TABLE 3

Sensitivity/specificity of different combinations of inclusion criteria for a hypothetical trial of neutrophil elastase (NE) inhibition aiming to enrol patients with >20 µg·mL−1 sputum NE activity at baseline

Sensitivity
(95% CI) %
Specificity
(95% CI) %
PPV
(95% CI) %
NPV
(95% CI) %
Sputum colour grade ≥293.3 (86.6–97.3)46.5 (41.4–51.6)32.2 (29.9–34.6)96.2 (92.5–98.1)
Sputum colour grade 3/4 only58.7 (48.6–68.2)79.1 (73.8–83.7)51.3 (33.3–58.2)83.6 (80.1–86.6)
P. aeruginosa patients only37.5 (28.2–47.5)92.4 (88.6–95.3)65.0 (53.5–75.0)79.8 (77.2–82.1)
P. aeruginosa+grade 3/4 sputum and a history of ≥2 exacerbations per year24.0 (16.2–33.4)98.7 (97.0–99.6)83.3 (66.2–92.7)82.6 (81.0–84.1)
Sputum colour grade ≥2 and ≥2 exacerbations per year65.4 (55.4–74.5)76.1 (71.5–80.3)42.8 (37.3–48.4)89.0 (86.0–91.3)
Sputum colour grade ≥2, MRC dyspnoea score ≥3, ≥3 lobes involved on CT and ≥2 exacerbations per year37.5 (28.2–47.5)91.6 (88.4–94.2)54.9 (44.6–64.8)84.3 (82.2–86.2)
≥3 exacerbations per year, ≥2 lobes involved on CT and infection with any organism (including P. aeruginosa)16.4 (9.8–24.9)91.3 (88.1–94.0)34.0 (23.0–47.0)80.0 (78.5–81.4)

PPV: positive predictive value; NPV: negative predictive value; P. aeruginosa: Pseudomonas aeruginosa; MRC: Medical Research Council; CT: computed tomography.