Diagnostic accuracy of FEV1/forced vital capacity ratio z scores in asthmatic patients - 04/09/15
, M. Bradley Drummond, MD, MHS a, Christine Wei, MS a, Charles Irvin, PhD b, David Kaminsky, MD b, Meredith McCormack, MD, MHS a, Robert Wise, MD aAbstract |
Background |
The FEV1/forced vital capacity (FVC) ratio is used as a criterion for airflow obstruction; however, the test characteristics of spirometry in the diagnosis of asthma are not well established. The accuracy of a test depends on the pretest probability of disease.
Objective |
We wanted to estimate the FEV1/FVC ratio z score threshold with optimal accuracy for the diagnosis of asthma for different pretest probabilities.
Methods |
Asthmatic patients enrolled in 4 trials from the Asthma Clinical Research Centers were included in this analysis. Measured and predicted FEV1/FVC ratios were obtained, with calculation of z scores for each participant. Across a range of asthma prevalences and z score thresholds, the overall diagnostic accuracy was calculated.
Results |
One thousand six hundred eight participants were included (mean age, 39 years; 71% female; 61% white). The mean FEV1 percent predicted value was 83% (SD, 15%). In a symptomatic population with 50% pretest probability of asthma, optimal accuracy (68%) is achieved with a z score threshold of −1.0 (16th percentile), corresponding to a 6 percentage point reduction from the predicted ratio. However, in a screening population with a 5% pretest probability of asthma, the optimum z score is −2.0 (second percentile), corresponding to a 12 percentage point reduction from the predicted ratio. These findings were not altered by markers of disease control.
Conclusion |
Reduction of the FEV1/FVC ratio can support the diagnosis of asthma; however, the ratio is neither sensitive nor specific enough for diagnostic accuracy. When interpreting spirometric results, consideration of the pretest probability is an important consideration in the diagnosis of asthma based on airflow limitation.
Le texte complet de cet article est disponible en PDF.Key words : Asthma, spirometry, accuracy, z score, airflow obstruction
Abbreviations used : ALA-ACRC, FVC, IQR, LODO, NHANES
Plan
| The Asthma Clinical Research Network is supported by National Institutes of Health (NIH)/National Heart, Lung, and Blood Institute (NHLBI) grants 5U10HL051845, 5U10HL051831, 5U10HL051834, 5U10HL051843, 5U10HL056443, 5U10HL051810, and 5U10HL051823. |
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| Disclosure of potential conflict of interest: A. Lambert has been supported by a National Institutes of Health (NIH) training grant (T32 HL007534 32) and has received consultancy fees from GLG Council. C. Irvin is a member of several external advisory committees for NIH grants around the country and has received royalties from UpToDate. M. McCormack has received research support from the NIH/National Institute of Environmental Health Sciences (R21ES 024021 and P50 ES015903) and has received royalties from UpToDate. R. Wise has received consultancy fees from GlaxoSmithKline, Boehringer Ingelheim, Novartis, Astra Zeneca, Teva, Mylan, Spiration, Genentech, Janssen, Bristol Myers Squibb, Pulmonx, Medimmune, Merck, Forest Labs, and Sunovion and has received research support from Pearl Therapeutics, Boehringer Ingelheim, GlaxoSmithKline, AstraZeneca, Sunovion, and Forest. The rest of the authors declare that they have no relevant conflicts of interest. |
Vol 136 - N° 3
P. 649 - septembre 2015 Retour au numéro
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