How Is LPR Diagnosed?
Why Most Tests Miss It —
and What Actually Works
If you've had persistent throat symptoms and been told nothing is wrong, you're not alone. Laryngopharyngeal reflux is notoriously difficult to confirm with standard tests — because those tests were designed for a different condition. This guide compares every available diagnostic method and explains which ones are reliable for LPR.
Why LPR Is So Hard to Confirm
LPR causes a recognisable cluster of throat symptoms — persistent cough, hoarseness, globus sensation, throat clearing — but these symptoms overlap with dozens of other conditions, from post-nasal drip to anxiety. For a full account of the symptoms and what drives them, see our LPR symptoms guide. The problem on this page is different: even when LPR is suspected, confirming it is surprisingly difficult with the tools most clinicians have available.
The core issue is that LPR is not simply "heartburn reaching the throat." Standard reflux tests — pH monitoring, endoscopy, symptom questionnaires — were validated for gastro-oesophageal reflux disease (GERD), which behaves differently. GERD is primarily driven by acid pooling in the oesophagus. LPR is driven by brief, often non-acid reflux events that deposit pepsin — the stomach's digestive enzyme — onto the laryngeal and pharyngeal tissues. This pepsin can be reactivated by dietary acids and continues causing damage even after the reflux event itself has ended.
Because pepsin — not acid — is the primary agent in LPR, tests that measure acid at fixed time points can miss it entirely. This isn't a minor technical footnote: it is the reason thousands of patients are told their tests are normal despite genuine ongoing disease. The mechanism behind this is explained in depth on our pepsin and reflux page — but the diagnostic implication is clear: to reliably confirm LPR, you need a test that detects pepsin directly.
- pH monitoring measures acid — misses non-acid pepsin reflux
- Laryngoscopy shows laryngeal signs but cannot confirm reflux as the cause
- RSI questionnaire scores symptoms — useful for screening, not diagnosis
- Endoscopy misses LPR in most cases — designed for oesophageal disease
- Empirical PPI trial unreliable — PPIs have limited effect on LPR
Diagnosis Methods for LPR — Compared
Each method has a different role, different limitations, and a different level of access. Here is what the evidence shows about each one.
Reflux Symptom Index (RSI) Questionnaire
The RSI is a validated nine-item questionnaire asking patients to score the severity of their throat and voice symptoms. Developed by Belafsky et al. (2002), it was designed as a rapid clinical screening tool — not a diagnostic test. A score of 13 or above is considered consistent with LPR, but the RSI cannot confirm that reflux is actually occurring. It is entirely subjective, easily influenced by other conditions that cause similar symptoms, and produces no biomarker. Studies comparing RSI to objective measures consistently show poor diagnostic accuracy when used alone (Divakaran et al. 2020; Spyridoulias et al. 2015).
Laryngoscopy / Nasendoscopy
Laryngoscopy allows an ENT specialist to visualise the larynx directly and look for signs associated with LPR — redness, swelling of the arytenoids, posterior laryngitis, vocal fold changes. These signs are scored using the Reflux Finding Score (RFS). The problem is that these findings are non-specific: they can be caused by LPR, but also by infection, allergy, vocal overuse, and environmental irritants. The findings show poor inter-rater reliability and cannot confirm reflux as the underlying cause without corroborating evidence. Laryngoscopy is essential for ruling out more serious pathology and contributes to a diagnostic picture — but on its own it is insufficient (Divakaran et al. 2020).
24-Hour pH Monitoring
pH monitoring is often described as the gold standard for GERD diagnosis. A thin catheter is passed through the nose and positioned in the oesophagus or pharynx to record acid exposure over 24 hours. For classic GERD, it performs well. For LPR, its limitations are significant. It measures acid — but many LPR reflux events are weakly acidic or non-acid, particularly after meals when gastric contents have been partially buffered. These events still carry pepsin and cause damage, but they produce no pH signal. Crossfield et al. (2013) demonstrated that pepsin is detectable in patients whose pH monitoring appears normal — showing directly that pH monitoring misses active LPR. The test also requires a hospital visit, tolerating a nasopharyngeal catheter for 24 hours, and specialist interpretation.
MII-pH Impedance Monitoring
Combined multichannel intraluminal impedance and pH monitoring (MII-pH) is a significant improvement over pH monitoring alone. By measuring electrical impedance changes caused by fluid movement in the oesophagus — regardless of acid content — it can detect non-acid reflux events. This makes it substantially better suited to LPR than standard pH monitoring. However, MII-pH is only available at specialist tertiary centres, requires an overnight or 24-hour hospital stay, and involves the same nasopharyngeal catheter as pH monitoring. Waiting times are typically many months. For the vast majority of patients with suspected LPR, it is practically inaccessible without a specialist ENT or gastroenterology referral and even then may involve significant delay. Specialist gut clinics such as the Functional Gut Clinic offer in-clinic LPR investigations for patients who require this level of assessment.
Peptest — Salivary Pepsin Detection
Peptest is a CE-IVD certified diagnostic test that detects pepsin directly in saliva samples. Since pepsin can only be present in the throat if gastric contents have refluxed, its presence is direct biochemical evidence of reflux — regardless of whether that reflux was acidic or not. Three samples are collected at home at clinically relevant time points (morning, after symptoms, after meals), then posted to the RD Biomed laboratory in Hull. Results are returned within 48 hours, with a GP-ready summary letter.
In the largest UK clinical study (Dettmar et al. 2019, n=1,033 across five NHS voice clinics), Peptest demonstrated 100% specificity — every positive result confirmed reflux with zero false positives. A peer-reviewed study published in the Journal of Clinical Medicine found Peptest outperformed both the RSI questionnaire and the Reflux Finding Score for detecting LPR in clinical populations. Read the study →
In NHS clinical practice, Consultant Speech and Language Therapist Jane Shaw at Doncaster and Bassetlaw Hospitals NHS Trust now uses Peptest in place of 24-hour pH monitoring for investigating voice disorders and suspected LPR — citing its non-invasive nature, speed, and diagnostic precision. Read the ENT & Audiology News feature →
Diagnostic Methods Head-to-Head
| Method | What It Detects | Invasive? | Home Use? | Detects Non-Acid Reflux? | Typical Access | LPR Accuracy |
|---|---|---|---|---|---|---|
| RSI Questionnaire | Symptom severity (subjective) | No | Yes | No | Immediate | Poor alone |
| Laryngoscopy | Laryngeal signs (non-specific) | Yes | No | No | ENT referral (weeks–months) | Insufficient alone |
| 24hr pH Monitoring | Oesophageal/pharyngeal acid | Yes | No | No | Specialist referral (months) | Misses non-acid LPR |
| MII-pH Impedance | All reflux events (acid + non-acid) | Yes | No | Yes | Tertiary centre only (months+) | Good, but inaccessible |
| Peptest | Pepsin — direct biochemical evidence | No | Yes | Yes | Order today, results 48hrs | 100% specificity |
The Reflux Symptom Index (RSI)
The Reflux Symptom Index was developed by Belafsky et al. and published in the Journal of Voice (2002). It asks patients to rate nine symptoms on a scale of 0–5 based on how problematic each has been in the last month. A score of 13 or above is considered abnormal and consistent with LPR.
To use the RSI, rate each symptom from 0 (no problem) to 5 (severe problem) and add the scores together:
Important limitation: A high RSI score indicates that your symptoms are consistent with LPR — but it cannot confirm that reflux is actually causing them. These nine symptoms overlap with multiple other conditions. The RSI was designed as a clinical screening tool to support further investigation, not as a standalone diagnosis. Studies comparing RSI to objective measures of reflux (pH monitoring, salivary pepsin) show that many patients with high RSI scores do not have confirmed reflux, while some with confirmed reflux score below 13 (Spyridoulias et al. 2015; Divakaran et al. 2020).
RSI flags the likelihood. Peptest confirms the cause. If your score is 13 or above, a Peptest can tell you definitively whether pepsin — the biochemical marker of reflux — is present in your saliva. A positive result means reflux is occurring. A negative result means your symptoms are unlikely to have a reflux cause and points to investigation of other conditions.
Peptest Accuracy: What the Research Shows
The most important figure for a diagnostic test is specificity — the probability that a positive result is genuinely positive. In the Dettmar et al. 2019 study across five NHS voice clinics (n=1,033), Peptest demonstrated 100% specificity: every patient who tested positive had confirmed reflux. There were zero false positives. This means a positive Peptest result is a highly reliable indicator that reflux is occurring.
Sensitivity — the probability of detecting reflux in all patients who have it — ranges from 73% to 87% across published studies (76% in Dettmar 2019; 87% in Nguyen et al. 2023 in a Vietnamese clinical population). This variation reflects the episodic nature of reflux: if a patient does not reflux during the sampling window, pepsin will not be detectable, even if they reflux regularly at other times. This is why Peptest uses three samples taken at different time points — maximising the chance of capturing a reflux event.
For comparison, a 2024 peer-reviewed study published in the Journal of Clinical Medicine found that Peptest outperformed both the RSI questionnaire and the Reflux Finding Score for detecting LPR in a clinical population. Read the full study summary →
The clinical evidence base is detailed on our clinical studies page, which collates all published Peptest research.
How Peptest Works
The three-sample kit arrives at your door within a few days of ordering. You collect saliva samples in the morning, after symptoms arise, and after a meal, then post them to our ISO 13485:2016 accredited laboratory in Hull. Your written result — including a GP-ready summary letter — is returned within 48 hours of the lab receiving your samples. Full instructions, the science behind the test, and what to expect are covered in detail on our Peptest product page →
Order Peptest £79.95 · Free UK DeliveryWhat a Positive or Negative Result Means
Positive Result — Pepsin Detected
A positive result means pepsin has been detected in your saliva. Since pepsin can only reach the throat via gastric reflux, this is direct biochemical evidence that reflux is occurring. Given Peptest's 100% specificity in the Dettmar 2019 study, a positive result is a highly reliable confirmation.
Your result letter will indicate the pepsin concentration detected. Higher concentrations generally correlate with more frequent or severe reflux activity. Your GP summary letter can be used to support a referral, treatment discussion, or — if you're already being investigated — as objective corroboration of your symptoms.
Negative Result — Pepsin Not Detected
A negative result means pepsin was not detected in your samples at the time of collection. Because reflux is episodic, this does not definitively rule out LPR — it means that a reflux event did not occur during your sampling window. If your symptoms are ongoing and your RSI is high, it may be worth repeating the test at a different time, or taking samples when symptoms are most active.
A negative result is also diagnostically valuable: it indicates your current symptoms are unlikely to have an active reflux cause, which supports investigation of other contributing conditions such as post-nasal drip, vocal cord dysfunction, or chronic laryngitis with a non-reflux origin.
Every Peptest result is accompanied by a written GP letter explaining the test, its clinical basis, and your individual result. This letter is designed to support productive conversations with your GP or specialist — whether you're seeking a referral, discussing treatment options, or providing objective evidence to support your symptoms. No additional cost, no paperwork required on your part.
Frequently Asked Questions
Yes. Peptest detects pepsin — not acid — so taking proton pump inhibitors does not prevent a meaningful result. In fact, this is one of Peptest's key advantages over pH monitoring. PPIs reduce acid production but do not eliminate reflux events or the pepsin they carry. Crossfield et al. (2013) demonstrated that salivary pepsin remains detectable in patients on PPI therapy who have persistent symptoms — confirming that reflux continues despite treatment. A positive Peptest result while on PPIs is strong evidence that your symptoms are reflux-driven, regardless of acid suppression.
Because reflux is episodic, a negative result on a given set of samples does not conclusively rule it out — it means pepsin was not present at the time of collection. If your symptoms are persistent and your RSI score is high, it is worth retesting at a different time or when symptoms are most active. A negative result is also useful diagnostically: it suggests your current symptoms may not have an active reflux cause and supports investigation of alternative explanations. Your GP letter will reflect this and can guide the next steps.
Yes. Peptest was developed by RD Biomed, founded by Professor Peter Dettmar, and has been used in NHS ENT and voice clinics — including the five NHS voice clinic sites in the Dettmar et al. 2019 study (n=1,033). The test is CE-IVD certified as a medical diagnostic device and processed in the same ISO 13485:2016 accredited laboratory in Hull. The home collection kit uses the same validated lateral flow immunoassay format as the clinical version.
Peptest is a CE-IVD certified diagnostic device with a published clinical evidence base, so it is a legitimate medical test that GPs and ENT specialists can act on. The GP letter included with every result explains the test's mechanism and accreditation, summarises your individual result, and provides context for clinical decision-making. Some GPs will be familiar with Peptest already; others may not, but the letter is written to give them everything they need. If you are already under an ENT or gastroenterology specialist, the result and letter can be shared directly to support your ongoing investigation.
Ready to Confirm Your Reflux?
You've seen how the diagnostic options compare. If you suspect LPR, Peptest gives you the clearest answer available at home — direct detection of the reflux marker, with a GP letter included, in 48 hours.
Order Peptest — £79.95 Free UK Delivery · Results in 48hrs · GP Letter IncludedCE-IVD certified · ISO 13485:2016 · UK Laboratory, Hull · No GP referral required
Or call us: +44 (0) 1482 935020