Filling time of a lamellar capillary-filling semen analysis chamber is a rapid, precise, and accurate method to assess viscosity of seminal plasma.

Among men from infertile couples, increased viscosity of the ejaculate has been reported to occur more frequently than in fertile men (Moon and Bunge, 1968; Bunge, 1970). During standard semen analysis, several semen variables are evaluated (Oehninger, 2000), but viscosity is rarely quantified. Since the current seminal variables have limited prognostic value (Castilla et al, 2006), extra variables are needed to improve male fertility diagnostics. Viscosity is a semen variable that has received relatively little attention in the literature. Hyperviscosity might be due to dysfunction of accessory sex glands. Associations have been made between hypofunction of seminal vesicles and hyperviscosity (Gonzales et al, 1993), and altered prostate function is associated with low zinc content in sperm chromatin and low chromatin stability (Björndahl and Kvist, 1990). When this integrity is altered, sperm quality declines. Seminal viscosity abnormality has been shown to be associated with male infertility and was found to accompany poor semen quality (Elzanaty et al, 2004) and altered sperm motility (Eliasson, 1973, Gonzales et al, 1993). It also has been shown that the epididymis and accessory sex glands play a role in the function of male gametes (Gonzales et al, 1992). Deviant viscosity can affect the quality of sperm cells. Hyperviscosity can attribute to biophysical alterations or chemical changes of the ejaculate that could impact sperm quality despite other normal sperm variables seen during semen analysis (Gonzales and Sanchez, 1994). To make viscosity a diagnostic variable, the relationship between viscosity and fertility needs to be determined. First the viscosity of semen must be quantified properly. Currently this remains a time-consuming job because specialized machinery is required. The method for viscosity assessment suggested by the World Health Organization (1999) is semiquantitative and in our opinion, inadequate for good quantitative assessments. A method that can be widely used and that expresses its results in centipoise (cP), the international unit of viscosity, is needed. It is known that the flow velocity in a capillary depends on the diameter of the capillary, the angle of contact, and the viscosity of the fluid. For this study, we used capillary-loaded semen analysis chambers from Leja. The properties of these chambers are well defined. According to theoretic assumptions, a linear relationship exists between filling time of the capillary and viscosity of the sample (Douglas-Hamilton et al, 2005). The aims of this study were to assess the relationship between the filling time of a capillary-loaded chamber and the viscosity of seminal plasma, to express the viscosity in cP, and to assess the accuracy and precision of the proposed method. Such a method will make it possible to describe the relationship between fertility and the semen variable viscosity. This will extend the number of variables available for the assessment of male fertility and will contribute to better models of male fertility.