Final answer:
The metabisulfite screen can cause sickling in cells with hemoglobin S, so it tests positive for sickle cell disease and trait.
Step-by-step explanation:
The statement is true. The metabisulfite screen is a laboratory test that causes cells with any amount of hemoglobin S (HbS) to sickle. This includes cells from individuals with sickle cell disease (homozygous recessive, ss) and those with sickle cell trait (heterozygous, AS). In sickle cell disease, all red blood cells have the incorrect hemoglobin and will sickle, while in sickle cell trait, some normal hemoglobin is present, which means not all cells will sickle. However, under the conditions of the test, cells with HbS can be induced to sickle, leading to a positive result in both conditions.