Reflux Testing Study: 24-Hour pH Results in 710 Patients

1. Introduction

Frequently diagnosed on the basis of symptoms alone, gastro-oesophageal reflux disease (GORD) is often treated before any objective testing is considered. Heartburn, regurgitation, throat irritation, and chronic cough are commonly attributed to reflux, often without physiological confirmation. Acid suppression therapy, such as proton pump inhibitors (PPIs), can therefore be prescribed before formal testing is considered.

The difficulty is that symptom-based diagnosis lacks specificity (extra-oesophageal presentations are particularly non-specific). Even when patients are referred for investigation, a normal endoscopy does not exclude pathological acid exposure. As a result, clinicians frequently encounter patients who continue to experience upper GI, ENT, or respiratory symptoms despite treatment, with limited clarity regarding the underlying mechanism.

Objective reflux testing is often regarded primarily as a tool to confirm a suspected diagnosis. Traditional medical training emphasises history and examination as the diagnostic foundation, with testing used as an adjunct to verify the diagnosis. Yet exclusion of a diagnosis can be equally valuable. Demonstrating the absence of pathological reflux prevents unnecessary treatment or escalation, redirecting investigation towards alternative mechanisms such as motility disorders, hypersensitivity, or functional disease.

To better understand the real-world diagnostic value of reflux testing, The Functional Gut Clinic performed an internal analysis of testing data across six UK sites between October 2025 and January 2026. This multi-site dataset provides an opportunity to examine how often reflux testing confirms pathological acid exposure, how often it does not, and how results vary across different referral settings. Together, it offers a clinically grounded evaluation of how reflux testing performs — not only as a confirmatory tool, but as a means of ruling out GORD.

2. Methods and Definitions

This study is a retrospective analysis of consecutive reflux studies conducted across six UK clinic sites between October 2025 and January 2026. The dataset includes patients referred via both NHS and private pathways. All patients underwent 24-hour oesophageal pH monitoring. [Needs to be confirmed – author note.]

Importantly, all studies were performed off acid suppression therapy (e.g., proton pump inhibitors) to provide a clearer reflection of baseline reflux physiology. For patients taking PPIs, an appropriate washout period was required prior to testing.

Acid exposure time (AET) was classified according to the Lyon Consensus criteria:

·Pathological acid exposure time (AET) >6%

·Borderline AET 4–6%

·Normal <4%

The borderline category represents a clinically indeterminate group in whom interpretation and onward management require careful physiological correlation. This cohort was included in the analysis to reflect the full diagnostic spectrum encountered in practice.

3. Overall Findings: The Big Picture

Across all six sites, 710 patients underwent 24-hour pH testing without acid suppression between October 2025 and January 2026. When analysed collectively, the results demonstrate a clear pattern in diagnostic yield.

Pathological acid exposure (AET >6%) was identified in approximately one-quarter of patients (~24.1%). A further 10.1% fell within the borderline range (AET 4–6%), representing a clinically indeterminate group. The remaining two-thirds (~65.8%) did not meet the threshold for pathological reflux.

A pathological reflux rate of one in four confirms that objective reflux testing meaningfully identifies acid-mediated disease in patients presenting with reflux-type symptoms. However, the larger proportion of negative results highlights an equally important reality: the diagnostic yield for exclusion exceeds that for confirmation.

4. Site Variation: What Differences Reveal About Referral Patterns

Across the six sites, all patients underwent the same testing protocol and were assessed off acid suppression. However, patient intake pathways were not controlled. One notable pattern emerges from the data: variation between private clinics and NHS referral centres.

London and Manchester received private patients exclusively. A smaller proportion of patients from these sites met criteria for pathological acid exposure (~16–17%), with negative rates exceeding 70%. Private referral pathways may reduce pre-test probability by bypassing secondary care triage.

In contrast, higher pathological rates were observed in Cambridge (31.6%) and Rugby NHS (34.3%). NHS referrals are more commonly initiated by GPs or hospital consultants, which may serve as a clinical filtering mechanism, leading to a higher pre-test probability of true reflux. That said, this pattern is not uniform. Edinburgh and Northampton NHS demonstrated rates closer to those seen in the private clinics. Indeed, Northampton NHS recorded the lowest positive rate in the cohort (15.2%).

5. The Clinical Significance of Negative Results

5.1 Why “Normal” Is Not a Failed Test

In clinical practice, confirmatory test results often carry greater psychological weight than negative findings. A positive result provides diagnostic certainty and a defined management pathway. By contrast, a normal result can feel inconclusive or even disappointing. Yet a normal result is not a failed test.

In this six-site analysis, nearly two-thirds of patients (65.8%) demonstrated normal acid exposure. This finding underscores the clinical value of confidently excluding pathological reflux. While confirmation may seem more immediately actionable, exclusion prevents inappropriate escalation — including prolonged or high-dose PPI therapy, referral for anti-reflux surgery, or consideration of invasive anti-reflux procedures in patients who have not responded to medical treatment.

5.2 Redirecting Management

Diagnosis in gastroenterology is rarely linear. Instead, it progresses through stages of clinical reasoning, where each test result informs subsequent decision-making. A negative reflux study removes one branch of the differential diagnosis, redirecting management toward alternative explanations.

Depending on the symptom profile, this may include oesophageal motility disorders, reflux hypersensitivity, functional heartburn, or non-oesophageal causes within the ENT or respiratory domains. Rather than proceeding with further acid suppression, additional physiological assessment can be considered. Oesophageal manometry, for example, can assess oesophageal contractility and exclude primary motility disorders. Such investigations are often not pursued until after prolonged PPI therapy unless objective reflux testing has clarified the underlying physiology.

Moreover, where reflux testing is integrated within broader physiological services, onward investigations can be coordinated efficiently. From the patient’s perspective, this provides a more coherent diagnostic pathway, streamlining progression toward a definitive explanation of symptoms.

6. The Borderline Group: The Most Nuanced Cohort

A positive reflux test result provides a clear pathway to treatment. Even a negative test rules out a differential diagnosis, guiding a physician toward further investigation. But a borderline result — which occurred in 10.1% of patients overall — is clinically indeterminate.

Defined as an AET between 4–6% by the Lyon Consensus, the borderline category represents a grey zone between normal physiology and confirmed acid reflux. There is no definitive treatment pathway for these patients.

Additional parameters beyond AET are often useful. Impedance-pH monitoring offers genuine advantages, measuring both acid and non-acid reflux. Physicians may consider the total number of reflux episodes, the pH of the refluxate, and the proximal extent of reflux. Together, these metrics can provide further information to support a reflux diagnosis, suggest reflux hypersensitivity, or favour a non-reflux explanation if the overall reflux burden is low.

A symptom button also adds value. Symptom Association Probability (SAP) assesses whether symptoms recorded during monitoring are temporally associated with reflux episodes. High AET with positive SAP indicates pathological reflux; normal AET with positive SAP suggests reflux hypersensitivity; normal AET with negative SAP points toward functional heartburn.

Whether management proceeds to further testing, a monitored trial of PPIs, or alternative treatment depends on the physician’s expertise and clinical judgement.

7. Why Testing Off PPIs Matters

Objective acid testing should not be performed while a patient is taking acid suppression therapy. Proton pump inhibitors reduce gastric acid production and can mask pathological acid exposure. Testing on PPIs may confirm whether reflux events are occurring, but it cannot reliably determine whether pathological acid reflux is present.

Off-therapy testing provides a cleaner diagnostic classification and allows meaningful symptom correlation using the event marker. Because all sites adhered to an “off PPI” protocol, results were generated under consistent physiological conditions, allowing valid comparison across centres. This methodological consistency strengthens the dataset as a whole.

8. Implications for Healthcare Professionals

The results of this analysis have important implications for healthcare professionals involved in the management of reflux-related symptoms. They re-emphasise the importance of objective diagnostic testing, demonstrate the value of a negative result, and encourage a more structured approach to determining whether acid reflux is truly present.

General practitioners (GPs) are often the first to prescribe PPIs or other acid-suppressing therapy when patients report reflux-type symptoms. However, as the data demonstrate, a substantial proportion of patients presenting with such symptoms were found to be negative for pathological reflux. While referral for endoscopy may exclude structural pathology, it does not define underlying reflux physiology. Objective reflux testing — and, where appropriate, oesophageal manometry — provides greater clarity regarding the mechanism of symptoms.

For gastroenterologists and upper GI surgeons, reflux testing offers an objective physiological basis for intervention. It reduces the risk of operating on functional disease and supports more confident decision-making before escalation to invasive treatment.

For ENT and respiratory physicians, the findings reinforce that LPR-type or extra-oesophageal symptoms are not uniformly acid-mediated. Objective reflux testing, therefore, has significant value in excluding reflux as a driver of symptoms and in informing whether patients should remain within specialty care or be appropriately redirected.

9. Limitations and Context

While this dataset represents a relatively large real-world cohort, it reflects a referral population rather than the general population. Many patients had already been assessed by GPs or specialists prior to undergoing reflux testing, which may have influenced the pre-test probability. There were also differences in sample size between sites, with Edinburgh contributing a smaller cohort (n=21). In addition, the analysis did not include formal symptom-correlation data; therefore, it is not possible to directly assess how pathological acid exposure relates to individual symptomatic experience.

10. Conclusion

The Functional Gut Clinic analysed reflux testing data from six UK sites, involving 710 patients. The findings demonstrate that the majority of patients tested did not have pathological reflux. Importantly, however, a negative result retains clear diagnostic utility. Excluding reflux removes a key differential diagnosis and redirects investigation toward alternative underlying mechanisms.

Objective testing provides physiological clarity in cases where empirical PPI therapy is often initiated before formal assessment. Even borderline cases, though diagnostically indeterminate, may benefit from further evaluation using impedance-pH monitoring to support more precise classification. Exclusion, therefore, can be as clinically valuable as confirmation.

The Functional Gut Clinic provides specialist reflux diagnostics across London, Manchester, Cambridge, and NHS sites, including Edinburgh, Rugby, and Northampton. In addition to reflux testing, oesophageal manometry and other motility investigations are available, supporting an integrated, clinician-led pathway for patients with both reflux and non-reflux gastro-oesophageal conditions.