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Bilateral versus unilateral cases of chronic rhinosinusitis with nasal polyps have notable clinical and laboratory differences that impact patient outcomes.
Patients with unilateral chronic rhinosinusitis with nasal polyps (CRSwNP) tend to have less severe disease than those with bilateral nasal polyps and generally have better outcomes than those with bilateral disease, according to findings recently published in Clinical And Translational Allergy.
Further, the two manifestations of the disease come with cellular and inflammatory characteristics and different risk factors for poor outcomes.
“Although bilateral nasal polyps are more common, unilateral [CRSwNP] is also frequently encountered. A previous study demonstrated better objective surgical outcomes in unilateral [nasal polyps] and suggested that the developmental mechanisms of unilateral and bilateral [nasal polyps] may differ,” Xicheng Song, MD, and colleagues wrote. “However, that study had a significant disparity in patient numbers between the two groups, and there remains a notable lack of research exploring unilateral [CRSwNP]. Consequently, there is a dearth of understanding regarding the clinical characteristics and treatment outcomes of unilateral [CRSwNP] and the distinctions between unilateral and bilateral cases.”
Dr. Song and colleagues gathered data from patients with CRSwNP treated between January 2016 and June 2021. All patients had been treated for at least one month but were still experiencing symptoms. The researchers gathered tissue and blood cell data, demographic information, Lund-MacKay and endoscopic scores, disease control conditions, and recurrence rates. They also performed multivariate Cox proportional hazard models to detect risk factors for poor outcomes.
Patient Demographics & Laboratory Measurements
The study included 596 adults with bilateral nasal polyps and 310 adults with unilateral nasal polyps. Patients in both groups were mostly men (62.9% in the unilateral group versus 71.98% in the bilateral group), and the median age in both groups was 51.
The two groups also showed differences in tissue and cellular measurements. Patients with bilateral disease had greater tissue eosinophil counts than their counterparts in the unilateral group, according to Wang and colleagues, with a median count of 30.27 per high-powered field (HPF), compared with 13.4 per HPF in the unilateral group (P<0.001). According to the researchers, these patients also had greater counts of a variety of blood inflammatory cells.
Disparities in Disease Outcomes & Risk Factors
The researchers noted that the two groups experienced different outcomes. Patients with bilateral polyps experienced disease recurrence at greater rates than the unilateral group, with a rate of 8.56% in the bilateral group and 1.29% in the unilateral group (P<0.001). The bilateral group also had a lower rate of disease control (49.83% vs 67.1%) and greater rates of symptoms related to disease control, such as post-nasal drip, olfactory dysfunction, and facial pain or pressure.
Other key findings included higher rates of smoking, allergic rhinitis, and tissue eosinophil counts in patients with bilateral nasal polyps.
The main risk factors predicting poor outcomes in the bilateral group were total computed tomography (CT) score (HR, 1.081; P=0.001), tissue eosinophil ratio (HR, 1.016; 1.004-1.029; P=0.01), and asthma (HR, 1.513; P=0.035), according to study findings. For the unilateral group, the main risk factor for poor outcome was blood basophil count (HR, 1.587; P=0.001).
The study was limited because it was carried out in a single center, and patients who initially had unilateral nasal polyps but had bilateral recurrence were excluded.
“In comparison to their unilateral counterparts, patients with bilateral CRSwNP experience greater disease severity and worse outcomes. Furthermore, the risk factors were dramatically different between the two groups,” researchers wrote. “Asthma comorbidity, tissue eosinophil infiltration, and increased total CT score were the primary risk factors for poor outcomes in patients with bilateral CRSwNP, with blood basophil being the major risk factor in unilateral CRSwNP.”
