Isotonic hyponatremia Isotonic hyponatremia Isotonic hyponatremia is a form of hyponatremia with mOsm measured between 280 and 295. It can be associated with pseudohyponatremia, or with isotonic infusion of glucose or mannitol. Certain conditions, such as extraordinarily high blood levels of lipid (hyperlipidemia/hypertriglyceridemia) or protein (hyperparaproteinemia), magnify the electrolyte exclusion effect. This interferes with the measurement of serum sodium concentration by certain methods, leading to an erroneously low "measurement" of sodium, or pseudohyponatremia. The methods affected are the flame-photometric and indirect (but not direct) ion-selective electrode assays. This is distinct from a true dilutional hyponatremia that can be caused by an osmotic
Serum free light-chain measurement Serum free light-chain measurement Immunoglobulin light chains that are circulating in serum in a free (unbound) state are called free light chains (FLCs). Measurement of the serum level of FLCs became practical as a clinical blood test in recent decades. These tests are used as an aid in the diagnosis and monitoring of multiple myeloma and related disorders. There are two types of immunoglobulin light chain produced in humans, designated by the Greek letters kappa (κ) and lambda (λ). Comparing the ratio of κ FLCs to λ FLCs in a person's serum against reference ranges indicates whether that person may