Mediterranean Journal of Hematology and Infectious Diseases

Background: The frequent need for blood transfusion in children with SCA creates the impression that IDA is rare in this class of children. Objectives: The objective of the study is to determine the prevalence of IDA in a population of under-five children with SCA in Lagos, Nigeria. Methodology: Serum iron, total iron binding capacity, transferrin saturation and serum ferritin were assayed in 97 under-five children with SCA and 97 age/sex matched controls. The diagnosis of IDA was established based on the following criteria: haemoglobin <11.0 g/dl plus two or more of the following: MCV <70fl, transferrin saturation (Ts) <16% or serum ferritin (SF) <25ng/dL Results: Overall prevalence of IDA was significantly higher among AA controls. In the younger age group, the prevalence of IDA was significantly higher among HbAA controls while in the older age group the odds of having IDA was three times higher among HbSS subjects but the difference was not statistically significant. Two of the three SCA children with IDA have history of previous blood transfusion. Conclusion: IDA is uncommon in pre-school aged children with SCA. A multi-centre study is necessary to yield large number of transfused subjects to examine the effects of blood transfusion on prevalence of IDA. Introduction. Sickle cell anaemia (SCA) contributes significantly to morbidity and mortality among children in sub-Saharan Africa. Much is known about the disease presentation and end organ manifestation but the iron status in patients with sickle cell disease (SCD) is still a matter of controversy. Iron status in patients with SCD is still a matter of continuing investigation. While some workers have reported prevalent iron deficiency in sickle cell disease patients, 2 – 5 others have emphasized its rarity. 7 In SCA, chronic haemolysis results in increased availability of iron directly from lysed red cells and Mediterr J Hematol Infect Dis 2013; 5; Open Journal System also from increased absorption of iron from the gastrointestinal tract. Additionally, the high load of iron provided by multiple blood transfusions 10 would suggest that iron deficiency is unlikely in SCA. However, in some parts of the world, the frequency of blood transfusion among children with SCA is now less as a result of improved management in recent years. Reduced frequency of transfusion implies a reduction in sources of iron and therefore, increased vulnerability to iron deficiency anaemia (IDA). This assertion is buttressed by a study in the USA which suggested that iron deficiency was commoner than expected in untransfused children with SCA. In addition, frequency and need for blood transfusion are not uniform for all children with SCA. Iron deficiency is a function of the imbalance of iron intake, iron absorption and iron loss. 13 Iron metabolism is unusual in that it is controlled by absorption rather than excretion. 12, 13 In practice iron supplementation is not usually offered in children with SCA for fear of iron overload resulting from an added effect of multiple blood transfusions. In the current report, anaemia was defined according to the WHO standard of haemoglobin concentration below 11G/dl. The reduction of body iron has three main stages: (i) iron depletion which refers to a decrease of iron stores, measured by a reduction in serum ferritin concentration; (ii) iron deficiency, when storage iron is depleted and there is insufficient iron absorption to counteract normal body losses (at this time, haemoglobin synthesis starts to become impaired and haemoglobin concentrations fall), measured by a reduction in serum ferritin, mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH); and (iii) iron deficiency anaemia, the most severe degree of iron deficiency, which refers to a decrease of iron in the red blood cells, measured by a reduction in serum ferritin, MCV, MCH and haemoglobin level. The distinction between “iron deficiency” and “iron deficiency anaemia” is important. They often go hand in hand, but it is possible to be iron deficient without being anaemic. Literature suggests that a low MCV for age, transferrin saturation less than 16% and serum ferritin less than 25 ng/ml are each 100% sensitive for IDA in SCD. – 5 With respect to specificity, serum ferritin less than 25 ng/ml is 100% specific for IDA in SCD. In the general children population, a serum ferritin value below 12ng/ml is usually diagnostic of iron deficiency. However, study has shown that in children with conditions characterized by chronic inflammatory or haemolytic anaemia such as sickle cell disease, a serum ferritin value less than 25ng/ml has been used to predict absent bone marrow iron stores and response to iron therapy. The transferrin saturation less than 16% and low MCV for age have specificities of 77 – 87% and 97% respectively for IDA in SCD. – 5 The sensitivities of same parameters except serum ferritin among children with haemoglobin AA were not different from that for children with SCD, In children with haemoglobin genotype AA, a serum ferritin value below 12 ng/ml is 100% sensitive for IDA. It has been suggested that the use of combination of tests to define iron status in a population improves the precision in diagnosis of IDA. The identification of IDA in children with SCA is important, as IDA contributes to worsening of inherent anaemia and may have negative long-term consequences on neurocognitive development 20 and growth. Studies of iron deficiency among SCA are few in Nigeria. The purpose of this study is to determine the prevalence of IDA in pre-school aged children with SCA. It is expected that the data generated will provide an assessment tool for the monitoring and assessment of IDA among children with SCA in our area of practice. Material and Methods. The cross-sectional study was conducted between December 2009 and February 2010 among children with SCA attending the Sickle Cell Disease Clinic and other Consultant Outpatient Clinics of the Department of Paediatrics, Lagos State University Teaching Hospital (LASUTH), Ikeja in Southwest Nigeria. LASUTH is an urban tertiary health centre. It is a major referral centre serving the whole of Lagos State, which is a major point of entry into Nigeria from different parts of the world and the economic nerve centre of Nigeria. LASUTH’s Department of Paediatric Sickle Cell Disease Clinic runs every Thursdays of the week. The Sickle Cell Disease clinic caters for children up to age 15 years. On average, each Sickle Cell Disease patients are seen in the sickle cell clinic 4 – 6 times annually. As well as medical check-up packed cell volume estimation are also carried out at each clinic visit. Also routine prophylaxis of antimalarials (daily proguanil 100 – 200mg) in addition to folate (5mg) is being currently offered to children with sickle cell anaemia accessing LASUTH’s Department of Paediatric Sickle Cell Disease Clinic. Those with acute medical problems are managed in the paediatric wards or the Children Emergency Room. Approval for the study was obtained from the Ethics Committee of LASUTH. Consecutive SCA patients who came for routine follow up clinic and have satisfied the study criteria were recruited. Healthy controls were children with haemoglobin genotype “AA,” from the General Outpatient and follow-up clinics and healthy children attending other specialist clinics (e.g. Paediatric Dermatology Clinic) and were Mediterr J Hematol Infect Dis 2013; 5: Open Journal System matched for age, and sex. The studied sample size consisted of 194 children, 97 each with haemoglobin genotype SS and AA. Data were summarized for two age categories: age less than two and age two to five years The sample size calculation was based on estimated prevalence of IDA of 13% 22 and 69% 23 among Tanzanian children with SCA and Nigerian children respectively with 90% power at the 5% level of difference between the two groups in a two-tailed test. The haemoglobin genotype of each study subject and control was determined using cellulose acetate paper for electrophoresis in alkaline medium. Inclusion criteria a. Age six months to five years b. Confirmed Hb SS by electrophoresis c. Subjects in steady state i.e. absence of any crisis in the preceding four weeks and absence of any symptoms or sign attributable to an acute illness. Exclusion criteria a. Denial of consent b. Children on long-term transfusion therapy c. Children who had received a blood transfusion within three months prior to the study d. Children with a history of prematurity or low birth weight e. Children who had received iron supplementation within three months prior to recruitment. The inclusion criteria for the controls were the same as for subjects except that the haemoglobin genotype was AA and they had no symptoms or signs attributable to acute illness in the preceding four weeks. Also, the exclusion criteria for the controls were the same as for subjects except that the haemoglobin genotype was AA. Five millilitres of blood were drawn from a convenient peripheral vein and was transferred into plain tubes. The vacuum tubes were labelled and placed in a cool box containing ice-packs. The samples were protected from light at all times using sheets of black plastic. They were transported to the Research Laboratory of the Department of Paediatrics, LASUTH within 8 12 hours. After centrifugation the serum was separated and stored at minus 20oC until assay. The unsaturated or latent iron-binding capacity (UIBC) was measured by spectrophotometric techniques. Transferrin saturation (expressed as percentage of total iron binding capacity) was calculated using the formula: 100 X the serum iron concentration divided by total iron binding capacity. Serum iron was measured using Iron Ferrozine test kit (Biosystems, Spain) while the TIBC was measured by using Iron/Total Iron Binding Capacity reagent set (TECO Diagnostics, USA). Serum ferritin was measured by using human ferritin enzyme immunoassay test kit (Diagnostic Automation, USA). The diagnosis of IDA was established based on the following criteria: haemoglobin <11.0 g/dl plus two or more of the following: MCV <70fl, 26, 27 transferrin saturation (Ts) <16% 26, 27 or serum ferritin (SF) <25ng/dL. 27 Cut-off points were based on laboratory standards and other studies. Social class was determined from occupation and educational attainment of parents using the scheme proposed by Oyedeji. The subjects were classified into one of five classes (I – V) in descending order of social privilege. The data was analyzed using the Statistical Package for Social Science (SPSS) version 17.0. Level of significance was set at p < 0.05. Table 1. Demographic characteristics of the study population Characteristics AA SS ALL