Artifacts in plasma volume changes due to hematology analyzer-derived hematocrit.

Area of Science:

• Sports Medicine
• Clinical Chemistry
• Biotechnology

Background:

• Hematocrit (Hct) is a key indicator of red blood cell concentration.
• Plasma osmolality can influence Hct measurements and subsequent plasma volume calculations.
• Accurate Hct and plasma volume data are crucial for athlete monitoring, including the World Anti-Doping Agency (WADA) Athlete Biological Passport (ABP).

Purpose of the Study:

• To quantify the impact of altered plasma osmolality on Hct measurements.
• To assess the implications of these Hct changes for plasma volume calculations.
• To evaluate the relevance of these findings for WADA's ABP.

Main Methods:

• Two studies involving male volunteers were conducted.
• Study 1: Blood samples had their osmolality altered in vitro using saline solutions.
• Study 2: Plasma osmolality was manipulated in vivo through prolonged exercise; Hct was measured manually and via an automated hematology analyzer (AHA).

Main Results:

• Increasing sample osmolality significantly decreased spun packed cell volume (manual Hct) but not AHA Hct.
• A 10 mOsm·kg change in plasma osmolality resulted in a 0.8 Hct unit and 1.6% plasma volume difference.
• Exercise-induced hyperosmolality showed discrepancies between manual and AHA Hct, leading to different calculated plasma volume changes (8.7% vs. 11.3% reduction).

Conclusions:

• Significant changes in plasma osmolality create discrepancies in Hct measurements, particularly with automated analyzers.
• These discrepancies introduce errors in plasma volume calculations, potentially affecting interpretations in sports science and anti-doping.
• Findings highlight the need to consider plasma osmolality when measuring Hct for WADA ABP and similar applications.