MPO and Renal insufficiency: Given that the FFS includes age > 65 years, cardiac involvement, renal insufficiency, gastrointestinal involvement, and absence of ear, nose, and throat (ENT) involvement [17], the observed difference may be partly explained by the greater number of patients aged > 65 years, lower ENT involvement, and increased renal involvement in the MPO-ANCA-positive group, although these individual components did not reach statistical significance.