From the Guidelines
An RDW of 18.6% in a male's CBC within a 2-year timeframe is considered elevated and potentially significant, indicating increased variation in red blood cell size (anisocytosis) that may be associated with iron deficiency anemia, vitamin B12 or folate deficiency, hemolytic anemia, or certain chronic diseases 1. This elevated value should not be interpreted in isolation but evaluated alongside other CBC parameters such as hemoglobin, hematocrit, and MCV (Mean Corpuscular Volume) to determine the underlying cause. Further investigation is recommended, including:
- A review of previous CBC results to assess trends
- Additional blood tests, such as serum ferritin, transferrin saturation, and reticulocyte count, to determine the underlying cause of the elevated RDW
- Clinical correlation with any symptoms the patient may be experiencing, such as fatigue, weakness, or shortness of breath The significance of this elevated RDW ultimately depends on the clinical context and other laboratory findings, so consultation with a healthcare provider for proper evaluation and management is necessary 1. It is also important to note that the diagnosis of iron deficiency anemia should be based on a combination of laboratory tests, including serum ferritin, transferrin saturation, and RDW, as well as clinical evaluation 1. In patients with inflammation, the diagnostic criteria for iron deficiency anemia may be different, and a serum ferritin level up to 100 μg/l may still be consistent with iron deficiency 1. Therefore, a comprehensive evaluation, including laboratory tests and clinical correlation, is necessary to determine the significance of an elevated RDW and to guide further management.
From the Research
RDW Significance in CBC
- RDW (Red Blood Cell Distribution Width) is a measurement of the variation in size and volume of red blood cells (RBCs) 2.
- An RDW of 18.6 is considered high, as normal values typically range from 11.8 to 14.5% 3.
- Elevated RDW is associated with various illnesses, including cardiovascular diseases, and can be an early risk factor for cardiovascular and renal comorbidities 2.
Association with Diseases
- High RDW is strongly associated with mortality, as well as incident coronary artery disease (CAD), heart failure, peripheral vascular disease, atrial fibrillation, stroke, and cancer 3.
- RDW has long-term predictive value (≥4.5 years after assessment) for the majority of outcomes, including mortality and common diseases 3.
- Elevated RDW combined with white blood cell count (WBC) has a better sensitivity than CURB-65 scores in predicting ICU admission and mortality in adult community-acquired pneumonia patients 4.
Clinical Implications
- RDW can be a useful clinical marker for inclusion in wellness assessments, as it may predict onsets of a wide range of common conditions and mortality 3.
- Testing for iron deficiency, which can cause elevated RDW, is indicated for patients with anemia and/or symptoms of iron deficiency, and should be considered for those with risk factors such as heavy menstrual bleeding, pregnancy, or inflammatory bowel disease 5.
- Further evaluation and monitoring may be necessary for individuals with high RDW, as it can be an indicator of underlying health issues 6, 3.