Measuring sputum eosinophils is still the best method of identifying eosinophilic airway inflammation, authors of a review conclude.

In a systematic review and meta-analysis of 24 adult studies and eight studies involving children Daniel Korevaar from the University of Amsterdam and colleagues assessed the sensitivity, specificity, and predictive value of FeNO, blood eosinophils and serum total igE as minimally invasive surrogate markers for airway eosinophilia.

They found that most of these surrogate markers had a lower sensitivity and specificity in identifying airways eosinophilia compared to the gold standard induced sputum.

“At the optimal cutpoint, sensitivities and specificities of these markers for detecting sputum eosinophilia are moderate, and their use would lead to many false positives or false negatives,” they wrote in the Lancet Respiratory Medicine.

An accompanying editorial said considering the limits of surrogate markers “one might ask once again whether practicing clinicians should measure airway eosinophilia in patients with asthma.”