Sensitivity and specificity of FTs and LLN spirometric criteria by age group, persons aged 40–95 years without diagnosed asthma, Health Survey for England 2010 and UK Household Longitudinal Survey Wave 2 (2010–2012)
| 40–64 (n=5544) | 65–95 (n=2335) | 40–64 (n=5544) | 65–95 (n=2335) | |
|---|---|---|---|---|
| FT using LLN as reference standard | LLN using FT as reference standard | |||
| False positives (%) | 5.1 | 25.6 | 0.4 | 0.0 |
| False negatives (%) | 2.5 | 0.0 | 28.0 | 57.6 |
| Sensitivity | 0.975 | 1.000 | 0.720 | 0.424 |
| Specificity | 0.949 | 0.744 | 0.996 | 1.000 |
| PPV | 0.720 | 0.424 | 0.975 | 1.000 |
| NPV | 0.996 | 1.000 | 0.949 | 0.744 |
| κ coefficient | 0.801 | 0.479 | 0.801 | 0.479 |
| Likelihood ratio positive | 18.98 | 3.90 | 200.65 | N/A |
| Likelihood ratio negative | 0.027 | 0.000 | 0.281 | 0.576 |
| FT (stage II+) using LLN as reference standard | LLN using FT (stage II+) as reference standard | |||
| False positives (%) | 1.3 | 8.9 | 6.3 | 5.2 |
| False negatives (%) | 49.2 | 26.7 | 16.0 | 39.1 |
| Sensitivity | 0.508 | 0.733 | 0.840 | 0.609 |
| Specificity | 0.987 | 0.911 | 0.937 | 0.948 |
| PPV | 0.840 | 0.609 | 0.508 | 0.733 |
| NPV | 0.937 | 0.948 | 0.987 | 0.911 |
| κ coefficient | 0.597 | 0.596 | 0.597 | 0.596 |
| Likelihood ratio positive | 38.82 | 8.28 | 13.27 | 11.67 |
| Likelihood ratio negative | 0.499 | 0.292 | 0.170 | 0.412 |
FTs, fixed thresholds; LLN, lower limit of normal (below the 5th centile of z-scores); NPV, negative predictive value; PPV, positive predictive value.