Asthma is a common airway inflammation, but current methods for diagnosing it are poor. Here we meta-analyze the available evidence on the ability of exhaled nitric oxide (eNO) in asthma to serve as a diagnostic marker of asthma. We systematically searched the PubMed and EMBASE databases, published data on sensitivity, specificity and other measures of diagnostic accuracy of eNO in the diagnosis of asthma were meta-analyzed. The methodological quality of each study was assessed by QUADAS-2 (quality assessment for studies of diagnostic accuracy). Statistical analysis was performed by employing Meta-Disc 1.4 software and STATA. And the measures of accuracy of eNO in the diagnosis of asthma were pooled using random-effects models. A total of nineteen publications reporting twenty-one case-control studies were identified. Pooled results indicated that eNO showed a diagnostic sensitivity of 0.78 (95% CI 0.76 to 0.80), specificity was 0.74 (95% CI 0.72 to 0.76). PLR was 3.70 (95% CI 2.84 to 4.81) and NLR was 0.35 (95% CI 0.26 to 0.47). DOR was 11.37 (95% CI 7.54 to 17.13). Exhaled nitric oxide show insufficient sensitivity and specificity for diagnosing asthma, eNO measurements may be useful in combination with clinical manifestations and conventional tests such as pulmonary function tests, assessment of bronchodilator response and bronchial challenge tests.
Keywords: Exhaled nitric oxide; asthma; diagnosis; eNO; meta-analysis.