Peak nasal inspiratory and expiratory flow measurements--practical tools in primary care?

General practitioners diagnose and treat numerous patients with nasal problems but have no objective equipment to aid diagnosis. We studied the characteristics of peak nasal inspiratory (PNIF) and expiratory (PNEF) flows to explore their utility for primary care use. One hundred healthy volunteers, 50 men, 50 women, performed PNIF and PNEF measurements in standardised laboratory circumstances. Repeatability was tested for a subgroup of 20 women who performed two consecutive series of PNIF and PNEF at a 2-minute interval. Diurnal variability was tested with a subgroup of 10 men and 10 women who recorded PNIF and PNEF values at home every morning and evening for 7 days. Distribution of individual values for both PNIF and PNEF was wide and independent of subject's age, height, or gender. Repeatability was poor and diurnal variation substantial. PNIF and PNEF lack the properties of good clinical tests and thus cannot be recommended for primary care use.