Sample viscosity can be a source of analytical error when discrete sampler-dilutors are used

Area of Science:

• Clinical Chemistry
• Biomedical Engineering
• Laboratory Medicine

Background:

• Hyperviscosity syndrome presents diagnostic challenges due to altered physiological properties.
• Accurate protein quantification is crucial for patient management.
• Automated laboratory analyzers may exhibit performance variations with non-ideal sample matrices.

Purpose of the Study:

• To investigate the discrepancy in total protein measurements for a hyperviscosity syndrome patient.
• To identify the cause of viscosity-dependent errors in the DuPont aca analyzer.
• To propose a method for mitigating these analytical errors.

Main Methods:

• Comparative analysis of total protein concentration using the biuret method on DuPont aca and SMA 12/60 analyzers.
• Evaluation of the impact of sample temperature and aspirated volume on aca measurements.
• Assessment of alternative sampling methods, including manual syringe addition and Micromedic sampler-dilutor.

Main Results:

• The DuPont aca reported significantly lower total protein (80 g/L) compared to the SMA 12/60 (105 g/L) for the patient's serum.
• Viscosity-dependent errors in the aca were confirmed, influenced by sample temperature and volume.
• Error magnitude in the aca was reduced with a Micromedic sampler-dilutor and eliminated by manual syringe addition.

Conclusions:

• Automated sampling systems, particularly the DuPont aca, are susceptible to viscosity-dependent errors in protein assays.
• Sample viscosity significantly impacts the accuracy of automated clinical analyzers.
• Manual syringe addition is recommended for analyzing highly viscous samples (e.g., serum in hyperviscosity syndrome) with the DuPont aca to ensure accurate results.