A clinical prediction rule for diagnosing human infections with avian influenza A(H7N9) in a hospital emergency department setting

Table 4 Performance indices for the clinical prediction rule

Index	Estimate (95%CI)
Index	Derivation indices (n = 2,724)	Internal validation by bootstrapping (n = 2,724)	Optimism-corrected indices (n = 2,724)
Sensitivity	0.940 (0.895, 0.984)	0.958 (0.890, 0.994)	0.929 (0.881, 0.954)
Specificity	0.799 (0.783, 0.815)	0.751 (0.614, 0.885)	0.799 (0.783, 0.815)
Likelihood ratio
Positive test result	4.670 (4.124, 5.309)	3.853 (2.570, 7.747)	4.624 (3.986, 4.887)
Negative test result	0.076 (0.019, 0.134)	0.056 (0.009, 0.125)	0.090 (0.056, 0.147)
Area under ROC curve	0.966 (0.951, 0.981)	0.961 (0.952, 0.966)	0.960 (0.944, 0.976)

Obtained from internal validation by using a bootstrap analysis in which the cohort was resampled 1,000 times with replacement.Likelihood ratio for a positive test result refers to the likelihood of assignment to the high-risk group after step 2. Likelihood ratio for a negative test result refers to the likelihood of assignment to the low-risk group after steps 1 or 2. CI, confidence interval; ROC, receiver-operating characteristic.