A Longitudinal Renal Health Outcome for Clinical Trials in Acute Kidney Injury?

I’m curious about the logic of your categories given that you’re transforming several continuous and categorical variables into a 7-point scale. How can you be confident that a given level of urine output represents a worse degree of kidney injury than a certain change in a biomarker? Another approach could be treating the best objective measure (or proxy) of AKI as a continuous variable analyzed ordinally. Let’s take urine output as an example. You could say that anything above a certain threshold (like 0.5 ml/kg/hr) is normal and anything lower than that would be worse, ending up with ordered categories like: \ge 0.5\, ml/kg/hr,\, 0.49 ml/kg/hr\, \dots 0 ml/kg/hr. Various interventions or death could be categories that are worse than no urine output alone. I don’t know how doable such a thing is computationally, but I’m wondering if something like this might better address the categorization problem.