How accurate is the sickle cell test?

Very accurate. Sickle cell disease is caused by a gene (dna) mutation that alters one of the two globins that combine with heme to form hemoglobin. Testing can look for the altered sickle cell shape in the smear (least accurate), altered migration of hemoglobin by electrophoresis (very accurate), or for the sickle beta-globin mutation by dna testing (extremely accurate). Newbown screens use neonatal heel stick.
Dep on test. The hemoglobin electrophoresis is very accurate in diagnosing sickle cell disease and is the preferred diagnostic test. The old "sickle cell screen" is not as accurate. If the electrophoresis shows that you have sickle cell disease combined with an additional abnormal hemoglobin, additional testing may be needed to sort out what is combined with the sickle cell disease.