Hi all. I'm posting this here rather than under lab tests as its more of a general point for discussion. The sed rate and inflammation As you may be aware the erythrocyte sedimentation rate (ESR), often referred to as the sed rate, is a common blood test that serves as a non specific marker of inflammation as might be found in an acute phase infection. A high sed rate is also associated with certain autoimmune diseases and inflammatory conditions such as rheumatoid arthritis. http://en.wikipedia.org/wiki/Erythrocyte_sedimentation_rate Normal sed rates may be calculated depending on age and gender. One set of ranges defines a normal finding as : Less than 15 mm/hr for men under 50 years Less than 20mm/hr for women under 50 years. A sed rate lower than these cut-off points is rarely given much clinical significance (other than indicating an absence of infection/inflammation) except where a small number of specific diseases are suspected e.g. polycythaemia (a condition where a patient makes too many red blood cells), with extreme leucocytosis (patient has too many white blood cells), and with some protein abnormalities. Low sed rates in ME/CFS patients. Somewhat paradoxically, given that ME/CFS patients regularly show high levels of c-reactive protein (CRP) and IL6 which are reliable markers of inflammation, there have been a number of threads here and elsewhere in which forum members report low or zero sed rates. Mine tested at 3 last time around. Cheney is reputed to have stated that his ME/CFS patients have the lowest sed rates he has ever seen. So do we have inflammation or not? Hyperviscosity It appears that the sed rate is not a particularly reliable measure as it can be affected by a range of factors including the plasma viscosity (thickness or resistance to flow) of the blood where viscosity is negatively correlated with the sed rate (i.e. high viscosity gives a low or zero sed rate). Hyperviscosity may be due to a range of conditions grouped under hyperviscosity syndrome or be a downstream effect of, for example, chronic alcohol abuse . High viscosity might be expected to result in reduced blood flow to all organs, and impaired microcirculation to the skin and extremities. Spontaneous bleeding often from mucous membranes results from the viscous blood causing damage due to increased shear stress. Has anyone had either or both sed rate and plasma viscosity tested?