Sickle Cell Disease

Sickle Cell Disease (SCD) is defined as ‘a group of inherited blood cell disorders’1. People diagnosed with this disease have abnormal haemoglobin called sickle haemoglobin (Haemoglobin S or HbS) which distorts the red blood cells into a crescent shape rather than the typical biconcave disk.2 Haemoglobin is the protein in red blood cells which transports oxygen from the lungs to the body cells.2 As capillaries are characteristically one red blood cell thick, this deformed haemoglobin can cause blockages in the capillaries thus impairing blood flow.2 As blood and oxygen are essential for human life, a disease like this can be fatal if left untreated. SCD also decreases the life span of a red blood cell resulting in anaemia referred to as Sickle Cell Anaemia (SCA).2 The challenges and progress regarding SCD are discussed in the peer review article ‘Central Nervous System [CNS] Complications and Management in Sickle Cell Disease’3 written by Michael Debaun and Fenella Kirkham. I have chosen to analyse the primary research article ‘Controlled Trial of Transfusions for Cerebral Infarcts in Sickle Cell Anaemia’4 in regards to its contribution to the review article.

‘CNS Complications and Management in SCD’ is a peer review article written for the medical journal ‘Blood’ which is published by the American Society of Haematology. With an Impact Factor of 10.452, ‘Blood’5 is the most cited peer reviewed journal in the field of haematology. It targets an international audience and publishes weekly articles covering all aspects of haematology whether it be immunology, hematologic oncology or vascular biology. This article, however, discusses in depth the complications which can arise as a result of SCD, more specifically the occurrence of strokes in SCD patients as well as the effectiveness of preventative measures and treatments in regards to this. The article takes into account many case studies of patients across the world, assessing the multiple causes of stroke in SCD patients and gathering data to increase our understanding of the disease and attempt to discover the most reliable treatment. Due to the in depth discussion and array of medical jargon used in the article, the assumed audience appears to be scientific experts, especially in the field of haematology. However, the information presented in this article could also be targeted at any medical student or doctor looking to gain a more holistic understanding of both disease and the human body. The article could also be useful for doctors looking to determine the most effective modern treatment for a patient with SCD and to prepare themselves for any complication that could arise.

The majority of this article falls under the scientific discipline of haematology. Haematology is defined as ‘the branch of medicine, involving study and treatment of blood’4. Originally I thought this article could also be associated with the field of Genetics as I knew SCD was an autosomal recessive disease. However, my preconceived ideas about this article were incorrect as it more specifically addresses the complications within the CNS, making Neurology a more appropriate discipline for the article to be associated with, as this discipline deals with the structure, function and disorders regarding the nervous system.7

I chose this article because I am interested in hereditary diseases as well as neurology. I find the complex functioning of the human body, specifically the functioning of the central nervous system, to be fascinating. As this article discusses the occurrence of strokes within Sickle Cell Disease patients, specifically children, I decided it would be a perfect choice for me to study. This article encompasses a multiplicity of scientific jargon, so I pinpointed and researched the words which I deemed to be of greatest importance. By simply looking up the words ‘infarct’ and ‘ischemic’ in a dictionary, I began to draw meaning from the text, resulting in a sound understanding of the ideas being discussed. Although some of the medical jargon such as encephalography, venous thrombosis and erythrocytapheresis remained a mystery to me, I was able to gain meaning from the word by understanding its origin. I recognised that erythrocytapheresis must have originated from erythrocyte, which is the scientific name for a red blood cell. This knowledge allowed me to contextualise the information I was receiving. The article first identifies the risk factors for stroke in SCD patients whilst distinguishing which risk factors are more prevalent in children vs adults.3 These risk factors include low oxygen saturation, acute infections, cardiovascular factors and rapid increase in haemoglobin.3 After addressing many of the scenarios which can cause cerebral infarcts or strokes, the article goes on to discuss treatment options, specifically transfusion therapy.3 The article references many case studies which use blood transfusion therapy, also known as hydroxyurea therapy and eventually came to the conclusion that this therapy is effective in children but there is currently no effective treatment for adults with SCD.3

The article references 99 different articles, most of which are primary research articles. The year of publication vary across the references, ranging from 1994 to 2015. There are a range of journals cited including the most influential scientific journal in the world (based on it’s impact factor of 55.873) ‘The New England Journal of Medicine’. Many of the articles referenced contain controlled case studies involving different factors of SCD associated with strokes and stroke prevention.

The primary research article I chose performed a controlled trial to determine the effectiveness of transfusion therapy in preventing strokes in children with Sickle Cell Anaemia.4 196 children between the ages of 5 and 15 were studied, half were given regular blood transfusions and half were observed over a period of 3 years.4 The results stated that 6% of patients in the transfusion group had a stroke or enlarged cerebral infarct whilst 14% of patients in the observation group had strokes or infarcts.4 This study was one of the major contributors to the review article, providing recent evidence (as it was published in 2015) that transfusion therapy is one of the most effective treatments for preventing strokes, especially in children with SCD.4

Secondary literature is usually less concise than primary literature, it incorporates and discusses many different ideas, synthesising them into a singular article allowing the reader to gain a broad perspective of what is being studied. Primary literature, however, focuses on an individual aspect of a topic giving the reader a more complex understanding of the topic. It provides them with the scientific details and results behind the conclusions drawn in a peer review article.

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