Refrigerated storage stability of 11 humoral parameters in two different venous blood collection tubes over a 7-day period.

OBJECTIVES

Humoral parameters like immunoglobulins, complement components, and free light chains (FLC) are vital for diagnosing immune and hematological disorders. To minimize pre-analytical errors and reduce turnaround time, this study evaluated the 7-day stability of 11 analytes (IgG, IgG subclasses 2-4, IgA, IgM, C1 esterase inhibitor, C3c, C4, and FLC Kappa/Lambda) to determine if manual aliquoting can be eliminated in favor of direct primary tube sampling.

METHODS

Blood from 27 healthy volunteers was collected into lithium heparin (LH) and LH-gel separator (LH-GS) tubes. Baseline measurements (Day 1) from aliquoted samples were compared against samples stored at 2-8 °C and re-tested on Days 3 and 7 using the Optilite® analyzer. Stability was defined by the percent difference (%PD) against total error (TEa) limits.

RESULTS

IgG (and subclasses), IgA, IgM, and C4 remained highly stable through Day 7 in both tube types. FLCs (Kappa/Lambda) showed a progressive negative bias but stayed within acceptable limits. Conversely, C3c exhibited significant positive bias, exceeding stability limits by Day 7 (%PD 10.39 in LH); it was only stable up to Day 3. No interference from the gel separator was detected.

CONCLUSIONS

Aliquoting can be safely omitted for most humoral parameters, allowing for direct primary tube sampling and streamlined workflows. While FLCs remain reliable for 7 days, C3c requires a strict 3-day window. Both LH and LH-GS tubes are suitable, supporting laboratory optimization and ISO 15189 compliance while maintaining analytical quality.