Direct and Indirect Coombs test:
Direct Coombs’ test:
Is used to detect antibodies already attached onto the red blood cell. This could be for cases such as immune mediated haemolytic anaemias.
- Add AHG to washed red cell
- Washed = removing the patient’s own plasma
- Wait and see if there is agglutination.
Indirect Coombs’ test:
This test is used to determine antibodies in patient’s serum that is unbound to their red blood cells. This is useful in cases such as crossmatching prior to transfusion, and also in pre-natal screening of pregnant women.
- Serum from the patient is cultured with RBCs of a known antigenicity from another patient.
- This process allows binding of antibodies to RBCs in vitro
- AHG then added to RBC
- Wait and see if there is agglutination
Lactate Dehydrogenase (LDH) levels
Is an enzyme found in almost all cells. There are many indications to test for LDH levels. During haemolytic anaemias, the lysis of red blood cells causes a release of LDH into the blood. Thus it is reasonable to expect LDH levels as a marker of hemolysis.
Another indication for observing LDH levels is when the patient experiences muscle trauma or injury as it can also indicate tissue damage.
- Kumar P, Clark M. Kumar & Clark Clinical Medicine. 5th ed. London: Elsevier limited; 2002.
- Hoffbrand A, Moss P. Essential Haematology. 6th ed. Oxford: Wiley-Blackwell; 2011.