Impact of Exact P -value Computation for Clinical Diagnostics with the HPO. Simulations for Clinical Diagnostics using the HPO. Patient (phenotype) data was simulated and queried against the complete database of all 4992 annotated diseases. The best result is obtained if the original disease is assigned the rank one (y-axis) by the search algorithm. Different approaches are compared (x-axis). Data were generated without error NONE and with NOISE (top row, left and right) and with IMPRECISION and both IMPRECISION and NOISE (bottom row, left and right) as explained in the Methods section. The mean rank is shown below each boxplot.