Application of a dried blood spot based proteomic and genetic assay for diagnosing hereditary angioedema

BACKGROUND: Hereditary angioedema (HAE) with C1‐inhibitor deficiency (C1‐INH‐HAE) is a rare disease caused by low level (type I) or dysfunction (type II) of the C1‐inhibitor protein with subsequent reduction of certain complement protein levels. METHODS: To develop and test the reliability of a two‐tier method based on C1‐INH and C4 quantitation followed by genetic analysis from dried blood spot (DBS) for establishing the diagnosis of C1‐INH‐HAE. C1‐INH and C4 proteins have been quantified in human plasma using a classical immuno‐assay and in DBS using a newly developed proteolytic liquid chromatography–mass spectrometry method. Genetic analysis was carried out as reported previously (PMID: 35386643) and by a targeted next‐generation sequencing panel, multiplex ligation‐dependent probe amplification and in some cases whole genome sequencing. RESULTS: DBS quantification of C1‐INH and C4 showed the same pattern as plasma, offering the possibility of screening patients with AE symptoms either locally or remotely. Genetic analysis from DBS verified each of the previously identified SERPING1 mutations of the tested C1‐INH‐HAE patients and revealed the presence of other rare variations in genes that may be involved in the pathogenesis of AE episodes. CONCLUSIONS: C1‐INH/C4 quantification in DBS can be used for screening of hereditary AE and DNA extracted from dried blood spots is suitable for identifying various types of mutations of the SERPING1 gene.