1) The document proposes refinements to McCullagh's proportional odds model (POM) for analyzing ordinal categorical data and applies the enhanced model to a new dataset on Dravet syndrome patients. 2) The refinements involve adjustments to the formulation of the latent variable and null hypothesis to address violations of the POM assumption of parallel logit surfaces that often occur in practice. 3) Results on simulated data show the proposed model has type I error and power comparable to other methods and outperforms some existing tests, while application to a Dravet syndrome dataset finds rare phenotypes more common in severe, young cases and genes that protect or exacerbate the disease depending on the individual.