New simple and quick method to analyze serum variant transthyretins: direct MALDI method for the screening of hereditary transthyretin amyloidosis

Abstract

Background Hereditary transthyretin amyloidosis (ATTRv amyloidosis) is caused by a variant transthyretin (TTR), which is a serum protein secreted by the liver. Mass spectrometry (MS) is a useful tool that can detect variant TTRs in serum samples from patients with ATTRv amyloidosis. We previously reported several mass spectrometric methods to detect variant TTRs in serum samples. Those methods require cumbersome immunoprecipitation with anti-TTR antibodies and significant time to analyze the variant TTRs. In our study here, we developed a new simple and quick method to detect variant TTRs in serum samples by means of matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) MS without immunoprecipitation (direct MALDI). Methods By using direct MALDI, we analyzed 288 serum samples obtained from patients who were clinically suspected having amyloidosis to investigate the usefulness of this direct MALDI method to detect variant TTRs in serum samples. Results The method completed the process within 30 min. We successfully identified variant TTRs in serum samples from patients, except for a few patients with TTR Glu61Lys and Glu89Gln mutations because of the small mass shift of those variant TTRs from wild-type TTR. We also found that the mass shifts of variant TTRs measured by direct MALDI corresponded to theoretical mass changes. Conclusion Our results suggest that the direct MALDI method is useful for the screening of ATTRv amyloidosis.

Use of biomarkers to diagnose and manage cardiac amyloidosis

“…This method has been tested for 15 types of TTR mutations with a 91% specificity. 44 The possibility of replacing genetic analyses with these methods to diagnose ATTRv remains to be established.…”

“…Recently, a novel MALDI‐TOF approach has been developed, which does not require a sample pre‐purification phase and can provide results within 30 min. This method has been tested for 15 types of TTR mutations with a 91% specificity 44 . The possibility of replacing genetic analyses with these methods to diagnose ATTRv remains to be established.…”

Current approaches to the diagnosis and management of amyloidosis

“…Sanger sequencing of the target amyloidogenic gene(s) remains the gold standard method to diagnose carrier status, although the diagnosis may be made using next‐generation sequencing gene panels 72 and mass spectrometric detection of variant amyloidogenic proteins in serum or tissue biopsy samples 73 …”

“…Sanger sequencing of the target amyloidogenic gene(s) remains the gold standard method to diagnose carrier status, although the diagnosis may be made using nextgeneration sequencing gene panels 72 and mass spectrometric detection of variant amyloidogenic proteins in serum or tissue biopsy samples. 73 Given the rarity of these disorders, diagnosis and management of hereditary amyloidosis is best conducted or overseen by expert centres. Guidelines have been developed for the diagnosis of ATTRv amyloidosis as well as for monitoring asymptomatic TTR variant carriers.…”