Can haemoglobin concentration define anaemia in women and men?
X Liu, M Guo, Z Huang, D MonteroAbstract
Introduction
If haemoglobin concentration (HbCONC) is used to define anaemia, an association with aerobic capacity (VO2peak) would be anticipated, given their shared dependence on oxygen carrying capacity in red blood cell. However, HbCONC reflects not only total circulating haemoglobin mass (HbMASS) but also plasma volume. In contrast, HbMASS—independent of plasma volume—has been established as a determinant of VO2peak in both women and men. Plasma volume may therefore confound the association between HbCONC and VO2peak in the general population, potentially compromising the validity of HbCONC as a criterion for anaemia.
Purpose
To test whether plasma volume confounds the relationship between HbCONC and VO2peak in the general population.
Methods
Healthy women (n=226; age, 41.4±18.4 years) and men (n=235; age, 42.1±18.4 years) across adulthood (18-78 years) were included. Following 15 min rest in supine position, HbCONC was measured in antecubital venous blood. HbMASS and plasma volume were determined via the carbon monoxide-rebreathing method. VO2peak was determined via incremental exercise test. HbCONC was additionally measured immediately after the exercise test (HbCONCPEAK) in the majority of study subjects (n=417). The relationships of haemoglobin variables with VO2peak were assessed by linear regression analyses and the relationship between HbCONC and VO2peak was further adjusted by plasma volume. Pearson correlation coefficients (r) were used to reflect the strength of the linear relationships.
Results
HbCONC ranged from 10.1 to 15.0 g·dL-1 in women and from 11.7 to 17.8 g·dL-1 in men. HbCONC did not associate with VO2peak in women (Figure 1, P=0.093) or men (P=0.165). HbCONCPEAK was positively associated with VO2peak in women (r=0.15, P=0.038) and men (r=0.20, P=0.004). HbCONC adjusted by plasma volume positively associated with VO2peak in women (r=0.23, P<0.038) and men (r=0.39, P<0.001). HbMASS positively associated with VO2peak in women (r=0.34, P<0.001) and men (r=0.53, P<0.001).
Conclusions
HbCONC is not associated with VO2peak in women or men due to the confounding effect from plasma volume. HbMASS, which is independent of plasma volume, consistently associates with VO2peak in both sexes. HbMASS may represent a more physiologically robust metric for defining anaemia in the general population.Figure 1