Test Catalog

Test Id : KCSFP

Immunoglobulin Kappa Free Light Chain, Spinal Fluid

Useful For
Suggests clinical disorders or settings where the test may be helpful

Diagnosis of multiple sclerosis and other demyelinating conditions

Method Name
A short description of the method used to perform the test

Only orderable as part of a profile. For more information see MSP3 / Multiple Sclerosis (MS) Profile, Serum and Spinal Fluid.



NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Kappa Free Light Chain, CSF

Lists additional common names for a test, as an aid in searching

Cerebrospinal fluid Free Light Chain

Free Light Chain, cerebrospinal fluid

Free Light Chain, spinal fluid

Multiple Sclerosis (MS)

Oligoclonal Banding

Spinal fluid Free Light Chain

Specimen Type
Describes the specimen type validated for testing


Ordering Guidance

For evaluation of multiple sclerosis, the following are available:

-SFIG / Cerebrospinal Fluid (CSF) IgG Index Profile, Serum and Spinal Fluid

-OLIG / Oligoclonal Banding, Serum and Spinal Fluid

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Only orderable as part of a profile. For more information see MSP3 / Multiple Sclerosis (MS) Profile, Serum and Spinal Fluid.


Specimen Type: Spinal fluid

Container/Tube: Sterile vial

Specimen Volume: 1 mL

Collection Instructions: Label specimen as spinal fluid.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross icterus OK

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
CSF Frozen (preferred) 28 days
Refrigerated 72 hours
Ambient 24 hours

Useful For
Suggests clinical disorders or settings where the test may be helpful

Diagnosis of multiple sclerosis and other demyelinating conditions

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system (CNS). The clinical diagnosis of MS is centered on each individual patient, while applying diagnostic guidelines. Immunoglobulin free light chain (FLC) presence in cerebrospinal fluid (CSF) is an alternative for diagnosis of MS using nephelometry. Light chains are produced in excess during antibody formation and secreted from the plasma cells or plasma blasts. Quantitative FLC assays use antisera directed against epitopes that are exposed only when the light chains are free (unbound to heavy chain) in solution. FLC immunoassays can be used to specifically quantitate FLC even in the presence of large concentrations of polyclonal immunoglobulins.


Routine use of isoelectric focusing electrophoresis coupled with IgG-specific immunoblotting (IgG-IEF) identifies immunoglobulins specific to the CNS. This method is part of the diagnostic criteria used in cases of MS, ie, oligoclonal banding (OLIG). However, OLIG / Oligoclonal Banding, Serum and Spinal Fluid is a labor-intensive technique that includes subjective interpretation of IgG bands from paired CSF and serum.


This test, when considered positive at a concentration greater than or equal to 0.1000 mg/dL as a medical decision point, has a sensitivity of 70% with a specificity of 87%, which is comparable in terms of sensitivity and specificity to oligoclonal banding. The differences between this FLC test and the OLIG analysis are not statistically significant.


The MSP3 panel combines the ease of use and interpretation of the quantitative measurement of kappa free light chains in CSF and allies it to the traditional interpretation of oligoclonal bands for optimized efficiency in laboratory testing for demyelinating diseases and improved test utilization.

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.

Only orderable as part of a profile. For more information see MSP3 / Multiple Sclerosis (MS) Profile, Serum and Spinal Fluid.


Medical decision point: 0.1000 mg/dL

Provides information to assist in interpretation of the test results

When result is greater than or equal to 0.1000 mg/dL, the kappa free light chain concentration measured in cerebrospinal fluid (CSF) is at or greater than the threshold associated with demyelinating disease. This is a positive result. These findings, however, are not specific for multiple sclerosis (MS) because CSF-specific immunoglobulin synthesis may also be detected in patients with other neurologic diseases (infectious, inflammatory, cerebrovascular, autoimmune, and paraneoplastic). Clinical correlation is recommended. Automatic reflexing to oligoclonal bands will occur.


When result is less than 0.0600 mg/dL, the kappa free light chain concentration measured in CSF is lower than the threshold associated with demyelinating disease. This is a negative result. Testing for oligoclonal banding is not performed. Clinical correlation is recommended.


When result is from 0.0600 to 0.0999 mg/dL, the kappa free light chain concentration measured in CSF is slightly elevated but not above the medical decision point of 0.1000 mg/dL associated with demyelinating disease. This is a borderline result. Reflexing to oligoclonal bands will be automatically performed and clinical correlation is recommended.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

No significant cautionary statements

Supportive Data

The McDonald revised criteria states that diagnosis of demyelinating disease can be assumed when 2 unique bands are found in cerebrospinal fluid (CSF) using the oligoclonal banding (OLIG) test.(1)


Based on a published Mayo Clinic study with 325 subjects, this test alone demonstrates comparable performance to OLIG along with increased sensitivity for demyelinating diseases.(2) Replacing an OLIG test with this test would alleviate the need for serum and CSF IgG and albumin, and calculated conversions.


After this initial study, a second larger cohort was used to validate kappa free light chain (FLC) results with a larger number of samples.(3) This study found that in comparison to the current standards of detecting 2 unique CSF bands, kappa FLC results at a value greater than or equal to 0.1000 mg/dL showed comparable sensitivity and specificity to OLIG to support diagnosis of MS. Kappa FLC offers a standardized quantitative measure with a single CSF sample without the need of paired serum, with comparable sensitivity and specificity.


Using MSP3 and the reflex approach, Mayo Clinic studies with over 1300 subjects report 75.5% sensitivity and 86% specificity to identify demyelinating disease from non-demyelinating disease.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Thompson AJ, Banwell BL, Barkhof F, et al: Diagnosis of multiple sclerosis: 2017 revisions of the McDonald criteria. Lancet Neurol. 2018 Feb;17(2):162-173

2. Gurtner KM, Shosha E, Bryant SC, et al: CSF free light chain identification of demyelinating disease: comparison with oligoclonal banding and other CSF indexes. Clin Chem Lab Med. 2018;56:1071-1080

3. Saadeh R, Pittock S, Bryant S, et al: CSF kappa Free Light Chains as a Potential Quantitative Alternative to Oligoclonal Bands in Multiple Sclerosis. American Academy of Neurology Annual Meeting. Philadelphia, PA. 2019

4. Fortini AS, Sanders EL, Weinshenker BG, Katzmann JA: Cerebrospinal fluid oligoclonal bands in the diagnosis of multiple sclerosis. Isoelectric focusing with IgG immunoblotting compared with high-resolution agarose gel electrophoresis and cerebrospinal fluid IgG index. Am J Clin Pathol. 2003;120:672-675

5. Awad A, Hemmer B, Hartung HP, Kieseier B, Bennett JL, Stuve O: Analyses of cerebrospinal fluid in the diagnosis and monitoring of multiple sclerosis. J Neuroimmunol. 2010;219:1-7

6. Hassan-Smith G, Durant L, Tsentemeidou A, et al: High sensitivity and specificity of elevated cerebrospinal fluid kappa free light chains in suspected multiple sclerosis. J Neuroimmunol. 2014;276:175-179

7. Presslauer S, Milosavljevic D, Brucke T, Bayer P, Huebl W: Elevated levels of kappa free light chains in CSF support the diagnosis of multiple sclerosis. J Neurol. 2008;255:1508-1514

8. Presslauer S, Milosavljevic D, Huebl W, et al: Validation of kappa free light chains as a diagnostic biomarker in multiple sclerosis and clinically isolated syndrome: A multicenter study. Mult Scler. 2016;22(4):502-510

9. Presslauer S, Milosavljevic D, Huebl W, Parigger S, Schneider-Koch G, Bruecke T: Kappa free light chains: Diagnostic and prognostic relevance in MS and CIS. PLoS ONE. 2014;9(2):e89945

10. Makshakov G, Nazarov V, Kochetova O, Surkova E, Lapin S, Evdoshenko E: Diagnostic and prognostic value of the cerebrospinal fluid concentration of immunoglobulin free light chains in clinically isolated syndrome with conversion to multiple sclerosis. PLoS One. 2015;10(11):e0143375

Method Description
Describes how the test is performed and provides a method-specific reference

In this nephelometric method, the light scattered onto the antigen-antibody complexes is measured. The intensity of the measured scattered light is proportional to the amount of antigen-antibody complexes in the sample under certain conditions.


Antigen-antibody complexes are formed when a sample containing antigen and the corresponding antiserum are put into a cuvette. A light beam is generated with a light emitting diode (LED), which is transmitted through the cuvette. The light is scattered onto the immuno-complexes that are present. An antigen-antibody complex is formed in the final measurement.


The result is calculated by subtracting the value of the final measurement from the initial measurement. The distribution of intensity of the scattered light depends on the ratio of the particle size of the antigen-antibody complexes to the radiated wavelength.(Instruction manual: Siemens Nephelometer II. Siemens, Inc; Version 2.3, 2008; Addendum to the Instruction Manual 2.3, 08/2017)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

3 to 5 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

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  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

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 instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

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 Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
KCSFP Kappa Free Light Chain, CSF 48774-4
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
KCSFP Kappa Free Light Chain, CSF 48774-4

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports