What lab values are decreased in megaloblastic anemia?

In megaloblastic anemia, the primary characteristic is the impaired DNA synthesis during red blood cell formation, typically due to deficiencies in vitamin B12 or folate. As a result, the lab values that are commonly decreased include hemoglobin (Hgb) and hematocrit (Hct), which reflect the overall oxygen-carrying capacity of the blood and the proportion of blood volume occupied by red blood cells, respectively.

Additionally, folate and serum B12 levels are crucial in this context. A deficiency in either vitamin B12 or folate leads to the abnormal development of red blood cells, resulting in larger, immature cells known as megaloblasts. Consequently, the amounts of both folate and serum B12 will be decreased in individuals with megaloblastic anemia.

The other options include various combinations of lab values that do not accurately represent the changes seen in megaloblastic anemia. Specifically, while MCV (mean corpuscular volume) may be elevated due to the large size of the megaloblasts, other lab values like serum iron or transferrin levels may not necessarily decrease directly as a result of this condition in the same way that Hgb, Hct, folate, and serum B12 do.