A special brain scan test designed to detect IDH-mutated glioma, a type of brain tumor, is less accurate than previously thought when distinguishing tumors from normal brain tissue. According to Gram Research analysis of 48 patients, the test correctly identified tumors only 62 to 76 percent of the time and normal tissue 78 to 85 percent of the time. The test’s accuracy is reduced because other brain chemicals, particularly GABA, look similar to the tumor marker on the scan, causing false alarms in normal tissue.
Doctors use a special brain imaging test to detect a specific type of brain tumor called IDH-mutated glioma. The test looks for a chemical marker called 2HG that appears in these tumors. However, Gram Research analysis reveals the test isn’t as reliable as previously thought when comparing tumor tissue to normal brain tissue. The problem occurs because other brain chemicals can look similar to 2HG on the scan, leading to false alarms. This research shows doctors need to be more careful when interpreting these results, especially in patients taking special diets.
Key Statistics
A 2026 study of 48 patients found that TE-optimized MRS correctly identified IDH-mutated glioma 62 to 76 percent of the time and correctly identified normal brain tissue 78 to 85 percent of the time, lower than previous research suggested.
Research shows that the brain chemical GABA creates strong negative correlations with 2HG across all spectral modeling strategies, leading to false-positive 2HG detection in normal brain tissue.
A case study documented in this research demonstrated that acetone from a ketogenic diet can interfere with 2HG detection on brain MRI scans, potentially causing misdiagnosis.
The Quick Take
- What they studied: How well a special brain scan test can tell the difference between brain tumors with a specific mutation and normal, healthy brain tissue.
- Who participated: 48 patients who either had been diagnosed with or were suspected of having IDH-mutated glioma, a type of brain tumor.
- Key finding: The test correctly identified tumors 62 to 76 percent of the time and correctly identified normal tissue 78 to 85 percent of the time, which is lower than doctors expected based on previous research.
- What it means for you: If you or a loved one gets this brain scan test, doctors should be cautious about the results and may need to do additional tests to confirm. The test is helpful but not perfect, especially when looking at normal brain tissue.
The Research Details
Researchers studied 48 patients who had or might have a specific type of brain tumor. They used a special MRI machine set to 3 Tesla (a measure of magnetic strength) to scan both the tumor tissue and normal brain tissue from the same patients. The machine was tuned specifically to detect a chemical called 2HG, which appears in these tumors. They used computer software called LCModel to analyze the scan results and figure out how well the test could tell tumors apart from normal tissue.
The researchers looked at how different computer analysis methods affected the results. They tested whether changing how the computer interpreted the data would make the test more or less accurate. They also looked for cases where the test might give false alarms by detecting 2HG in normal tissue when it wasn’t actually there.
This research approach is important because previous studies only compared tumor tissue to other types of tumor tissue. This study is the first to carefully compare tumor tissue to normal, healthy brain tissue from the same patients. This is more realistic because doctors need to know if the test can correctly identify normal tissue as normal, not just if it can tell different types of tumors apart. Understanding these limitations helps doctors use the test more carefully and know when they need additional confirmation.
This study involved a reasonable number of patients (48) and used standardized equipment and analysis methods. However, the study was relatively small, which means results might vary with larger groups. The researchers tested multiple analysis methods, which strengthens their findings. The study was published in a peer-reviewed medical journal, meaning other experts reviewed it before publication.
What the Results Show
The test correctly identified brain tumors 62 to 76 percent of the time, depending on which computer analysis method was used. This means that in about 1 out of 4 to 1 out of 3 cases, the test missed a tumor that was actually there. The test correctly identified normal brain tissue as normal 78 to 85 percent of the time. These numbers are lower than what previous research suggested, which is an important finding.
The researchers discovered that a brain chemical called GABA (gamma-aminobutyric acid) was interfering with the test results. GABA is a normal chemical in the brain, but it looks similar to 2HG on the scan. This similarity caused the computer to sometimes think it was seeing 2HG when it was actually seeing GABA. This problem happened consistently across all the different computer analysis methods tested.
The study also included a striking example of a patient who was following a ketogenic diet, which is a high-fat, low-carbohydrate diet. In this patient, a chemical from the diet called acetone interfered with the 2HG detection. This shows that factors outside the brain, like diet, can affect how accurate the test is.
The researchers tested several different ways to set up the computer analysis, including changing how strict the baseline was and whether to include macromolecules (large molecules in the brain) in the analysis. Interestingly, none of these changes significantly improved the test’s ability to distinguish tumors from normal tissue. This suggests the problem isn’t with how the computer analyzes the data, but rather with the fundamental overlap between 2HG and other brain chemicals.
Previous research suggested this test was very accurate at telling IDH-mutated tumors from other types of tumors, with sensitivity and specificity above 90 percent. However, those studies compared tumor to tumor, not tumor to normal tissue. This new research shows the test performs less well when the comparison is between tumor and normal brain, which is the real-world scenario doctors face. This finding suggests previous estimates of the test’s usefulness may have been too optimistic.
The study included only 48 patients, which is a relatively small group. Results from small studies can vary more than results from larger studies. The study only looked at one type of brain tumor (IDH-mutated glioma) and one type of MRI machine (3 Tesla). Results might be different with other machines or other types of brain lesions. The study didn’t include many patients on special diets, so the interference from diet chemicals might be more common than this study suggests. The researchers couldn’t test all possible factors that might interfere with the test.
The Bottom Line
Doctors should use this test as one tool among several, not as the only way to diagnose IDH-mutated glioma. If the test shows 2HG is present, doctors should confirm the result with other tests like genetic testing or biopsy. Doctors should be aware that normal brain tissue can sometimes appear to have 2HG on this test, leading to false alarms. Patients on special diets, particularly ketogenic diets, should let their doctors know before getting this test. Confidence level: Moderate to High, based on the study’s methodology and findings.
This research matters most for neurologists, neurosurgeons, and radiologists who use this test to diagnose brain tumors. It’s important for patients who have been told they might have IDH-mutated glioma and are considering this test. It’s less relevant for people without brain tumor concerns. Patients on ketogenic diets who need brain imaging should discuss this with their doctors.
The test results are available immediately after the scan, but doctors should wait for confirmation from additional tests before making treatment decisions. Confirmation through genetic testing or biopsy typically takes several days to a few weeks.
Frequently Asked Questions
Can a brain scan test accurately detect IDH-mutated glioma tumors?
The test detects tumors 62 to 76 percent of the time, which is less accurate than doctors previously believed. It can also incorrectly suggest tumors are present in normal tissue 15 to 22 percent of the time, so doctors should confirm results with additional testing.
What causes false results in 2HG brain scans?
A normal brain chemical called GABA looks similar to 2HG on the scan, causing the test to sometimes report false positives. Additionally, chemicals from special diets like the ketogenic diet can interfere with accurate 2HG detection.
Should I get this brain scan test if I suspect a brain tumor?
This test can be helpful as part of your diagnostic workup, but it shouldn’t be your only test. Discuss with your neurologist whether this test makes sense for your situation and what additional tests might confirm the results.
Does diet affect the accuracy of brain tumor scans?
Yes, research shows that special diets like the ketogenic diet can produce chemicals that interfere with 2HG detection. Tell your doctor about any special diets before getting this scan so they can interpret results carefully.
What should I do if my brain scan shows 2HG?
Don’t assume you have a tumor based on this test alone. Work with your doctor to get additional confirmation through genetic testing, biopsy, or other imaging. The test can produce false positives, so multiple tests help ensure accurate diagnosis.
Want to Apply This Research?
- If you’re being monitored for a brain tumor, track the dates of your MRI scans and note any additional tests done to confirm results. Record whether you’re on any special diets or medications that might affect scan interpretation.
- Before getting this brain scan, discuss with your doctor any special diets you’re following, medications you’re taking, or recent changes in your health. Keep detailed records of all your medical imaging and test results in one place for easy reference.
- If you have a diagnosed IDH-mutated glioma, work with your medical team to establish a regular monitoring schedule. Compare results from multiple scans over time rather than relying on a single scan result. Maintain communication with your doctor about any factors that might affect test accuracy.
This article summarizes research about a specialized brain imaging test and should not be used for self-diagnosis. If you have concerns about brain tumors or have been told you need this test, consult with a qualified neurologist or neurosurgeon who can evaluate your individual situation. Brain scan results should always be interpreted by medical professionals in the context of your complete medical history and other diagnostic tests. Do not make medical decisions based solely on this article.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.