A stepwise data interpretation process for renal amyloidosis typing by LMD-MS.

Area of Science:

• Proteomics
• Biomarker Discovery
• Clinical Diagnostics

Background:

• Systemic amyloidosis classification relies on deposited amyloid fibril protein (AFP) for targeted therapy.
• Immunoglobulin light chains are the most common AFP.
• Laser microdissection combined with mass spectrometry (LMD-MS) shows promise for precise amyloidosis typing, but data interpretation remains challenging.

Purpose of the Study:

• To establish a comprehensive data interpretation procedure for LMD-MS-based amyloidosis typing.

Main Methods:

• Analyzed formalin-fixed paraffin-embedded specimens from renal amyloidosis and non-amyloid nephropathies using LMD-MS.
• Trained a data interpretation procedure on 42 specimens and validated it on 50 additional specimens.
• Utilized Area Under Receiver Operating Curve (AUROC) analysis for amyloid accompanying proteins (AAPs) to discriminate amyloidosis from non-amyloid nephropathies.

Main Results:

• Developed a stepwise interpretation procedure achieving 88% accuracy in validation specimens.
• Identified AFP types using P-score, λ-κ variable, and H-score.
• Demonstrated significantly different AAP expression levels between amyloidosis and non-amyloid nephropathies, with averaged AAPs showing a high AUROC of 0.966 for diagnosis.

Conclusions:

• Successfully established a proteomic data interpretation procedure for LMD-MS-based amyloidosis typing.
• The developed procedure demonstrates high practicability for clinical application.
• Amyloid accompanying proteins show potential as alternative diagnostic indicators for amyloidosis.