A comparison of healthcare utilization and outcomes following skin vs. serum-specific IgE allergy testing

Objective: To compare the cost, healthcare utilization, and outcomes between skin and serum-specific IgE (sIgE) allergy testing. Methods: This retrospective cohort study used IBM (R) MarketScan claims data, from which commercially insured individuals who initiated allergy testing between January 1 and December 31, 2018 with at least 12 months of enrollment data before and after index testing date were included. Cost of allergy testing per patient was estimated by testing pattern: skin only, sIgE only, or both. Multivariable linear regression was used to compare healthcare utilization and outcomes, including office visits, allergy and asthma-related prescriptions, and emergency department (ED) and urgent care (UC) visits between skin and sIgE testing at 1-year post testing (alpha = 0.05). Results: The cohort included 168,862 patients, with a mean (SD) age of 30.8 (19.5) years; 100,666 (59.7%) were female. Over half of patients (56.4%, n = 95,179) had skin only testing, followed by 57,291 patients with sIgE only testing and 16,212 patients with both testing. The average cost of allergy testing per person in the first year was $430 (95% CI $426-433) in patients with skin only testing, $187 (95% CI $183-190) in patients with sIgE only testing, and $532 (95% CI $522-542) in patients with both testing. At 1-year follow-up post testing, there were slight increases in allergy and asthma-related prescriptions, and notable decreases in ED visits by 17.0-17.4% and in UC visits by 10.9-12.6% for all groups (all p < 0.01). Patients with sIgE-only testing had 3.2 fewer allergist/immunologist visits than patients with skin-only testing at 1-year follow-up (p < 0.001). Their healthcare utilization and outcomes were otherwise comparable. Conclusions: Allergy testing, regardless of the testing method used, is associated with decreases in ED and UC visits at 1-year follow-up. sIgE allergy testing is associated with lower testing cost and fewer allergist/immunologist visits, compared to skin testing.