PROTEIN PRECIPITATION AS A POSSIBLE IMPORTANT PITFALL IN THE CLINICAL CHEMISTRY ANALYSIS OF BLOOD SAMPLES CONTAINING MONOCLONAL IMMUNOGLOBULINS: 2 CASE REPORTS AND A REVIEW OF THE LITERATURE

AbstractTwo case reports are presented, both illustrating an analytical interference caused by monoclonal immunoglobulins. Falsely low results were obtained in the routine analysis of glucose, CRP and HDL-cholesterol.When analysing samples containing paraproteins, various problems can be encountered in the clinical laboratory: next to the antibody effect, pseudohyponatraemia, hyperviscosity, cryoglobulinaemia and gel formation have to be taken into account. In our two cases the interference was caused by paraprotein precipitation, causing an increased turbidity and an apparent increase of light absorbance at every wavelength due to light scattering, including the wavelengths used in the clinical chemistry assays. We review the literature on this sometimes overlooked interference in photometric/turbidimetric assays. This reaction is based on the insolubility of these proteins in specific physico-chemical circumstances in which many variables are involved, among others: pH and ionic strength, presence of pr...