Full Blood Count-Case C A 25 year old female: • anaemia • Never pregnant • No change menstrual flow & intermenstrual bleeding • Normal diet • No medications • No change in bowel habit or symptoms of GI/urinary blood loss • No abnormal physical change
Questions Diagnosis: Iron deficiency • Is the MCV consistent with the diagnosis? Explain. • What do the presence of pencil cells, target cells & Howell-Jolly bodies suggest? • Is B12 or folate deficiency suspected? evidence? • Are the lab findings typical of iron deficiency anaemia?
Differential diagnosis • Anemia is generally defined as a hematocrit <40% (hemoglobin <13.5 g/dL) in men or <37% (hemoglobin <12 g/dL) in women • MCV is a way of classifying anaemias morphologically, i.e. microcytic, normocytic and macrocytic • Microcytic anaemia can be caused by • Iron deficiency • Thalassaemia • Anaemia of chronic disease • Sideroblastic anaemia
MCV and iron deficiency • Microcytosis, or a decreased mean cell volume (MCV), is a characteristic feature of iron deficiency anaemia. Why? • Iron deficiency anaemia manifests in 5 stages: • Fe loss exceeds intake, causing progressive depletion of Fe storage. • Exhausted Fe stores cannot meet the needs of the erythroid marrow. • Anaemia with normal-appearing RBCs and indices occurs • Microcytosis (small size, low MCV) and then hypochromia (pale colour, low Hb) is present. • In advanced iron deficiency, anisocytosis (variable cell size) and poikilocytosis (variable cell shape) is seen.
MCV and iron deficiency • Is the MCV result consistent with iron deficiency? • MCV=74fL (80-100fL) • Analysing result: • MCV (mean cell volume) is a measure of the average volume of a single red blood cell. • A value <80fL indicates microcytosis, i.e. the red cells are smaller than usual. • Microcytosis in the presence of anisocytosis means indicates more advanced iron deficiency
MCV and iron deficiency • So initially it can be said that the MCV value of 74fL supports the diagnosis of iron deficiency. However it is not as low as would be expected in iron deficiency. • Since the MCV is an average value for the red cell volume, it must be considered in the context of the low folate level (which causes macrocytosis). • The reason postulated for the slightly lowered MCV is that it is a result of a “balancing out” of the microcytosis caused by the iron deficiency with the macrocytosis caused by the folate deficiency. • Therefore as in this case, patients with concurrent folate and iron deficiency may exhibit a normal or near normal MCV
PENCIL CELLS • Also known as ovalocytes, cigar cells or elliptocytes. • Are elongated hypochromic red blood cells. • Consists of a central area of pallor and haemoglobin at both ends of cell. A characteristic change that occurs in iron deficiency
TARGET CELLS • Scientific name: Codocytes • RBCs appear like a target with a bullseye. • Erythrocytes are thin and have an increased surface membrane area to volume ratio (decrease in haemoglobin content). • Have a central, haemoglobinised area surrounded by an area of pallor. The periphery of the cell contains a band of haemoglobin.
TARGET CELLS The presence of excessive target cells may indicate chronic diseases that cause: • Increases in surface membrane, associated with lipid disorders e.g. rare congenital deficiency of lecithin-cholesterol acyl transferase, and liver disease. • Decreased cytoplasmic volume, is associated with decreased production of haemoglobin (iron deficiency), or manufacture of defective haemoglobin (thalassaemia).
POST-SPELENECTOMY • A major function of the spleen is the clearance of opsonized, deformed, and damaged erythrocytes by splenic macrophages. • If splenic macrophage function is impaired or absent because of splenectomy (spleen removal), altered erythrocytes will not be removed from the circulation efficiently. • Therefore, increased numbers of target cells may be observed.
HOWELL-JOLLY BODIES • Are spherical inclusions of nuclear chromatin remnants in a RBCs (blue black appearance on Wright-stained smears). • They are nuclear fragments of condensed DNA, 1 to 2 µm in diameter, normally removed by the spleen. • They are seen in severe haemolytic anaemias, pernicious anaemia, thalassaemia, and in patients with dysfunctional spleens or after splenectomy.
Vitamin B12 and Folate Deficiency • B12 and folate deficiency share the same haemotological changes including: • Macrocytosis (MCV > 100fL) • Anisocytosis (size variation) • Megaloblastic bone marrow and anaemia • Oval red cells (ovalocytosis) • Hypersegmented neutrophils
Evidence for Vitamin B12 Deficiency • Vitamin B12 deficiency occurs when levels < 130 pmol/L • This patient has: • Serum B12 reading of 220pmol/L • Microcytosis (MCV < 80 fL) • These results are inconsistent with vitamin B12 deficiency.
Evidence for Folate Deficiency • Folate deficiency occurs when: • Serum folate < 11 nmol/L • Red cell folate < 510 nmol/L • This patient has: • Serum folate 2 nmol/L • Red cell folate 100 nmol/L • These results are consistent with folate deficiency.
Folate and B12 Deficiency Conclusion • This patient has serum and red cell folate levels consistent with folate deficiency. • Deficiency associated with folate and/or B12 causes megaloblastic anaemia. • Megaloblastic anaemia causes oval macrocytes, dyspoesis resulting in leukopenia and thrombocytopenia and hypersegmented neutrophils. • Hypersegmented neutrophils is found in moderate amounts in this patient but may be due to folate malabsorption.
Iron Deficiency Anaemia Diagnosis will be based on: • Reduced haemoglobin (man< 12.5- 13.8g/dL, woman<10-11.5g/dL) • Reduced mean cell volume (<80fL) • Reduced mean cell haemoglobin (<27pg) • Reduced mean cell haemoglobin concentration (<300g/L) • Blood film- microcytic, hypochromic red cells • Reduced serum ferritin (<10ug/L) • Reduced serum iron (man<14umol/L,woman <11umol/L) • Increased serum iron binding capacity (>75umol/L)
The following investigation may be required: • Full blood count and blood film examination • Haematinic assays (serum ferritin, vitamin B12 and folate) • Faecal occult bloods • Mid-stream urine • Endoscopic or barium studies of GI tract
Blood Film • Red cells from iron deficient patients contain less haemoglobin than normal. • The red cells appear pale (hypochromic) and smaller than normal (microcytic). • Therefore microcytosis, hypochromia and pencil cells may be present in iron deficiency anaemia. • The patient’s blood film presents hypochromic, microcytic cells, with moderate numbers of pencil cells.
Haemoglobin • The diagnostic criteria for iron deficiency anaemia vary (Hb<10-11.5g/dL for women & <12.5- 13.8g/dL for men) between studies. • The lower limit of the normal range of haemoglobin concentration should be used to define anaemia. • The limitation of using haemoglobin as a measure of iron status are its lack of specificity and its relative insensitivity. • To identify iron deficiency anaemia Hb must be measured together with more selective measurement of iron status. • The patient’s Hb concentration is 65g/L.
Mean Cell Volume (MCV) • Reduced MCV (microcytosis) occurs when iron deficiency becomes severe, following the development of anaemia • A cut off value of 80fL is accepted as lower limit of normal in adults. • The patient’s MCV is 74fL
Serum Ferritin • This is by far the most useful single measure of iron status • It accurately reflects the body stores and it is usually the earliest laboratory measure to change in iron deficiency • It is a sensitive test and is not affected by day to day fluctuation in iron intake. • A low serum ferritin is a certain proof that patient is iron deficient. • Appropriate lower limit of normal would be 15-16ug/L. • The patient’s serum ferritin level is 5ug/L/ • Further tests is usually only required in patient when doubt still remains as to the presence of iron deficiency.
Other Results • A raised platelet count is often seen in iron deficiency, but a normal or low count certainly doesn’t exclude diagnosis. The patient’s platelet count is raised at 500*109/L • WCC and WCC differential is normal for this patient, which is expected in iron deficiency anaemia. • Faecal occult blood testing for this patient is negative, which confirms there is no blood in faeces due to GI/Urinary blood loss. • Red serum folate and red cell folate is also reduced below the normal range for this patient. Therefore patient has a folate deficiency.
Does patient have Iron deficient anaemia? • Supportive results: • Serum ferritin levels <5 ug/L • Decreased hemoglobin (suggesting anaemia) • Blood film: hypochromic (low Hb) and microcytic (low MCV) cells • Presence of pencil cells/target Cells • High platelet count level • Hence it can be concluded that the patient has iron deficiency anaemia.