Use of Nasal Nitric Oxide in the Diagnosis of Allergic Rhinitis and Nonallergic Rhinitis in Patients with and without Sinus Inflammation.

Background: Nasal nitric oxide (nNO) has been evaluated in patients with chronic rhinosinusitis with and without nasal polyps. However, nNO levels in patients with allergic rhinitis (AR) and nonallergic rhinitis (NAR) have shown conflicting results in previous studies.

Objective: To evaluate the value of nNO in diagnosing AR and NAR and the impact of absence or presence of sinus inflammation (SI).

Methods: A total of 173 consecutive patients scanned with high-resolution computed tomography (CT) and 46 normal controls (NCs) were included in our study. Patients were evaluated according to their medical history, nasal symptoms, endoscopic examinations, and skin prick test results. On the basis of CT scans (Lund-Mackay score >2), all patients were subgrouped as AR with SI (ARwSI) and AR without SI (ARsSI), or NAR with SI (NARwSI) and NAR without SI (NARsSI). nNO levels were measured with the NIOX, and eosinophils in nasal smears were evaluated simultaneously. Receiver-operating characteristic analysis was performed for differential diagnosis of AR, NAR, and subgroups.

Results: Ninety-four patients were diagnosed with AR and 79 patients with NAR. The levels of nNO were significantly higher in patients with AR and in NCs compared with patients with NAR (939 ± 335 in AR and 813 ± 272 in NCs vs 670 ± 188 in NAR; P < .001 for both), and significantly higher in patients with AR compared with NCs (P < .05). On the basis of sinus CT scans, 49% patients with AR (46 of 94) were defined as ARwSI and 51% patients with NAR (40 of 79) were defined as NARwSI. Patients with ARsSI showed the highest nNO levels (1180 ± 289) compared with other subgroups (P < .001), and patients with NARwSI showed the lowest nNO levels (522 ± 120) compared with other subgroups (P < .001). nNO could be used to discriminate AR, NAR, and subgroups with acceptable sensitivity and specificity. Moreover, patients with nasal smear eosinophilia had lower nNO levels than did patients with NAR (P < .05).

Conclusions: nNO levels are different between patients with ARwSI/ARsSI and NARwSI/NARsSI, and may be used to discriminate these phenotypes.