κ and λ urine free light chains: a new method for quantification.

BACKGROUND: Immunofixation electrophoresis of urinary proteins, coupled with densitometric analysis, is the gold standard method for determining urinary monoclonal free light chains (FLCs), i.e. Bence Jones protein. Recently, immunochemical methods have been developed for Bence Jones protein quantification, but no such method has been widely adopted. This study evaluated a new antibody-based immunoturbidimetry method for urinary FLC quantification, using immunofixation electrophoresis as reference. METHODS: κ and λ FLCs were measured in urine specimens from 95 (training cohort) and 103 (testing cohort) patients by both immunofixation electrophoresis and immunoturbidimetry. RESULTS: There was almost perfect concordance in the training cohort between the new immunoturbidimetry assay and immunofixation electrophoresis and substantial agreement, with Cohen kappa of 0.85 and 0.75, for κ and λ FLC determination, respectively. Results were confirmed in the testing cohort, where Cohen kappa was 0.86 for κ and 0.94 for λ FLCs. The κ FLC assay had 88% sensitivity and 98%-100% specificity; the λ FLC assay had 94% and 96% sensitivity and 91% and 99% specificity in the training and testing cohorts, respectively. CONCLUSIONS: The new immunochemical method has a satisfactory performance and almost perfect agreement with immunofixation electrophoresis and gives the advantage of FLC quantification.

Invisible hemolysis in serum samples interferes in NSE measurement.

INTRODUCTION: The accuracy of serum neuron-specific enolase (NSE) measurements is critical, particularly in neurologic diseases and cancer. NSE measurements are compromised by slight, even invisible, hemolysis, which can produce apparently higher NSE levels, leading to inappropriate clinical decisions. In this article, we describe this issue and propose a solution for avoiding incorrect results. METHODS: Twenty blood samples from donors with NSE values that were within the reference interval were considered. Experimental hemolysis was induced in vitro to examine the relationship between the degree of hemolysis and the increase in serum NSE. The data were then subjected to statistical analysis. RESULTS: There was excellent correlation (r2 0.953) between the degree of hemolysis and the rise in NSE concentration. Each hemolysis unit (equal to 1 mg/dL of free hemoglobin) corresponded to a mean value of 0.29 ± 0.09 ng/mL NSE that was released from red blood cells. CONCLUSION: The hemolysis index must be measured in every sample with no evident hemolysis before assaying it for NSE. Moreover, if the degree of hemolysis is between 5 and 30 units, the increase in NSE (from 1.5 to 9.0 ng/mL) must be calculated, and the laboratory results should be appended with comments that suggest the approximate rise in NSE.

Monitoring Vitamin B12 in Women Treated with Metformin for Primary Prevention of Breast Cancer and Age-Related Chronic Diseases.

Metformin (MET) is currently being used in several trials for cancer prevention or treatment in non-diabetics. However, long-term MET use in diabetics is associated with lower serum levels of total vitamin B12. In a pilot randomized controlled trial of the Mediterranean diet (MedDiet) and MET, whose participants were characterized by different components of metabolic syndrome, we tested the effect of MET on serum levels of B12, holo transcobalamin II (holo-TC-II), and methylmalonic acid (MMA). The study was conducted on 165 women receiving MET or placebo for three years. Results of the study indicate a significant overall reduction in both serum total B12 and holo-TC-II levels according with MET-treatment. In particular, in the MET group 26 of 81 patients and 10 of the 84 placebo-treated subjects had B12 below the normal threshold (<221 pmol/L) at the end of the study. Considering jointly all B12, Holo-TC-II, and MMA, 13 of the 165 subjects (10 MET and 3 placebo-treated) had at least two deficits in the biochemical parameters at the end of the study, without reporting clinical signs. Although our results do not affect whether women remain in the trial, B12 monitoring for MET-treated individuals should be implemented.

Differential diagnosis between bone relapse of breast cancer and lambda light chain multiple myeloma: role of the clinical biochemist.

PURPOSE: The integration of expertise between oncologist and clinical biochemist for the monitoring and diagnosis of plasma cell dyscrasia is crucial. In some cases, medical laboratory scientists can provide an original contribution using the appropriate techniques to arrive at a diagnosis. METHODS: We report a case of 67-year-old woman who was admitted to our hospital for bone pain. Imaging studies showed multiple diffuse bone lytic lesions, and a laboratory screen revealed anemia and altered creatinemia; serum capillary zone electrophoresis confirmed a monoclonal peak in the γ-zone that had been known since 2011, typed as immunoglobulin G kappa by immunosubtraction electrophoresis. The patient had undergone surgery for breast cancer in 2013, and based on her clinical history, the oncologist suspected the presence of bone metastases from the breast cancer and opted for relative therapy. Immunosubtraction, however, showed a very small reduction in lambda free light chains in the beta zone, but it was difficult to establish if was a monoclonal component, and consequently additional tests were performed. DISCUSSION: A monoclonal component composed of only lambda free light chains was evidenced. This result in association with multiple diffuse bone lytic lesions observed led us to suspect multiple myeloma and not bone metastases from the breast cancer. Based on these observations, we encouraged the oncologist to conduct an osteomedullary biopsy, allowing us to make a diagnosis of low-grade stage II lambda light chain multiple myeloma. CONCLUSION: In this report, we show how the expertise of the clinical biochemist was instrumental in solving this case.