Calculation of diagnostic statistics using diagnosed asthma as the index of “disease present or absent” and airway hyperresponsiveness as the index of “test positive or negative”
| Disease present (diagnosed asthma) | Disease absent | Total | |
| Test positive (AHR) | 358 (a) | 220 (b) | 578 |
| Test negative | 557 (c) | 1919 (d) | 2476 |
| Total | 915 | 2139 | 3054 |
Sensitivity = a/(a+c) = 0.39; specificity = d/(b+d) = 0.90; positive predictive value = a/(a+b) = 0.62; negative predictive value = d/(c+d) = 0.78; positive likelihood ratio = sensitivity/ (1—specificity) = 3.9.