IgM in body fluid
Reference interval
- see IgM in serum
Principle
The Beckman Array Protein System, in conjunction with the IgM Reagent Test Kit, is intended for in vitro diagnostic quantitation of IgM of biological fluids by rate nephelometry.
As the central component of the Array System, the rate nephelometer measures the intensity of light as it is scattered by particles in suspension in a semi-disposable flow cell when a beam of light is passed through the cell. The particles are formed by the immunoprecipitin reaction that occurs when a specific antibody is brought into contact with the specific antigen. The resulting formation of complexes & the consequent change in the intensity of scattered light occurs at a rate that increases gradually at 1st, then rapidly, & finally proceeds through a peak rate of change (peak rate value) for the component being analyzed.
For Beckman specific protein test kits, the analyzer electronics system derives the peak value for the rate-of-change from the scattered light signal, converts that value into concentration units, presents the result on the CRT (TEST IN PROCESS INFORMATION Screen), & transmits it to the printer.
Clinical significance
- see IgM in serum
Specimen
200 uL of serum, CSF or urine. Store sample in freezer until ready for assay. Highly lipemic samples may result in inaccurate determination & should be redrawn on a fasting patient. Plasma is not recommended.
Antigen Excess
When running IgG, IgA, IgM, Kappa, Lambda, Haptoglobin or CSF Albumin it is sometimes possible to encounter specimens (for example, monoclonal proteins) which contain protein concentrations high enough to be in excess of the antibody in the reaction cell. In these cases, an antigen excess situation would lead to falsely low results if not detected. For this reason the Array antigen excess check monitors the kinetic reactions of these samples to ascertain if the potential for this condition of antigen excess exists. If the monitoring detects this potential situation, the system will make a third injection of antigen excess solution to verify whether free antibody remains in the reaction cell or not. If this third injection causes further reaction, free antibody is available and the result is reported. However, if the third injection does not trigger further reaction, the sample will be reassayed at a higher dilution.