Analytical and Standardization Challenges of Reticulocyte-Derived Indices (IRF and RMI) in Veterinary Hematology: A Narrative Review

Background: The immature reticulocyte fraction (IRF) and reticulocyte maturity index (RMI) are also recent and helpful tools in veterinary hematology for measuring bone marrow activity. Although it has the potential to distinguish between regenerative, pre-regenerative, and non-regenerative anemia in dogs and cats, discrepancies remain in the analysis tools and equipment, which compromise their extensive clinical reliability. Methods: Articles published between ۲۰۰۰ and ۲۰۲۴ that assessed IRF and RMI in small animals were reviewed to make the literature review. A comparison of data from major hematological analyzers, namely the Sysmex XN-۱۰۰۰V, ADVIA ۲۱۲۰/۲۱۲۰i, and XT-۲۰۰۰iV, was conducted in terms of reference ranges, pre-analytical variables, and diagnostic performance. Results: The reported values of IRF and RMI varied significantly across inter-analyzer and interspecies. The IRF in healthy dogs was ۲۲.۱ (ADVIA ۲۱۲۰i) and ۲۶.۹ (ADVIA ۲۱۲۰). In healthy cats, it ranged from ۲۲.۷ (Sysmex XN-۱۰۰۰V) to ۳۳.۳. Cutoff levels between bone marrow failure and other non-regenerative anemias varied by up to ۱۰ per cent in accordance with analyzer algorithms. The type of anticoagulant (EDTA and CTAD), storage time, and fluorescent dye (oxazine ۷۵۰ and polymethine) had a significant influence. However, there was agreement among the studies that IRF and RMI are more sensitive compared to other conventional parameters, such as absolute reticulocyte count or reticulocyte hemoglobin content (CHr), in detecting early erythropoietic activity. Conclusion: Although there are diagnostic possibilities, numerous calibration materials are not standardized, and the units of reporting, as well as the inter-laboratory quality control, do not allow for accurate comparison of the IRF and the RMI results. To accurately diagnose and follow up on the treatment of anemia and bone marrow recovery in companion animals, harmonized reference ranges and international adjustments of analyzed controllers would be necessary.

کلیدواژه ها:

Immature reticulocyte fraction ، Reticulocyte maturity index ، Analyzer comparison ، Regenerative anemia ، Veterinary hematology