When to start worrying about an increased Mean Corpuscular (MC) ratio in a patient with Diabetes Mellitus (DM)?

From the Guidelines

Diabetic patients should not worry about an increased Mean Corpuscular Volume (MCV) ratio, also known as macrocytosis, unless it is indicative of a vitamin deficiency, such as B12 or folate deficiency, or other underlying conditions like hypothyroidism or reticulocytosis, as stated in the European Consensus on the diagnosis and management of iron deficiency and anaemia in inflammatory bowel diseases 1.

When evaluating an increased MCV ratio in diabetic patients, it is essential to consider the underlying causes, as macrocytosis can be indicative of various conditions. According to the study 1, macrocytosis may arise from vitamin deficiency, thiopurine treatment, other medications, alcohol abuse, hypothyroidism, or reticulocytosis.

Key points to consider when evaluating an increased MCV ratio in diabetic patients include:

• The presence of inflammation, which can affect serum ferritin levels and mask iron deficiency 1
• The reticulocyte count, which can help distinguish between deficiencies and primary bone marrow disease 1
• Serum concentrations of haptoglobin, lactate dehydrogenase, and bilirubin to estimate hemolysis 1
• A comprehensive workup, including complete blood count with MCV, reticulocytes, serum ferritin, transferrin saturation, and CRP, as well as vitamin B12 and folic acid levels 1

In clinical practice, a thorough evaluation of the patient's medical history, physical examination, and laboratory results is necessary to determine the underlying cause of an increased MCV ratio. This approach will help guide appropriate treatment and management, ultimately improving patient outcomes in terms of morbidity, mortality, and quality of life.

From the Research

Mean Corpuscular Volume (MCV) and Diabetes

• The MCV is a measure of the average volume of red blood cells, and an increase in MCV can be an indicator of various conditions, including vitamin B12 deficiency 2.
• In diabetic patients, an increased MCV can be a cause for concern, as it may indicate underlying vitamin B12 deficiency, which can affect blood sugar control and HbA1c levels 3.
• A study found that treatment of vitamin B12 deficiency with oral cyanocobalamin resulted in a decrease in HbA1c levels, suggesting that vitamin B12 deficiency can cause a false increase in HbA1c levels 3.

When to Start Worrying about Increased MCV Ratio

• There is no specific guideline on when to start worrying about an increased MCV ratio in diabetic patients, as it depends on various factors, including the underlying cause of the increase and the individual patient's condition.
• However, if a diabetic patient has an increased MCV, it is essential to investigate the underlying cause, including vitamin B12 deficiency, to ensure proper management of the condition 2.
• A study suggested that an MCV above a certain cutoff value can be an indicator of vitamin B12 deficiency, but the sensitivity and specificity of MCV as a diagnostic tool are not well established 2.

Diagnostic Value of MCV

• The diagnostic value of MCV in detecting vitamin B12 deficiency is limited, with a sensitivity of 17% to 77% depending on the population studied 2.
• The MCV should not be used as the only parameter to rule out vitamin B12 deficiency, and other diagnostic tests, such as serum B12 measurement, should be used to confirm the diagnosis 2.
• An increased MCV can be an early indicator of vitamin B12 deficiency, and prompt investigation and treatment can help prevent complications 4.