Assessment of a qualitative serological assay to screen for allergic sensitization in elderly subjects

We used a commercially available specific IgE qualitative serological assay to screen for allergic sensitization. Two hundred twenty-eight elderly subjects took part in the study. Skin-prick tests (SPTs) to a panel of relevant aeroallergens present in the study area were used as the diagnostic reference procedure (gold standard). Subjects with at least one positive SPT (≥3 mml n = 76) were considered to have developed an allergic sensitization. The qualitative assay correctly classified subjects as sensitized to an allergen or not sensitized in 257 of 288 cases (accuracy, 88.9%; 95% CI, 85.0-92.0%). The qualitative assay sensitivity was 70.0 (95% CI, 58.1-79.7) and specificity was 95.7 (95% CI, 92.1-98.0), positive predictive value (PPV) was 85.4 (95% CI, 85.1-93.4), negative predictive value (NPV) was 89.8 (95% CI, 85.1-93.4), positive likelihood ratio (LR(+)) was 16.5 (95% CI, 8.7-31.6), negative LR (LR(-)) was 0.31 (95% CI, 0.21-0.43), and the diagnostic odds ratio (DOR) was 52.2 (95% CI, 21.5-133.6). In the elderly subjects with respiratory symptoms, the qualitative assay correctly classified subjects as allergen sensitized or nonsensitized in 81 of 89 cases (accuracy, 91.0; 95% CI, 85.0-96.9). In this subgroup, the qualitative assay sensitivity was 94.6 (95% CI, 85.1-98.8), specificity was 84.8 (95% CI, 68.1-94.9), PPV was 91.3 (95% CI, 81.0-97.1), and NPV was 90.3 (95% CI, 74.2-97.9). LR(+) was 6.2 (95% CI, 3.0-14.2), LR(-) was 0.06 (95% CI, 0.02-0.17), and the DOR was 98.9 (95% CI, 18.0-621.4). The qualitative serological assay is a valuable tool for the diagnosis of allergic sensitization in a population of elderly subjects.