Pathology
Haematology
Regarding anaemia, which of the following statements is INCORRECT:
Answer:
Anaemia is defined as a reduction in haemoglobin concentration below the normal range for the age and sex of the individual. Women tend to have lower haemoglobin than men. Anaemia may occur from an actual reduction in total circulating haemoglobin mass, or with an increase in plasma volume e.g. in pregnancy, causing a dilutional anaemia. After acute major blood loss, anaemia is not immediately apparent because total blood volume is reduced and it takes up to a day for plasma volume to be replaced and hence the degree of anaemia to become apparent. The initial clinical features in acute haemorrhage are therefore a result of reduction in blood volume rather than that of anaemia. When anaemia develops slowly, the associated symptoms are often very mild as the body has time to adapt to the fall in haemoglobin. This involves mechanisms such as an increase in red cell 2,3 -diphosphoglycerate (2,3 - DPG), which shifts the oxygen dissociation curve to the right, allowing enhanced delivery of O2 to the tissues, and an increase in stroke volume and heart rate.Anaemia Overview
Pathology / Haematology / Anaemia
Last Updated: 18th September 2024
Anaemia is defined as a reduction in haemoglobin concentration below the normal range for the age and sex of the individual. Women tend to have lower haemoglobin than men.
Normal Values
Although laboratory values vary, typical values would be less than 135 g/L in adult males and less than 115 g/L in adult females. From the age of 2 years to puberty, less than 110 g/L indicates anaemia, and at birth less than 140 g/L indicates anaemia.
Anaemia may occur from an actual reduction in total circulating haemoglobin mass, or with an increase in plasma volume e.g. in pregnancy, causing a dilutional anaemia. Likewise, a reduction in plasma volume may mask anaemia or even cause an apparent polycythaemia. After acute major blood loss, anaemia is not immediately apparent because total blood volume is reduced and it takes up to a day for plasma volume to be replaced and hence the degree of anaemia to become apparent. The initial clinical features in acute haemorrhage are therefore a result of reduction in blood volume rather than that of anaemia.
Clinical Features
When anaemia develops slowly, the associated symptoms are often very mild as the body has time to adapt to the fall in haemoglobin. This involves mechanisms such as an increase in red cell 2,3 -diphosphoglycerate (2,3 - DPG), which shifts the oxygen dissociation curve to the right, allowing enhanced delivery of O2 to the tissues, and an increase in stroke volume and heart rate.
In acute onset anaemia, a lack of physiological adaptation leads to more marked symptoms and signs. Significant symptoms may also occur in more mild anaemia in older patients with impaired cardiovascular reserve.
Non-specific symptoms of anaemia include:
- fatigue
- dizziness
- headache
- palpitations
- tinnitus
- shortness of breath on exertion
- worsening of angina, congestive heart failure or intermittent claudication
Non-specific signs of anaemia include:
- pallor of mucous membranes or nail beds (if Hb < 90 g/L)
- tachycardia
- bounding pulse
- wide pulse pressure
- flow murmurs
- cardiomegaly
- in severe cases, signs of congestive cardiac failure
Causes
Anaemia can be classified according to the red cell size or mean cell volume (MCV), into microcytic, normocytic and macrocytic anaemia. This classification is not perfect, as some conditions can straddle two categories e.g. anaemia of chronic disease is usually normocytic, but may be microcytic or there may be combined macrocytic and microcytic causes cancelling each other out to produce an apparent normocytic anaemia.
- Microcytic anaemia (MCV < 78 fl)
- Iron deficiency
- Thalassaemia
- Other haemoglobin defects
- Anaemia of chronic disease (some cases)
- Congenital sideroblastic anaemia
- Normocytic anaemia (MCV 78 - 98 fl)
- Most haemolytic anaemias
- Anaemia of chronic disease (most cases)
- Mixed cases
- Macrocytic anaemia (MCV > 98 fl)
- Megaloblastic anaemia
- Vitamin B12 deficiency
- Folate deficiency
- Other causes
- Alcohol, liver disease, hypothyroidism, reticulocytosis, cytotoxic drugs, aplastic anaemia, pregnancy, myelodysplastic syndromes, myeloma, neonatal macrocytosis
- Megaloblastic anaemia
Typical Investigations
- Full blood count
- Stained blood film
- Haemoglobin electrophoresis or high performance liquid chromatography (HPLC)
- Haematinic levels (B12, folate, ferritin, iron and iron-binding capacity)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
