Photo Credit: iStock.com/Jevtic

Researchers found that nasal nitric oxide levels were similar in allergic and nonallergic rhinitis, undermining its reliability as a standalone biomarker for differentiation.

Nasal nitric oxide (nNO) concentrations do not differ significantly between individuals with allergic rhinitis (AR) and those with nonallergic rhinitis (NAR), according to a cross‑sectional investigation published online in Medicina. The finding challenged the utility of nNO as a standalone biomarker for distinguishing these rhinitis subtypes.

“Previous studies, comparing nNO levels in patients with AR and NAR, have shown controversial results so far,” stated Constantinos Pitsios, MD, PhD, and colleagues, “with some of them reporting an increase, others revealing a decrease, and some showing similar nNO levels among patients with AR and NAR.”

Volunteer Effort

The study enrolled 122 student volunteers from the University of Cyprus Medical School who completed a detailed questionnaire assessing nasal congestion, rhinorrhea, sneezing, and nasal itching experienced over the preceding 12 months, excluding episodes attributable to respiratory tract infections. Of these, 62 participants with rhinitis symptoms progressed to the clinical phase, which included comprehensive medical histories, clinical examinations, and skin prick tests for the 14 most relevant regional allergens. Nasal NO measurements were obtained with the NIOX VERO portable NO analyzer, following the procedure proposed by the American Thoracic Society and the European Respiratory Society.

Rhinitis Results

“The study took place during the pollen season when nasal allergic inflammation, due to either seasonal or perennial sensitizations, should be present in the majority of the AR volunteers,” researchers reported. “Nevertheless, the mean nNO concentrations in the AR group were 830 ± 247 ppb, and we surprisingly found similar results in the NAR group, with a mean of 851 ± 373 ppb.”

No statistical difference was found between the 2 groups (P=0.811).

Receiver operating characteristic curve analysis yielded an area under the curve of 0.511, “suggesting that the nNO measurement’s ability to differentiate AR from NAR is comparable to that of random guessing,” the team reported.

At the optimal diagnostic threshold of 736 ppb, nNO measurement had 61.5% sensitivity and 52.2% specificity in differentiating AR from NAR, values insufficient for reliable clinical application.

“The outcome of the present study was that no significant difference was detected in nNO levels between AR and NAR,” the researchers concluded. “Therefore, nNO cannot be used as an AR/NAR differentiator and is not a reliable diagnostic tool that can be used in clinical practice for the diagnosis of either subtype of rhinitis.”