Repeatability of peak nasal inspiratory flow measurements and utility for assessing the severity of rhinitis

Background: The measurement of peak nasal inspiratory flow (PNIF) provides a simple, cheap, fast and readily available tool for determining the extent of nasal airway patency. However, there are questions regarding its repeatability when used to assess the degree of nasal obstruction in large populations. Therefore, this study aimed to evaluate the repeatability of PNIF measurements and to assess their association with the signs and symptoms of rhinitis.

Methods: The PNIF, rhinitis symptoms, judged by Meltzer questionnaire and rhinitis signs, as determined by anterior rhinoscopy, were assessed in 283 adults representative of the general population. One training and two test PNIF measurements were recorded during the same session.

Results: The PNIF was highly reproducible (ICC = 0.92; 95% limits of agreement: +/- 36 l/min). The PNIF was strongly correlated with rhinitis signs, measured by anterior rhinoscopy (r(s) = -0.38, P < 0.0001) but was not correlated with rhinitis symptoms, measured by questionnaire (r(s) = -0.11, P = 0.057). Differences in PNIF for subjects categorized as asymptomatic, mild or moderate/severe on the basis of rhinitis signs, were highly significant (P < 0.0001), but less significant on the basis of rhinitis symptoms (P = 0.04). A PNIF cut-off of 115 l/min had moderately high specificity (72%) and sensitivity (65%) and a high negative predictive value (90%) for moderate/severe signs of rhinitis.

Conclusion: In a large general population-based sample of young adults, PNIF was highly reproducible and closely related to the signs of rhinitis, as determined by clinical examination. The PNIF provides information that is qualitatively different to that provided by symptom scores and may be useful to measure the extent of nasal obstruction.