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

Abstract

BACKGROUND: Decreased reticulocyte hemoglobin content (CHr) (Siemens ADVIA 2120) reflects iron-limited erythropoiesis (ILE). RETIC-HGB (IDEXX ProCyte Dx) is a novel marker of ILE for veterinary use. OBJECTIVES: We aimed to evaluate reference intervals (RIs) and the utility of RETIC-HGB and CHr in the diagnosis of feline ILE. MATERIALS AND METHODS: RIs were established in 59 healthy cats. Intra-assay coefficients of variation (CVs) and correlations between RETIC-HGB and CHr were assessed. Two hundred and seventy-five cats were classified as having ILE or not based on low plasma iron or low transferrin saturation along with anemia and/or altered RBC indices. CHr, RETIC-HGB, and serum amyloid A (SAA) were compared between the groups. The sensitivity and specificity of RETIC-HGB and CHr to diagnose ILE were analyzed to determine the RI lower limits. RESULTS: RIs for RETIC-HGB and CHr were 12.5-18.0 and 14.0-19.9&#xa0;pg, respectively. The CV was 3% for both variables. RETIC-HGB and CHr were moderately correlated (r&#xa0;=&#xa0;0.59) with a bias of -1.2 picograms (pgs). Twenty of the 275 cats were classified as having ILE. Compared with non-ILE cats, ILE cats had significantly lower median RETIC-HGB (14.3 vs 15.2&#xa0;pg, P&#xa0;=&#xa0;.0046) and mean CHr (14.7 vs 16.5&#xa0;pg, P&#xa0;<&#xa0;.0001) values and significantly increased median SAA (44.6 vs 2.3&#xa0;&#xb5;g/dl, P&#xa0;<&#xa0;.0001) values. Using the lower RI limits resulted in a low sensitivity and relatively high specificity to diagnose ILE in cats. CONCLUSIONS: ILE was characterized by decreased CHr and RETIC-HGB; however, sensitivity was low. The moderate correlation between RETIC-HGB and CHr is likely due to species differences and different methodology.