The CFS cohort in the present study
did not have blood chemistry abnormalities that would
warrant such a diagnosis. Thus the elevated prevalence
of low RBCV suggests that the CFS subjects may
have an anaemia type that goes undetected by standard
haematological evaluations. Normochromic normocytic
anaemia is one such condition that is defined by a
low RBCV, despite the presence of normal levels of
haematocrit, haemoglobin and serum ferritin, and red
blood cell count, size and shape [44]. This anaemia
type is common in chronic systemic disorders, such as
heart disease, renal failure, endocrine insufficiency,
hepatic disease, gastrointestinal malabsorption, rheumatological
conditions, chronic infections and cancer,
disorders that are exclusionary for a CFS diagnosis [20].
Thus CFS may be another chronic condition that results
in hypoproliferative anaemia. Current research suggests
that normochromic normocytic anaemia may arise from
a chronic inflammatory process that interferes with renal
erythropoietin production or signalling and by inhibiting
bone marrow red blood cell production [46]. Although a
chronic inflammatory condition accompanying CFS has
been hypothesized [47,48], such findings are inconsistent
and not yet confirmed [49].