Comparative measurement of thromboxane A2 metabolites in exhaled breath condensate by different immunoassays

Objective: Differences between detection techniques may be partly responsible for variable mediator concentrations reported in exhaled breath condensate (EBC). We compared two types of immunoassays to estimate thromboxane A(2) (TxA(2)) concentration. Materials and methods: Thromboxane B-2 (TxB(2)) levels were measured by enzyme immunoassay (EIA) and TxB(2)/2,3-di-nor TxB2 by radioimmunoassay (RIA) in 10 healthy subjects and 13 asthmatic patients. 2,3-Dinor TxB(2) was also determined by a separate EIA. Results: Thromboxane was detected in all samples by RIA, but only in about 75% of samples by EIA. 2,3-Dinor TxB(2) was detected in most samples. There was no agreement between the results of the different immunoassays. As compared to healthy subjects, exhaled breath condensates of asthmatic patients contained significantly more immunoreactivity by RIA and TxB(2) EIA (but not by 2,3-dinor TxB(2) EIA). Conclusion: RIA and EIA resulted in vastly different absolute values. The difference found between healthy volunteers and asthmatic patients however, suggests an increased level of TxA(2) in the airways of asthmatics.