Evaluation of reticulocyte hemoglobin content (RET‐He) in the diagnosis of iron‐deficient erythropoiesis in dogs

Abstract

Abstract:Background: Reticulocyte hemoglobin content provided by the Siemens ADVIA (CHr) is an established marker of iron deficiency. The IDEXX ProCyte Dx hematology analyzer now provides a similar variable, reticulocyte hemoglobin equivalent (RET-He). Objectives: The objective was to evaluate RET-He and its diagnostic utility in dogs, and to calculate a cutoff value for diagnosing iron-deficient erythropoiesis (IDE). Furthermore, the prevalence of RET-He values below this cutoff value was established. Methods: One hundred and seventy-one CBCs of healthy dogs were used to establish a RI. Stability of RET-He was evaluated by repeated measurements over 48 hours (n = 10). The 25-run coefficient of variation (CV) was calculated, and correlation and bias between measurements of RET-He and CHr were assessed (n = 190). A cutoff value for diagnosing IDE was calculated. The utility of RET-He in the detection of IDE was evaluated in 123 dogs. The prevalence of low RET-He values was assessed retrospectively in a multicenter study (2012)(2013)(2014) under participation of 7 veterinary clinics. Results: Reticulocyte hemoglobin equivalent with an RI of 22.2 to 28.6 pg was statistically stable over 48 hours (P = .10). The CV was 1.8%. A fair correlation (q = 0.74) between RET-He and CHr with a small bias of À0.6 pg was found. The cutoff value for diagnosing IDE was 20.9 pg (sensitivity: 85%; specificity: 99%).

Evaluation of reticulocyte hemoglobin content (RETIC‐HGB) for the diagnosis of iron‐limited erythropoiesis in cats

“…The overall stability of RETIC‐HGB (Figure 2) is in accordance with human 18 and canine studies 17,29 . In contrast to dogs, human RETIC‐HGB increased over time without statistical significance ( P = .14).…”

“…Compared with the manufacturer's RI (13.2‐20.8 pg), the RI determined in this study (12.5‐18.0 pg) was slightly narrower and had a marginally lower upper limit. Moreover, the RI was well below the RIs published for dogs (ie, 22.3‐29.6 pg 20 and 22.2‐28.6 pg 29 ) and had a slightly narrower range. Similar results have been found for CHr (1.43‐1.71 fmol [23.0‐27.6 pg] in dogs and 0.88‐1.22 fmol [14.2‐19.7 pg] in cats) 17 .…”

“…The correlation between RETIC‐HGB and CHr was moderate ( r s = 0.59). This result is interesting in the face of similar RIs obtained for both variables and might be explained by the different methodologies of both hematology analyzers 29 . CHr is calculated as the product of MCVr and CHCMr (CHr = MCVr × CHCMr).…”

“…Accordingly, storage‐related RBC and reticulocyte swelling can lead to physiologic or even increased RETIC‐HGB values, despite the presence of ID, 25 possibly contributing to a misinterpretation of the actual iron status. As the ProCyte Dx represents an in‐house hematology analyzer, sample storage at room temperature for more than 24 hours is unlikely 29 . Prolonged sample storage should, therefore, be considered a negligible factor.…”

“…The ProCyte Dx uses the mean value of the forward scattered light of reticulocytes labeled with fluorescent dyes (RET‐Y) to determine the hemoglobin equivalent of reticulocytes (RET‐He, new term RETIC‐HGB) 10 . Finally, the correlation of RET‐Y with MCH of the respective cell population (reticulocytes) results in a mathematical transformation into RET‐He/RETIC‐HGB 29 . Thus, cellular variables affecting light scattering, such as individual cellular sizes, likely resulted in greater RETIC‐HGB changes.…”