INTRODUCTION: Although 4 mast cell mediators can be routinely measured, the 
results of initial testing to evaluate symptoms of mast cell activation have not 
been widely reported.
OBJECTIVE: We examined the results of mast cell mediator tests used to assess 
patients with mast cell activation symptoms during a 5-year time span.
METHODS: After excluding patients with alternative diagnoses, records of 108 
patients were reviewed for initial mediator test results. Mediators included 
serum tryptase plus urinary N-methyl histamine (N-MH), leukotriene (LT)E4, and 
11β-prostaglandin (PG) F2α or 2,3-dinor-11β-PGF2α (BPG).
RESULTS: Most commonly, either a single measured elevation of 1 mediator (48.1%) 
or elevations of 2 (33.3%) mediators was found at baseline, during symptoms or 
at both time points. Elevated levels of a single mediator in order of frequency 
were: BPG > tryptase > LTE4 > N-MH, and for two mediators: BPG + tryptase (n = 
16 cases) > BPG + LTE4 (n = 9) > BPG + N-MH (n = 6). Elevations in 3 mediators 
(n = 8) or 4 mediators (n = 2) were much less frequent. Monoclonal mast cell 
activation syndrome (n = 6), and systemic and cutaneous mastocytosis (n = 4) 
were also infrequent. Baseline plus symptom-associated tryptase values were 
obtained in only 7 patients.
CONCLUSIONS: This survey suggests that elevations of 1 or 2 mediators are the 
most common (total 81.4% of cases) findings from initial tests for mast cell 
activation. Elevated levels of BPG were most commonly found both singly and in 
combination with other mediators, followed by the finding of elevated levels of 
tryptase. Baseline plus symptom-associated tryptase levels were measured in only 
a minority of patients.