Effects of specimen evaporation on quality control

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Analytical Science

Background:

• Serum sample integrity is vital for accurate diagnostic testing.
• Improper storage conditions can lead to significant alterations in analyte concentrations.
• External quality control (EQC) samples require consistent handling to ensure reliable performance monitoring.

Purpose of the Study:

• To investigate the impact of different storage conditions on serum sample weight and analyte concentrations over a four-hour period.
• To identify optimal storage methods that minimize sample degradation and maintain analyte stability.
• To highlight the importance of consistent sample handling for EQC pools.

Main Methods:

• Serum samples were subjected to various storage conditions including ambient air exposure, refrigeration (4°C), and different covering methods (sample tray cover, airtight cover) for four hours.
• Mean weight and mean concentration values for multiple analytes were measured and compared.
• A parallel study confirmed findings by assessing sample weight changes post-storage.

Main Results:

• Several storage methods resulted in analyte values deviating more than 2 standard deviations from the mean.
• A decrease in sample weight was observed after the four-hour storage period across various conditions.
• Storage at 4°C in sample cups with an airtight opaque shield effectively mitigated weight loss and concentration alterations.

Conclusions:

• Serum sample storage conditions significantly affect analyte stability and accuracy.
• Refrigerated storage (4°C) combined with an airtight opaque shield is recommended for maintaining serum sample integrity over short periods.
• Consistent and identical treatment of EQC samples compared to patient samples is essential to prevent erroneous out-of-control results.