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

Evaluation of the Blood Neutrophil-to-Lymphocyte Ratio (NLR) as a Diagnostic and Prognostic Biomarker in Dogs with Portosystemic Shunt

The neutrophil-to-lymphocyte ratio (NLR) can help in assessing inflammatory diseases, sepsis, and chronic hepatic conditions in humans. Dogs with congenital portosystemic shunts (PSSs) have signs of generalized inflammation, and the clinical signs can overlap with other conditions, including hypoadrenocorticism (HOC). Thus, the potential diagnostic and prognostic value of leukocyte ratios as surrogate markers was assessed in a retrospective case-control study including 106 dogs diagnosed with PSSs. The disease control groups were dogs with parenchymal hepatopathy (PH; n = 22) or HOC (n = 31). In the PSS dogs, the blood NLRs were associated with the severity of systemic inflammation but not with the shunt type, hepatoencephalopathy, systemic infection, or hypoglycemia. The baseline NLRs did not differ between the three disease groups, between medically and surgically treated PSS dogs, or between those with successful PSS ligation and dogs experiencing peri-/post-surgical complications. However, dogs requiring two consecutive surgical interventions had significantly higher NLRs, and an NLR of <2.53 distinguished dogs with successful shunt ligation in one surgery from those requiring two consecutive surgeries for PSS closure. The blood NLR might be a useful clinicopathologic variable in PSS, but its value in helping differentiate PSS from HOC cases appears low. Integrating the NLR into a diagnostic algorithm may allow for a prediction of the number of surgical interventions required.

Reference intervals for reticulocyte indices, immature reticulocyte fraction, and the percentage of hypochromic red blood cells in adult large breed dogs using the ADVIA 2120 hematology analyzer

Reticulocyte indices are used to characterize anemia, including the identification of regeneration. In people, the immature reticulocyte fraction (IRF), percentage of hypochromic red blood cells (%HYPO-RBC), and other reticulocyte indices have been used as earlier indicators of erythropoiesis and as valuable monitoring tools in the assessment of various therapies. The reference intervals (RI) of the IRF and %HYPO-RBC have not been reported in dogs. The objective of this study was to establish RIs for novel variables (IRF, %HYPO-RBC, and CH-delta) and assess RIs for more commonly reported reticulocyte indices in healthy dogs. RIs were calculated from blood results retrospectively collected from 106 client-owned healthy dogs at the time of induction into a blood donor program using the ADVIA 2120 hematology analyzer (Siemens Healthcare Diagnostics). For the calculation of RIs, appropriate tests were applied for outlier detection and normality assessment. For variables normally distributed, RIs and their respective 90% confidence intervals (CIs) were calculated using parametric methods, while for variables not normally distributed, robust methods were used and bootstrapping for calculating the 90% CIs. The following RIs were established: reticulocyte hemoglobin content (CHr) 24.5-28 pg, mean reticulocyte volume (MCVr) 85.9-99.3 fL, mean corpuscular hemoglobin concentration of reticulocytes (CHCMr) 271.0-306.3 g/L, IRF 10.4%-43.5%, CH-delta 0.5-4.3 pg, and percentage of hypochromic red blood cells (%HYPO-RBC) 0.10%-0.80%. The results of this study provide RIs for novel reticulocyte variables. Further studies are required to determine the clinical utility of IRF, %HYPO-RBC, and CH delta as early indicators of erythropoietic activity in canine patients.

Probable paraneoplastic leukocytosis in a dog with a gastrointestinal stromal tumor

A 9-year-old female spayed Boston Terrier presented for diagnostic investigation of lethargy, poor appetite, weight loss, and a marked leukocytosis. Significant muscle wasting and a palpable abdominal mass were present on physical examination. Abdominal imaging revealed the mass to be of small intestinal origin; consequently, an intestinal resection and anastomosis were performed without complication. The histopathologic diagnosis was a gastrointestinal stromal tumor, verified by immunohistochemical positivity to CD117 (KIT). Two weeks after discharge, the leukocytosis had resolved. Though the exact molecular mediator of the severe leukocytosis was undetermined, resolution following tumor removal suggests a paraneoplastic cause. To the authors' knowledge, this is the first reported case of probable paraneoplastic leukocytosis secondary to a gastrointestinal stromal tumor in the dog. Gastrointestinal tract imaging should be performed when this uncommon hematologic abnormality is present.

Diagnostic value of reticulocyte indices for the assessment of the iron status of cats with chronic kidney disease

Background

Reticulocyte indices have been suggested as alternatives to transferrin saturation (TSAT) for iron status assessment in humans and dogs but they have not been evaluated thoroughly in cats.

Objectives

To assess the value of the reticulocyte indices for the diagnosis of iron deficiency in cats with chronic kidney disease (CKD) and chronic hematuria associated with subcutaneous ureteral bypasses (SUBs).

Animals

Sixty‐four cats: 16 healthy, 14 CKD without SUB, and 34 CKD with SUB.

Methods

Prospective observational cross‐sectional study of cats presented for routine nephrology visits. Primary outcomes included assessment of the diagnostic values of erythrocyte indices (mean corpuscular volume, hemoglobin, and hemoglobin concentration: MCV, MCH, and MCHC) and reticulocyte indices (mean corpuscular volume, MCVr; corpuscular hemoglobin, CHr), using TSAT as reference.

Results

Iron deficiency was diagnosed in 9/64 cats (14%). A receiver‐operating characteristic curve analysis yielded a moderate discriminatory value for CHr in this diagnosis: area under the curve [AUC] = .75 (95% confidence interval, 0.48‐0.89); P = .006; sensitivity 67%, specificity 82% for a cutoff of 15.9 pg. This compared favorably to MCVr (AUC = .63; P = .29), MCV (AUC = .58; P = .45), MCH (AUC = .64; P = .19), and MCHC (AUC = .7; P = .03).

Conclusion and Clinical Importance

CHr added moderate value to the diagnosis of iron deficiency in cats with CKD.

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

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 pg, respectively. The CV was 3% for both variables. RETIC-HGB and CHr were moderately correlated (r_s = 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 pg, P = .0046) and mean CHr (14.7 vs 16.5 pg, P < .0001) values and significantly increased median SAA (44.6 vs 2.3 µg/dl, P < .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.

Comparison of iron staining and scoring methods on canine bone marrow aspirates

BACKGROUND

Insufficient iron for erythropoiesis can occur in multiple conditions, including absolute iron deficiency, which is often caused by chronic external hemorrhage in dogs. Distinguishing this from other causes of iron-restricted erythropoiesis allows appropriate intervention. Decreased marrow iron assessed by Prussian blue staining is a method to diagnose absolute iron deficiency, but scoring systems for marrow iron are not validated in dogs.

OBJECTIVES

Our objectives were to (a) evaluate the technical performance of two bone marrow iron scoring systems used in human medicine and (b) examine the effects of destaining and restaining on iron stores after Wright-stained marrow slides are destained and restained with a Prussian blue stain.

METHODS

Two marrow aspirate slides were included from each of 12 ill dogs in which marrow was collected during clinical evaluation. One slide was directly stained with Prussian blue. The other was first stained with Wright stain, then destained and restained with Prussian blue. Three blinded observers scored the presence of iron in each of the 24 randomized slides using the Gale (scale 0-6) and sideroblast methods (percentage score). Slides were then re-randomized and rescored.

RESULTS

For the Gale method, interobserver agreement was fair, and intraobserver agreement was substantial to perfect. There was less agreement using the sideroblast method, with a significant observer effect. Iron scores were significantly lower in destained slides compared with those stained directly.

CONCLUSIONS

Interobserver and intraobserver agreements were acceptable for the Gale method, but the sideroblast method should be used cautiously. A destaining procedure before Prussian blue staining could decrease marrow iron scores.

Variability in the cleavage of exosome-associated transferrin receptor questions the utility of clinically useful soluble transferrin receptor assays for dogs, cats, and horses

Whole transferrin receptor (TfR) is present in reticulocyte exosomes. Soluble transferrin receptor (sTfR) is cleaved from whole TfR in human plasma, with the remnant cytoplasmic domain (cTfR) remaining membrane associated. In humans, sTfR is a biomarker that can detect iron deficiency in the presence of inflammatory disease. This condition is still a diagnostic dilemma in veterinary species. We aimed to (1) confirm the presence of exosomes and exosome-associated TfR in the serum of dogs, cats, and horses; and (2) to assess and compare the proportion of cTfR to total (cTfR + whole) in exosomal membranes of healthy and diseased dogs and cats and in healthy horses to indirectly predict their anticipated levels of circulating sTfR. We used discarded serum and whole blood samples from canine and feline patients, separated into healthy and diseased groups based on the health status of each patient, and healthy equine participants from a previous study. Ultracentrifugation, followed in some experiments by OptiPrep discontinuous density gradient fractionation, was used to isolate exosomes. Exosomes and associated TfR were identified using TEM and Western blot for TfR, respectively. Densitometry tracings of Western blots of serum exosomes were used to measure the proportion of cTfR to total TfR. Extracellular vesicles compatible with exosomes were successfully isolated and expressed TfR. The proportion of cTfR in dogs was greater than 50%, indicating that a majority of the whole TfR was cleaved to produce sTfR (and remnant cTfR). There was significant interindividual variation and no significant difference between healthy and diseased animals. The proportion of cTfR in cats was very low at 11%, indicating that very little sTfR was likely produced. There was a small yet significant difference between healthy and diseased cats. Healthy horses do not appear to cleave exosome-associated TfR. Diagnosis of iron deficiency in the presence of inflammatory disease remains a challenge in veterinary medicine. Our results indicate that TfR is poorly or unpredictably cleaved in veterinary species, revealing that there are species differences in exosomal TfR handling. These data suggest that development of an assay for the detection and quantification of sTfR in the species investigated may not be warranted.