haematocrit ( HCT , ( packed cell volume , PCV ))
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  • males 40-52%
  • females 36-48%

A raised haematocrit reflects haemoconcentration. This may be relative due to reduced plasma volume, or absolute (increased red blood cell mass):

  • reduced plasma volume - often result of dehydration e.g. alcohol, diuretic therapy. Also may occur in acute pancreatitis (there may be a decreased haematocrit in severe haemorrhagic pancreatitis), Addison's disease (because of water loss)
  • increased red cell mass - primary (polycythaemia rubra vera) or secondary e.g. chronic lung disease, smoking, altitude, tumours (hepatoma, fibroids, hypernephroma)

Notes:

  • true increased red cell mass can be assumed when the haematocrit is over 60% in males and 56% in females (1)
  • comparing individuals with a haematocrit which is in the upper normal range, or slightly elevated to those with a haemocrit values in the middle or lower part of the normal range
    • individuals with a haematocrit may be associated with an increase in thrombotic events and cardiovascular mortality (2)

Note that normal ranges vary with different commercial kits.

Reference:

  1. Pearson, T.C. Evaluation of diagnostic criteria in polycythemia vera. Seminars in Hematology 2001;38(1 Suppl 2): 21-24.
  2. Lowe, G.D. Rheological influences on thrombosis. Baillieres Best Practice & Research. Clinical Haematology 1999;12(3): 435-449.

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