Sickle Cell Anemia Research


Sickle cell anemia (SCD) is an “autosomal recessive inherited hemoglobinopathy” that causes vaso-occlusive crises and hemolysis due to an abnormal substitution of amino and glutamic acids on the β-globin chain (Keikhaei, Yousefi, & Bahadoram, 2016, p. 252). Nowadays, hydroxyurea (HU) remains the only method that helps alleviate the symptoms of SCD efficiently. Researchers observe it can increase fetal hemoglobin levels, enhance the overall hemoglobin volumes, and decrease the level of reticulocytes in patients’ blood (Araujo et al., 2016). Thus, in the given paper, the literature pertaining to the effects of HU on various SCD manifestations will be evaluated. All the reviewed articles directly or indirectly answer the formulated PICOT question − will patients with SCD taking HU to be associated with decreased hospitalization and pain crisis rates compared to those not taking HU in the period over six months? It is suggested that HU significantly reduces the chance for the development of SCD-related complications and enhances patients’ laboratory parameters resulting in a reduced number of exacerbations and hospital referrals.

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Literature Review

Common Themes

The six articles selected for the study are devoted to the research of HU effects on patients with SCD. Some of the papers focus on how the therapy influences lifelong morbidity. For instance, Nevitt, Jones, and Howard (2017) note that it can decrease the frequency of pain episodes in patients and prevent various life-threatening complications. Ajuro et al. (2016) also analyze the effects of HU on painful crises and such SCD-related complications as infections. However, unlike other studies, in their research, no significant difference in the manifestation of these health problems was observed among patients who took HU and those who did not.

Fitzhugh et al. (2015) investigate HU’s impacts on organ damage. For this, they focused on underlying mechanisms of the drug’s function, i.e., its ability to increase fetal hemoglobin levels. A similar observation is also made by Keikhaei et al. (2016) − the researchers reveal that, through the stimulation of fetal hemoglobin levels, HU can decrease the severity and frequency of SCD exacerbations.

Another important effect of HU found by Fitzhugh et al. (2015) is the increase in patients’ life expectancy. A similar theme can be observed in the study by Sandhu and Cohen (2015) who state that the administration of HU therapy can potentially prolong patients’ lives. However, they observe that the remedy cannot effectively address the issue of patients’ predisposition to acute and chronic SCD-associated complications including iron overload, chronic kidney disease, etc. The emphasis on the review of chronic complications in older patients with the disease is that what differentiates Sandhu and Cohen’s (2015) study from other works included in this paper. They discussed the most prevalent chronic conditions in the sample to identify their links with reduced life expectancy in the given population group.

The theme in the study by Badawy et al. (2017) is different from all others − it focuses on patients’ perceptions of HU efficacy. The researchers are among “the first to examine the relationship of patients’ perceptions of SCD and hydroxyurea” (Badawy et al., 2017, p. 5). They consider that positive perceptions define individuals’ adherence to treatment and, therefore, contribute to overall medical intervention outcomes.

Some studies derive evidence from the same authors. For instance, Fitzhugh et al. (2015) and Badawy et al. (2017) use the work called “Pulmonary hypertension as a risk factor for death in patients with sickle cell disease” by Gladwin et al. (2004). The information provided by these authors is used in the study to support the findings with the data on SCD comorbidities and explain the pathophysiological mechanisms associated with the disease. Gladwin was also one of the co-authors in other works reviewed by some other researchers of the selected articles. For instance, Sandhu and Cohen (2015) and Keikhaei et al. (2016) use two distinct papers about SCD written by him and his colleagues. Other evidence utilized in the literature reviews is derived from the works by different authors.

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Data, Research Questions, and Conclusions

The data collected in all the six studies support the conclusions made by researchers and, in their turn, the findings correspond with the formulated research questions. Sandhu and Cohen (2015) assessed hemoglobin levels in patients of different ages, identified the duration of their HU treatment and the present SCD-related comorbidities. As a result, they managed to identify the major clinically significant markers of the disease that define life expectancy in adult patients over 40. The findings correspond with the formulated research questions as Sandhu and Cohen (2015) aimed to find prevalent comorbidities in aging individuals undergoing HU therapy and provide recommendations for their management.

Fitzhugh et al. (2015) evaluated data over the period of ten years. They identified the age of individuals and the causes of their death, assessed hemoglobin values, as well as different SCD phenotypes. The researchers found out that pulmonary disease was the major cause of death in the sample. Since the disorder is related to organ dysfunction, it can be regarded as a predictor of mortality in SCD. At the same time, patients with higher fetal hemoglobin levels showed the tendency to live longer. In this way, Fitzhugh et al. (2015) answered their research question about whether HU can delay organ damage and increase life expectancy. Similar data and conclusions were obtained by Keikhaei et al. (2016) who aimed to evaluate what effects does HU have on clinical and hematological signs of SCD over one year, as well as Nevitt et al. (2017) who conducted a systematic literature review to evaluate HU’s efficiency in decreasing pain crises in people of different ages.

Araujo et al. (2016) collected data from the medical records of 50 patients. They assessed the frequency of painful crises as well as the presence of comorbidities, such as hypertension, in them before and after HU therapy administration. The results revealed, “no significant differences between the patients receiving HU compared to those who were not being treated with HU with regard to painful crises, infections, hospitalizations and number of transfusions, unlike other studies that indicated an improvement in these clinical outcomes” (Araujo et al., 2016, p. 44). It is possible to presume that small sample size could compromise the credibility of results. Moreover, it is observed that some study participants did not adhere to treatment protocols and did not take HU regularly.

Badawy et al. (2017), analyzed data on patients’ perceptions of HU therapy and identified their links to treatment adherence, number of hospitalizations, and emergency visits. It is observed that individuals with a higher number of hospital admissions showed worse emotional responses to both SCD and HU, and those who perceived HU as inefficient did not adhere to treatment well. It made researchers conclude that a positive perception of the treatment contributes to better patient outcomes.

Additional Questions

  • If worse perceptions of SCD and HU are correlated with poorer health-related quality of life (Badawy et al., 2017), what are the possible methods to stimulate patients’ positive perceptions and consequently increase their adherence to treatment?
  • How dermatologic, neurologic, gastrointestinal, and hematologic adverse events associated with HU treatment (Keikhaei et al., 2016) can define patient hospitalization rates?
  • If the sample comprised of fifty patients limits the research capabilities (Araujo et al., 2016), what is the optimal size of the sample associated with high-quality findings?


The evidence provided in the papers offers different views on the issues of HU effects on SCD-related pain crises and hospitalization. Moreover, it can help to refine the PICOT question and the overall research process in a way that will lead to minimum interpretation biases. Currently, the formulated question is very general. The factors of age and HU dosage are not considered in it. However, the given variables may significantly influence the research outcomes.

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The findings of the literature review revealed direct links between the recommended HU dose and patient survival (Fitzhugh et al., 2015). At the same time, the dosage can depend on patients’ age and the severity of their conditions. Usually, it varies from 15 to 35 mg/kg/day (Fitzhugh et al., 2015). Moreover, the age of study participants seems to be an important variable because, as it is observed by Sadhu and Cohen (2015), older patients with SCD may have advanced stages of acute and chronic disease-associated comorbidities, as well as conditions related to aging, that may define the frequency of hospitalizations and pain crises in them. For younger patients, the results may be different. Therefore, to reduce possible biases, it will be better to focus on a particular population group, e.g., the pediatric one (age 10-18). However, since in some of the articles the small sample size is regarded as a limitation, it is important to ensure that the number of research participants is big enough. Additionally, in the study by Araujo et al. (2016), the analyzed sub-groups were highly heterogeneous, and it complicated their comparison. Thus, the researcher should pay attention to the factor of homogeneity regarding SCD clinical manifestations in patients who take HU and those who do not.


Araujo, A. M., Bezerra, M. L., Borjes Jr., S. P., Dias, J. S., Lopes, A. F., Neto, V. M., … Sant’Ana, P. G. (2016). Clinical and laboratory profile of patients with sickle cell anemia. Brazilian Journal of Hematology and Hemotherapy, 39(1), 40-45.

Badawy, S. M., Thompson, A. A., Jin-Shei, L., Penedo, F. J., Rychlik, K., Liem, R. I., & Lai, J. (2017). Adherence to hydroxyurea, health-related quality of life domains, and patients’ perceptions of sickle cell disease and hydroxyurea: A cross-sectional study in adolescents and young adults. Health & Quality Of Life Outcomes, 15(136), 1-10.

Fitzhugh, C. D., Hsieh, M. M., Allen, D., Coles, W. A., Seamon, C., Ring, M., … Taylor, J. G. (2015). Hydroxyurea-increased fetal hemoglobin is associated with less organ damage and longer survival in adults with sickle cell anemia. PLoS ONE, 10(11), e0141706.

Keikhaei, B., Yousefi, H., & Bahadoram, M. (2016). Hydroxyurea: Clinical and hematological effects in patients with sickle cell anemia. Global Journal of Health Science, 8(3), 252–256.

Nevitt, S. J., Jones, A. P., & Howard J. (2017). Hydroxyurea (hydroxycarbamide) for sickle cell disease. Cochrane Database of Systematic Reviews, 4(CD002202).

Sandhu, M. K., & Cohen, A. (2015). Aging in sickle cell disease: Co-morbidities and new issues in management. Hemoglobin, 39(4), 221-224.

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