Natural History of <i>Alternaria</i> Sensitisation and Association With Asthma and Rhinitis From Childhood to Adulthood

ABSTRACT Background Sensitisation to Alternaria is clinically important in asthma and rhinitis, but its life‐course patterns and optimal diagnostic markers are unclear. We aimed to characterise Alternaria sensitisation trajectories from childhood to adulthood; we compared skin prick testing (SPT), whole‐extract specific IgE and rAlt a 1, and assessed their longitudinal association with asthma and rhinitis in the Isle of Wight birth cohort. Methods Participants were assessed at 4, 10, 18 and 26 years. Alternaria sensitisation was measured by SPT (all ages) and serum IgE to whole Alternaria extract and rAlt a 1 (10, 18, 26 years). “Any Alternaria” denoted positivity to any assay. Alternaria, asthma and rhinitis trajectories (10–18–26 years) were classified as Never, Any positive or Persistent. Associations used χ 2 trend tests and Poisson regression with robust errors. Results Among 434 participants with complete Alternaria data, trajectories were Never 84.1%, Any 11.1% and Persistent 4.8%. Alternaria trajectories showed graded associations with asthma, and more strongly with rhinitis (trend p &lt; 0.001 for both), with highest risks for persistent asthma and rhinitis. Across ages, rAlt a 1 discriminated asthma risk better than whole‐extract in youth, whereas effects converged by 26 years. For rhinitis, effect sizes were similar across assays and ages. Assay agreement strengthened with age, becoming substantial by 18 years and near‐perfect by 26 years. Conclusions Alternaria sensitisation consolidates from late adolescence and, when persistent, tracks with persistent asthma and rhinitis. Longitudinal analysis shows rAlt a 1 discriminates asthma risk better than whole‐extract in youth, while assays are largely interchangeable in adulthood.