Pain from tender points called trigger points (TrPs) is a common feature of many conditions such as headaches; neck, jaw, shoulder, chest or back pain; and carpal tunnel syndrome. When pressed with just the right amount of pressure, these trigger points reproduce the person’s pain pattern. But how reliable is this test to diagnose trigger points? What’s a trigger point and what isn’t?
That’s the question these researchers from the University of Sydney in Australia posed in this study.
To find the answer, they reviewed the studies published so far. They looked for studies that tested whether the commonly used test of digital palpation is really reliable. In other words, would each examiner using the same test on the same patient get the same results?
The current palpatory test is described as using enough pressure from the examiner’s finger to cause the examiner’s own nail bed to blanch (turn white) when pressure is applied to the patient. The pressure is applied to the patient’s muscle over points known (from previous studies) to be tender.
We don’t have any other way to test for trigger points yet. Other research has been done to find a reliable test that could be used. Some of the techniques tested so far have included muscle biopsy, electromyography (EMG), microdialysis, and various imaging techniques. Palpating trigger points remains the most commonly used method of diagnosis.
Studies collected and reviewed investigated the reliability of physical examination (specifically palpation) to identify trigger points. Journals and textbooks were searched and studies reviewed for quality. In each study accepted for inclusion in this study, trigger points were labeled as active or latent.
Active means the affected person was having pain in a pattern typically associated with that particular trigger point. Latent means the pain was present only after the trigger point was pressed. Only patients reporting painful symptoms can have an active TP. Anyone can have (latent) trigger points without knowing it.
The authors report a variety of problems with the different studies included. Some were deficient in research design. Some did not mention if the examiners were blinded to the findings of other examiners. This could influence the results. For example, higher levels of reliability are reported when examiners aren’t blinded to the results of others. They are more likely to be influenced by the results reported by other examiners.
Some studies used expert examiners. This would not really test the reliability when the average clinician used the test. Most of the studies just reported whether or not the trigger point was present or absent. With all of these differences, comparing and interpreting the results of the studies was impossible.
None of the final studies included in this study focused just on reliability of palpatory testing for active trigger points. The kind of statistics needed to answer the question of how accurate is the standard digital palpation test for trigger points just weren’t available. There were too many loose ends in how the research was done and inconsistent reporting techniques.
Reliability was better in studies that used experts to conduct the testing. That suggests this test (digital palpation) isn’t reliable when applied by the typical practitioner.
The authors of this study take their own findings one step further. They point out that it’s one thing to reliably identify trigger points using palpation. It’s another to agree on the location of where trigger points exist. If examiners can’t agree on the exact location of an active trigger point, can treatment applied to trigger points be effective?
The authors conclude that there isn’t a reliable diagnostic test for trigger points — or at least, no study has reported one. They suggest that anyone identifying trigger points using digital palpation should let their patients know the diagnosis is questionable. Treatment based on the diagnosis may not be successful without an accurate diagnosis with specific treatment for that diagnosis.
And, if measuring trigger points before treatment isn’t reliable, then the test can’t be considered reliable for measuring them after treatment either. Evaluating the effectiveness of treatment using the presence (or elimination) of trigger points (via palpation) may not be acceptable either.
Clearly, there is a need for future studies of high quality that will accurately discern the reliability of tests performed in the diagnosis of trigger points. The authors offer several suggestions for how to create and conduct an optimal study of reliability.