Understanding Anaemias for PLAB 1
Anaemias are a common and crucial topic in medical examinations like PLAB 1. This module will cover the fundamental aspects of anaemias, their classification, common types, diagnostic approaches, and management principles, with a focus on UK guidelines.
What is Anaemia?
Classification of Anaemias
Anaemias can be classified based on several criteria, including the underlying cause, red blood cell morphology, and the body's response.
| Classification Basis | Description | Examples |
|---|---|---|
| Etiology (Cause) | Based on the underlying reason for red blood cell deficiency. | Decreased production, increased destruction (haemolysis), or blood loss. |
| Red Blood Cell Morphology (MCV) | Categorized by the mean corpuscular volume (MCV), which reflects the average size of red blood cells. | Microcytic (small cells), Normocytic (normal size cells), Macrocytic (large cells). |
| Pathophysiology | Describes the mechanism by which anaemia develops. | Impaired erythropoiesis, haemolytic anaemia, anaemia of chronic disease. |
Morphological Classification (MCV)
The Mean Corpuscular Volume (MCV) is a key parameter in classifying anaemias. It helps narrow down the potential causes.
Microcytic anaemias are characterized by red blood cells that are smaller than normal (low MCV). This is often due to impaired haemoglobin synthesis. Common causes include iron deficiency anaemia, thalassaemia, and anaemia of chronic disease (though this can also be normocytic). The body struggles to produce enough haemoglobin, leading to smaller red blood cells that are less efficient at carrying oxygen.
Normocytic anaemias have red blood cells of normal size (normal MCV). These can arise from acute blood loss, haemolytic anaemias where red blood cells are destroyed prematurely, or certain chronic diseases affecting bone marrow function. The production or survival of red blood cells is compromised, but their size remains within the normal range.
Macrocytic anaemias involve red blood cells that are larger than normal (high MCV). This is typically due to impaired DNA synthesis, which affects the maturation of red blood cells. Common causes include vitamin B12 deficiency, folate deficiency, and certain medications or alcohol abuse. The cells grow larger as they mature abnormally.
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Common Types of Anaemia
Understanding the specific characteristics of common anaemias is vital for diagnosis and management.
Iron Deficiency Anaemia (IDA)
Vitamin B12 Deficiency Anaemia
Folate Deficiency Anaemia
Haemolytic Anaemias
Haemolytic anaemias are a group of disorders characterized by premature destruction of red blood cells (haemolysis). They can be inherited or acquired.
Key signs of haemolysis include jaundice (due to increased bilirubin), splenomegaly, and elevated lactate dehydrogenase (LDH) and unconjugated bilirubin, with a decreased haptoglobin level.
Anaemia of Chronic Disease (ACD)
Diagnosis of Anaemia
A systematic approach is essential for diagnosing anaemia, involving history, examination, and laboratory investigations.
Full Blood Count (FBC) including haemoglobin, MCV, MCH, MCHC, and red blood cell count. A peripheral blood film is also crucial.
Further investigations depend on the initial findings and suspected cause:
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Management Principles (UK Guidelines)
Management of anaemia is guided by the underlying cause and severity. NICE (National Institute for Health and Care Excellence) guidelines provide a framework for care in the UK.
General Management Strategies
The cornerstone of management is identifying and treating the root cause. This may involve dietary changes, iron or vitamin supplementation, treating underlying conditions, or blood transfusions for severe anaemia.
Always consider the patient's overall clinical picture, including comorbidities and potential drug interactions, when formulating a management plan.
Specific Treatments
Iron deficiency anaemia is treated with oral iron supplements (e.g., ferrous sulfate), with intravenous iron reserved for cases of intolerance or malabsorption. Vitamin B12 and folate deficiencies are treated with parenteral or oral supplements, respectively. Haemolytic anaemias may require immunosuppressive therapy, splenectomy, or blood transfusions depending on the aetiology.
Key Takeaways for PLAB 1
Focus on the common causes of anaemia, their characteristic MCV, and key diagnostic features. Understand the differential diagnosis for each morphological type and the general principles of management according to UK guidelines.
Iron deficiency anaemia.
Vitamin B12 deficiency anaemia.
Learning Resources
Provides comprehensive guidance on the diagnosis and management of iron deficiency anaemia in adults and children, aligned with UK clinical practice.
An accessible overview of anaemia, its causes, symptoms, and treatments from the National Health Service (NHS), useful for understanding patient-facing information.
A detailed learning module covering the diagnosis and management of anaemia, often used by healthcare professionals for continuing professional development.
An in-depth explanation of haemolytic anaemias, their classification, pathophysiology, and diagnostic approaches from a reputable medical resource.
Guidance from the Royal College of Physicians on the diagnosis and management of iron deficiency anaemia, offering a clinical perspective.
A comprehensive overview of megaloblastic anaemias, including vitamin B12 and folate deficiency, with diagnostic criteria and treatment strategies.
Explains common blood tests used to diagnose anaemia and interpret their results, helping to understand the laboratory basis of diagnosis.
A blog post specifically tailored for PLAB 1 preparation, highlighting key concepts and common exam questions related to anaemias.
Information on vitamin B12 deficiency, its causes, symptoms, and treatment, which is directly relevant to megaloblastic anaemia.
Details on folate deficiency anaemia, including its causes, symptoms, and management, essential for understanding megaloblastic anaemias.