Telomere loss in AA. Telomere loss is expressed as distance in kilobases (TRF^O-E) from the age-appropriate point on the normal regression line of TRF against age. Normals: (▵; n = 60), mean TRF^O-E = 0.069 kb. Patients with acquired AA: active AA, persistent cytopenias (⧫; n = 40), mean TRF^O-E = −0.776 kb; recovered AA, normal blood count (○; n = 20), mean TRF^O-E = −0.789 kb.