Investigating Systemic Mastocytosis

METHOD

1. Collect a sample of urine shortly after an attack for urinary methyl histamine, which will be excreted in the following hour. A spot urine is adequate.
2. Also collect a clotted sample of blood for serum tryptase.
3. Collect a further sample of urine and blood 24h later to serve as a baseline for comparison.
   - Thus two samples of serum and two samples of urine should be sent together for assay of urinary methyl histamine and serum tryptase to Chemical Pathology on a white miscellaneous form.

INTERPRETATION

Normal methyl histamine: 5-20 ng/ml.
Typical patient with systemic mastocytosis: >100 ng/ml
Typical patient following beesting: >2000 ng/ml
Normal plasma tryptase <1