Introduction

Beta thalassemia major is an autosomal recessive disease that leads to severe hemolytic anemia, usually in the second half of infancy. [1] Historically, beta thalassemia major was associated with marked osseous changes, particularly facial and limb deformities attributed to bone marrow expansion and cortical thinning caused by ineffective erythropoiesis. [2] The introduction of regular transfusion therapy in the mid-1960s to maintain a near-normal hemoglobin level resulted in the diminution or prevention of bone deformities. Therefore, the detection of low bone mass in many regularly transfused and well-chelated beta thalassemia major patients and other transfusion-dependent thalassemia (TDT) over the last decade was quite unexpected. [2] In thalassemia, marrow expansion causing mechanical interruption of bone formation, leading to cortical thinning, is still considered the main reason for the distortion and fragility of bones in thalassemic patients.

However, the pathogenesis of osteoporosis in thalassemic patients is very complex. The etiology of bone disease in thalassemia is poorly understood and involves multiple factors influencing the reduction in bone mineral density (BMD), mainly but not limited only to genetic factors, endocrine causes like hypoparathyroidism, diabetes mellitus, hypogonadism, iron overload, chelation toxicity, vitamin deficiency (vitamin C and D), and reduced physical activity. [3] The present study aimed to investigate the BMD in pediatric TDT patients and its relationship with mean pre-transfusion Hb, iron overload status, vitamin D and PTH levels, and various other biochemical parameters.

Material and Methods

After obtaining Institutional Ethics Committee and the BORS committee approval, this cross-sectional, observational study was conducted in 84 consecutive patients with TDT between the age group of 8-18 years undergoing regular packed red cell (PRC) transfusion and on iron chelation for a minimum period of two years, attending the Thalassemia daycare Centre in a tertiary care hospital from January 2019 to June 2020 (18 months). Patients having pre-existing bone diseases due to any other causes were excluded from the study.

Osteoporosis was defined as a T score of 2.5 standard deviations below the normal mean BMD for the respective age, whereas a T score between 1.5 and 2.5 standard deviations below normal for the age was defined as osteopenia as per the definition given by WHO. The data collected was analyzed using the SPSS Version 15.0 package. Data was given as Mean ± SD for continuous variables, median and range for non-normal data, and number and percentage for categorical variables. Comparison of mean between 2 groups was carried out by Student’s unpaired t-test for numerical normal data. Mann Whitney U test was applied for comparison of non-normal data. Fisher Exact Probability test or Chi-square tests were applied to compare percentages for categorical data between 2 or more groups. Logistic regression analysis was used to identify risk factors related to osteoporosis among thalassemic patients. All statistical tests were two-tailed. Alpha (α) Level of Significance was taken as P ≤0.05.

Results

Amongst the study subjects 49 (58.3%) patients were males and 35 (41.6%) were females with a male: female ratio of 1.4:1 and maximum patients (45.2%) were in the age group of 9-14 years. 92.9% of patients belonged to the lower class and 7.1% upper lower class. 57.2% of patients were stunted, of which 29.8% were moderately stunted and 27.4% were severely stunted. 11.9% of the study group were severely thin and 11.9% had a very low pre-transfusion Hb of less than 7g/dl. Most of the study subjects (72.6%) were on deferasirox and 47.6% were on chelation therapy for 5-8 years. Though the prevalence of low bone mass was high in thalassemias only 7.1% had symptoms of bone disease. 93% of study subjects had hepatomegaly and 91% had splenomegaly. Out of total 84 subjects, 50(59.5%) had a SMR staging of stage 1, 16(19%) had stage 2 and 16(19%) had stage 3, 1(1.2%) had stage 4 and 1(1.2%) had stage 5 SMR staging.

Table 1: Clinico-epidemiological profile

The mean values of biochemical and hematological parameters are shown in Table 2.

pre-transfusion Hb, Annual PRC requirement, Iron chelating agents, duration of chelation, serum calcium, phosphorous, alkaline phosphatase, PTH and Vitamin D levels (p>0.05). It was found that there was a high prevalence of hypoparathyroidism, hypocalcemia, hypovitaminosis D and increased levels of serum phosphorus and ferritin among those with low BMD,

Discussion

In the present study, most of the patients (45.2%) were in the age group of 9-14 years with a mean age of 12.58±0.57 years and male to female ratio was 1.4:1, suggesting male preponderance which is similar to the study done by Bejaoui et al [5] and Merchant et al. [6] Majority of patients belonged to lower socioeconomic strata (92.9%) which can be explained by the fact that our centre predominantly caters to the need of this class of society. 57.2% were stunted, of which 29.8% were moderately stunted and 27.4% were severely stunted. Among the severely stunted, 53.6% were in the age group of 14-18years and 21.1% in the age group of 10-14years which is similar to the study of Borgna- Pignatti et al. [7] There was a statistically significant association between height and the duration of the disease process in thalassemia. As age advanced the prevalence of stunting increased, the cause for which was multi-factorial. It is also now proven beyond doubt by various studies that improving calorie take and supplementation of micronutrients like Zinc, Vitamin D and Carnitine is known to have a positive effect on the linear growth in thalassemia patients.11.9% of study subjects were severely thin with a BMI of less than -3SD.15.8% of patient aged between 9-14years were severely thin and 11.9% male and 14.3% were female which is comparable with the study done by Asadi Pooya et al. [8]

This suggests that although height is affected significantly, weight is appropriate for that height hence resulting in a normal BMI in a majority of a patients. 11.9% had a very low pre-transfusion Hb of less than 7g/dl with the mean pre-transfusion hemoglobin being 7.76±0.57 g/dl which is correlated with previous studies. [6],[9],[10] The difference in mean Hb between the current study and the other studies [6][9][10] may be attributed to the differences in the educational level, socioeconomic status and proximity to the health care centre with regular follow-up. The mean annual PRC requirement was 175.56±37.77 ml/kg/year which is comparable with the study conducted by Bejaoui et al [5] and Merchant et al. [6] However, mean pre-transfusion hemoglobin is considered a better indicator of transfusion status and annual PRC requirement is primarily used to decide on the need for splenectomy and to calculate the amount of iron loading that occurs due to blood transfusions.

48(57.2%) of them had a severe iron loading in the liver. 8(9.5%) had severe iron loading in heart while 8(9.5%) patients had mild iron loading. These findings follow the previously conducted studies. [10] [15][16][17][18][19].

Bone strength is determined by bone mineral density (BMD). Biomechanical studies have shown a strong correlation between mechanical strength and BMD measured by DXA. [20] There was a statistically significant association between age and low BMD by DXA whole body (P value 0.021) suggesting that BMD reduces significantly with age which is comparable with the study done by Vogiatzi et al [2] and Pollak et al.[21] However, no statistically significant association was found between BMD and gender, pre-transfusion Hb, annual PRC requirement, iron chelating agents and duration of chelation. Serum calcium, phosphorous, alkaline phosphatase, PTH, and vitamin D levels also did not have any statistically significant association with BMD. There was no statistically significant association between BMD and biochemical parameters like LFT and RFT. These results are similar to the previous studies [6][11][22]. However, it was found that there was a higher prevalence of hypoparathyroidism, hypocalcemia, increased Serum Phosphorous levels and hypovitaminosis D among the thalassemics with low BMD. These findings may be attributed to Iron deposition in the Parathyroid gland, poor dietary intake, reduced outdoor physical activities and inadequate chelation therapy. Although higher ferritin levels were noted in patients with low BMD there was no statistical significance between the two in the present study. Multiple studies from around the globe of varying sample sizes like by Merchant et al, [6] Jensen et al, [11] Saboor et al, [17] Karimi et al [22] and Vogiatzi et al [23] did not find any direct significant correlation between the serum ferritin levels and low BMD.

Iron overload by MRI T2* of the liver had no statistical association with BMD which is correlated with a study conducted by Goh et al [24] and Ebrahimpour et al, [25] however iron overload in the myocardium by MRI T2* showed statistical significant association with BMD which is similar to the study conducted by Ebrahimpour et al, [25] suggesting that severe iron overload in the myocardium was a significant risk factor and associated with low BMD as determined by DXA Spine.

Ethics committee approval:The protocol andinformed consentwere approved by the institute's ethical committee.

Declaration of competing interest:The authors declare no conflict of interest.

Acknowledgements:The authors would like to acknowledge NSDL for their support towards the thalassemia patients at our centre.

References