AQP4 and myeloid sarcoma: In all other cases, the decision on whether or not to test for AQP4-IgG testing should be made individually; however, broad, unselected screening of patients with MS that do not meet the above-mentioned criteria is discouraged, especially in regions of the world in which NMOSD accounts only for a small proportion of IDD cases, since this practice may result in an unfavorable ratio of false-positive to true-positive results.