Sickle cell screen

The expected result is Negative; a positive screen is followed by a full haemoglobin variant analysis to tell sickle cell trait from sickle cell disease.

This is a quick laboratory test that checks whether the blood contains haemoglobin S, the form of haemoglobin found in sickle cell trait and sickle cell disease. It gives a yes or no answer and does not say how much haemoglobin S is present, so it cannot tell a carrier (trait) from someone with the disease.

Doctors request it before an anaesthetic in people whose family background makes sickle cell more likely, in antenatal care, and when looking into unexplained pain, anaemia or red cell breakdown. A positive result is always followed by the fuller haemoglobin variant analysis.

• Sickle cell trait, where one gene is carried and there are usually no symptoms
• Sickle cell disease
• Combined sickle and other haemoglobin variant conditions

• A negative result means no haemoglobin S was detected at the level the test can find

• A recent blood transfusion can give a negative result in someone who carries haemoglobin S, or a positive one in someone who does not
• The screen is not reliable in babies under six months, because they still have mostly fetal haemoglobin
• Rarely, a very high blood protein level or a very low haemoglobin gives a misleading result

No fasting needed. A single screen result is enough; a positive result is followed by haemoglobin electrophoresis or HPLC.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.