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Free κ and λ Light Chains Plus Ratio, Quantitative, Urine
- Free Light Chains, Quantitative, Urine
- Kappa Free Light Chains, Quantitative, Urine
- Kappa:Lambda Free Light Chains Ratio, Quantitative, Urine
- Kappa:Lambda Free Light Chains, Quantitative, Urine
- Lambda Free Light Chains, Quantitative, Urine
- Light Chains, Free κ and λ, Quantitative, Urine
• Free κ light chains: 1.35−24.19 mg/L
• Free λ free light chains: 0.24−6.66 mg/L
• κ:λ free light chain ratio: 2.04:10.37
Immunoglobulin molecules consist of two identical heavy chains (α, δ, ε, γ, or μ) which define the immunoglobulin class and two identical light chains (κ or λ). Each light chain is covalently linked to a heavy chain and the two heavy chains are linked covalently at the hinge region. In healthy individuals, the majority of light chains in serum exists in this form, bound to heavy chain; however, low levels of free light chain (FLC) are found in serum of normal individuals due to the overproduction and secretion of FLC by the plasma cells. While the molecular weight of both light chains is approximately 22.5 kilodaltons, in serum, κ free light chain (κ-FLC) exists primarily as a monomer and λ free light chain (λ-FLC) as a covalently-linked dimer with a molecular weight of approximately 45 kilodaltons. This will lead to a differential glomerular filtration rate for κ-FLC and λ-FLC and may explain the observed ratio of κ-FLC to λ-FLC of 0.625 in serum compared to the ratio of bound κ to λ of 2.0.
The laboratory will perform FLC analysis on urine, but a serum sample is preferred for many reasons. Analogous to glucose metabolism, FLC spill into the urine only after the tubular reabsorptive capacity is exceeded. Thus, the serum FLC ratio has been shown to be abnormal in patients with monoclonal gammopathy despite normal urine FLC ratios or normal urine immunofixation. Serum tests are also more sensitive for the detection of residual monoclonal FLC after treatment and for the early detection of monoclonal FLC after relapse in patients with monoclonal gammopathy.
FLC levels in urine are normally low. In a healthy kidney, the tubular cells selectively reabsorb all FLC so their presence in urine is probably due to secretion into the urinary tract.
The appearance of higher levels of polyclonal FLC in urine may be indicative of kidney or autoimmune disease. An abnormal urine FLC ratio may be indicative of malignant lymphoproliferative disease such as multiple myeloma. The monoclonal urinary FLC associated with lymphoid malignancy is called a Bence-Jones protein.
Urine (random or 24-hour)
Ship the specimen as soon as possible.
Causes for Rejection
Values obtained with different assay methods should not be used interchangeably in serial testing. It is recommended that only one assay method be used consistently to monitor each patient's course of therapy. This procedure does not provide serial monitoring; it is intended for one-time use only. If serial monitoring is required, please use the serial monitoring number 121243 to order.
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|121228||Free K+L Lt Chains,Qn,Ur||121229||Free Kappa Lt Chains,Ur||mg/L||27365-6|
|121228||Free K+L Lt Chains,Qn,Ur||121230||Free Lambda Lt Chains,Ur||mg/L||27394-6|
|121228||Free K+L Lt Chains,Qn,Ur||121231||Kappa/Lambda Ratio,U||33559-6|