Presentation (CTI)

OBJECTIVES: Allergy assessment in the United Kingdom remains concentrated in specialist settings despite substantial primary-care burden and long waiting times, limiting timely access to care and inefficiently using specialist capacity. Nine National Health Service (NHS) pilot pathways were introduced as policy-led service redesigns, shifting allergy evaluation earlier in the care pathway through structured symptom assessment and pre-referral serologic specific IgE testing. This analysis used discrete event simulation (DES) to evaluate the system-level impact of scaling these pathways to inform commissioning and pathway design decisions.
METHODS: A DES model was developed using real-world epidemiologic and care-pathway parameters from recent Clinical Practice Research Datalink analyses, supplemented by published literature on allergy presentation rates, referral behavior, prescribing patterns, and coincident asthma incidence. NHS usual-care trajectories were modeled from first presentation through pathway completion. Redesigned pathway parameters reflected NHS pilot specifications, including early testing, structured triage, and modified referral rules. Outcomes included referral appropriateness, avoidable specialist activity, diagnostic-phase costs, asthma-related events, and policy-relevant system indicators such as waiting-list duration and throughput. Scenario analyses varied gatekeeping strength, uptake rates, and key demand parameters.
RESULTS: The redesigned pre-referral pathway improved early differentiation of allergic versus non-allergic disease, reducing unnecessary specialist referrals and supporting more appropriate access to specialist care. In conservative scenarios, referrals declined by approximately 25 percent, and under stronger gatekeeping and higher primary-care retention, reductions approached 60 percent. Simulation results indicated improved system flow, with conservative scenarios reducing specialist waiting lists by approximately four months. Diagnostic cost per referred patient remained stable because testing shifted earlier in the pathway rather than increasing overall volume.
CONCLUSIONS: Model results suggest that systematized primary-care allergy assessment can reshape patient flow, reduce pressure on specialist services, and improve pathway throughput, informing commissioning and access-focused service redesign. Prospective evaluation will clarify long-term effects, complementing modeled evidence to support decision making.