The RASP (Refractory Asthma Stratification Programme)-UK study group is examining the predictive value of using serum periostin, FeNO, and BEC as a composite biomarker to predict exacerbation risk, with preliminary results indicating that use of the three biomarkers in a ‘composite’ score further differentiated patients on the basis of exacerbation rate (57). This evidence concerns the gene POSTN and asthma.