MP43-19 DROP-OUT RATES FROM ACTIVE SURVEILLANCE FOR DISEASE PROGRESSION REMAIN CONSISTENT AND NOT NEGLIGIBLE OVER TIME. A PLEA FOR LONG-TERM ASSESSMENT BASED ON A LARGE, PROSPECTIVELY COLLECTED ACTIVE SURVEILLANCE COHORT. (1st May 2022) - Nocera, Luigi; Leni, Riccardo; Stabile, Armando; Gandaglia, Giorgio; Mazzone, Elio; Sorce, Gabriele; Pellegrino, Francesco; Barletta, Francesco; Scuderi, Simone; Gallina, Andrea; Fossati, Nicola; Zaffuto, Emanuele; et al.