Change in tetranor PGDM urine levels after low and standard oral graded aspirin challenge. 5a. After low-dose aspirin challenge there was no significant change in tetranor PGDM levels in either group. 6b. After standard graded aspirin challenge, there was a significant increase in tetranor PGDM levels in AERD patients with FEV1 decrease of ≥20% (n=10, p=0.001). There was a decrease in tetranor PGDM levels in AERD patients with FEV1 decrease of <20% (n=6), and in ATA patients (n=13), (p=0.02 and p<0.01, respectively).