During an anaphylactic reaction or other reaction leading to clinical symptoms caused by mast cell degranulation, serum total tryptase concentrations usually increase substantially above baseline. Chronic mast cell activation is more difficult to diagnose because in some of these patients the tryptase levels are constantly elevated and may point to an occult form of mastocytosis. The most widely used approach to determine tryptase levels is by immunoassay. Here we introduce a novel, high throughput automated platform that utilizes magnetic microparticles in combination with fluorescence and chemiluminescence signals to quantify tryptase present in human serum. We demonstrate the analytical and clinical performance of the new chemiluminescent microparticle immunoassay for detection of total tryptase levels in this study.

The precision and functional sensitivity of the tryptase chemiluminescent microparticle immunoassay were evaluated in accordance with CLSI EP05-A3. Limit of Blank (LoB) and Limit of Detection (LoD) were estimated in accordance with CLSI EP17-A2. Assay linearity was assessed in accordance with CLSI I/LA20-A3. Cross reactivity of potential endogenous and exogenous interferences was evaluated in accordance with CLSI EP07-A2. Method comparison against a commercially available tryptase assay was performed in accordance with CLSI EP09-A3 and CLSI EP24-A2.

The chemiluminescent microparticle immunoassay analyzer produced overall repeatability of <8% CV and within-lab precision of <10% CV for the tryptase assay. Functional sensitivity was determined to be excellent with LoB and LoD of < 1 µg/L across multiple instruments and reagent lots.  The performance of the assay exhibited good linearity across the reportable range of 1 to 200 µg/L. No significant reactivity was observed for cross reactive, endogenous, and exogenous potentially interfering substances. The system also generated acceptable correlation when compared to a commercially available tryptase assay on over 100 human serum samples.

The tryptase assay on the chemiluminescent microparticle immunoassay analyzer exhibited strong analytical and clinical performance for the determination of tryptase level in human serum samples.