Diagnosis

 

To identify for Sickle Cell Anaemia three types of tests are used:

 

Sickle cell test (Hgb S test):

 

This test identifies the presence of abnormal Haemoglobin S in the blood. Blood is taken from the back of a hand of inside of the elbow.

This test cannot identify the subtype of Sickle Cell disease.

Iron or blood transfusion in the last 3 months can cause a false negative result.

 

Haemoglobin Electrophoresis:

 

This test is to test the type of Haemoglobin in the blood. As many types of Haemoglobin exist: HbA, HbA2, HbF, HbS, HbC, Hgb H, and Hgb M. Healthy adults only have significant levels of HbA and HbA2.

HbF is foetal haemoglobin and some diseases can be characterised with raised levels of this protein.

 

Normal adult levels of haemoglobin are:

 

  • Hgb A1: 95% to 98%
  • Hgb A2: 2% to 3%
  • Hgb F: 0.8% to 2%
  • Hgb S: 0%
  • Hgb C: 0%

In infants and children:

 

  • Hgb F (newborn): 50% to 80%
  • Hgb F (6 months): 8%
  • Hgb F (over 6 months): 1% to 2%

If HbS is raised in individuals they may have Sickle Cell Anaemia.

Iron or blood transfusion in the last 12 months can falsify these results.

 

Complete Blood Count (CBC):

 

This is a test that measures the number of red blood cells, white blood cells, total haemoglobin, the percentage of red blood cells (haematocrit) and the size of the red blood cells (mean corpuscular volume) in the blood.  

 

It can also be used to provide information on the haemoglobin size and content of red blood cells by using Mean Corpuscular Haemoglobin (MCH) and Mean Corpuscular Haemoglobin Concentration (MCHC)

  • RBC (varies with altitude):
    • Male: 4.7 to 6.1 million cells/mcL
    • Female: 4.2 to 5.4 million cells/mcL
  • WBC: 4,500 to 10,000 cells/mcL
  • Haematocrit (varies with altitude):
    • Male: 40.7 to 50.3 %
    • Female: 36.1 to 44.3 %
  • Haemoglobin (varies with altitude):
    • Male: 13.8 to 17.2 gm/dL
    • Female: 12.1 to 15.1 gm/dL
  • MCV: 80 to 95 femtoliter
  • MCH: 27 to 31 pg/cell
  • MCHC: 32 to 36 gm/dL

(cells/mcL = cells per microliter; gm/dL = grams per deciliter; pg/cell = picograms per cell)

Anaemia is characterised by a low haemoglobin count. Infections caused by the disease would show up as a high white blood cell count.

This Complete Blood Count is the most common way to identify Sickle Cell and is used in many countries that have prevalent Sickle Cell Anaemia.

This shows a normal blood test, such as used in Sickle Cell tests

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