Amyloid Protein Identification, Fat Aspirate, LC MS/MS
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Amyloidosis is a group of hereditary and acquired diseases that are unified by extracellular tissue deposition of misfolded proteins resulting in end organ damage. Amyloidosis can be a systemic or localized disease. Although many cases of amyloidosis are hereditary, most are acquired as the result of an underlying monoclonal B cell/plasma cell malignancy, as a phenomenon of aging, or as the result of long-standing chronic inflammation. Specific amyloid-related diseases are therefore associated with specific amyloid proteins. These include kappa or lambda immunoglobulin light chains (AL amyloid), transthyretin (ATTR amyloid), serum amyloid A (SAA amyloid) and other uncommon subtypes. Because treatment of amyloidosis patients differs radically for the different amyloid subtypes, it is critically important to accurately identify the proteins that constitute the amyloid deposits.
Regardless of the subtype, many patients with amyloidosis have deposits that involve the subcutaneous fat. Consequently, needle aspiration of fat is a simple method that is well tolerated by patients to obtain a specimen for the potential diagnosis of amyloidosis. In the typical situation a patient who is suspected of having amyloidosis is subjected to fine-needle aspiration of their abdominal subcutaneous fat. A portion of the specimen is smeared on slides and stained with Congo red stain, which, if positive, indicates that amyloid deposits are present. If they are, the remainder of the specimen can be analyzed by this mass spectrometry method to determine the identity of the specific amyloid protein.
Definitive identification of amyloid proteins
An interpretative report will be provided.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
No significant cautionary statements
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Theis JD, Dasari S, Vrana JA, et al: Shotgun-proteomics-based clinical testing for diagnosis and classification of amyloidosis. J Mass Spectrom 2013;48(10):1067-1077
2. Dogan A: Chapter 21: Classification of amyloidosis by mass spectrometry-based proteomics. In Amyloid and Related Disorders: Surgical Pathology and Clinical Correlations. Edited by MM Picken, A Dogan, GA Herrera. First edition. New York, Springer Science, 2012, pp 261-272
3. Vrana JA, Gamez JD, Madden BJ, et al: Classification of amyloidosis by laser microdissection and mass spectrometry-based proteomics analysis in clinical biopsy specimens. Blood 2009;114(24):4957-4959
4. Picken MM: New insights into systemic amyloidosis: the importance of diagnosis of specific type. Curr Opin Nephrol Hypertens 2007;16:196-203