In clinical practice, an accurate diagnosis of patients with moderate to severe anemia is essential. Among them, vitamin B12 and folic acid deficiencies are common**. In order to accurately diagnose these nutrient deficiencies, a series of laboratory tests are necessary. This article will explain in detail how metabolites can be used to diagnose vitamin B12 and folate deficiency in specific scenarios.
If lobar megalobar anemia consistent with vitamin B12 deficiency and neuropsychiatric disorders are suspected, but serum vitamin B12 is between 200 and 300 pg mL and serum folic acid exceeds 4 ng mL, elevated serum methylmalonic acid and homocysteine will indicate the diagnosis of vitamin B12 deficiency. This is because methylmalonic acid and homocysteine are important markers of metabolic disorders in the body when vitamin B12 is deficient.
If serum vitamin B12 is less than 200 picogram mL and serum folic acid is also less than 2 nanogram mL, this finding will be consistent with combined vitamin B12 and folic acid deficiency. However, it is important to note that one third of patients with folate deficiency may also experience low vitamin B12 levels. Therefore, in this case, the addition of information from high methylmalonic acid will confirm the diagnosis of a combined deficiency of folic acid and vitamin B12. In under-resourced settings, an alternative to obtaining more expensive metabolite levels is to simply redraw vitamin B12 levels after folate deficiency;If vitamin B12 levels remain low, this will retrospectively point to an underlying vitamin B12 deficiency and trigger the need for vitamin B12 replacement in that patient**.
If cytomegalocytic anemia is suspected, and serum vitamin B12 exceeds 300 pg mL and serum folic acid is between 2 and 4 ng mL, then finding an increase in serum homocysteine will support the diagnosis of folate deficiency. This is because homocysteine is an important product in the metabolism of folate and vitamin B12, and when these two nutrients are deficient, homocysteine levels rise. However, if serum homocysteine is normal, this would indicate a giant cell process unrelated to vitamin deficiency. In such cases, the differential diagnosis needs to focus on other possible **, such as the response to chemotherapy, immunosuppression, or antiretroviral drugs, or rare manifestations of an intrinsic hematologic disorder such as erythrocytic leukemia or myelodysplastic syndrome (particularly 5q-syndrome).
In summary, vitamin B12 and folate deficiency can be effectively diagnosed by measuring metabolite levels. In specific scenarios, based on the patient's symptoms and laboratory test results, the physician can accurately diagnose** and provide the patient with appropriate ** recommendations. This is of great significance for improving the patient's best outcomes and quality of life.