What is the significance of a low Red Blood Cell (RBC) count with normal hemoglobin levels?

From the Guidelines

Having low red blood cell (RBC) count with normal hemoglobin levels is a condition that requires immediate medical evaluation to determine the underlying cause, as it may be indicative of normocytic anemia, which can be caused by recent blood loss, chronic kidney disease, bone marrow disorders, or certain medications. This situation necessitates a comprehensive medical assessment to identify the root cause, as treatment must be tailored to address the underlying condition. Common causes of normocytic anemia include recent blood loss, chronic kidney disease, bone marrow disorders, or certain medications 1. If you're experiencing symptoms like fatigue, weakness, or dizziness, it is crucial to consult a healthcare provider promptly. They will likely order additional tests such as a complete blood count, reticulocyte count, iron studies, vitamin B12 and folate levels, and possibly kidney function tests to determine the cause of the low RBC count with normal hemoglobin levels.

Some key points to consider in the evaluation of normocytic anemia include:

• The mean corpuscular volume (MCV) is used to characterize anemia, with normocytic anemia having an MCV between 80-100 fL 1
• The reticulocyte count is a crucial test to distinguish between production problems (low reticulocyte index) and destruction or loss of red blood cells (high reticulocyte index) 1
• Iron studies, including iron and total iron binding capacity (TIBC), can help diagnose absolute iron deficiency, which is a common cause of anemia 1
• Vitamin B12 and folate levels can help diagnose deficiencies that may be causing anemia 1
• Kidney function tests can help diagnose chronic kidney disease, which is a common cause of anemia 1

It is essential to note that the management of anemia, particularly in critically ill patients, has evolved, and guidelines now recommend a more conservative approach to transfusions, with a hemoglobin threshold of <7.0 g/dL for transfusion in adults without extenuating circumstances 1. Therefore, it is crucial to consult a healthcare provider to determine the best course of action, as treatment must be individualized based on the underlying cause and the patient's clinical condition.

From the FDA Drug Label

In the Normal Hematocrit Study, the yearly transfusion rate was 51.5% in the lower hemoglobin group (10 g/dL) and 32. 4% in the higher hemoglobin group (14 g/dL). Overall, more than 95% of patients were RBC transfusion-independent after receiving PROCRIT for 3 months The answer to the question of low RBC with normal hemoglobin is that low RBC counts can still occur even with normal hemoglobin levels.

• RBC transfusion independence was achieved in more than 95% of patients after receiving PROCRIT for 3 months 2.
• The yearly transfusion rate was lower in patients with higher hemoglobin levels (32.4% in the higher hemoglobin group vs 51.5% in the lower hemoglobin group) 2.

From the Research

Low RBC Normal Hemoglobin

• Low RBC (red blood cell) count with normal hemoglobin levels can be an indication of iron deficiency or other underlying health conditions 3, 4.
• Reticulocyte hemoglobin content (CHr) is a useful parameter in diagnosing iron deficiency and iron deficiency anemia, as it reflects the current erythropoiesis status 5, 6.
• Studies have shown that CHr has a moderate sensitivity and specificity for diagnosing iron deficiency, and is less affected by inflammation than other biomarkers such as serum iron, transferrin saturation, and ferritin 3.
• CHr can be used to differentiate between iron deficiency anemia, vitamin B12 deficiency anemia, and mixed anemia, and can also be used to monitor the response to iron therapy 5, 7.
• The use of reticulocyte hemoglobin content (MCHr) has been shown to be effective in detecting iron deficiency in non-anemic adults, with a sensitivity of 84.1% and specificity of 71.1% 4.
• A meta-analysis of 14 studies found that reticulocyte hemoglobin values less than 26 pg can distinguish iron-deficiency anemia, while 26 to 31.5 pg can distinguish iron deficiency, with an area under the curve (AUC) of 0.889 7.

Reticulocyte Parameters

• Reticulocyte parameters such as CHr, MCVr (reticulocyte mean corpuscular volume), and CHCMr (corpuscular mean hemoglobin concentration of reticulocyte) can be useful in the differential diagnosis of mixed anemia, iron deficiency anemia, and vitamin B12 deficiency anemia 5.
• These parameters can help identify the underlying cause of anemia and monitor the response to treatment 6.
• The use of reticulocyte parameters can provide a simple and cost-effective way to diagnose and manage iron deficiency and anemia 3, 7.

Diagnostic Value

• Reticulocyte hemoglobin content (CHr) has been shown to be a reliable test for the investigation of iron deficiency, with a diagnostic value comparable to or better than traditional biomarkers such as serum ferritin 4, 7.
• The diagnostic value of CHr can be improved by standardizing the cutoff values and using it in combination with other laboratory parameters such as hemoglobin and mean cell volume (MCV) 3, 7.