The Clinical Value Of Serum Free Light Chain Measurement In Multiple Myeloma

Multiple myeloma (MM) is the second most common form of haematological malignancy after non-Hodgkin lymphoma. The age-adjusted annual incidence is about 2.5~7.2 per 100,000. In our country the annual incidence is about 1 per 100,000. The malignant proliferation of B lymphocytes occurs in the MM patients and a mass of free light chains (FLCs) are discharged from the plasma cells to the serum. When the excessive FLCs overwhelm the proximal tubules'absorption mechanisms, they will be secreted form the kidney with the urine, which is called Ben Jones protein (BJP). The diagnosis of MM always depends on the clinical manifestation, monoclonal immunoglobulins in serum or urine, FLC in the urine and the presence of excess monoclonal plasma cells in the bone marrow, but all the methods can not detect all the MM patients, especially for the light chain multiple myeloma(LCMM) and nonsecretory multiple myeloma(NSMM). The evaluation of the efficiency often depends on the IFE, SPE, the urine FLCs and the bone marrow biopsy, but most of them are qualitative detection, they can not detect quantitatively, therefore, they can not reflect the efficiency of chemotherapy timely, accurately and quantitatively. But the half time of the FLC in the serum (2-6 hours) is shorter than the immunoglobulins(2-21 days) significantly, so the detection of the FLCs can see the response to the treatment in real time. When the immunoglobulin become normal in the serum, the sFLC may be abnormal all the same, indicates that the sFLC can detect the residual disease more sensitively. The new guidelines for the diagnose and management of the MM and AL amyloidosis include the use of sFLC measurements.This study trys to detect the sFLC of the healthy people in our country by using the immuno-nephelometric assay in order to establish the normal referance of the sFLC and explore the clinical significance in the diagnosis and response monitoring of MM.Method: to detect the sFLC of 403 healthy people who took physical examination in our hospital using the immuno-nephelometric assay and then establish the normal reference of the sFLC, Choose 26 patients who had been treated in our cancer center and explore the clinical significance of sFLC in the diagnosis and response monitoring of MM.Result: the normal reference intervals of Chinese healthy people in our region are as bellows:κFLC :5.81-24.04mg/L(95% range),λFLC:6.72-22.81 mg/L(95% range),ratio of FLC(rFLC): 0.59-1.46(95% range), the level of sFLC and rFLC has no relationship with the sex, but with the age. The sFLC levels are all abnormal in all the 26 patients. The ratio of sFLC abnormality is 100%. In 23 patients who have been diagnosed MM, we find that the positive rate of sFLC(100%) is significantly higher than the traditional methods(for the serum immnofixation electrophoresis(IFE), the positive rate is 91.3%, for urine FLC is 90%, and for SPE is only 55%, for immunoglobulin test is 54.5%). The sFLC levels of 7 LCMM patients are all abnormal, and 6 of them have abnormal uFLC, 5 of them have positive IFE, but only one of them has positive SPE. Compared with SPE, IFE Ig and uFLC, the sFLC measurement can detect the chemotherapy response more rapidly and accurately.Conclusion: 1. the normal reference intervals of Chinese healthy people in our region are as bellows:κFLC :5.81-24.04mg/L,λFLC:6.72-22.81 mg/L,ratio of FLC(rFLC): 0.59-1.46, the level of sFLC and Rflc has no relationship with the sex, but with the age. 2. In the diagnosis of MM, the sensitivity of sFLC is the same as IFE and uFLC, but better than SPE, 3. The sFLC measurement is very important for the LCMM. 4. The FLC measurement is very important for response monitoring of MM.