Prevalence and factors associated with severe anaemia amongst under-five children hospitalized at Bugando Medical Centre, Mwanza, Tanzania

This was a hospital-based, cross sectional, prospective study conducted at BMC, in Mwanza. BMC is one of the four referral hospitals in Tanzania, located in the northwestern part of Tanzania, it admits 10,000 children aged 6 to 59 months annually.

Recruitment was done serially after obtaining an informed consent. All children aged 6–59 months who were admitted at BMC and their guardian or parents consented to participate in the study were included. Children with active haemorrhage, bleeding disorders, history of blood transfusion and/or surgery within two months prior to admission were excluded. All children were managed according to BMC paediatric treatment guidelines.

Information regarding patients age, sex, residence, birth weight, natal history of prematurity, breast feeding practices, age at introduction of other types of food, types of complementary food in the first year of life, habit of taking tea and 24 h dietary recall were obtained from parents/guardians. Additional information that was taken included family history of SCD, history of chronic illness, blood transfusion and being on medication. Caretaker occupation, information about family size and education level of the parents were also obtained. Recruited patients were assessed for conjunctival and palmar pallor. A thorough physical examination of these children was performed. Nutritional evaluation was done according to WHO reference standard for malnutrition (WHO technical report series, 1995) for under-five years of age using Z-score (see Table 1) and participants were classified into mild, moderate and severe malnutrition.

Haemoglobin estimation was done by Haemo_control EKF diagnostic machine (EKF diagnostics, Germany). All participants with haemoglobin less than 11 g/dl by haemocue had a complete blood count using an automated haematology analyzer CELL DYN 3700 (Abbott Laboratories, USA). Sickling test was done to detect the presence of haemoglobin S using the sodium metasulphite test. Haemoglobin electrophoresis was done at Muhimbili National Hospital (MNH) laboratory in Dar es salaam, Tanzania to identify haemoglobin genotypes in all children with positive sickling test as well as those with negative sickling test but with symptoms and signs, and peripheral smear results suggestive of SCD. Peripheral smear (using Leishman stain, Ranbaxy, India) was done to look at morphological characteristics of anaemia. Serum ferritin (Ferritin ELISA, Genway Biotech, USA) and C - reactive protein (Direct Latex test, Veda Lab, France) were done in all children with moderate and severe anaemia. Blood smear for malaria parasites was done using Giemsa stain (Ranbaxy, India) and the number of asexual parasite/200WBC was counted. To ensure the quality of the blood slides for malaria parasites and peripheral blood smears, two readings were done by two different experienced laboratory technologists. A laboratory scientist was consulted as a third reader when discordance was noted and Quality control was done by experienced laboratory scientist. HIV testing was done according to the national algorithm. For children below 18 months, DNA PCR for HIV was done in children with positive rapid test, and for those with negative rapid test, but born to HIV positive mothers [9]. For children with HIV positive test, CD4 count (FACS Calibur, BD Germany) was done to detect the severity of immune suppression. All operational definitions used in this study were as defined in Table 1.

Data were double entered using Microsoft Excel 2007, cleaned and analyzed using STATA version 11 (StataCorp, Texas). Categorical variables were reported as proportion and were compared using either Pearson chi squared test or Fischer’s exact test for small numbers. Continuous data were described as means (standard deviation) or medians (interquartile range) depending on the distribution of data. To determine factors associated with severe anaemia univariate and multivariate logistic regression analyses were done. Factors with a p-value of ≤ 0.1 on univariate logistic regression were subjected to multivariate logistic regression analysis. Crude and adjusted odds ratios were calculated to quantify the strength of association between severe anaemia and risk factors. The 95 % confidence interval was determined and risk factors with a p-value of less than 0.05 were considered significant.

Ethical clearance was obtained from the CUHAS-BMC ethics committee. The protocol and importance of the study was explained to the participants’ parents or guardians before recruitment into the study, followed by a signed informed consent by a parent or guardian. Those who refused to participate in the study were given service equal to that of all the other children. Treatment was done according to the BMC paediatric department protocol.

This was done by morphological examination of the peripheral blood film. Seven different morphological types of anaemia were observed; microcytic hypochromic, normocytic normochromic, mixed hypochromic, macrocytic normochromic, mixed normochromic, macrocytic hypochromic and microcytic normochromic anaemia [10].

*Mixed (anisocytosis) means RBCs containing microcytic and macrocytic cells.

Haemoglobin categories were as described below:

The indications for doing haemoglobin electrophoresis were positive sickling test or a peripheral smear suggesting the presence of SCD or first line family with SCD. Also, the presence of physical features suggestive of SCD like bossing of the skull, malocclusion of teeth and gingival hypertrophy were taken into consideration.

For the period from November 2012 to February 2013, 1,050 children were admitted to BMC paediatric wards. Of these, 602 were out of age limit and 448 children aged 6 to 59 months were eligible for determination of prevalence of anaemia. Anaemia was found in 346 (77.2 %) children. The prevalence of mild, moderate and severe anaemia were 16.5 % (74/448), 33 % (148/448) and 27.7 % (124/448) respectively.

To analyze for morphological types of anaemia and factors associated with severe anaemia, 37 children were excluded from 346 children, due to the following reasons; 32 children had blood transfusion prior to admission, 1 child underwent surgery and 4 children had active bleeding. Therefore 309 children were interviewed and examined (Fig. 1). Of 309 children 57.3 % (177/309) were male and 67.3 % (208/309) were below 2 years. The mean age was 23.2 months [IQR 11–33]. Eighty eight percent (272/309) of the children were from Mwanza region. Majority of caretakers were peasants 48.9 % (151/309) and 65.7 % (203/309) had at least primary education. Seventy nine percent (244/309) were weaned earlier than 6 months and 38.8 % (120/309) were severely malnourished. Median haemoglobin was 7.7 g/dl [IQR 5.7–9.7] and according to severity of anaemia median haemoglobin levels for mild, moderate and severe anaemia were 10.4 g/dl [IQR 10.1–10.8], 8.3 g/dl [IQR 7.6–9.1] and 5.2 g/dl [IQR 4.4–6.2] respectively (Table 2).

The commonest type of anaemia was microcytic hypochromic anaemia occurring in 37.5 % (116/309) of children, followed by 33.3 % (103/309) with normocytic normochromic anaemia. One child (0.33 %) had microcytic normochromic anaemia (Fig. 2).

On univariate analysis, factors associated with severe anaemia were child’s age >2 years [OR = 1.9; 95 % CI = 1.1 - 3.0; p-value = 0.012] and habit of taking tea with meals [2.1 (1.3–3.4); 0.002]. Low level of caretaker’s education [2.4 (1.1–5.3); 0.031], unemployment of caretakers [2.1 (1.3–3.5); 0.004] and malaria parasitaemia [4.0 (2.2–7.3); 0.001] were also associated with severe anaemia. On multivariate analysis, the factors associated with severe anaemia were unemployment [2.2 (1.2–4.0); 0.007], malaria parasitaemia [4.0 (2.1–7.8); <0.001] and presence of haemoglobin S [2.0 (1.1–3.5); 0.018] (Table 2). Low birth weight and HIV were not significantly associated with severe anaemia. There was no significant association between severe anaemia and nutritional status i.e. wasting (mild malnutrition, moderate malnutrition and severe malnutrition) [Table 3].

Serum ferritin was done on children with moderate and severe anaemia. Of the 239 children, 22.6 % (54/239) had low serum ferritin levels; the proportion of those with low serum ferritin levels was higher in the group with moderate anaemia 53.7 % (29/54) compared to 46.3 % (25/54) with severe anaemia. This was not statistically significant (p-value = 0.559). Among 309 patients of the study population, 27.5 % (85/309) fulfilled the criteria for haemoglobin electrophoresis. One of the caretakers declined electrophoresis testing in one patient; therefore 27.2 % (84/309) samples were processed. Of these 40.5 % (34/84) were SS, 36.9 % (31/84) were AS and 19 % (16/84) were AA. SS and AS were significantly associated with severe anaemia (p-value = 0.012).

Among the children with moderate and severe anaemia, 41 % (98/239) had microcytic hypochromic anaemia. In correlating morphological types of anaemia and serum ferritin levels, 90.9 % (50/55) of patients with low serum ferritin levels had microcytic hypochromic anaemia (Table 4).

As a referral hospital, it is likely that the patients were highly selected, with the more severe forms of anaemia being seen in this setting. There was limitation in diagnostic facilities to determine causes of anaemia. This included unavailable folate levels, B12 levels, thalassemia, G6PD deficiency and bone marrow biopsy for those with possible bone marrow failure.