Red Cell ClinPath Flashcards
Types and Causes of Spiculated RBC
Echinocytes - most often storage/ageing of RBC. Also CKD
Acanthocytes (irregular projections) - altered lipid membrane, BM disease, liver disease, increased fragility from DIC or cancer
Keratocytes (blisters) progress to schistocytes - fragmentation injury; liver disease, oxidative stress, iron deficiency
Causes of Spherocytes
partial phagocytosis secondary to immune mediated disease
also seen post transfusion or with Zn toxicity and other heinz body anaemias
Causes of Eccentrocytes
Oxidative stress due to toxicity, endogenous oxidants or inherited G-6-P deficiency
Causes of increased/decreased MCV
INCREASED - regenerative response, some poodles, B12/folate deficiency
DECREASED - iron deficiency; liver disease, PSS, inflammatory disease
Normal with anaemia - CKD, PSS; endocrine disease, inflammatory disease
Causes of decreased MCHC
Deficiency in iron, B12 or folate
Lead poisoning
Inherited defective Hgb
Calculation of corrected retic % and its benefit
retic % x (patient HCt / normal Hct)
Takes into account degree of anaemia and whether the response is appropriate.
Expected findings in different causes of anaemia
Haemolysis - increased TP; increased bili; +/- haemoglobinemia/haemoglobinuria, strong regenerative response
Evidence of red cell fragmentation or increased membrane phagocytosis
Haemorrhage: low or normal protein; regenerative/pre-regenerative
Chronicity: Fe deficiency with decreased MCV and MCHC; may see mild red cell fragmentation injury. Low serum iron, TIBC and % transportin saturation
Non-regenerative - if mild-moderate more likely extrameduillary causes; if severe may be other cytopaenias
Differentials for haemolytic anaemia
- Immune mediated - primary/secondary
- Increased macrophage activity in HHS
- Fragmentation injury from DIC, neoplasia, vasculitis, myelofibrosis; iron deficiency
- Membrane defects from inherited disorders: PFK (Springer and Cocker Spaniel); PVK (WHWT)
- Hypophosphataemia (feline hepatic lipidosis)
- Oxidant injury (esp cats with reduced RBC antioxidant capacity)
- Infectious - Mycoplasma, Lepto, Babesia
DDx for Non-regenerative anaemia
Mild-moderate indicates extramedullary disease
- endocrine (thyroid, cortisol, DM)
- CKD
- Inflammatory disease
- B12, Cu, Fe deficiency
Severe/other cytopaenias
- Myeloproliferative disease
- Pure red cell aplasia
- Myelophthesis
- Toxins (aflatoxin)
- Drugs (oestrogen, phenobarbitone, methimazole, TMS)
- Infectious (FeLV, FIP, Ehrlichia)
- Paraneoplastic (sertoli cell tumour, lymphoma)
- Myelofibrosis (PFK deficiency,
What is immature reticulocyte fraction and what is the evidence of its use including Sens/Spec
Based on the RNA levels, reticulocytes are classified as fractions of low- (LFR), medium-(MFR), or high-fluorescence reticulocytes (HFR), with HFR being the most immature reticulocytes
IRF, which is calculated as the sum of the percentages of MFR and HFR, is superior to ARC because it does not include the LFR which is the majority of ARC (which takes longer to increase as a result).
Retrospective Case control study (relatively small numbers) found IRF was significantly higher in dogs with regenerative anaemia and those with pre-regenerative anaemia compared to healthy controls and dogs with non-regenerative anaemia. In most cases the cause of anaemia was haemorrhage - so utility for other causes is less clear.
While ARC was not different between PRA and NRA.
With a cutoff value of 27, IRF had 81.8% sensitivity and 93.3% specificity, which was superior to RPI to detect preregenerative anemia.
Many dogs had received transfusion prior to IRF measurement which could affect results
Tests to evaluate Iron Stores and their limitations
Serum iron - measures iron bound to transferrin which is liberated in acidosis. May be lowered by inflammatory disease, reduced GI absorption, Cu deficiency; PSS or chronic blood loss.
Increased in haemochromatosis; hepatic necrosis; haemolysis, and steroid administration
Haemolysis may falsely elevate serum Fe
Total iron binding Capacity (TIBC) - measures serum transferrin about 33% is usually bound to iron. May be affected by reduced hepatic synthesis or enteric/renal losses. Elevated in iron deficiency or necrotising hepatitis (and lipaemia/haemolysis). Downregulated by inflammatory cytokines
% Saturation - calculated from iron and TIBC. So affected by same factors a.a
Low Fe,%and TIBC without anaemia is more likely inflammatory or other systemic disease.
Ferritin - storage form of iron, considered better total body store indicator. decrease in deficiency but increase with inflammation, liver disease, haemochromotosais,
Faecal occult blood - detects Hgb. Can be positive if eating meat based diet or high endogenous peroxidases in diet. False negatives occur if ingesting citrus or removal of iron by colonic flora. Also intermittent bleeding
Decreased reticulocyte haemoglobin content has a 93.8% sensitivity and 76.9% specificity for identifying iron deficiency in cats
Typical iron panel changes for Fe deficiency, inflammation, PLE/liver failure, and haemolytic anaemia
Fe deficient: low Fe normal TIBC with decreased %saturation. Should be interpreted with haemogram showing microcytosis and hypochromic anaemia. Same changes can be seen with inflammatory disease
Inflammation - decreased Fe and TIBC with normal % saturation. Seen in acute inflammation, more chronic tends to look like the above.
Reduced transferrin production occurs in PLE or liver disease –> normal serum iron with reduced TIBC and normal to increased % saturation
Haemolysis increases serum iron with normal TIBC and increased %saturation. This can also be seen with ineffective erythropoiesis and non-regenerative anaemia.
Performance of automated retic parameters in anaemic cats
JFMS 2018
- Ret% - sensitive 100% but not specific (<75%)
- Ret Production index was 92% specific but not sensitive (<15%)
- Reticulocyte number had sensitivity adn specificity of >80%
By using higher cut offs the accuracy of these tests improved.
Confirm regeneration when the pretest probability is high, but when probability is moderate the RPI should be used
What is reticulocyte production index
Reticulocyte production index - accounts for degree of anaemia and rate of erythrocyte maturation in circulation (assumes it is the same as for humans)
RPI of 1 is normal, >1 means increased production
Categories of Erythrocytosis and DDX
Relative - dehydration, splenic contraction.
Absolute - increased RBC production
Primary - BM disease independent of EPO. Polycythaemia vera
Secondary - due to increased EPO
APPROPRIATE - chronic hypoxaemia due to right to left shunting in CVS disease (ie PDA); CO poisoning; severe respiratory disease or high altitude.
INAPPROPRIATE - constitutive EPO production, PaO2 normal (renal tumours, rare paraneoplastic condition; mild in some endocrinopathies).
Reason for high frequency of non-regenerative anaemia in cats?
Poorly understood, likely a combination of number of chronic diseases cats suffer from and cats propensity to develop anaemia from oxidant injury due to lack of N-acetyl transferase
How does B12 deficiency cause anaemia
Inhibition of purine and thymidylate synthetases impair DNA synthesis within erythroblasts resulting in their apoptosis
How is Iron deficiency diagnosed in cats
MCV and MCHC are insensitive markers
Reticulocyte indices are better indicators
Decreased retic Hgb has 94% Sens, 77% Spec for iron deficiency
Measurement of iron parameters may further differentiate iron deficiency anemia from anemia of inflammation, although the distinction can still be difficult. Serum iron levels are low in both conditions. Ferritin is typically decreased in iron deficiency anemia and increased in anemia of inflammation.
%saturation of <20% is suggestive of Fe deficiency
How are PIMA, PRCA, AA, MDS, Secondary dysmyelopoiesis and myelofibrosis differentiated in the cat
CBC, BM cytology and histopathology
PRCA - normocytic, normochromic, non-regenerative anaemia without other cytopaenias. BM has reduced red cell precursors
PIMA - normocytic macrocytic (if agglutinating) anaemia (+/- thrombocytopenia and neutropenia)
Positive SAT/DAT, ghost cells. BM has erythroid hyperplasia, with low M:E +/- erythrophagocytosis. Often see fibrosis and mild dysplasia.
AA- pancytopaenia with BM revealing decreased/absent haematopoietic tissue replaced by fat (requires histo)
MDS - bi or pancytopenia due to ineffective erythropoiesis. Macrocytosis is common
BM: <30% erythroblasts. Dysplastic changes in all cell lines. Associated with FeLV regressive infection, considered pre-leukaemic disease.
Secondary dysmyelopoiesis - non-regenerative anaemia without macrocytosis. Increased BM cellularity with mild dysplastic changes most prominent in erythroid cell line. Blasts are NOT increased. Seen with immune mediated disease, FIP, toxins, drugs
Myelofibrosis - findings are dependent on underlying pathology causing this. Although often detected late in process so cannot be determined. Dx based on histo and staining for reticulin.
Spherocyte and SAT Sens and Spec
> 5/10 hpf
(74% sens, 95% spec)
1:4 dilution
(sens 88% Spec 40-100) stronger specificity with higher dilution but sensitivity decreases
May be affected by disorders causing hyperglobulinemia
Limitations of DAT and flow cytometry
Sens and Spec
Cannot be performed if persistent agglutination after washing
DAT sens 60-82% reported (95% cats)
Spec 95-100%
FC - sens 67-100%; Spec 87-92%
Both affected by immunosuppressive treatments prior to sampling (although does not immediately result in negative sample)
A suggested advantage of flow cytometry compared with DAT is the generation of a more quantitative result, potentially allowing monitoring of therapeutic success.
