![]() The determination of biological variation is conducted on healthy subjects and is useful to determine how lab tests are interpreted. The important elements are the changes in human physiology within an individual over time, and inherent differences between individuals ( 4). While serum protein electrophoresis analysis has been available for over 50 years, published reports for free light chains began in 2001 ( 3).Īll measured medical parameters exhibit biological variation. ![]() It is more important now than ever before to make early diagnosis of MM and early relapse for patients who have achieved remission or partial remission. Fortunately, highly effective drugs have become available such as lenalidomide, bortezomib, pomalidomide, and daratumumab, the last of which was recently approved by the US Food and Drug Administration for monotherapy and in combination with other agents. ![]() ![]() The life expectancy of untreated patients is 2 to 5 years from diagnosis. The incidence of MM has increased worldwide in the past 30 years and currently stands at 2.1 cases per 100 000 ( 2). He was treated with a combination of daratumumab, pomalidomide, and dexamethasone, which resulted in a second and more complete remission. The patient was diagnosed as having a relapse and was monitored over the next few months. The findings were “progression of osseous metastatic disease in the axial and proximal appendicular skeleton and non-specific hypermetabolic soft tissue nodule in the right hypopharynx.” Despite this result, the serum calcium remained within the reference limit. In April 2018, the patient underwent a whole-body computed tomography/positron emission tomography (CT/PET) scan and the images were compared to February 2017 when the patient was in remission ( Fig. 1, F shows the SPE scan). A further increase was observed in January 2018 (4 months later with an 85% increase over baseline) and a more prominent monoclonal band on SPE ( Fig. 1, E). These values were clinically significant as they exceeded the test’s reference change value (RCV), established by biological variation studies to be 13.4% ( 1). In September, a slightly more prominent SPE band was observed along with a 70% increase in the K/λ ratio relative to 3 months before ( Fig. 1, D). Although there were some individual variances in the individual concentrations, the K/λ ratio was unchanged, therefore these fluctuations reflect normal variances in the day-to-day immune status and were not consistent with recurrence of multiple myeloma (MM). Free kappa and lambda light chain concentrations are shown in Table 1 and were tested using the Freelite assay (Binding Site). Figure 1, A to C (January to June 2017) shows representative SPE densitometric scans during this time of partial remission, showing a very faint band in the gamma globulin region (see arrows). He returned to the hematology–oncology clinic on a monthly or bi-monthly basis for follow-up SPE and free light chain analysis. For the next few years, his condition was stable. The patient was treated with thalidomide and dexamethasone which demonstrated partial remission. CD138 staining revealed numerous large clusters of stain in the focal areas of greater than 90% of cells. A bone marrow biopsy was performed and revealed the presence of 30 to 40% plasma cells. Subsequent immunofixation electrophoresis (IFE, Sebia) showed that the band consisted of monoclonal IgG-kappa antibodies. A 60-year-old male with a history of type 2 diabetes and hypertension, exhibited a 1.93 g/dL monoclonal protein band by serum protein electrophoresis (SPE Hydrasys, Sebia).
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