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Background: Laryngopharyngeal reflux (LPR) with or without aspiration can cause atypical symptoms, asthma and pulmonary fibrosis. No method has been accurate or sensitive for the diagnosis of LPR. The aim of this study was to establish the normative data for LPR and proximal reflux events in an asymptomatic cohort using hypopharyngeal multichannel intraluminal impedance-pH (HMII). Methods: This is an IRB approved prospective trial. Participants were contacted through community advertising. Patients with past or current history of GERD, LPR or antisecretory medication use were excluded. Absence of symptoms was confirmed using the reflux symptom index and GERD-HRQoL questionnaires. Subjects underwent unsedated transnasal endoscopy; patients with esophageal findings of reflux were excluded. 24-hour HMII was then performed before and after a 2-week course of proton pump inhibitors (PPI). All subjects with a positive DeMeester Score were excluded from the final analysis. Catheter configuration consisted of pH probes located in the hypopharynx and 5cm proximal to the esophagogastric junction; impedance electrode pairs were located in the hypopharynx and proximal and distal esophagus. LPR events were considered present with retrograde bolus transit across all ring sets and ultimately reaching the hypopharynx. Assuming a Poisson distribution, 95th percentiles for proximal reflux and LPR events were calculated and used as boundaries defining for normal vs. pathologic LPR. Subsequently, a cohort of 15 LPR patients who had a complete response to medical or surgical therapy was used for comparison with the normative data; all patients had pre-treatment LPR events recorded using the same catheter configuration. We defined this patient set as “true LPR.” Results: Forty (18 male, 22 female, mean age 33 years) subjects were enrolled. Six subjects were excluded because of a positive DeMeester score or sensor noise. Thirty-four subjects completed one, and 26 completed both HMII testing periods off and on PPI. There was no difference in the total number of total reflux events between off and on PPI (Median, 22 and 24, respectively, p=0.89). One subject had 1 LPR event off PPI. On PPI, two subjects had 1 and 3 LPR events, respectively. The 95th percentile occurrence of LPR off and on PPI were 0 and 1, respectively; 95th percentile for proximal reflux was 4 for both off and on PPI. Patients with treatment responsive LPR had pre-treatment HMII values greater than the 95th percentile of normal patients in all criteria except total number of reflux events (Table 1). Conclusion: This study establishes the normative data for LPR. LPR events are extremely rare in patients without GERD or LPR symptoms as measured with HMII. One or more LPR events should be considered abnormal in patients with LPR symptoms regardless of whether there is a positive DeMeester score.
Comparison between normal subjects and Treatment Responsive LPR patients

HMII Measurements	Normal Subjects (off PPI): N=34	Treatment Responsive LPR Patients (off PPI): N=15	p-value
DMS	3.1 (1.2-5.4)	9.3 (5.8-19.5)	0.002
# Total reflux events	22 (8.3-32)	24.5 (14.5-31)	0.26
# Proximal reflux events (2cm distal to UES)	1 (0-2.75)	10.5 (6.3-16.8)	<0.001
#LPR events	0 (0-0)	1 (1-2)	<0.001
Predominate position of events	Upright	Upright

Variables were compared using Pearson’s chi-squared test and a p-value<0.05 was considered significant. The values are expressed as the median and interquartile range (IQR).