Doctors may be misdiagnosing rare mast cell disorders in patients with declining kidney function, according to new research showing that chronic kidney disease (CKD) itself raises tryptase levels in the blood. A study from the Mayo Clinic Enterprise found that as kidney disease progresses, tryptase levels climb significantly, potentially triggering unnecessary and invasive diagnostic workups for conditions like systemic mastocytosis (SM) or hereditary alpha tryptasemia (HAT) that patients don't actually have.

What Are Tryptase Levels and Why Do They Matter?

Tryptase is an enzyme released by mast cells, immune system cells that play a role in allergic reactions and inflammation. Doctors measure serum baseline tryptase (sBT) in the blood to help diagnose mast cell disorders. However, the Mayo Clinic study of 120 nephrology patients revealed that tryptase levels rise predictably as kidney function declines, independent of any mast cell disease.

The researchers tracked tryptase levels across CKD stages and found a clear pattern. In stage 1 CKD (mild disease), median tryptase measured 4.2 nanograms per milliliter. By stage 4 (severe disease), it jumped to 10.7 ng/mL. Even in stage 5 (end-stage kidney disease), where most patients were undergoing hemodialysis, levels remained elevated at 6.8 ng/mL.

How Does Kidney Disease Affect Tryptase Levels?

The exact mechanism isn't fully understood, but researchers believe that as kidney function declines, the kidneys become less able to clear tryptase from the bloodstream. The statistical analysis confirmed a strong link between worsening kidney function and higher tryptase levels, with over 95% certainty that the relationship was real and not due to chance.

The findings echo results from a Spanish study that also documented significantly higher tryptase in patients with stage 4 and 5 CKD and those on hemodialysis compared with those in earlier disease stages.

Why This Matters for Patient Care

The clinical implications are significant. When a patient with declining kidney function shows an elevated tryptase level, doctors may launch extensive diagnostic testing for mast cell disorders, including bone marrow biopsies, genetic testing, and specialized imaging. These procedures are invasive, costly, and emotionally taxing. The new research suggests many of these workups may be unnecessary.

"By incorporating renal function into tryptase interpretation, unnecessary diagnostic evaluations for conditions like systemic mastocytosis or hereditary alpha tryptasemia may be avoided in patients with chronic kidney disease," the study authors wrote.

Study Authors, Mayo Clinic Enterprise

Steps to Improve Tryptase Interpretation in Kidney Disease

• Check kidney function first: Clinicians should obtain an estimated glomerular filtration rate (eGFR) test at the same time as tryptase measurement to assess kidney function and interpret results in context.
• Consider CKD as an explanation: Before launching a mast cell disorder workup, doctors should weigh whether declining kidney function alone could explain the elevated tryptase rather than assuming a rare disease is present.
• Develop kidney-specific reference ranges: Researchers are calling for larger, multi-institution studies to establish CKD-specific tryptase reference ranges or develop eGFR-based adjustment models that account for kidney function.

The study authors acknowledged several limitations, including small sample sizes in certain CKD stages and the retrospective design of the research. They called for larger, prospective studies involving multiple institutions to clarify the relationship between renal function and tryptase levels and to establish clearer clinical guidelines.

For patients with CKD, the takeaway is straightforward: if you have an elevated tryptase result, ask your doctor whether your kidney function was considered in the interpretation. A simple conversation about your eGFR could prevent unnecessary testing and worry.