D2.192 - Comparison of the Multiplex ALEX Method and Single-Plex ImmunoCAP Method in the Diagnosis of Seasonal Allergic Rhinitis in Adults Caused by Birch Pollen

Seasonal allergic rhinitis caused by birch pollen (SAR-B) affects a significant proportion of the adult population in Europe. Component-resolved diagnostics (CRD) enables precise identification of the primary allergen and targeted indication for allergen immunotherapy (AIT). Comparison of diagnostic methods is necessary to optimize clinical algorithms. Our aim was to compare the diagnostic efficiency of ALEX (multiplex) and ImmunoCAP (single-plex) methods in adult patients with SAR-B, considering clinical severity.

Retrospective analysis of 72 patients from Brno (Czech Republic) tested for birch pollen components using both methods. Clinical assessment was performed by two independent experienced physicians; disagreement was resolved by a third arbitrator. Patients were stratified into mild versus moderate-to-severe SAR-B. Excluded: 9 <18 years, 6 without birch pollen link, 4 with inconsistent severity assessment. Final analysis: 53 adult patients.

Mild SAR-B (n=13): Bet v 1 positivity in 10 patients; 9 positive in both methods (90%; 95% CI: 55.5%–99.7%; Cohen's κ = 0.889). One patient positive only in ImmunoCAP (borderline RAST class 1). One patient positive for Bet v 2 without Bet v 1. Two patients (15.4%; 95% CI: 1.9%–45.4%) seronegative, consistent with local allergic rhinitis (LAR-B).

Moderate-to-severe SAR-B with possible AIT indication (n=40): Of 34 Bet v 1 positive patients, 33 positive in both methods (97.1%; 95% CI: 85.2%–99.5%). One patient positive only in ALEX (borderline RAST 1). Six patients (15.0%; 95% CI: 5.5%–28.3%) seronegative (LAR-B).

All Bet v 1 positive patients (n=44): Agreement in 42 of 44 (95.5%; 95% CI: 84.9%–98.7%; Cohen's κ = 0.902). ImmunoCAP sensitivity: 97.7% (43/44). ALEX sensitivity: 97.7% (43/44). In mild group: ImmunoCAP 100% vs ALEX 90%. In moderate-to-severe group: ImmunoCAP 97.1% vs ALEX 100%.

Other components: Non-Bet v 1 components minimally represented – Bet v 2 in 7 patients (13.2%), Bet v 4 in 1 patient (1.9%), Bet v 6 in 3 patients (5.7%). Only one case without Bet v 1.

Bet v 1 completely dominates in laboratory verification as monosensitization or dominant component, supporting a simple, cost-effective diagnostic strategy focused on Bet v 1. ALEX and ImmunoCAP show excellent agreement (95.5%; κ = 0.902) for identifying this primary birch allergen in both mild and moderate-to-severe SAR-B. Both methods exhibit high sensitivity (ImmunoCAP 97.7%, ALEX 97.7%), with practically equivalent performance in moderate-to-severe cases. Borderline RAST class 1 results are rare but may cause discordance. Our results do not demonstrate superior sensitivity of either method for local allergic rhinitis cases.