Dear Ask The Doctor: Last year I had a blood test done which came back positive for the sickle cell trait. I want to do a second blood test to be sure, but first I'd like to know if there is any possibility of a false-positive in a sickl cell test. If it makes any difference, I had fasted for a full 24 hours prior to the test, thinking it was required. Thanks in advance.
Dear Patient: False positive sickle cell test is possible. It depends on the type of test offered by the lab
Any condition which leads to less oxygen supply to body such as living in high altitude areas,iron deficiency anaemia , blood tests done after exertion, and if one has blood transfusion in recent past.
I do not think fasting has any impact on the test results.
Newer tests screening by hemoglobin electrophoresis have eliminated the majority of false positive tests.