Salivary pH testing in Laryngopharyngeal Reflux Disease

Abstract

To determine salivary pH in patients with Laryngopharyngeal Reflux (LPR) and compare it with that of normal individuals. A cross sectional analytical study was done. Adults with LPR as determined by Reflux Symptom Index (RSI) > 13 and Reflux Finding Score (RFS) > 7 were included in LPR group. Normal healthy adult participants with Reflux Symptom Index ≤ 3 and Reflux Finding Score ≤ 2 were included in non LPR group.32 participants were included in each groups. Salivary pH was determined in all participants using a standardized pH meter. Difference in salivary pH between two groups was statistically analyzed. The mean salivary pH in LPR group was 7.43 ± 0.77 and in non LPR group 7.0 ± 0.77. There was a statistically significant difference between the mean salivary pH between the two groups as determined by p value 0.004. The results of our exploratory study showed statistically significant difference in salivary pH between LPR and non LPR group. The salivary pH in 10(31.2%) out of 32 participants in LPR group was beyond the normal range and surprisingly the value was > 7.6, which was in contrast to acidic pH that was expected as per hypothesis. The rest 68.8% in LPR group had pH in the normal range. However salivary pH as a modality for diagnosing LPR cannot be concluded from such preliminary study with a small study population. This study forms a basis for future research for the role of salivary pH in LPR with better study designs and finer modalities of pH testing.

Introduction

In the year 2002, the American Academy of otolaryngology and Head and Neck Surgery described Laryngopharyngeal Reflux (LPR) as a separate clinical entity and discussed the differences in pathophysiological mechanisms from GERD (Gastroesophageal Reflux Disease) [1]. LPR accounts for around 10% of otolaryngology consultations [2]. Though LPR and GERD have different pathophysiological mechanisms described, they can occur simultaneously [1].The primary issue in LPR is considered to be dysfunction in the upper and/or lower esophageal sphincter [3]. The clinical symptoms of LPR are often vague and nonspecific. It remains a challenge to the clinician to determine whether the chief complaints of the patient such as hoarseness of voice, foreign body sensation in throat, cough are due to reflux or due to other conditions like allergies, post nasal drip, chronic rhinosinusitis [4]. Definitive diagnosis of LPR is difficult with current standard methods [1, 5]. Multichannel intraluminal impedance pH throughout 24-h monitoring is considered gold standard to assess if extraesophageal symptoms are due to GERD [5]. It is an invasive and expensive diagnostic test [6]. Oropharyngeal pH monitoring by Restech measurement system as a tool to diagnose LPR has been reported by few studies but lack of agreement on normal and abnormal cut off values and also lack of well-planned diagnostic accuracy study designs in the field limits its usage in day to day clinical practice [7, 8].

In an attempt to identify simple and reliable tests to diagnose LPR, researchers have now reported role of identifying pepsin in saliva as diagnostic marker for LPR [9, 10].The refluxate in LPR mainly consists of pepsin, bile salts, acids which causes irritation of laryngopharyngeal mucosa leading to symptoms of LPR [11]. Leichen et al. in 2019 in their state of the art review reiterated the need for establishment of multiparametric diagnostic approach for LPR [5].

Human saliva is a complex biofluid with a pH ranging from 6.2 to 7.6¹². Saliva has been used as a promising diagnostic tool in various diseases as it is easy to perform and also noninvasive. There are no studies in existing literature which have used salivary pH as a diagnostic tool in LPR. In current clinical practice LPR is very frequently encountered and a lack of gold standard test in its diagnosis has motivated researchers to find studies which would be least invasive yet effective to diagnose and treat the condition. With this background of diagnostic challenges in LPR and the need for multiparametric approach for its diagnosis, we wanted to determine whether salivary pH is altered in patients with LPR. This is an exploratory study to find whether salivary pH is affected in patients with LPR.

The objective of the study was to determine salivary pH in patients with LPR and compare it with that of normal individuals.

Methods

The study was conducted in OPD setting of Otolaryngology department in a tertiary medical centre. Instutional ethics committee approval was obtained before commencement of the study. Written informed consent was obtained from all the participants of the study.

Study design: Cross sectional Analytical study design.

Study duration: 5 months (June 2023-October 2023).

Sample Size Calculation: Due to lack of previous studies on salivary pH in LPR, sample size estimate could not be done. In the study period of 5 months we have included thirty two patients with LPR in one group and thirty two normal individuals in the other group.

Study Population: Thirty two participants with LPR and thirty two participants without LPR were included in the study.

Inclusion criteria:

1. Adults > 18 years with LPR as determined by Reflux Symptom Index > 13 and Reflux Finding Score > 7 were included in LPR group.

2. Normal healthy adult participants with Reflux Symptom Index ≤ 3 and Reflux Finding Score ≤ 2 were included in non LPR group.

Exclusion criteria:

1. Patients with Upper Respiratory Tract Infections, history of head and neck cancers, history of laryngeal or pharyngeal surgeries, dental caries, aphthous ulcers.

2. Patients on antacids/ Proton pump inhibitors, anticholinergics, antihistaminics, antipsychotics or antiparkinsonian drugs anytime in the previous 1 month.

3. Patients with history of smoking, tobacco chewing, systemic illness like Rheumatoid arthritis, AIDS, chronic malnutrition, dehydration.

The patients who presented to ENT OPD with history suggestive of LPR were evaluated as follows for:

Belafsky Reflux Symptom Index(RSI)

The patients were evaluated for symptoms of LPRD using standardized RSI questionnaires. It includes a set of nine self administered questions. The score ranges between zero and a maximum of 45. RSI of > 13 is considered to be suggestive of relux [13].(Table 1).

Table 1.

Reflux system index

Within the last month how have the following affected you?	0 = no problem 5 = Severe problem 0                                        1                                           2                                            3                                                     4                                                          5
Hoarseness/Problem with Voice
Excess mucus in throat/PND
Intermittent Requirement to clear throat
Difficulty in swallowing food/liquid/pills
Coughing after you ate
Breathing Difficulties or Choking episodes
Troublesome or annoying cough
Sensation of something sticking to your throat or lump in your throat
Heartburn, Chest pain, Indigestion or stomach acid coming up

Belafsky Reflux Finding Score(RFS)

Flexible laryngoscopy was performed by a trained Otolaryngologist with video/photo documentation. RFS scores range from zero to highest score of 26. A score of > 7 was considered suggestive of LPR [14]. (Table 2)

Table 2.

Reflux finding score

RFS parameters	White Light Endoscopy
Subglottic edema Absent = 0 Present = 2
Ventricular obliteration Partial = 2 Complete = 4
Erythema/hyperemia Arytenoids only = 2 Diffuse = 4
Vocal fold edema Mild = 1 Moderate = 2 Severe = 3 Polypoid = 4
Diffuse Laryngeal edema Mild = 1 Moderate = 2 Severe = 3 Obstructing = 4
Posterior commissure hypertrophy Mild = 1 Moderate = 2 Severe = 3 Obstructing = 4
Granuloma/Granulation tissue Absent = 0 Present = 1
Thick endolaryngeal mucus Absent = 0 Present = 1
TOTAL Score

After determining the RSI and RFS, those participants with RSI > 13 and RFS > 7 were included in the LPR group.

Salivary pH determination

The patients underwent Salivary PH determination after 2 h of Flexible laryngoscopy. In these two hours patients were instructed not to consume any food or beverages. After 2 h the patients were instructed to rinse their mouth with 50 ml of distilled water. Unstimulated saliva was then collected in a sterile container for 3 min. Around 5–7 ml of saliva was collected. The salivary pH was measured using a pH meter (Ionix, pH and EC meter, China). The pH meter was calibrated prior to measurement by using buffer solution of pH 4 at 25 degree centrigrade and pH 6.86 at 25 degree centigrade. The salivary pH was then documented. The pH meter was calibrated weekly to confirm that the readings were accurate. Normal range of salivary pH was considered in the range 6.2–7.6.

Non LPR group

Thirty two normal individuals without any history of LPRD were evaluated for RSI and RFS. In this study we have included those participants with RSI ≤ 3 and RFS ≤ 2 in non LPR group. Salivary pH was determined similarly for non LPR group as well.

Data Analysis

Data analysis was done using SPSS version 28. Quantitaive data was mentioned as Mean ± Standard deviation. Differences in salivary pH and other parameters between the two groups were measured using independent t test and chi square test. p < 0.05 was considered to be statistically significant.

Results

There were 32 participants in LPR group and 32 participants in non LPR group. Out of 32 participants in LPR group 11 were females (34.4%) and 21 (65.6%) were males. Among non LPR there were 16 males and 16 females (50%). There was no statistically significant difference in gender amongst LPR group and non LPR as indicated by p value of 0.26 by chi square test. The mean age of participants in LPR group was 39.22 ± 10.85 years and in non LPR 36.09 ± 8.71 years. There was no statistically significant difference in age between the two groups as indicated by p value of 0.20 determined by independent t test.

The average Reflux Symptom Index in LPR group was 16.78 ± 0.97 and in non LPR group 3.7 ± 0.933 and the average Reflux Finding Score in LPR group was 8.69 ± 1.06 and in non LPR group 0.4 ± 0.5. There was a statistically significant difference in Reflux Symptom Index and Reflux Finding score between LPR and non LPR group (p < 0.001).

The mean salivary pH in LPR group was 7.43 ± 0.77 and in non LPR group 7.0 ± 0.77 (Fig. 1). There was a statistically significant difference between the mean salivary pH between the two groups as determined by p value 0.004 (Independent t test). There were no participants amongst both groups with pH less than 6.2. However 10 participants in LPR group (31.2%) had salivary pH > 7.6 and the rest 22 ( 68.8%) had pH between 6.2 and 7.6. All participants in non LPR group had salivary pH in the range 6.2–7.6. (Fig. 2)

Fig. 1.

Mean Salivary pH in LPR group and non LPR group

Fig. 2.

Salivary pH distribution in LPR and Non LPR groups. Note ° and * indicate extreme values

Discussion

This is an exploratory study to evaluate salivary pH in individuals with LPR and compare it with that of normal healthy individuals. A universally acceptable gold standard test to diagnose LPR is not defined yet [15]. Traditional impedance pH test used as a gold standard in diagnosis of Gastroesophageal reflux has not been much of use in throat to diagnose LPR due to false positive and false negative results [17]. It is also important to note that pathophysiology and symptomatology of LPR and GERD are different. LPR occurs due to small amount of refluxate especially during day time leading to damage of laryngeal tissue and thus laryngeal symptoms [17]. Apart from clinical symptoms, clinical response to behavioural and antireflux medications, signs of mucosal injury as visualized by flexible laryngoscopy and demonstration of reflux events by impedance pH monitoring are usually used in the diagnosis of LPR.

Lack of single gold standard test to diagnose LPR has motivated researchers across the globe to look for more tests that can be easily confirm the diagnosis of LPR in an era where there is a steep rise in cases of LPR.

A study on 180 participants by Horvath L et al. [16] in Switzerland on oropharyngeal pH monitoring for diagnosis of LPR showed better sensitivity of pH monitoring than RSI and RFS (95% vs. 78% and 94%) and also better specificity than that of RSI( 93% vs. 54%) and similar specificity to that of RFS (93%vs 94%). However, there are many other studies and trials that have published that Oropharyngeal pH monitoring may not have a value in the diagnosis of LPR [18–20].

Salivary pepsin determination has been used in detection of LPR. Weitzendorfer M et al. [21] found a significant correlation between values of salivary pepsin and measurement of RSI score. A metaanalysis by Jing Wang et al. [22] regarding pepsin in saliva as a diagnostic biomarker in LPR concluded that pepsin in saliva has moderate value in diagnosis of LPR.

With the background that gastric pepsin found in saliva in patients with LPR and also alterations in Oropharyngeal pH in such patients, our study used salivary pH as a possible tool to diagnose LPR.As per the traditional teaching of acid refluxate in pathophysiology of LPR symptoms and signs we expected a tendency of acidic pH in the cases however we found that in majority of the cases the salivary pH was well maintained in the normal range (68.8.%), surprisingly 10 cases (31.2%) had abnormal pH on higher side i.e. >7.6.

Alkaline refluxate is likely related to duodenogastric reflux [23]. In 1999, Stein HJ et al. [24] quoted that it’s both gastric and duodenal components individually or in combination contribute to GERD. A recent study by Li J et al. [25] on multichannel intraluminal impedance pH monitoring in 344 patients, reported that 74.1% of reflux events were non acid reflux events.

Though the salivary pH between cases and controls showed a statistically significant difference, it is unclear whether salivary pH can be used in the battery of tests used in diagnosis of LPR.

The limitations of our study include small sample size, lack of inclusion of other diagnostic tests other than RSI and RFS in the study and only one time recording of salivary pH in participants. As per RSI, symptoms of the participants in last 1 month are considered. Duration of symptoms was not analyzed in this study hence it could not be correlated with those who had had abnormal salivary pH. Larger population, diagnostic accuracy test study designs can be employed in future research before drawing conclusions. However this study forms a basis that definitely salivary pH can be studied further in patients with LPR.

Conclusions

The results of our study showed statistically significant difference in salivary pH between LPR and non LPR group. However salivary pH as a modality for diagnosing LPR cannot be concluded from such preliminary study. Larger study population, detailed history on duration of symptoms, diagnostic test accuracy study design and further refinement in procedure of testing salivary pH needs to be considered in future research.

Funding

No Funding was received for the conduct of this study

Declarations

Ethical Committee Clearance

Obtained (BVDUMC/IEC/61)dated 15.04.2023

Written Informed Consent

Obtained from all participants

Conflict of Interest

The authors declare that there are no financial or conflict of interest.