This work concerns the modelling of stratified two-phase turbulent flows with interfaces. We consider an equation for an intermittency function alpha(x, t) which denotes the probability of finding an interface at a given time t and a given point x. In Waclawczyk and Oberlack (2011) a model for the unclosed terms in this equation was proposed. Here, we investigate the performance of this model by a priori tests, and finally, based on the a priori data discuss its possible modification and improvements