Methods: 12 AR (+ nasal allergen provocation test (NAPT), + skin testing/sIgE to DP), 12 LAR (+ NAPT, - skin testing/sIgE to DP) and 6 healthy controls (-NAPT, - skin testing/sIgE to DP) were recruited. DP-ImmunoCAP solid phase was applied directly in the lower turbinate of each nostril for 10 minutes 24 hours after NAPT with DP and analyzed following the manufacturer´s instructions. ROC curve was performed to obtain the optimal cut-off point of nasal sIgE value to calculate sensitivity (S), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV). Outcomes were compared with NAPT result (gold standard test). Study was approved by local ethics committee.
Results: At 24 hours, all AR subjects had a positive sIgE determination (>0.35 kU/L) and were negative in all controls (mean sIgE control 0.04 kU/L, AR 6.2 kU/L, LAR 0.16 kU/L). ROC curves showed that 0.085 was the optimal cut-off point to discriminate LAR subjects from controls, with S 66.7% SP 83.3%, PPV 88.8% and NPV 55.5%, area under the curve (AUC)=0.854. When this cut-off point is applied to AR, the S is 100% SP 83.3% with AUC 0.99.
Conclusions: Direct determination of nasal sIgE demonstrated good values of S and SP in both AR and LAR patients.