Inter-rater and intra-rater reliability
The inter-rater and intra-rater reliability for grading of redness of nasopharynx was 0.84 (95% CI: 0.68-0.99, P<0.01) and 0.80 (95% CI: 0.64-0.96, P<0.01) respectively. The inter-rater and intra-rater reliability for granular posterior pharyngeal wall was 0.72 (95% CI: 0.52-0.91, P<0.01) and 0.79 (95% CI 0.61-0.96, P<0.01) respectively. The inter-rater and intra-rater score for the RFS was 0.63(95% CI :0.31-0.80, P<0.01) and 0.99 (95% CI:0.98-0.99, P <0.01).
DISCUSSION
There were more than half of patients who complained of bothersome PND among patients with rhinitis and this is related to the severity of rhinitis symptoms and the presence of secretions in the posterior nasal cavity. It is well known that rhinitis impairs the quality of life (QoL)(10) but PND is often overlooked. This is comparable to Jaruvongvanich et al (11) which reported that 56.3% of patients with allergic rhinitis had at least moderately severe postnasal drip.
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The presence of secretions was associated with the PND group among this rhinitis population and is 78% sensitive with a likelihood ratio positive of 1.41%. This suggests that the secretions in the posterior nasal cavity are contributing to the PND sensation bothering the patients and should alert ORL doctors to treat the associated PND. This can be done with routine intranasal steroids (11) and nasal douching but its efficacy for PND needs further study(12).
Surprisingly, redness of the nasopharynx was found to be higher among patients with rhinitis only compared to the postnasal drip group. This would suggest that the erythema in the nasopharynx is due to inflammation associated with rhinitis itself (13)rather than irritation from PND. This inflammation may also lead to hyposensitivity of the inflamed mucosa. It was previously reported that patients with PND have nasopharyngeal hyposensitivity secondary to inflamed mucosa which may also explain why certain patients with secretions in the posterior nasal cavity do not complain of postnasal drip (14). The presence of hemorrhagic spots and the granular posterior pharyngeal wall was equally present among rhinitis patients with or without PND.  These endoscopic features are likely due to other stimulating factors such as rhinitis itself, LPR, and breathing in dry air (7,15).
Among these rhinitis participants, LPR was only present in 10.2% in the whole study population and the proportion of LPR was not significantly different (13 v 5%, P=0.2). This suggests that LPR may not play a major role for the symptoms of PND among rhinitis patients. Physicians should not be too hasty to prescribe anti- reflux medications for PND among rhinitis. These patients should be treated with intranasal steroids and nasal douching first. Secretions found in the posterior nasal cavity may potentially be a useful sign that the PND is due to rhinitis and not LPR. Although the RSI is higher in the PND group, this is not surprising as RSI also assess for symptoms similar to PND. Furthermore, RSI has been reported to be associated with more severe rhinitis symptoms(16). Therefore, RSI should not be used as standalone to diagnose LPR among rhinitis patients and should always be combined with RFS.
The redness of the nasopharynx and granular posterior pharyngeal wall that was assessed appeared to have good test characteristics. Both inter-and intra-observer Cohen’s Kappa and ICCs were good and, likely that the use of reference images and predefining the appearance of redness and granularity of posterior pharyngeal wall contributed to this finding. The limitation of this study is the lack of a Hypopharyngeal-Esophageal Multichannel Intraluminal Impedance with dual pH probe (HEMII-pH) testing which is considered as gold standard to confirm the diagnosis of LPR. Although RSI and RFS have been proposed as a diagnostic tool for LPR, there is still debate about this since both tools are subjective in nature. Future studies in investigating the relationship of postnasal drip with LPR should include this test(17). Another limitation is that diffuse redness of the nasopharynx was not further graded according to the severity (mild, moderate to severe) and this is best performed using specifically designed software. Redness of nasopharynx and hemorrhagic spots without secretions may be more suggestive of LPR, but this requires further study which separates LPR, rhinitis only and healthy control.
In conclusion, majority rhinitis patients suffer from PND which is bothersome. Secretion seen in posterior nasal cavity may be a useful sign to support presence of PND among rhinitis patients. These nasal endoscopic features should be studies in other patient population to further define its diagnostic utility for PND.
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