From the Guidelines
Checking and trending reticulocyte counts in patients with sickle cell crisis is crucial for assessing bone marrow response to anemia and guiding clinical management. Reticulocytes are immature red blood cells, and their count helps evaluate the bone marrow's ability to compensate for hemolysis during a crisis. A normal or elevated reticulocyte count (typically 2-3 times normal) indicates appropriate bone marrow compensation for hemolysis, as seen in patients with vaso-occlusive crises 1. However, a low or falling reticulocyte count during crisis suggests bone marrow suppression or aplastic crisis, often triggered by parvovirus B19 infection, which requires prompt intervention.
Key Considerations
- Serial measurements of reticulocyte counts are essential, as trends provide more information than single values.
- During severe pain crises, reticulocyte counts should be checked at presentation and monitored every 1-2 days if there are concerns about worsening anemia.
- The reticulocyte production index (RPI), which adjusts the reticulocyte count for the degree of anemia, provides an even more accurate assessment of bone marrow response.
- Values below 2 during crisis suggest inadequate erythropoiesis that may require more aggressive management, including transfusions with extended matched red cells that also lack the offending antigen, as recommended by the American Society of Hematology 2020 guidelines for sickle cell disease: transfusion support 1.
Clinical Implications
- Monitoring reticulocyte counts helps distinguish between different types of crises (vaso-occlusive versus aplastic) and guides transfusion decisions.
- In patients with hyperhemolysis, recognition is critical, as additional transfusions should be avoided if possible, and alternative treatments such as IVIg, high-dose steroids, eculizumab, and/or rituximab may be considered 1.
- A low reticulocyte count during crisis may indicate a need for more aggressive management, including transfusions and other supportive measures, to prevent worsening anemia and potential multiorgan failure.
From the Research
Reticulocyte Count in Sickle Cell Crisis
- The reticulocyte count is a measure of the number of young red blood cells in the blood, which can indicate bone marrow activity and erythropoiesis 2.
- In patients with sickle cell disease, the reticulocyte count can be elevated due to chronic hemolysis and tissue hypoxia 2, 3.
- Studies have shown that reticulocyte count can be used to predict vaso-occlusive crisis (VOC) development in sickle cell disease patients 3.
- A combination of reticulocyte count, immature reticulocyte count, and fluorescent reticulocyte fraction can be used to predict VOC development with a sensitivity of 81.8% and a specificity of 88% 3.
Clinical Utility of Reticulocyte Count
- However, some studies have questioned the usefulness of reticulocyte count in the evaluation of acute vaso-occlusive sickle-cell crisis, suggesting that it may not be necessary in the emergency department setting 4.
- Admission decisions in patients with sickle cell crisis appear to be associated with elevations in white blood cell count rather than reticulocyte count or hemoglobin level 4.
- Other factors, such as post-procedure neutrophil count, may be more predictive of endogenous erythropoiesis in patients with sickle cell disease undergoing chronic red cell exchange 5.
Trending Reticulocyte Count
- Trending reticulocyte count may be useful in monitoring the response to treatment and predicting VOC development in sickle cell disease patients 3.
- However, the clinical utility of trending reticulocyte count in the management of sickle cell crisis is not well established and requires further study 4, 5.