Essay: Overview of sickle cell disease

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  • Overview of sickle cell disease
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SCD is one of the most common genetic conditions of the blood characterized by chronic hemolysis and acute, potentially life-threatening complications. [2] It includes SCA (HbSS), sickle cell’hemoglobin C disease, sickle beta thalassemia, and others. [2,32] This chronic and possibly quite disabling condition mostly affects persons with African, Mediterranean, Middle Eastern and Indian ancestry. [2, 32] According to the most recent statistics, it was estimated that about a quarter million children born with SCD yearly all over the globe. [1] Also, the prevalence of SCD been reported to be around 60,000 in the U.S. and 10,000 in the United Kingdome. [1]
The results of genetic analyses discovered five major sickle haplotypes; Senegal, Benin, Bantu (also called CAR), Cameroon, and the Arab-Indian haplotype. [6] However, SCD is an autosomal recessive disorder and two identical sickle hemoglobin (HbS) alleles (also called hemoglobin SS disease, or SCA) are usually found. [1,2,32] However, occasionally patients may carry 2 dissimilar alleles, i.e. HbS and another hemoglobin mutation such as sickle hemoglobin C (HbC) disease or beta thalassemia (Table 1). [1,2] As result of that, in the individuals with SCD, hemoglobin S will have the highest proportion among the different types of hemoglobin. In contrast to the normal hemoglobin, hemoglobin S polymerizes in case of deoxygenation causing the change of the erythrocytes shape into sickle-like shape. Moreover, the young red blood cells are more adhesive to venular endothelium and leukocytes, leading to VOCs (painful crises) and ischemia, eventually. [1,32] The spleen is one of the frequently damaged organs because of the recurrent splenic infarction, which will consequently increase the rate of infections in those patients. [1] However, vaso-occlusion is only one of several mechanisms causing chronic organ damage. [1]
Table 1:Description of SCD genotypes. [6]
VOCs is a distinctive feature for SCD. At the time of the vaso-occlusive attack, persons with SCD suffer from unpredictable sever intermittent pain which can occur in the chest, abdomen, or the bones and require hospitalization. [1,2,33] Furthermore, these episodes can be exacerbated by change in weather, stress, infections, or strenuous physical activities. [33] Another key feature of this disease is the acute chest syndrome which is characterized by the presence of new pulmonary infiltrate and 1 or more of the following; cough, tachypnea, dyspnea, or fever. [2] Other medical manifestations of SCD include anemia, aplastic crisis (severe anemia), cholelithiasis, splenomegaly or splenic sequestration. [2]
SCD is one of the most prevalent diseases detected at the early stages of life. [1] Despite that reviewing the peripheral smear can give a rapid diagnosis to SCD, confirmation must be done by hemoglobin electrophoresis. [2,34] Additional tests include complete blood count (CBC) and reticulocyte count, urinalysis, and chest x-ray can be done accordingly. [2]
In general, the management of the sickle cell crisis is supportive therapy, which include analgesics and adequate hydration. [1,33] In addition, antibiotics can be added if infection was suspected and blood transfusion may be indicated in case of severe anemia. [1]
Also, patients with acute chest syndrome can be managed by oxygen, antibiotics, bronchodilators and transfusions. [1] On the other hand, surgical intervention can be indicated in some cases such as splenic sequestration. [2] However, clinical trials found that in adults with ‘ 3 painful crises/year, hydroxyurea may be very helpful. Hydroxyurea acts by elevating the level of HbF, which will eventually leads to decrease in the sickle cell crises. [35] Additionally, it’s recommended to vaccinate all of the SCD sufferer with pneumococcal vaccine, haemophilus influenzae type b vaccine, meningococcal vaccine, and annual influenza vaccine. [1] Finally, the use of hematopoietic cell transplantation as curative option is still evolving and data about its efficacy are limited.[36]
SCD patients experience a very wide spectrum of symptoms and complications. The complications could be acute such as osteomyelitis, or chronic such pulmonary hypertensions and others. [1,2] Therefore, they have a shorter life span than the general population. Based on a study conducted in Jamaica, the median survival was 53 years for males and 58.5 years for females. [37] In fact, this is totally depend on the individual phenotype; in other words, patients with severe phenotype has a poor survival and vice versa. [1]
The cognitive function was investigated on a cross sectional study conducted on adults from Jamaica [n=149] and compared with normal controls [n=47] from the community and the results significantly indicated that persons with SCD had a poorer neurocognitive function compared to the general population. [38] In addition, the Pain in Sickle Cell Epidemiology Study (PiSCES) on the other hand concluded that the comorbidity of depression and anxiety might be associated with more pain in patients with SCD. [22]
SCD patients create a great burden on the health system. In the U.S., a historical cohort of SCD-related data from eight states showed that SCD is correlated with high rate of acute care encounter and rehospitalization. [39] Another prospective cohort done in the U.S. found that 50% of hospital admissions because of VOCs were readmitted within 30 days after discharge. [40] Between 1989-1993, the total annual cost of hospitalizations was 475 million dollar (in 1996 dollars) [4]
The burden of SCD can be reduced by lowering the number of high-risk marriages. Therefore, several guidelines has been developed by different countries in order to suppress the spread of the disease .The American College of Obstetricians and Gynecologists guidelines, as an example, recommended that individual with high risk must be offered screening, and couples with risk to have a diseased child must be offered genetic counseling. [41] Similar recommendations can be also seen in the British as well as in the Canadian guidelines. [42,43]
Sickle cell disease in Saudi Arabia
SCD was first described in Saudi Arabia at 1963 in the Eastern province. [44] Afterward, several screening studies have been followed in different areas of the kingdome. [45-48] Initially, three major foci for HbS gene and other genetic anomalies were recognized. Furthermore, in 1980s, a comprehensive national screening program discovered a difference in the frequency of HbS gene in different parts of the country. [45,47,49,50,51] Studies were also done to understand the natural history of SCD, and revealed two major forms of the disease: a mild form and a severe form. The milder form is commonly noticed in the Eastern region of Saudi Arabia. According to the ??-globin gene haplotypes reports, patients from the Eastern region with the milder form has been found to have the Saudi-Indian haplotype, while the Benin haplotype was found in the Western province with a severe form of the disease. [52]
Table 2: phenotypes of SCD in Saudi Arabia (Eastern vs Western). [6]
SCD is highly prevalent in the Eastern region as well as the Southwestern region of Saudi Arabia. [5,6] However, there is no solid data about the true prevalence of SCD in Saudi Arabia. It was estimated that the prevalence of sickle-cell trait falls between 2% to 27%, while the prevalence of SCD was up to 2.6% in some regions. [6] Furthermore, the highest prevalence was found in the Eastern province. Most of these information were collected from the premarital screening program, which undervalue the true rate of the disease. [6] To illustrate, based on newborn screening program, the prevalence in the Eastern province was 21% for sickle cell trait and 2.6% for SCD. Also, the prevalence of SCD in the Eastern province was estimated by the premarital screening program, which underestimated the real prevalence of SCD (nearly 17% for sickle cell trait and 1.2% for SCD). [46,53] Therefore, the newborn screening should be used to identify the true rate of the disease in Saudi Arabia.
The most recent reports about the effectiveness of the premarital screening program found a remarkable decrease in the high-risk marriages and increase in the voluntary cancellations. [7] This demonstrates a very successful example for primary prevention. On the other hand, adding the neonatal diagnosis permits the application of a certain prophylactic measures (e.g. parents education). This is can lead to a better quality of life. [6]
As stated previously, there are two major phenotype in Saudi Arabia; the mild (benign) phenotype is usually seen in the Eastern patients and the sever phenotype in Western patients. Unlike the Western patients, alpha thalassemia coinheritance is more common in the Eastern patients .The mild type is also characterized by higher risk to develop avascular necrosis of the femoral head and late persistent splenomegaly. Meanwhile, acute chest syndrome and the recurrence of acute chest syndrome are markedly higher in the West than in East. VOCs occur equally in the two types, despite it takes place later on life in the Eastern patients. [6] Table 2 summarizes the features of the two types.
SCD mortality data are so limited in Saudi Arabia. A study done in the Eastern province displays 73% deaths happen below 30 years. Moreover, the leading cause of death was acute chest syndrome followed by infections. [8]
Depression: epidemiology and burden
Depression is a psychiatric disorder characterized by depressed mood, reduced positive affect, and loss of interest in the usual activities. Major depressive disorder, dysthymia, and minor depressive disorder are some of numerous depression subtypes reported in the literature. [54]
The diagnosis of each subclass is based on the presence of certain depressive symptoms over a period of time. For instance, According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria, the persistence of five or more of specific depressive symptoms for at least two consecutive weeks is required for diagnosing major depressive disorder. [55] The current evidence showed that the combination of pharmacotherapy and psychotherapy for the treatment of depression is more effective than the use of a single approach alone. [56]
The prevalence of depression is greater in females than males, and in younger than older adults. [57,58] In addition, the frequency of depression increases with chronic conditions like stroke, Parkinson disease, heart diseases, cancers, and autoimmune connective tissue diseases such as Systematic Lupus Erythematosus (SLE). [59-63] On the other hand, the concurrent existence of untreated or poorly treated major depression has been shown to have a substantial impact on the morbidity and mortality for a several medical conditions. [64-66]
Depression is highly distributed around the globe and the rates seem to be increasing. [67] As per the World Health Organization (WHO) report, 121 million individuals worldwide have depression. [68] Another survey conducted in ten countries showed that the lifetime prevalence of major depression was from 3%-17%. [67] In the U.S. , major depressive disorder is common among adults. Furthermore, in 2006 and 2008, the estimated prevalence of depression was 9% among 235,067 adults from 45 states. [69] Also, the lifetime prevalence of major depressive disorder in U.S. adults is 17%. [67] Similarly in Europe the estimated prevalence of depression was 8.5%. [70] However, in Pakistan the overall prevalence of depression and anxiety disorder was about 34 %. [71] Additionally, Qatar has a prevalence of 27.8%. [72] Therefore, depression is a common issue in several countries.
Locally in Saudi Arabia, data about the prevalence of depression in the general population is not available now. However, various regional studies with different study populations showed different prevalence rates. [73-75] Three distinct studies were included in a systematic review and meta-analysis conducted by Al Ibrahim et al. and the overall prevalence of depression was 41%. [73] In Taif, a study was done on 490 secondary school students found that one third of the sample suffered from depression. [74] Another study conducted on primary health care patients [n= 280] and the results displayed a prevalence rate of 12%. [75] A recent cross sectional study was conducted in Riyadh region at three big primary health care centers [n= 477] and nearly half of the sample was depressed. [76]
The risk of suicide increased with depression. [77] Based on the WHO report, its predicated by 2020 that depression will be responsible for more lost disability-adjusted life-years (DALYs) than all other disease, except for coronary heart disease (i.e. depression will be the second leading cause of disability worldwide). At present, depression is the second leading cause of DALYs lost worldwide in the age 15’44 years for both males and females combined. [68] Furthermore, depression results in huge economic burden, causing the loss of billions of dollars in the U.S. only. [78]
In the Arab world, a recent study showed that major depressive disorder was leading cause of years of life lived with disability (YLDs) in 1990, 2005, and 2010. In addition, the results of the former study demonstrated that the DALYs from depression have been increased since 1990. [79] In Saudi Arabia, another recent paper showed that major depressive disorder was the leading cause of DALYs in female in 2010. [80] Therefore, awareness and screening high-risk group is crucial.
Screening recommendations differ from country to another. While the Canadian guidelines were against the routine screening, the guidelines from the National Institute for Health and Clinical Excellence (NICE) propose targeted screening for individuals at high risk of developing depression, such as those with past history of depression, and chronic medical conditions (e.g. diabetes, coronary heart disease, and others). [54,81] Additionally, NICE recommended the use of the Patient Health Questionnaire-2 (PHQ-2) for suspected cases.
Despite the alarming rates of depression in Saudi Arabia, there is limited data about the rate of depression in the general population. There is no information about the cost of treatment of depression and the benefit of screening programs. Moreover, there is no particular protocol for screening depression. [76] Therefore, efforts must be made by the Saudi Ministry of Health to fill this knowledge gap.
Sickle cell disease and depression in adults
Similar to other chronic diseases, psychiatric difficulties and depression are common in SCD. This can be contributed to many factors including; the disease chronicity, physical symptoms, the social stressors and others. In general, the rates of depression in SCD range between 18% to 44%. [18-30,82] One of the early studies to explore this association, a paper reporting a three cases that were managed with antidepressant and family therapy, and proposed that depression occurs more common than previously anticipated. [30] Afterward, 89 patients with SCA was examined using the Chronic Illness Problem Inventory (CIPI) by Barrett et al. and found depression to be a common issue among these patients. [17] In contrast to the previous studies, the Hamilton rating scale has been employed to assess depression in 30 patients with SCA and 31 sickle cell traits and the finding was indicting no association between SCA and depression in all of the patients. [28] However, Molock and Belgrave review at 1994 stated that depression is far common in SCD patients than among controls. [29]
Over years, different instruments have been used to evaluate depression in SCD. [5,18-30] Frankfurter Befindlichkeitskala (FBS) and the 12-item General Health Questionnaire (GHQ-12) were the tools in one of the studies to interview 170 adults with SCD and advised the health care providers to ask their patients about their social life and to provide them with psychiatric referral. [16] In a different study the Goldberg General Health Questionnaire and the Leeds Self-Assessment for depression and anxiety were applied on 38 SCA patients and matched controls and found 3 folds increase in the anxiety and depressive symptoms in SCA patients compared to the controls. [15] Wilson Schaeffer et al. assessed 440 adults’ patients using the Center For Epidemiologic Studies ‘Depression scale (CES-D) and reported a prevalence rate of 18%. [82] A convenience sample of 27 male and 23 female was examined by the Beck Depression Inventory (BDI) in order to assess the prevalence of depression in SCD patients, and the results were indicative of a high rate of depression among SCD patients compared to the general population. [25] Similarly, depression was higher than the general population found in a cross sectional study used the BDI fast screen in 232 African American adults with SCD. [24] One hundred and two patients with SCD and 103 African American individual without SCD were tested using the 10-item Center For Epidemiological Studies Depression scale (CES-D) to evaluate the relationship between elevated depressive symptoms and the clinical severity of SCD and concluded that the observed association is merely due to the adverse economic conditions correlated with SCD. [83] Although self-reporting is not a preferable strategy while conducting a research, a recent survey was conducted in 30 male and 37 female with SCD to evaluate the self-reported rates of depression and the results show that 36% of the sample self-reported depression while 22% had mild depression by the BDI. [21]
The association between pain and depressive symptoms has been addressed in some studies. The results of the pain in sickle cell epidemiology study, which is a prospective cohort designed mainly to estimate the prevalence of depression on 308 SCD adults, showed that approximately 27% were depressed and suggested that depression and anxiety predicted more daily pain in SCD patients. [22] In 2010, a Bahraini prevalence study enrolled 138 SCA with VOCs and 105 SCA without VOCs and administrated Depression Anxiety Stress Scale (DASS-21) and the results suggested a positive correlation between painful crises and anxiety disorder. [19]
Worldwide, various studies explored the relationship of depression and SCD. [18-30,82] In Africa, for example, two studies examined this topic. [11,20] A large study conducted in Nigeria to investigate the impact of SCD in 408 participants reported that about 50% of the sample had depressive feelings. [11] One more international study took place in Jamaica aims to estimate the prevalence of depression in SCD patients [n=277] and controls [n=65] and depression rate was 21.6% in SCD patients and 9% in the controls. [20] However, no study was published addressing this issue in the Middle East aside from the formerly described Bahraini study. [19]
The results of above-mentioned studies were not conclusive. Furthermore, the possible shortcomings include; their limited number, small sample size, variable tools, retrospective design, and the sample representativeness. However, most of the studies that found a positive association recommended psychiatric evaluation and intervention for those patients and asked for further research. [33]
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