Abstract
To evaluate the sensitivity, specificity and predictive values of fractional exhaled nitric oxide (FENO) for the diagnosis of asthma in general practice.Prospective diagnostic study with 160 patients attending 10 general practices for the first time with complaints suspicious of obstructive airway disease (OAD). Patients were referred to a lung function laboratory for diagnostic investigation. The index test was FENO measured with a portable FENO analyser based on electrochemical sensor. The reference standard was the Tiffeneau ratio (FEV1/VC) as received by spirometric manoeuvre and/or results of bronchial provocation. Bronchial provocation with methacholine was performed to determine bronchial hyper-responsiveness (BHR) in the event of inconclusive spirometric results.88 (55%) were female; their average age was 43.9 years. 75 (46.9%) patients had asthma, 25 (15.6%) had COPD, 8 (5.0%) had an overlap of COPD and asthma, and 52 (32.5%) had no OAD. At a cut-off level of 46 parts per billion (ppb) (n = 30; 18.8%), sensitivity was 32% (95%CI 23-43%), specificity 93% (95%CI 85-97%), positive predictive value (PPV) 80% (95%CI 63-91%), negative predictive value (NPV) 61% (95%CI 52-69%) when compared with a 20% fall in FEV1 from the baseline value (PC20) after inhaling methacholine concentration <or= 16 mg/ml. At 76 ppb (n = 11; 6.9%) specificity was 100% (95%CI 96-100%) and PPV was 100% (95%CI 72-100). At a cut-off level of 16 ppb (n = 68; 42.5%), sensitivity was 79% (95%CI 67-88), specificity 55% (95%CI 45-64), PPV 50% (95%CI 40-60), NPV 82% (95%CI 72-90 [corrected] when compared with a 20% fall of FEV1 after inhaling methacholine concentration <or= 4 mg/ml. Two [corrected] patients with unsuspicious spirometric results have to be tested with FENO to save one bronchial provocation test.Asthma could be ruled in with FENO > 46 ppb. Mild and moderate to severe asthma could be ruled out with FENO <or= 16 ppb [corrected]. FENO measurement with an electrochemical sensor might be reasonable with respect to the time consuming procedure of bronchial provocation, which carries also some risk of severe bronchospasm. Further research is necessary to evaluate the effectiveness of this dual diagnostic strategy. The number needed to diagnose might be improved when the diagnostic precision could be enhanced by future technical developments.
Highlights
Study: FENO £ 16 ppb better than FENO £ 12 ppb to rule out mild and moderate to severe asthma
In our study to evaluate the diagnostic accuracy of FENO measurement with NioxMino® for the diagnosis of asthma in general practice, we found the cut-off at FENO £12 ppb to rule out mild and moderate to severe asthma with a negative predictive value of 81% (95%CI 64–91%) [1]
We overlooked in the ROC analysis that the overall diagnostic accuracy improves slightly when the cut-off is chosen at FENO £16 ppb [see table 1]
Summary
Study: FENO £ 16 ppb better than FENO £ 12 ppb to rule out mild and moderate to severe asthma. In our study to evaluate the diagnostic accuracy of FENO measurement with NioxMino® for the diagnosis of asthma in general practice, we found the cut-off at FENO £12 ppb to rule out mild and moderate to severe asthma with a negative predictive value of 81% (95%CI 64–91%) [1]. We overlooked in the ROC analysis that the overall diagnostic accuracy improves slightly when the cut-off is chosen at FENO £16 ppb (revised table two) [see table 1].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
