External validation of the AAA + survival model in a large Chinese cohort with essential thrombocythaemia

Summary Triple A Plus (AAA+) is a recently proposed survival prediction model for essential thrombocythaemia (ET) intended for settings in which next‐generation sequencing is unavailable. However, independent validation in non‐Western populations remains limited. A retrospective cohort of 995 consecutive patients diagnosed with ET at a single centre between 2001 and 2022 was screened. Primary external validation was performed in 850 patients who had complete baseline variables required for the original AAA+ calculation. In the external‐validation cohort ( n = 850; deaths = 116), AAA+ demonstrated strong discrimination for overall survival ( C ‐index 0.892, 95% confidence interval 0.866–0.917). Time‐dependent analyses indicated superior discrimination across follow‐up, with 5‐ and 10‐year area under the curve values of 0.902 and 0.912, respectively, exceeding those of AAA (0.873 and 0.894) and International Prognostic Score for Essential Thrombocythemia (0.759 and 0.857). For 10‐year all‐cause mortality, decision‐curve analysis based on locally recalibrated absolute risks showed that AAA+ provided favourable net benefit across most clinically relevant thresholds. Diagnostic period‐adjusted analyses showed higher hazards of death in intermediate‐ and high‐risk patients than in low‐risk patients, with no clear evidence of temporal heterogeneity or monotonic attenuation of the AAA+ risk gradient over time. AAA+ exhibited robust risk stratification and good discrimination for overall survival in this large Chinese ET cohort.