The diagnosis of laryngopharyngeal reflux (LPR), also known as silent reflux, is a real challenge.
It is not possible to directly measure reflux in the airways. With reflux, I mean the whole mix of stomach acid, half-digested food, and enzymes. You can only measure factors that occur as a result of reflux, such as a change in pH in the throat. There is substantial variability in the results of these indirect measurements, and as a consequence, the precision of reflux testing is not as high as one would desire.
Another problem is that most tests only take a snapshot, whereas reflux is a dynamic and ongoing process. Two measurements at different time points can deliver different results. Even if the analysis takes place over 24 hours, the severity of the reflux can vary from day to day, for instance, due to different eating behaviors. Other factors, such as stress, can also influence reflux.
A single negative test is not sufficient to rule out silent reflux.
LPR Tests
The following tests are commonly used for the diagnosis of silent reflux:
1. Manometry
The esophagus transports swallowed food into the stomach with the help of wave-like movements. In the same way, the esophagus can also move reflux back from the stomach. These movements are called peristalsis, which can be measured by manometry. Manometry also measures the pressure with which the sphincters (valves at the upper and lower ends of the esophagus) keep the stomach closed.
The biggest downside of this method is that it only takes a snapshot. Many patients with reflux do not have sphincters that are too weak, but rather, they open too frequently. It is not possible to observe this phenomenon in a single measurement, and for this reason, manometry often gives normal results in people with LPR.
2. 24-hour pH monitoring
pH monitoring assesses the pH in the throat. The pH is a measure of acidity. pH monitoring is a standard procedure for detecting acidic reflux in the esophagus, but it is also used to assess the pH in the throat, which is relevant for LPR.
In silent reflux, though, the damage is not caused by acid but by pepsin.[1] Pepsin is an enzyme from the stomach that reaches the throat and airways by being carried in the reflux. Some people have weakly acidic reflux. This might lead to a negative test result, and patients are told they do not have LPR. However, their reflux might still contain enough pepsin to cause LPR symptoms. For this reason, this test is not always correct in LPR patients.[2]
It is essential to use a pH-monitoring device that is specialized for silent reflux. The measurement of liquid reflux in the esophagus has no value for LPR diagnosis. It cannot tell whether the reflux is reaching the airways. Most people with positive LPR test results have a perfectly fine esophagus. The most well-known test that measures airway reflux is called “Restech”. However, there are other manufacturers as well. There is some disagreement in the medical community which manufacturer makes the most accurate pH-probes.
Despite its limitation, I and many physicians I talked to consider pH-monitoring the best test for LPR. However, only if the monitoring is done in the throat, not just the esophagus.
3. Laryngoscopy
Laryngoscopy is a method of inspecting the larynx, or voice box, visually. Silent reflux can cause redness, swelling, and mucous obstructions, all of which can be seen in a laryngoscopy.
The problem is that other conditions, such as allergies, can cause very similar signs. Furthermore, the judgment as to whether the larynx looks abnormal is very subjective and requires a lot of experience with the disease. Most physicians, including ENTs, do not have that skill. The same patients might be diagnosed as normal by one physician, while another might diagnose severe LPR. How physicians diagnose LPR based on visual symptoms varies wildly. For this reason, laryngoscopy is not a reliable method for the diagnosis of LPR.[3]
However, laryngoscopy is suitable for ruling out other causes of the symptoms.
4. Gastroscopy
Gastroscopy is a method of visualizing the esophagus, the stomach, and optionally the upper part of the gut. It is a standard diagnostic method for reflux and other digestive diseases. In silent reflux, however, the stomach and esophagus usually look normal.[4] A gastroscopy, though, can also detect a hernia, which is the cause of reflux in a small number of patients or can at least aggravate it.
5. Gastric emptying scan
A gastric emptying scan is rarely performed because it is quite expensive.
The scan gives information about how long it takes the stomach to empty itself after a meal. It can be useful in certain subsets of patients who also have symptoms of poor gastric motility and delayed gastric emptying.
6. Barium swallow test
This test is also performed rarely. It visualizes the swallowing process with the help of X-rays. It’s useful if a patient has swallowing problems.
7. Test for detecting pepsin in the saliva
There are relatively new tests that can detect pepsin in the saliva. In theory, they can directly measure the main factor that causes silent reflux symptoms.
Unfortunately, these tests are not very accurate and not yet well accepted among physicians. Another problem is that they only take a snapshot. LPR is a dynamic process, and a single saliva sample is not enough to give an accurate picture of the scale of the condition. At the same time, a negative test does not mean that reflux does not occur at a different time of the day.[5]
However, I think if those tests become more accurate with further development, they could prove interesting. Simply because they are easy, fast, not invasive and relatively cheap.
8. Electrogastrography (EGG)
An EGG can assess the activity of stomach muscles, which can give crucial clues about the cause of gastric motility problems. It is usually used together with a gastric emptying scan that detects gastroparesis or delayed gastric emptying. Such problems of gastric motility are often connected to reflux.[6],[7]
An EGG works in a similar way to an electrocardiogram (ECG), which measures the activity of the heart muscle. The difference is that the electrodes are attached to the belly instead of the chest.[8]
While the technology behind the EGG is old, using it to diagnose reflux and problems with gastric motility is a more recent development. There are currently not that many physicians yet who perform the EGG. However, the number is growing.
Symptoms are crucial for the diagnosis of LPR.
One single test to clearly diagnose LPR does not exist. The most specialized test is Restech pH monitoring. However, pH testing can only show if there is reflux, not why. Other tests help secure the diagnosis and narrow down what causes the reflux.
Symptoms give essential clues and should always be taken into consideration. With a detailed assessment of the symptoms, the likelihood of silent reflux can be estimated. The reflux symptom index (RSI) for LPR helps you to find out whether your symptoms point towards LPR.[9]
Symptoms should also be monitored over some time to see what factors influence them. This takes a lot of time, which doctors usually don’t have. For this reason, the diagnosis of silent reflux requires being proactive. When symptoms last for a long time and other causes can be excluded, LPR is a likely cause.
References
[1] Johnston N, Dettmar PW, Bishwokarma B, Lively MO, Koufman JA. Activity/stability of human pepsin: implications for reflux attributed laryngeal disease. Laryngoscope. 2007;117(6):1036-9.
[2] Maldhure S, Chandrasekharan R, Dutta AK, Chacko A, Kurien M. Role of PH Monitoring in Laryngopharyngeal Reflux Patients with Voice Disorders. Iran J Otorhinolaryngol. 2016;28(89):377–383.
[3] Campagnolo AM, Priston J, Thoen RH, Medeiros T, Assunção AR. Laryngopharyngeal reflux: diagnosis, treatment, and latest research. Int Arch Otorhinolaryngol. 2014;18(2):184–191.
[4] Vaezi MF. New tests for the evaluation of laryngopharyngeal reflux. Gastroenterol Hepatol (N Y). 2013;9(2):115–117.
[5] Sifrim D. The Role of Salivary Pepsin in the Diagnosis of Reflux. Gastroenterol Hepatol (N Y). 2015;11(6):417–419.
[6] Yin J, Chen JD. Electrogastrography: methodology, validation and applications. J Neurogastroenterol Motil. 2013;19(1):5–17.
[7] Chen CL, Lin HH, Huang LC, Huang SC, Liu TT. Electrogastrography differentiates reflux disease with or without dyspeptic symptoms. Dig Dis Sci. 2004 May;49(5):715-9.
[8] McCallum RW, Soykan I. What is the value of electrogastrography in reflux disease? OESO foundation. Mai 1998. Accessed on Oct 11, 2019.
[9] Belafsky PC, Postma GN, Koufman JA. Validity and reliability of the reflux symptom index (RSI). J Voice. 2002;16(2):274-7.