Welcome to the MEDIT & CME Academy blog! If you're a postgraduate medical doctor preparing for the MRCP (UK) Part 1 examination, you've come to the right place. In this post, we'll delve into a crucial topic within Clinical Haematology: Iron-Deficiency Anaemia.
A solid understanding of this condition is vital for both the exam and your future clinical practice.
Introduction: Iron-Deficiency Anaemia and the MRCP (UK)
As you prepare for the MRCP (UK) Part 1, you'll encounter numerous questions on anaemia. Iron-deficiency anaemia is not only the most common type globally but also a frequent feature in exam scenarios. Therefore, mastering its pathophysiology, diagnosis, and management is essential.
This blog post will provide a structured approach to understanding iron-deficiency anaemia, aligning with the MRCP (UK) syllabus and helping you achieve exam success.
Learning Outcomes: What You Need to Know
By the end of this post, you should be able to:
Describe the normal metabolism of iron, including dietary absorption (duodenum), transport (transferrin), storage (ferritin), and recycling.
Identify common causes of iron-deficiency anemia, including nutritional deficiency, chronic blood loss (e.g., gastrointestinal bleeding, menorrhagia), increased requirements (e.g., pregnancy, growth), and malabsorption (e.g., celiac disease, post-gastrectomy).
Explain the clinical features of iron-deficiency anemia, including fatigue, pallor, breathlessness, angular cheilitis, glossitis, and koilonychia.
Recognize the signs and symptoms of severe anemia and chronic iron deficiency, such as cognitive impairment and pica.
Interpret key laboratory findings in iron-deficiency anemia, including low haemoglobin, microcytic hypochromic red cells (low MCV and MCH), low serum ferritin, low serum iron, high total iron-binding capacity (TIBC), and low transferrin saturation.
Differentiate iron-deficiency anemia from other microcytic anaemias, such as thalassaemia, anaemia of chronic disease, and sideroblastic anaemia.
Describe the steps in evaluating the underlying cause of iron deficiency, including screening for gastrointestinal blood loss (e.g., faecal occult blood test, endoscopy) and assessing dietary intake.
Outline the principles of management for iron-deficiency anemia, including dietary counselling, oral iron supplementation, parenteral iron therapy in cases of intolerance or malabsorption, and addressing the underlying cause.
Discuss the side effects of iron supplementation, including gastrointestinal symptoms such as constipation, diarrhoea, and nausea, and strategies to improve tolerance.
Explain the importance of monitoring response to treatment, including reticulocyte count, normalisation of haemoglobin levels, and replenishment of iron stores (serum ferritin).
Understanding Iron Metabolism
Iron is crucial for oxygen transport and various enzymatic processes. A thorough understanding of its metabolism is fundamental for diagnosing and managing iron-deficiency anaemia. Dietary iron is absorbed primarily in the duodenum. Heme iron (from animal products) is more readily absorbed than non-heme iron (from plant-based sources).
Absorption is enhanced by vitamin C and inhibited by phytates and tannins. Once absorbed, iron is transported in the plasma bound to transferrin. It's stored as ferritin, mainly in the liver, spleen, and bone marrow. Red blood cell breakdown releases iron, which is then recycled.
Causes of Iron-Deficiency Anaemia
Iron-deficiency anaemia arises when iron demand exceeds supply. Common causes include:
Nutritional Deficiency: Inadequate dietary intake, particularly in vegetarians, vegans, and individuals with poor diets.
Chronic Blood Loss: Gastrointestinal bleeding (e.g., ulcers, colorectal cancer, NSAID use), menorrhagia, and hookworm infection. Identifying the source of chronic blood loss is paramount.
Increased Requirements: Pregnancy, lactation, and periods of rapid growth in children.
Malabsorption: Conditions like celiac disease, post-gastrectomy states, and inflammatory bowel disease impair iron absorption.
Clinical Presentation
Patients with iron-deficiency anaemia often present with:
Fatigue and Weakness: Due to reduced oxygen-carrying capacity.
Pallor: Pale skin and mucous membranes.
Breathlessness: Especially on exertion.
Angular Cheilitis: Cracking at the corners of the mouth.
Glossitis: Inflammation of the tongue.
Koilonychia: Spoon-shaped nails.
Pica: Craving non-food items (e.g., ice, dirt). This is more common in severe or chronic cases.
Cognitive Impairment: Can occur in severe or long-standing cases.
Laboratory Diagnosis
Key laboratory findings include:
Low Haemoglobin: Reduced red blood cell mass.
Microcytic Hypochromic Red Cells: Low MCV (mean corpuscular volume) and MCH (mean corpuscular haemoglobin).
Low Serum Ferritin: Best indicator of iron stores.
Low Serum Iron: Measures the amount of iron bound to transferrin.
High Total Iron-Binding Capacity (TIBC): Reflects the increased availability of transferrin binding sites.
Low Transferrin Saturation: Percentage of transferrin bound to iron.
Differential Diagnosis
It's crucial to differentiate iron-deficiency anaemia from other microcytic anaemias:
Thalassaemia: Often associated with a normal or elevated red blood cell count and normal to low TIBC levels and normal to elevated ferritin levels .
Anaemia of Chronic Disease: Usually normocytic or mildly microcytic, with normal or elevated ferritin.
Sideroblastic Anaemia: May be microcytic or macrocytic, with ringed sideroblasts in the bone marrow.
Evaluation of Underlying Cause
Identifying the cause is vital. Investigations may include:
Detailed History and Physical Examination: To identify potential sources of blood loss or malabsorption.
Faecal Occult Blood Test (FOBT): To screen for gastrointestinal bleeding.
Endoscopy (Upper and Lower): If FOBT is positive or if there's a high suspicion of GI bleeding.
Assessment of Dietary Intake: To identify nutritional deficiencies.
Management
Management involves:
Dietary Counselling: Increasing iron intake through iron-rich foods.
Oral Iron Supplementation: Ferrous sulphate is commonly used. Take on an empty stomach for better absorption, and not more than once daily.
Parenteral Iron Therapy: Indicated in cases of intolerance to oral iron, malabsorption, or significant blood loss.
Addressing the Underlying Cause: Treating conditions like ulcers or menorrhagia.
Side Effects of Iron Supplementation
Common side effects include gastrointestinal symptoms like constipation, diarrhoea, nausea, and abdominal pain. Strategies to improve tolerance include starting with a low dose and gradually increasing it, taking iron with food (although absorption is reduced), and using different iron formulations.
Monitoring Response to Treatment
Monitor response with:
Reticulocyte Count: Should increase within a week of starting iron therapy.
Haemoglobin Levels: Should normalise within a 4-8 weeks.
Serum Ferritin: To assess replenishment of iron stores.
Conclusion
Iron-deficiency anaemia is a common and important condition to master for the MRCP (UK).
By understanding its pathophysiology, causes, clinical features, diagnosis, and management, you'll be well-prepared to tackle related exam questions and provide excellent patient care. Remember to consider the differential diagnoses and always investigate the underlying cause of iron deficiency.
We hope this comprehensive overview has been helpful in your MRCP (UK) Part 1 preparation. For more in-depth learning and expert guidance, don't forget to check out our Haematology MRCP Part 1 Short Course at CME Academy: https://www.cmeacademy.online/courses/haematology-mrcp-part-1.
Good luck with your studies!