A-130 Evaluation of the potential benefits of reticulocytes integrated in the CBC routine on sthemA 801 analyzer

Abstract Background Reticulocyte (RET) count is a key parameter to assess the bone marrow’s ability to produce red blood cells (RBC) in response to physiological challenges. While not mandatory part of the complete blood count, clinicians can request this test as needed. Laboratory can also add it as reflex testing based on hemoglobin (HGB) levels for example. This study aimed to evaluate the medical value of systematically performing reticulocyte counts alongside complete blood counts (CBC) on all samples enabled by the sthemA 801 analyzer. Methods We randomly collected 1004 samples in a French center over a 2-month period. The sthemA 801 was used as a reference for data collection and statistical analysis. We identified the number and percentage of samples for which RET was requested by clinicians, those without prescription and RET >150 G/L (a commonly accepted threshold for reticulocytosis) and those with in addition HGB =10 g/dL (the threshold proposed by the French Group of Cellular Hematology (GFHC) for RET reflex testing). A chi-square test was used to define whether the notion of prescription and HGB levels had an impact on the percentage of positive RETs. Finally, we reviewed medical records of samples with incidental findings of RET > 150 G/L associated with HGB = 10 g/dL to identify the most likely causes of reticulocytosis. Results Among the 1004 samples included in the study, 74 (7.4%) had a prescription for RET and 123 (12.3%) had a RET > 150 G/L. Prescription status did not affect the percentage of positive RET (p=0.2058) and 89.4% (110/123) of samples with reticulocytosis went missed. HGB levels had a significant impact on the percentage of positive RET identified (p<0.0001). Using an HGB threshold of 10 g/dL allowed the detection of 69.1% (76/110) of samples with positive RET. Finally, 34 samples with RET > 150 G/L remained undetected. Among them, 12 were related to road traffic accident or postoperative bleeding, 9 were multifactorial (resolution of inflammation or immunosuppressants combined with another cause), 4 involved iron supplementation for iron deficiency anemia, and 2 had a known constitutional RBC disorder (one sickle cell disease and one hereditary spherocytosis). The absence of clinical data for three patients prevented a definitive conclusion. Interestingly, one patient had compensated hemolysis of undetermined cause. She was a 46-year-old woman who had been followed for more than 20 years and had multiple comorbidities, but none of them could explain the chronic compensated hemolysis. An inherited RBC disorder was suspected and will be further explored. Conclusion We found that over 3% of samples with RET > 150 G/L might go unnoticed in daily hospital practice, despite clinicians having the option to request them and the use of GFHC expertise rules in the laboratory. Reticulocytes being part of the CBC routine on sthemA801 analyzer could benefit patients receiving iron supplementation or erythropoietin therapy as well as those with persistent inflammation, by closely monitoring the resolution of anemia. Additionally, it could facilitate earlier diagnosis of immune or constitutional compensated hemolysis and subacute hemorrhages.