Evaluate the Quality of Canine Spermatozoa



The hypo-osmotic swelling test (HOS test) is a simple and inexpensive test to evaluate the functional integrity of sperm cell membranes. According to the existing literature, its simple applicability has turned it into a valuable additional parameter to standard canine semen analysis. In the recent years, much research has been conducted in this field. The aim of this systematic review was to evaluate the quality of published literature in canine reproduction concerning the HOS test. Using two distinguished databases, 38 articles were detected and analysed subsequently according to various aspects, for example study design, population, semen sampling and implementation concerning the HOS test. Although there are numerous articles available, the diagnostic value of the HOS test remains ambiguous. Until now, neither a recognized test protocol nor reliable reference values have been defined. Most of the trials evaluated show serious methodological flaws and therefore do not permit drawing reliable conclusions. According to our results, approximately half of the studies (n = 20) included a sample size of five or less animals. None of the studies examined the inter- or intraobserver agreement for the HOS test. Further research is warranted including appropriate statistical methods and a sufficient number of animals to establish a standardized test protocol as well as reliable reference values. Most importantly, it is required to clarify a correlation between the HOS test and the fertilizing capacity to determine the diagnostic value of the HOS test.