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Table 1 Sensitivity, specificity, PPV and NPV of questionnaire-based definitions of atopy compared to the gold standard of SPT and sample size calculations for a nested cohort study

From: How do questionnaire definitions of atopy status affect sample size calculations for asthma cohort studies in a population of Canadian children?

Number of atopic conditions Sensitivity Specificity Youden’s index PPV NPV Sample size for nested cohort study
1 54.3% 65.8% 20.1% 72.6% 46.3% 344
2 24.4% 98.7% 23.1% 96.9% 44.8% 2948
3 4.7% 100.0% 4.7% 100.0% 39.3% 21034