Table 4

 The diagnostic accuracy across different cut-off points for referral for chest x ray investigation

Referral cut-offNumber of workers (%)* per sum score categoryNumber of workers with chest x ray ILO profusion category ⩾1/1 (n = 37) n (%)†Number of workers without chest x ray ILO profusion category ⩾1/1 (n = 1254) n (%)‡Sensitivity (%)Specificity (%)NPV (%)
*Proportion of all workers (n = 1291).
†Proportion of workers with positive x ray within the sum score category.
‡Proportion of workers with negative x ray within the sum score category.
Sum scores ⩾21065 (82.5)37 (3.5)1028 (96.5)100.018.0100.0
Sum scores ⩾3684 (53.0)37 (5.4)647 (94.6)100.048.4100.0
Sum score ⩾3.75567 (43.9)33 (5.8)534 (94.2)89.257.499.4
Sum score ⩾4.0494 (38.3)31 (6.3)463 (93.7)83.863.199.2
Sum score ⩾4.25293 (22.7)22 (7.5)271 (92.5)59.578.498.5
Sum scores ⩾4.75270 (20.9)21 (7.8)249 (92.2)56.880.198.4
Sum scores ⩾5.25119 (9.2)13 (10.9)106 (89.1)35.191.598.0