Subcutaneous Fat Aspirate
Demonstration of amyloid deposits as a practical procedure for the diagnosis of all forms of amyloidosis
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Amyloidosis is a group of disorders characterized by abnormal production and deposition of amyloid fibrils. Deposition distorts normal tissue architecture and impairs organ function.
The early symptoms of amyloidosis are often nonspecific (eg, weakness, fatigue, weight loss, edema, paresthesia). Macroglossia and periorbital edema are highly specific findings but are present in <20% of patients. Patients often present with renal disease, congestive heart failure, sensorimotor peripheral neuropathy, and orthostatic hypotension.
While biopsy of an affected organ (eg, kidney, heart, rectum, sural nerve) is almost always diagnostic, it is usually not necessary. Fat tissue is a common site of amyloid deposition in amyloidosis and is easily obtained by needle aspiration with minimal risk.
See Laboratory Approach to the Diagnosis of Amyloidosis and Laboratory Screening Tests for Suspected Multiple Myeloma in Special Instructions.
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.
Negative (reported as positive or negative)
Fat aspiration (FA) has a reported sensitivity of 72% and a specificity of 99% for amyloidosis.(2) If the degree of clinical suspicion for amyloidosis is high and the FA is negative, further investigation, including biopsy of an affected organ is indicated.
The laboratory will provide an interpretive report.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
At least 3 to 6 particles of fat should be obtained for an adequate analysis.
This test provides a low yield and is therefore not recommended in evaluating patients with isolated peripheral neuropathy who have no other findings suggestive of amyloidosis.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Gertz MA, Rajkumar SV: Primary systemic amyloidosis. Curr Treat Options Oncol 2002 Jun;3(3):261-271
2. Gertz MA, Li CY, Shirahama T, Kyle RA: Utility of subcutaneous fat aspiration for the diagnosis of systemic amyloidosis (immunoglobulin light chain). Arch Intern Med 1988;148:929-933
3. Andrews TR, Colon-Otero G, Calamia KT, et al: Utility of subcutaneous fat aspiration for diagnosing amyloidosis in patients with isolated peripheral neuropathy. Mayo Clin Proc 2002;77:1278-1279