This policy is mainly based upon evidence-based guidelines from the American Gastroenterological Association (AGA, 2001).
Esophageal pH recording provides quantitative data on both esophageal acid exposure and on the correlation between patient symptoms and reflux events. Despite these strengths, the inherent weakness of the technique is its inability to prove causality between symptoms and acid reflux. Alternatively, causality is reasonably assumed in clinical practice by the alleviation of suspected reflux symptoms during a therapeutic trial of a proton pump inhibitor (PPI). In view of this viable alternative, the AGA (2001) has concluded that the major indications for esophageal pH monitoring are in documenting the failure of either medical or surgical therapy.
For standard ambulatory esophageal pH monitoring, a nasogastric catheter fitted with a pH probe is inserted through the nose into the lower esophagus. The catheter is attached to a data logger that is worn on the body. The catheter is left in place for 24 to 48 hrs. Over this period, the probe measures the amount of acid refluxing in the esophagus and the pattern of occurrence throughout the day. The patient reports any symptoms, such as pain, waterbrash, wheezing and coughing, and their timing. Some ambulatory pH monitors have a button for the patient to press when he/she is having symptoms in order to alert the physician reading the study that they were having symptoms at a particular time. This helps the physician to determine if symptoms are related to acid reflux.
Because the use of a nasogastric catheter is awkward and distressing to the patient, a newer catheter-free approach has been developed (the Bravo pH Monitoring System, Medtronic, Minneapolis, MN) that uses a tiny disposable capsule pH monitor that is pinned to the lower esophagus via an endoscopic approach. The capsule transmits pH data to a data logger that is worn on the body. After several days, the disposable capsule is sloughed off the esophagus and passes out of the digestive tract.
An assessment of the evidence supporting catheterless esophageal pH monitoring by the National Institute for Health and Clinical Excellence (NICE, 2006) concluded that “[c]urrent evidence on the safety and efficacy of catheterless oesophageal pH monitoring appears adequate to support the use of this technique provided that normal arrangements are in place for consent, audit and clinical governance.” The assessment noted that catheterless pH monitoring would be particularly appropriate in children and other patients who may not tolerate the nasal intubation required for catheter-based monitoring. The assessment also noted that catheterless pH monitoring may be unsuitable for some patients, for example patients with pacemakers.
Dickman and Fass (2006) stated that "pH testing remains a commonly used evaluative tool in clinical practice. However, the original tool that included a nasally placed pH catheter was plagued with a variety of shortcomings, primarily the effect of the procedure on patients' lifestyle and thus on reflux-provoking activities. The miniaturization of evaluative techniques in gastroenterology was the impetus for the development of the wireless pH capsule and the SmartPill. These modalities improve patients' tolerability of the required test and provide a unique opportunity for expansion of indications and data collection. The introduction of the multi-channel intraluminal impedance with a pH sensor allowed the detection of gastroesophageal reflux (GER) that is non-acidic. However, the value of the technique beyond the realm of academic gastroenterology remains to be elucidated. Recently, there was a renewal of interest in Bilitec 2000. The technique, which has never found a clear clinical role, has been recommended as an important tool in evaluating patients who failed PPI therapy. However, data to support its clinical value in this situation have remained scant".
Wenner et al (2007) evaluated and compared the subjective experience of patients undergoing esophageal pH monitoring by means of the wireless pH capsule method or the conventional catheter-based method. Using a randomized study design, patients referred for esophageal pH testing underwent both wireless and traditional catheter-based 24-hr pH recording with a 7-day interval. The wireless pH capsule was placed during endoscopy and followed by 48-hr pH recording. All patients answered a questionnaire, including a 10-cm visual analog scale (VAS), which described the perceived severity of symptoms and the degree of interference with normal daily activities during the pH tests. A total of 31 patients (16 women and 15 men) were included in the analysis. The severity of all adverse symptoms associated with the wireless technique was significantly lower compared with the catheter-based technique (median VAS 2.1 versus 5.1, p < 0.001). Wireless pH recording was associated with less interference with off-work activities and normal daily life, median VAS 0.6 and 0.7 compared with 5.0 and 5.7, respectively, for the catheter-based technique (p < 0.0001). Patients actively working during both tests reported less interference with normal work during the capsule-based test than during the catheter-based pH test (median VAS 0.3 versus 6.8, p = 0.005). Twenty-seven patients (87 %) stated that, if they had to undergo esophageal pH monitoring again, they preferred the wireless test over the catheter-based pH test (p < 0.0001). The authors concluded that these findings showed that a significant majority of patients undergoing esophageal pH monitoring preferred the wireless pH capsule over the traditional catheter-based technique because of less adverse symptoms and less interference with normal daily life.
Davids and colleagues (2008) stated that laryngo-pharyngeal reflux (LPR) -- GER above the upper esophageal sphincter -- is a common problem encountered by otolaryngologists. Despite consensus guidelines, the presentation, diagnosis, and treatment remain controversial. These researchers surveyed Canadian otolaryngologists to assess current perspectives. Web-based questionnaires were e-mailed to 135 otolaryngologists. Respondents were categorized by subspecialty as head and neck (H&N) or non-H&N (rhinology, otology, laryngology, facial plastics, general and pediatric otolaryngology). Data were analyzed to determine differences in proportions between groups. The response rate was 48 of 135 otolaryngologists. Symptoms considered to be strongly or moderately associated with LPR included globus sensation, excessive throat clearing, sore or burning throat, hoarseness, chronic cough, and dysphonia. The laryngoscopic signs considered strongly associated with LPR were edema, intra-arytenoid changes, and granulomata. The majority of otolaryngologists in both the H&N (12 of 15) and non-H&N groups (27 of 32) use flexible laryngoscopy for investigation and diagnosis of LPR. Proton pump inhibitors in addition to lifestyle modifications are recommended by both groups as 1st- and 2nd-line therapy for an initial course of 6 to 12 weeks, with long-term therapy extended for 4 to 12 months. The authors concluded that Canadian otolaryngologists do correlate specific signs and symptoms with LPR patients. This is consistent across sub-specialties within the field. Flexible fibre-optic laryngoscopy is the preferred diagnostic tool. Although evidence based on randomized controlled trials has yet to demonstrate a reproducible, statistically significant improvement in LPR from treatment, 1st-line pharmacotherapy (in addition to lifestyle changes) is generally provided as a PPI, with the duration of therapy being somewhat variable and less than that recommended by the current literature.
Mel-S (2008) stated that LPR is a a widely recognized disorder in otolaryngological practice. However, the signs and symptoms attributed to this disorder are non-specific and treatment is usually empirical. The author noted that there is still much to learn about the pathophysiological mechanisms of LPR and there is still much controversy on diagnostic as well as therapeutic parameters for this condition. There is no consensus on the diagnosis and treatment of LPR and the majority of clinicians depend mainly on clinical findings and empirical treatments rather than more specific investigations. The author concluded that the concept of LPR is still controversial. The current practice of empirical treatment with PPIs is based on weak evidence. However, this practice seems to be widely accepted and will not change until further clinical and laboratory studies improve the understanding of this condition.
Gupta and Sataloff (2009) shared the same view on LPR as Mel-S (2008). These investigators noted that despite numerous research efforts, the diagnosis and treatment of LPR remain elusive and unproven. Acid-induced changes in laryngo-pharyngeal mucosa have been confirmed by histological evidence. However, the implications of this for laryngeal signs and symptoms are unclear. Diagnosis remains controversial, confounded by a lack of standardization and accepted evidence-based norms. Whereas treatment is generally believed by clinicians to be effective in alleviating signs and symptoms attributed to LPR, incontrovertible data confirming efficacy are scarce. Confounding the issues further, there are numerous studies that purport to show that various widely used treatments are not effective, although the scientific merit of virtually all of these studies has been challenged. The authors concluded that LPR remains a controversial diagnosis. Treatment with PPIs persists despite weak evidence supporting or refuting their utility, and well-designed studies are needed to understand diagnosis, treatment, pathyophysiology, and long-term health consequences of LPR and its treatment.
DiFiore et al (2005) examined the temporal relationship between apnea and gastro-esophageal reflux (GER) and assessed the effect of GER on apnea duration. A total of 119 preterm infants underwent 12-hour cardiorespiratory monitoring studies using respiratory inductance plethysmography, heart rate, oxygen saturation (SaO2), and esophageal pH. The studies were scored for GER (pH less than 4 for greater than or equal to 5 seconds) and apnea greater than or equal to 15 seconds or greater than or equal to 10 seconds that occurred within 30 seconds of GER. Apnea greater than or equal to 10 seconds was used to assess whether GER would prolong apnea duration. There were a total of 6,255 episodes of GER. Only 1 % of GER episodes were associated with apnea greater than or equal to 15 seconds, and there was no difference in apnea rate before, during, or after GER. There was also no difference in rate of apnea greater than or equal to 10 seconds before versus during GER; however, there was a decrease in apnea rate immediately after GER. The presence of GER during apnea did not prolong apnea duration, and GER had no effect on the lowest SaO2 or heart rate during apnea. The authors concluded that there is no evidence of a temporal relationship between acid-based GER and apnea in preterm infants. In addition, GER does not prolong apnea duration and does not exacerbate the resultant decrease in heart rate and SaO2. Moreover, the 2006 summary proceedings from the Apnea Prematurity Group of the National Institutes of Child Health and Human Development (Finer et al, 2006) termed the relationship between apnea of prematurity (AOP) and GERD unsubstantiated.
Slocum et al (2007) stated that GER and AOP are both common occurrences in premature infants. However, a causal relationship between the 2 remains controversial. Strong physiologic evidence indicates that a variety of protective reflex responses may elicit laryngeal adduction and apnea. Although a potential link between GER and apnea may exist through this pathway, clinical studies can be cited to either support or refute such a link in premature infants. The majority of GER episodes do not appear to be related to apnea. In a specific subset of events, a causal relationship may exist. Whether this is related to the character of the reflux episode or to a predisposition in a subpopulation of infants is unclear. The authors presented the evidence for and against an association between GER and apnea, discussed techniques used in their evaluation, and identified approaches for future investigation.
Corvaglia et al (2009) evaluated the relationship between GER detected by combined multi-channel intraluminal impedance-pH measurement and AOP in 26 preterm infants. Although the findings showed that 154 apneas out of 1,136 were triggered by GER (p = 0.034), the authors concluded that further studies are needed to recognize clinical features that identify those patients who are more susceptible to GER-triggered apneas.
The American College of Radiology's Appropriateness Criteria on "Vomiting in infants up to 3 months of age" (Bulas et al, 2011) stated that "The role of imaging in evaluating the vomiting infant is to define whether and where there is a point of anatomic obstruction. Secondarily, one should note whether there is GER or delayed gastric emptying. Diagnostic studies that are complementary to imaging examinations include esophageal pH monitoring, esophageal motility studies, endoscopic evaluation of the esophagus, and multichannel intraluminal impedance".
The AGA's medical position statement on the management of Barrett's esophagus (2011) noted that "The guideline developers recommend against attempts to eliminate esophageal acid exposure (proton pump inhibitors [PPIs] in doses greater than once daily, esophageal pH monitoring to titrate PPI dosing, or antireflux surgery) for the prevention of esophageal adenocarcinoma (strong recommendation, moderate-quality evidence)".