A method for off-line nasal nitric oxide measurement.

We conducted a study to test the accuracy of an immediate and delayed off-line technique for measuring nasal nitric oxide (NO) by comparing it with on-line measurements. With the assistance of one volunteer, we obtained these measurements during 30 sessions over a period of 2 months. Off-line measurements were made immediately following the acquisition of NO samples and 1, 2, and 4 hours later. NO samples were obtained from nasal air collected in syringes. We found that the correlation between on-line measurements and the immediate and delayed off-line measurements ranged from 95 to 98%, according to a Bland-Altman analysis. We conclude that off-line nasal NO measurements can be reliably used in clinical practice and research projects, thus obviating the need for patients/subjects to be in close proximity to the analyzer. Off-line nasal NO measurements can effectively substitute for on-line measurements when the latter technique is not practical.