Anaemia: mean cell volume and red cell distribution width helped diagnose anaemia cause.

Clinical bottom line (level 4)

  1. Red cell distribution width went up with deficiencies (whether iron, folate or B-12), and the anaemic haemoglobinopathies.
  2. Red cell distribution width did not go up in chronic diseases, unless they were accompanied by deficiencies.
Bessman et al: American Journal of Clinical Pathology 1983; 80: 322-326
Expires June 2002

The study

Setting: university hospital, USA

1270 patients (aged ?, ?% male) 57% well health-care students, 19% haematology in- or out-patients, 27% hospital in-patients with anaemia

Independent unblinded reference standard, applied in all patients from a non-consecutive inappropriate spectrum.
Reference standard:
  • final diagnosis- 'standard criteria' (mainly not defined)
Diagnostic test:
  • mean cell volume (MCV)- reference range 79-101 fL
  • red cell distribution width (RDW)- reference range <15.1%

The evidence

  • low MCV and normal RDW- possible cause:
    • chronic disease
    • heterogeneous thalassemia
  • low MCV and high RDW- possible cause:
    • iron deficiency
    • red blood cell fragmentation (artificial valve)
    • haemoglobin H
    • S beta-thalessemia
  • normal MCV and normal RDW- possible cause:
    • any chronic disease (including chronic liver disease)
    • haemorrhage
    • haemolysis
    • transfusion
    • haemoglobin AS, haemoglobin AC
    • CLL with <150 x 10 3 white blood cells/l
    • hereditary spherocytosis
  • normal MCV and high RDW- possible cause:
    • early iron or folate (or both) deficiency
    • haemoglobin SS, haemoglobin SC
    • myelofibrosis
    • sideroblastic anaemia
  • high MCV and normal RDW- possible cause:
    • aplastic anaemia
    • preleukaemia
  • high MCV and high RDW- possible cause:
    • folate or B-12 deficiency
    • immune haemolytic anaemia
    • white blood cell/l
    • cold agglutination with >150 x 10 3

Comments

  1. Red cell distribution width is the Coulter Counter's equivalent to anisocytosis on the blood smear (ie. a measure of how much cell size varies).
  2. This classification method needs to be prospectively validated.

Citation

  1. Bessman JD, Gilmer PR, Gardner FH: Improved classification of anemias by MCV and RDW. American Journal of Clinical Pathology 1983; 80: 322-326
Contributor: Chris Ball and Clare Wotton, June 2000
Reviewer:

Clinical Question.
Patient healthy, anaemic or haematology patients
Intervention or Exposure mean cell volume and red cell distribution width
Comparison final diagnosis
Outcome diagnosis of cause of anaemia