Let’s talk about MCAS — Mast Cell Activation Syndrome. The tests we have? Honestly… not that helpful. Most have low sensitivity — meaning they can miss the diagnosis even when it’s really there. Serum tryptase? Often normal in MCAS. Urine prostaglandins, leukotrienes? Only elevated if you test right after a flare and the sample is handled perfectly. Real-world sensitivity? Likely under 50%. Here’s the key: one of the diagnostic criteria for MCAS is improvement with therapy. So if your symptoms i