INVESTIGATION OF SEMIQUANTITATIVE MARROW IRON SCORING AND RETICULOCYTE HEMOGLOBIN CONTENT (CHr) IN HEALTHY AND ILL CANINES WITH AND WITHOUT CLINICAL EVIDENCE OF BLOOD LOSS.

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 considered the gold standard to diagnose absolute iron deficiency but scoring systems are not validated in dogs. The performance of standardized semiquantitative marrow scoring of iron deposits in dogs has not been previously reported or correlated to iron biomarkers in blood.[1-4]

Objectives: Objectives included evaluation of the effects of different staining sequences, evaluation the technical performance of bone marrow scoring systems used in human medicine, and assessment of the clinical utility of marrow iron scoring (Gale method) and reticulocyte hemoglobin content (CHr) in healthy and clinically ill canines with and without evidence of blood loss.

Results: Established human scoring via the Gale iron bone marrow classification method (scale 0-6) can be applied to healthy and ill canine bone marrow aspirates stained with Prussian blue with acceptable intraobserver (substantial to perfect) and interobserver agreement (fair).[5] The Gale score did not correlate with the CHr [reticulocyte hemoglobin content] as expected, given that CHr can be affected by different types of iron restricted erythropoiesis. The odds of a low CHr (equal or less than 24.4 pg) in a canine patient is approximately 3 times higher in patients that have a low median Gale score (2 or less). Descriptive statistics for Gale marrow scoring in clinically healthy research canines were as follows: range (4-5), mean (4.3), and median (4.17). Most dogs with a low Gale score and low CHr (equal or less than 24.4 pg) had absolute iron deficiency; however, a few dogs had evidence of additional iron sequestration and functional iron deficiency. A low Gale score and normal CHr could indicate a subclinical iron deficiency.

Conclusions: The Gale scoring method performs well on canine bone marrow aspirates but should always be interpreted together with CHr and other laboratory data and clinical findings for accurate evaluation for one or more potential processes of iron restricted-erythropoiesis in the patient.