Test ID: NEFA
Free Fatty Acids, Total, Serum
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Evaluation of metabolic status of persons with endocrinopathies
Detection of pheochromocytoma and of glucagon-, thyrotropin-, and adrenocorticotropin-secreting tumors
Monitoring of control of diabetes mellitus (serum-free glycerol is a very useful companion test in assessing diabetes and may be ordered by special request from Mayo Medical Laboratories). The correlation with insulin resistance and downstream cardiovascular risk may be a useful treatment aid in some patients.
Method Name A short description of the method used to perform the test
Enzymatic Colorimetric
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
FATTY ACIDS, FREE (FFA)
Free Fatty Acids, Serum
NEFA (Nonesterified Fatty Acids)
Non Esterified Fatty Acids
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Fasting-overnight (12-14 hours).
2. Patient must not consume any alcohol for 24 hours before the specimen is drawn.
3. Spin down within 45 minutes of draw.
4. Immediately freeze specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross reject |
| Lipemia | Mild OK; Gross reject |
| Icterus | Mild OK; Gross reject |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Frozen | |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
All but 2% to 5% of serum fatty acids are esterified. The "nonesterified" or "free" fatty acids are protein-bound. The amount of free fatty acids in the serum rises after a fatty meal, but tends to fall after ordinary meals. Levels are elevated in obesity.
Lipoactive hormones such as epinephrine, norepinephrine, glucagon, thyrotropin, and adrenocorticotropin release free fatty acids. Tumors producing such hormones cause release of excessive quantities of free fatty acids. Serum free fatty acids are also increased in patients with uncontrolled type 2 diabetes mellitus and are an indicator of insulin resistance. Free fatty acids are associated with increased reactive oxygen species (ROS), probably mediated by free fatty acid activation of NADPH oxidase. The link between increased ROS and decreased nitric oxide production is a contributor to endothelial dysfunction.
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.
> or =16 years: 0.00-0.72 mmol/L
Reference values have not been established for patients that are <16 years of age.
Interpretation Provides information to assist in interpretation of the test results
Abnormally high levels of free fatty acids are associated with uncontrolled diabetes mellitus and with conditions that involve excessive release of a lipoactive hormone such as epinephrine, norepinephrine, glucagon, thyrotropin, and adrenocorticotropin.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Patient should fast for 12 to 14 hours; however, in prolonged fasting or starvation, free fatty acid levels rise as much as 3-fold.
Patient should abstain from alcohol for at least 24 hours.
In order to eliminate the generation of free fatty acids from triglycerides by serum lipases (causing erroneous elevations), serum should be frozen soon after it is drawn and shipped frozen.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Dole VP: A relation between non-esterified fatty acids in plasma and the metabolism of glucose. J Clin Invest 1956;35:150-154
2. Imrie H, Abbas A, Kearney M: Insulin resistance, lipotoxicity and endothelial dysfunction. Biochim Biophys Acta, 2010 Mar;1801 (3):320-326
Method Description Describes how the test is performed and provides a method-specific reference
Unesterified (free) fatty acids are measured by direct analysis of serum. Serum free fatty acids react with CoA in the presence of ATP, Mg(++), and acyl-CoA synthetase to form thiol esters of CoA. The esters are oxidized by acyl-CoA oxidase to produce hydrogen peroxide, which reacts with a signal compound to produce purple adduct. The free fatty acid concentration is proportional to the absorbance at 550 nm. Ascorbate oxidase is included as a reagent to completely remove any ascorbic acid in the specimen, which would interfere with the oxidative reactions. (Unpublished Mayo method)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 7 a.m.-5 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
82725
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| NEFA | Free Fatty Acids, Total, S | 15066-4 |
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