Doctors use blood tests to check for parathyroid gland problems, but different laboratories use different testing methods that can give confusing results. This study found that when doctors use age-specific reference ranges (normal values that change based on how old you are) instead of one-size-fits-all ranges, they get much more accurate and consistent diagnoses. The research shows that using the right comparison numbers for each person’s age and test type helps doctors avoid misdiagnosing a condition called normocalcaemic primary hyperparathyroidism, where the parathyroid gland is overactive but calcium levels appear normal.

The Quick Take

  • What they studied: Whether using age-adjusted normal ranges for parathyroid hormone blood tests gives more accurate and consistent results across different laboratory testing methods
  • Who participated: 46 people who had been identified as having a parathyroid problem (normocalcaemic primary hyperparathyroidism) using one type of blood test, tested with two different laboratory methods
  • Key finding: When doctors used age-specific normal ranges instead of standard ranges, agreement between the two different test methods improved dramatically—from only 35% agreement to 67% agreement on who actually had the condition
  • What it means for you: If you’re being tested for parathyroid problems, make sure your doctor uses age-adjusted normal ranges and ideally uses the same test method for follow-up appointments. This helps avoid false diagnoses and ensures you get the right treatment.

The Research Details

Researchers took blood samples from 46 people who had been diagnosed with a parathyroid problem using one laboratory’s test method (Abbott). They then tested the same blood samples using a different laboratory’s method (Roche). They compared how many people were diagnosed with the condition using each method with standard normal ranges, then repeated the comparison using age-specific normal ranges that account for the fact that parathyroid hormone levels naturally increase as people get older.

The key innovation was recognizing that parathyroid hormone levels change with age, independent of other factors like vitamin D levels or kidney function. The researchers applied newly developed age-specific reference ranges to see if this improved consistency between the two different test methods.

This approach is important because it addresses a real-world problem: different laboratories use different equipment and methods, which can lead to different results for the same person’s blood sample.

Blood test results are only useful if doctors know what ’normal’ means. Currently, each laboratory provides its own ’normal range’ based on their specific equipment and methods. This study shows that these ranges don’t account for age differences, leading to inconsistent diagnoses when the same person is tested by different laboratories. Using age-specific ranges makes the tests more reliable and helps doctors make better decisions about who actually needs treatment.

This is a focused research study that directly addresses a practical clinical problem. The sample size of 46 people is relatively small, which means results should be viewed as promising but needing confirmation in larger studies. The study’s strength is that it uses real patient samples tested by two major laboratory methods, making the findings relevant to actual medical practice. The research was published in a peer-reviewed medical journal, indicating it met scientific standards for publication.

What the Results Show

Using the standard normal ranges provided by each laboratory, the two test methods disagreed significantly. Of 46 people identified as having a parathyroid problem by the Abbott test, only 16 people (35%) were also identified as having the problem by the Roche test. This means 30 people (65%) got different results depending on which test method was used—a major problem for diagnosis and treatment decisions.

When the researchers applied age-specific normal ranges instead, the agreement between methods improved dramatically. Now 31 people (67%) had consistent results showing normal parathyroid hormone levels, 8 people (17%) had consistent results showing the parathyroid problem, and only 7 people (15%) still had disagreement between methods.

This shift is significant because it means that using age-adjusted ranges reduced the number of people incorrectly diagnosed with the parathyroid condition from 30 down to 7. In other words, many people who appeared to have a problem using standard ranges actually had normal results when age was taken into account.

The research confirms that parathyroid hormone naturally increases with age, independent of other factors that doctors typically check like vitamin D levels, kidney function, or calcium levels. This finding supports the need for age-specific normal ranges rather than single ranges that apply to everyone. The study also demonstrates that the two major laboratory methods (Abbott and Roche) can now be compared more fairly when using method-specific and age-specific ranges.

Previous research has noted that different laboratory methods give different results for parathyroid hormone tests, but this study is among the first to systematically show how much age-specific reference ranges improve consistency. The findings align with growing recognition in medical science that ’normal’ values often need to be adjusted for age, similar to how blood pressure and cholesterol targets differ by age group.

The study included only 46 people, which is a relatively small number. Results would be more convincing with a larger group. The research only compared two laboratory methods (Abbott and Roche), so results may not apply to other testing methods. The study didn’t follow people over time to see if using age-specific ranges actually led to better health outcomes—it only looked at whether diagnoses were more consistent. Additionally, the study didn’t include information about how different age groups were represented in the original reference interval studies, which could affect the results.

The Bottom Line

If you’re being tested for parathyroid problems, ask your doctor to use age-specific reference ranges when interpreting your results (moderate confidence level). For follow-up testing, request that the same laboratory method be used for consistency (high confidence level). If you’ve been diagnosed with normocalcaemic primary hyperparathyroidism, discuss with your doctor whether your diagnosis should be reconsidered using age-adjusted ranges (moderate confidence level).

This research is most relevant to people being evaluated for parathyroid disorders, particularly those with normal calcium levels but elevated parathyroid hormone. It’s also important for doctors, laboratory professionals, and healthcare systems that need to standardize how they interpret parathyroid hormone tests. People with symptoms like bone pain, kidney stones, or muscle weakness who are being tested for parathyroid problems should especially be aware of this information.

If your diagnosis changes based on using age-specific ranges, you should see clarification within one test cycle (usually a few weeks). If you’re being treated for a parathyroid problem, switching to age-adjusted ranges might mean you need to reconsider your treatment plan, which could take several weeks to months to fully adjust.

Want to Apply This Research?

  • Track parathyroid hormone levels at each test with the date, age at time of test, laboratory method used (Abbott, Roche, or other), and the reference range provided by that laboratory. This creates a clear record of whether results are consistent across tests.
  • When scheduling parathyroid hormone tests, note which laboratory method was used for previous tests and request the same method for follow-up testing. Ask your healthcare provider to confirm they’re using age-specific reference ranges when interpreting your results.
  • Maintain a log of all parathyroid hormone test results including the specific laboratory method, your age at the time of testing, and the reference range used. Compare results over time using the same method and age-adjusted ranges. If you switch laboratories, discuss with your doctor how to interpret the new results in context of your previous tests.

This research discusses how parathyroid hormone tests should be interpreted, but it does not provide medical advice. If you have been diagnosed with or are being evaluated for a parathyroid disorder, discuss these findings with your healthcare provider. Do not change any treatment based on this information without consulting your doctor. The diagnosis and management of parathyroid conditions requires professional medical evaluation and should not be based solely on this research summary. If you have symptoms like bone pain, kidney stones, muscle weakness, or fatigue, seek evaluation from a qualified healthcare professional.