Interpretation of Results
Freelite is a sensitive, specific marker of kappa and lambda free light chains in serum.
This handy pocket sized guide contains relevant information on Freelite normal ranges and a useful chart to help interpret Freelite results. Also included is the latest information on MGUS risk stratification and the International uniform response criteria.
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Interpretation of serum free light chain results
Freelite results should be considered under the following categories and investigated appropriately.
1. Normal samples. Serum κ, λ and κ/λ ratio are all within the normal ranges. If accompanying serum electrophoretic tests are normal it is most unlikely that the patient has a monoclonal gammopathy.
2. Abnormal κ/λ ratios. Support the diagnosis of a monoclonal gammopathy and require an appropriate tissue biopsy. Borderline elevated κ/λ ratios occur with renal impairment and may require appropriate renal function tests.
3. Low concentrations of κ, λ or both. Indicate bone marrow function impairment.
4. Elevated concentrations of both κ and λ with a normal κ/λ ratio. May be due to the following:
- Renal impairment (common)
- Over-production of polyclonal FLCs from inflammatory conditions (common)
- Biclonal gammopathies of different FLC types (rare)
5. Elevated concentrations of both κ and λ with an abnormal κ/λ ratio.
Suggest a combination of monoclonal gammopathy and renal impairment.
| Sector | Kappa | Lambda | κ/λ Ratio | Interpretation |
|---|---|---|---|---|
| 1 | Normal | Normal | Normal | Normal Serum |
| 2 | Low | Low | Normal | BM suppression without Monoclonal Gammopathy |
| 3 | High | Monoclonal Gammopathy with BM Suppression | ||
| 4 | Low | |||
| 5 | Normal | Normal | Normal Serum with BM Suppression | |
| 6 | Low | Monoclonal Gammopathy with BM Suppression | ||
| 7 | High | Low | ||
| 8 | Normal | Low | High | |
| 9 | Normal | Normal Serum with BM Suppression | ||
| 10 | Normal | High | Monoclonal Gammopathy with BM Suppression | |
| 11 | Low | |||
| 12 | High | Normal | Polyclonal Ig increase or renal impairment | |
| 13 | Low | Monoclonal Gammopathy without BM Suppression | ||
| 14 | High | Low | High | Monoclonal Gammopathy with BM Suppression |
| 15 | Normal | High | Monoclonal Gammopathy without BM Suppression | |
| 16 | Normal | Polyclonal Ig increase or renal impairment | ||
| 17 | High | Normal | ||
| 18 | High | Monoclonal Gammopathy with renal impairment | ||
| 19 | Low | |||
| BM = | Bone marrow | |||
Plot your patient's result using our Kappa/Lambda plotter
Serum reference ranges
The most extensive serum free light chain normal range study has been conducted at The Mayo Clinic, USA, using Binding Site Freelite assays for the BN™II. In this study serum samples from 287 normal subjects aged from 20 to 90 years were assayed for free kappa and free lambda. The results from this trial are shown in the table below.
| Normal Adult Serum | Mean Concentration | Median Concentration | 95 Percentile Range |
|---|---|---|---|
| Free Kappa | 8.36 (mg/L) | 7.30 (mg/L) | 3.30-19.40 (mg/L) |
| Free Lambda | 13.43 (mg/L) | 12.40 (mg/L) | 5.71-26.30 (mg/L) |
| Mean | Median | Total Range | |
| Kappa/Lambda ratio | 0.63 | 0.60 | 0.26-1.65 |
Kappa/Lambda ratio
The combination of individual concentrations of the free light chains and their ratio distinguishes a monoclonal increase from excess polyclonal production and renal dysfunction.
The ratio of kappa to lambda in serum is the opposite of that seen in urine, with kappa being lower than lambda. This is despite the fact that there are approximately twice as many kappa producing plasma cells as lambda producing cells.
The explanation for this is kappa molecules (25kDa), that are normally present in serum as monomers, are filtered through the kidney at approximately three times the rate of the lambda molecules (50kDa) which are present as dimers. So although the production rate of lambda in normal patients is lower than kappa, the serum concentration of lambda is actually higher, due to slower renal clearance. This also explains why, in the urine, the reverse is seen with kappa being present at approximately twice the level of lambda.
- Click here to see what happens to free light chains in the kidney
- Download Literature - Interpretation of Results - Code MKG243
- Download FRENCH Literature - Interpretation of Results - Code MKG282.1E
