Introduction

Sickle cell anaemia [SCA] is characterised by presence of an abnormal haemoglobin HbS. It is due to genetic replacement of valine from the 6^th position in the β globin chain by glutamic acid.1 The World Health Organization accepted SCA as a global public health problem in 2006.2 As per WHO report3 there is unceasing addition of new cases of sickle cell carriers and sickle cell homozygous every year. Globally India accounts for 14.5% of the total new-borns with SCD.4 SCD is the inherited disorder; largely found in people of African, Indian and Arab ancestry.5, 6, 7 First Indian case of sickle cell was detected in the Nilgiri hills of south India by Lehman and Cutbush in 1952.8 Later, Dunlop and Mazumder reported cases of sickle haemoglobin among the tribal tea garden workers of Upper Assam.9 Further studies conducted in India found that prevalence of sickle cell anaemia is higher among tribal populations particularly from a few pockets of Maharashtra, Gujarat and Madhya Pradesh.10

Major function of Haemoglobin is transportation of gases. Haemoglobin is a conjugated protein having four globin chains. Combinations of α gene with β, δ and γ genes give rise to the formation of various types of haemoglobins. Association of α2 β2 forms haemoglobin A₀ [HbA₀] which makes 97% of total haemoglobin in adult, α2 δ2 forms Haemoglobin A₂ [HbA₂] accounts for 2% and haemoglobin F formed by α2 γ2 is less than 1% in adult hemoglobin.11 Normally HbF is 95 to 98% at birth which gradually decreases to less than 1% at the end of one year of age.12 Similarly HbS is absent unless individual has sickle cell disease.13 Sickle cell anaemia homozygous HbSS is severe and express Sickle Cell Disease [SCD]. SCD patients are at risk of infectious diseases including pneumonia, blood stream infections, meningitis, and bone infections. Sickled cells can clog blood vessels leading to damage and increase susceptibility to cardiovascular diseases at an early age.14 Chronic haemolytic anaemia, painful episodes of Vaso-occlusion, risk of infections, acute chest syndrome and damage of multiple organs are clinical complications.15, 16 Among haemoglobins, HbS has the lowest affinity for Oxygen as compared to HbA and HbF.17 Sickle haemoglobin [HbS] has tendency to polymerise under hypoxia and stress whereas higher levels of HbA₂ and HbF can inhibit the polymerization of HbS.18, 19 Therefore higher concentrations are beneficial in sickle cell anaemic individuals. Also HbF prevents erythrocyte sickling by exclusion from polymer formed by HbS. Present therapeutic research is aiming to maintain high levels of HbF, reduce 2,3 BPG and increase oxygen to reduce ill effect.20 Naturally elevated levels of HbF are reported in tribal communities having sickle cell anaemia.21 Elevated levels of HbF (30%) in Hereditary persistence of HbF (HPFH) eliminates symptoms of sickle cell disease and haemolytic anaemia.22 In contrast to the high polymerization tendency, HbS shows a protective role against malaria.

Therefore, the present study was performed on patients of sickle cell anaemia from tribal regions of North East Gujarat to assess the beneficial effect of HbA₂ and HbF levels on general health by comparing with normal healthy individuals of the same age group.

Aim

To assess beneficial effect of higher than normal level of HbF and HbA2 in tribal patients of SCA from North East Gujarat.

Objectives

To evaluate levels of different Haemoglobin fractions in normal healthy Individuals and tribal patients having sickle cell anaemia for more than 5 years. To correlate levels of HbA₂ and HbF in Sickle cell anaemia patients with their general health status.

Materials and Methods

Present prospective, analytical, case control study was carried out at Central Clinical Biochemistry lab of Zydus Medical College and Hospital, Dahod.

Participant registration: Random sampling method was adopted for selection of participants for the present study. The study population comprised 50 Sickle cell anaemia patients of both genders having sickle cell anaemia for more than 5 years. Participants having records of tribal community and presence of sickle cell anaemia were randomly selected from the Outpatient department. Fifty healthy subjects devoid of any type of hemoglobinopathies were randomly picked up as controls. Study population was divided into two groups. Group-I comprised known cases of sickle cell anaemia patients and Group-II was control subjects.

Results

A total of 100 subjects were registered for present study. Among which 50 subjects were from tribal communities and had sickling tests positive. They had this disease for more than 5 years. Another 50 subjects taken as a control group exhibited sickling test negative and had no symptoms of anaemia.

Data from 50 tribal sickle cell anaemia patients of both genders shows 16 males and 34 females with a mean age of 11.3 Years (range 6 to 37 years, male mean age 9.8years and female mean age 13.4years). Among 50 control subjects of both gender shows 21 males and 29 females with mean age of 15.9years (range 5 to 40 years, male mean age 16.2 years and female mean age 15.1 years).

As shown in Table 1 Mean total haemoglobin (THb) levels in sickle cell anaemia is 8.62 ± 1.28 gm/dl which is lower as compared to 13.51 ± 0.44gm/dl in healthy control.

HbF, HbS and HbA₂ levels in the SCA group are significantly elevated (p < 0.001) when compared with the control group. Whereas mean HbA0 levels in the SCA group [7.28 ± 6.42%] are significantly reduced (P<0.001) compared to the control group [95.59 ± 1.05%].

Concentration of HbA2, HbS and HbF in SCA are 5.14 ± 1.68%, 72.70 ± 8.43% and 12.80 ± 6.76% respectively; these values of haemoglobin fractions are found elevated when compared with respective values of control group 2.69 ± 1.26%, 00 ± 00% and 1.41 ± 0.51%.

A total of 18 sickle cell anaemia tribal patients (12 male and 6 female) reported clinical concern whereas 32 sickle cell anaemia tribal patients either did not have any clinical alerts or it was very minor. Among 18 patients reported clinical concern 03 needed repeated hospitalisation, 08 patients had high frequency of cold and cough [reduced immunity], 03 patients expressed chest pains, 07 patients expressed occasional painful episodes, 02 patients had haemolytic anaemia and only one individual had vaso-occlusion findings. When this sick group of patient’s HbF fraction was correlated it was found that their HbF concentration was less than 3% whereas those who did not show clinical complains have HbF levels more than 5%, Among 32 non complaining group, 42.6% patient’s HbF levels were more than 9%.

Discussion

Sickle cell anaemia is a noteworthy but less recognised global health problem which takes away life of young ones.25 Sickle cell disease is a molecular defect where sickle haemoglobin polymerizes at reduced oxygen tensions and deforms red cells into the characteristic rigid sickle shape. Such inflexible red cells cannot pass through the microcirculation resulting in early destruction and intermittent vaso-occlusion resulting in tissue damage and pain.13 This crunch arising from sickled haemoglobin is inhibited in patients with elevated HbF level. Although all patients with SCA have the same molecular defect, there is considerable clinical variation seen among them ranging from deaths at early childhood25 to a normal life span with few complications.26, 27

Foetal haemoglobin (HbF, α₂γ₂) can inhibit the deoxygenation induced polymerization of sickle haemoglobin (HbS, α₂βS₂) which drives the pathophysiology of sickle cell disease.28 Patients with increased levels of HbF often tend to have a relatively mild clinical course as HbF reduces the tendency of HbS to polymerize within the red cell. This highlights the need to maintain high HbF levels along with HbA2 in SCA.

The switch from HbF to HbS in sickle cell anaemia is delayed, and stable levels of HbF are not reached until age 5 to 10 years. Our results of HbA, HbA2, and HbF among healthy control groups were consistent with other studies.29 In the present Study levels of haemoglobin variants among sickle cell anaemia cases are compared with haemoglobin of normal healthy individuals. Total haemoglobin level among SCA patients is low, plausible cause may be chronic haemolysis. Our Hb levels are lower than similar studies performed by Kohchale SR(2015) in western Maharashtra.30 We observed clinically moderate anaemia in patients with SCA. Along with haemolysis, additional contributing factors may be poor nutrition, recurrent infection in tribal children.

Present study also observed a significantly elevated level of HbS along with HbA₂ and HbF in SCA patients and significantly decreased level of HbA0 as compared to the control group. Our results are in agreement with studies done by Ajjack EA(2014) and Shirley L (2009).31, 32 Earlier reports show 6% to 7.4% HbF concentrations among SCA our results of HbF are higher (12.80% ± 6.76%) than earlier reports. Tribal communities with SCA have expressed higher levels of HbF. Higher expression of HbF in adulthood amends morbidity and mortality in SCA. High concentration of HbF in HPFH nullifies the effect of sickle anaemia. Thus looking at the longevity of life and less clinical crises among tribal sickle anaemia patients substantiates the ameliorating effect on general health status.

Conclusion

Decreased level of HbA0 compensated by increased concentration of HbF and HbA2 among SCA indicates beneficial effect on general health of tribal sickle cell anaemic patients of North East Gujarat. Though the sample size was small, a similar study with a large sample size is desired.

Source of Funding

None.

Conflict of Interest

None.