PTGDR2 and asthma: As more recurrent NP subjects had concomitant asthma (Table 1) and previous research had reported the higher expression of CRTH2 in asthma (33), to further address whether the CRTH2 difference between rNP and Non-rNP was driven by asthma, we analyzed the expression of CRTH2 in nasal polyps obtained from asthmatic and non-asthmatic subjects.