Laboratory testing for sickle cell, as for other haemoglobinopathies, includes a routine blood test known as a Complete Blood Count (CBC), which involves measuring the level of haemoglobin and other parameters, such as the Mean Corpuscular Volume (MCV), and the Mean Corpuscular Haemoglobin (MCH), both of which may be within normal range in HbS carriers, in contrast to those carrying α- or β-thalassaemia.
Another test that is used to determine the carrier state includes a laboratory process known as haemoglobin electrophoresis, which enables the measurement of the quantity of the major (HbA) and minor (HbA2) components of adult haemoglobin, foetal haemoglobin (HbF) and HbS. In the case of HbS carriers, the HbS fraction will constitute up to 40% of the total haemoglobin. The presence of HbS may also be confirmed in a very simple way in a test tube, referred to as the Solubility Test.
Other ways to diagnose HbS include Isoelectric Focusing (IEF), which is another kind of electrophoresis, High Pressure Liquid Chromatography (HPLC) and Capillary Chromatography, all of which are considered today as methods of reference for screening as well as confirming the diagnosis of full blown haemoglobinopathies.
If the above tests are inconclusive, especially if combinations with other variants or thalassaemias are involved, and do not allow the laboratory scientists to provide a confirmed diagnosis, other more specialised tests are available. These are genetic tests, i.e. tests which examine the genetic material – the DNA of the blood of the individual but also often of other members of the family.
Like β & α-thalassaemia carriers, a person who carries HbS will always carry it in his/her genes throughout his/her life, and the carrier status cannot be acquired or transmitted through the environment, transfusion or other means by which people become infected. Carriers who have inherited HbS from their parents could pass it on to their children through their genes.