Microcentrifuge or Automated Hematological Analyzer to Assess Hematocrit in Exercise? Effect on Plasma Volume Loss Calculations.

The assessment of plasma volume loss (∆PV) induced by exercise can be estimated from changes in hematocrit (Htc) and hemoglobin (Hb), and it is essential when investigating the metabolic or biologic response to exercise of circulating biomarkers. We aimed to ascertain whether the estimation of ∆PV may differ when Hb and Htc are determined by automated hematological analyzer (AHA) versus manual methods. Twenty-five healthy male subjects performed a maximal running incremental exercise. Blood samples were taken before exercise, immediately after exercise, and after a 30-min recovery. Hb and Htc (Htc-AHA) were determined by an AHA. Htc was also determined by microcentrifugation (Htc-M). The ∆PV immediately after exercise and after recovery was calculated. The serum concentrations of several specimens were determined and corrected for ∆PV derived from Htc-AHA (∆PVAHA) and from Htc-M (∆PVM). Htc-M was found to be higher than Htc-AHA at all time points (p < 0.001). However, no differences were observed between ∆PVM and ∆PVAHA either post exercise (∆PVM -12.43% versus ∆PVAHA -12.41%, p = 0.929) or after recovery (∆PVM 1.47% versus ∆PVAHA 1.97%, p = 0.171). No significant differences were found between both ∆PV corrected concentrations of any biomarker (p ≥ 0.076). In conclusion, both AHA and the microcentrifuge may be reliably used to estimate ∆PV during exercise.