Comparative Analysis of Four Matrix Dilution Methods for Eliminating IgM Paraprotein Interference in Prealbumin and Uric Acid Assays: Based on Two Case Reports.

BACKGROUND

IgM paraproteins frequently cause spurious results in biochemical assays; however, standardized strategies to eliminate such interference remain limited. This study systematically compares four dilution matrices to identify effective methods for correcting IgM-mediated interference in prealbumin (PA) and uric acid (UA) measurements.

METHODS

Two cases of IgM-type monoclonal gammopathy (IgM-κ: 5.37 g/L; IgM-λ: 25.8 g/L) presenting with spurious PA and UA results were investigated. Four interference-mitigation strategies were evaluated: dilution with deionized water, 0.9% saline, 18% hypertonic saline, and prealbumin reagent 1 containing polyethylene glycol (PEG). Analytical performance was assessed using recovery rates, result stability across dilution factors, and reaction curve analysis.

RESULTS

For PA measurement, dilution with prealbumin reagent 1 (2-fold) or deionized water (3-fold) effectively eliminated IgM interference, restoring results to clinically plausible concentrations with recovery rates of 101.4% and 99.5% in control samples. For UA measurement, optimal correction was achieved using 18% hypertonic saline (2-fold) or deionized water (3-fold), yielding recovery rates of 101.6% and 102.8%, respectively. Higher dilution factors resulted in reduced analytical reliability in IgM-positive samples but not in controls.

CONCLUSIONS

Effective elimination of IgM paraprotein interference requires assay-specific pretreatment strategies. PEG-based dilution is optimal for PA immunoturbidimetric assays, while osmotic modulation with hypertonic saline is most effective for UA measurement. Deionized water dilution provides a practical, broadly applicable alternative. These simple protocols are suitable for routine clinical laboratory implementation.