Sickle cell anaemia can be diagnosed using a blood test to check for defective haemoglobin. A small amount of defective haemoglobin would suggest that you have the sickle cell trait (you're a carrier of the sickle cell gene), but don't have sickle cell anaemia.ickle cell anaemia can be diagnosed using a blood test to check for defective haemoglobin. A small amount of defective haemoglobin would suggest that you have the sickle cell trait (you're a carrier of the sickle cell gene), but don't have sickle cell anaemia.