Osmotic fragility - red cell

Last updated: Friday, 30, April, 2004

This test is probably obsolete and is rarely ordered.

MBS Online Search Page: Click here for details

Item Process

5 mL blood in lithium heparin, or defibrinated blood.


Susceptibility to osmotic lysis is tested using fresh blood or blood incubated at 37°C for 24 hours.

Median corpuscular fragility (MCF) is the saline concentration causing 50% lysis.

Reference Interval

MCF 4.0-4.45 g/L (68-81 mmol/L) NaCl in fresh samples.

4.65-5.9 g/L (79-100 mmol/L) in incubated samples.


The test is rarely used in the investigation of haemolytic anaemia; confirms the presence of spherocytes.


Abnormal results are found in a number of hereditary haemolytic anaemias; results are not diagnostic.


Dacie JV. The Haemolytic Anaemias. 3rd ed. Churchill Livingstone 1985.