Table 2

Brock model performance in centres A and B

AUCRisk threshold (%)Sensitivity (%)Specificity (%)PPV (%)NPV (%)
Centre A
 Brock (full)0.901BTS: 1075861099
Optimum: 6.084808100
 Brock (parsimonious)0.894BTS: 107685999
Optimum: 9.080849100
 Size-only0.876Equal specificity*: 10.47186999
Optimum: 4.786787100
Centre B
 Brock (full)0.911BTS: 1081841499
Optimum: 8.286801399
 Brock (parsimonious)0.881BTS:1080771099
Optimum: 13.875851599
 Size-only0.866Equal specificity*: 3.871841399
Optimum: 2.880791199
  • *Fixed to equal specificity as the full Brock model at 10% malignancy risk.

  • AUC, area under the curve; BTS, British Thoracic Society; NPV, negative predictive value; PPV, positive predictive value.