The testing procedure will be more efficient if tests which are expected to give a similar result (positive or negative) are more likely to occur in the same pool. When the samples are taken it would be a simple matter to indicate if the patient has no, slight or severe symptoms. I am no virologist, but I would have thought that this would have some relationship to the probability of a positive test result. How good would these predictions have to be to make a useful improvement in pooled-testing efficiency? There is a cost: grouping will delay some samples. Despite that, I would have thought this could be a very quick and cheap win. I imagine this is not a new idea. Your (statistical) thoughts?