Dong K, et al. - Using novel proteomic technologies, researchers investigated blood protein biomarkers that could predict clinical response to azithromycin therapy in cystic fibrosis (CF) children and adolescents. They found that after 28 days of azithromycin, there was a significant correlation of early change in the levels of 15 plasma proteins with alterations in forced expiratory volume in 1 second % predicted from day 0 to day 28, this correlation was not maintained to day 168. PEx (pulmonary exacerbations) risk by day 168 of treatment was predicted by early change in serum calprotectin levels after 28 days of azithromycin. On the basis of a calprotectin cut-off to maximize test sensitivity (88%) and specificity (68%), at least one PEx developed in 40% of cases with a calprotectin attenuation less than the cut-off vs only 8% of cases with calprotectin reduction greater than the cut-off.