|Year : 2020 | Volume
| Issue : 3 | Page : 190-195
Pattern of haemoglobin phenotypes in newborn infants at the national hospital abuja using high performance liquid chromatography
Ramatu Mohammed-Nafiu1, Lamidi Isah Audu2, Mu'uta Ibrahim3, Tambi T Wakama4, Effiong J Okon1
1 Department of Paediatrics, National Hospital, Abuja, Nigeria
2 Department of Paediatrics, Barau Dikko Teaching Hospital, Kaduna State University, Kaduna, Nigeria
3 Department of Paediatrics, Aminu Kano Teaching Hospital, Bayero University, Kano, Nigeria
4 Department of Haematology, National Hospital, Abuja, Nigeria
|Date of Submission||19-Feb-2020|
|Date of Decision||17-Apr-2020|
|Date of Acceptance||19-Apr-2020|
|Date of Web Publication||17-Jul-2020|
Dr. Lamidi Isah Audu
Department of Paediatrics, Barau Dikko Teaching Hospital, Kaduna State University, Kaduna
Source of Support: None, Conflict of Interest: None
Background: Haemoglobin (Hb) disorders are among the most common blood genetic disorders worldwide, and they constitute an important cause of morbidity and mortality, especially in Nigeria. Despite the clinical significance of early diagnosis, newborn screening for these conditions is not routinely done in Nigeria. Objective: This study was undertaken to document the pattern of Hb phenotypes of newborn babies at the National Hospital Abuja and highlight the relevance of neonatal screening for early diagnosis of abnormal Hb phenotypes in Nigeria. Subjects and Methods: A prospective study of eligible newborn babies delivered in the hospital at the study site was undertaken following parental informed consent. Venous blood was collected from the babies into an ethylenediaminetetraacetic acid sample bottles. The samples were analysed using high-performance liquid chromatography (HPLC) techniques, and the Hb phenotypes obtained were documented. Data were analysed using the Statistical Package for Social Sciences (SPSS) version 20 (IBM-SPSS, Armonk, NY, USA). Results: Three hundred and eleven newborns (male = 173, female = 138) aged 0–28 days were recruited. Two hundred and thirty-six (75.9%) babies had Hb AA (FA) phenotype, 63 (20.3%) Hb AS (FAS), 6 (1.9%) Hb SS (FS), 4 (1.3%) Hb AC (FAC) and 2 (0.6%) had abnormal HbA variants. The overall prevalence of abnormal Hb phenotype was 24.1%. The results showed a significant association of sex (P = 0.003) and ethnicity (P = 0.047) with Hb phenotype. Conclusion: There is a wide spectrum of abnormal Hb phenotypes in Nigeria, and these phenotypes can easily be detected at birth using HPLC. We, therefore, recommend routine neonatal screening for sickle cell disease by HPLC in Nigeria.
Keywords: Haemoglobin phenotype, high-performance liquid chromatography, newborn infants
|How to cite this article:|
Mohammed-Nafiu R, Audu LI, Ibrahim M, Wakama TT, Okon EJ. Pattern of haemoglobin phenotypes in newborn infants at the national hospital abuja using high performance liquid chromatography. Niger Postgrad Med J 2020;27:190-5
|How to cite this URL:|
Mohammed-Nafiu R, Audu LI, Ibrahim M, Wakama TT, Okon EJ. Pattern of haemoglobin phenotypes in newborn infants at the national hospital abuja using high performance liquid chromatography. Niger Postgrad Med J [serial online] 2020 [cited 2020 Aug 13];27:190-5. Available from: http://www.npmj.org/text.asp?2020/27/3/190/289913
| Introduction|| |
Haemoglobinopathies which consist of various types of abnormal haemoglobin (Hb) phenotypes are among the most common genetic disorders worldwide. They are inherited as autosomal recessive genes from healthy carrier parents. They account for an annual estimate of 300,000–500,000 births across 193 countries including Nigeria and constitute a significant global public health problem., The most common are the sickle cell disease (SCD) and the thalassaemias.
SCD results from point mutation of the beta-globin chains (β) of adult Hb., In the sickle cell Hb, valine replaces glutamic acid in the sixth position of the β–chain. The homozygous sickle cell anaemia (HbSS) is the most common clinically significant form of SCD., In Nigeria, the estimated carrier prevalence is 24% and about 150,000 children with HbSS are born annually. Other variants of SCD include: HbSD, HbSC, HbSO− Arab, HbSβ+ thalassaemia and HbSβ thalassaemia.
In Africa, the World Health Organization estimates that SCD is responsible for 9% of all deaths in under-fives and as high as 15% in some countries in West Africa. Early diagnosis of SCD through newborn screening reportedly resulted in a significant reduction in mortality. Although routine neonatal screening programme for SCD has been implemented in most developed countries of the world, including the United States, Canada and the United Kingdom,,,, the contrary is the case in many sub-Saharan countries including Nigeria. A few studies from Africa by Rahimy et al. and Mcgann et al. in Benin Republic and Angola, respectively, have also demonstrated that newborn screening when implemented as a policy can drastically reduce morbidity and mortality from SCD. High-performance liquid chromatography (HPLC) is used as the primary screening method because it has quantitative capabilities as well as higher sensitivity and specificity than isoelectric focusing or two-tier electrophoresis using cellulose acetate and citrate agar electrophoresis. It is capable of detecting a wide range of Hb variants including HbF, HbA, HbS, HbC, HbD and HbE in a 2.5-min runtime.
This study was undertaken to describe the pattern of Hb phenotypes of newborn babies at the National Hospital Abuja and document the prevalence of abnormal Hb phenotypes using HPLC in neonatal screening for haemoglobinopathies. It was hoped that the findings would guide policy direction on newborn screening for SCD in Nigeria.
| Subjects and Methods|| |
The study was conducted at the labour ward and neonatal unit of the National Hospital Abuja over a period of 3 months from 1st August to 31st October 2016. The neonatal unit is a level 2 neonatal intensive care unit with a total capacity for 40 babies and an annual admission rate of 1000–1500, 55% of which are outborn babies. The labour ward has 16 delivery beds and a delivery rate of 2500–3000 per annum.
This was a cross-sectional, hospital-based descriptive study conducted on newborn babies.
Sample size determination
The sample size of 311 was determined using the Fisher's formula for calculating minimal sample size for descriptive studies i.e., n = z 2pq/d 2.
n = minimum sample size.
z = percentage point of standard normal distribution curve which corresponds to 95% confidence interval.
p = prevalence rate of carriers for sickle cell in Nigeria is 24%.
q = complimentary probability; q = 1−0.24 = 0.76.
d = degree of precision at 95% confidence limit; d = 5% = 0.05.
By substituting these values into the formula (and using a prevalence of 24% of carriers for sickle cell),
n = (1.96) 2 × 0.24 × 0.76/0.0025 = 280.
An attrition rate of 10% was assumed to account for anticipated dropout.
This brought the total sample size to = calculated sample size (280) ÷1 − attrition rate = 280 ÷ 1 − 0.1 = 280/0.9 = 311.
All newborns that satisfied the inclusion criteria were consecutively recruited into the study within the study period.
Data collection and procedures
Babies were recruited following parental consent. Any baby who had to be transfused before recruitment was excluded from study. A structured interviewer-administered questionnaire with identification number was administered to all parents of eligible neonates to document relevant sociodemographic and clinical information. These included the age, address, telephone number, gestational age (by early obstetric scan or last menstrual period), marital status, nationality and ethnicity. Each baby was clinically examined, and findings including anthropometry (weight [kg] and length [cm]) were documented. Two millilitres of venous blood sample was then collected from the baby into an appropriately labelled bottle (ethylenediaminetetraacetic acid specimen bottle) for complete blood count and Hb phenotype analysis. The sample was immediately sent to the laboratory (International Foundation against Infectious Diseases Laboratory, Abuja) and stored in the refrigerator at 4°C prior to analysis. HPLCwas done using the HPLC BIO-RAD VARIANT II haemoglobin testing system V2 (LB0002570, USA, 2012) according to the manufacturer's protocol.
At the end of each analysis, the results were printed out and read as percentages (%) on the chromatographic form, crosschecked and endorsed by the HPLC-trained laboratory scientist. The values in percentage of Hb phenotypes in each sample (chromatogram) were reported in the order of the highest to that with least values, and the allocation of the phenotype for each sample was based on the Hb with the highest percentage after the foetal Hb., In newborns, the phenotypic pattern FS is similar for HbSS and HbSβ thalassemia (SβO, Sβ+ and Sδβ+). However, to confirm the diagnosis of β-thalassaemia, the amount of HbA2 should be elevated above 3.5%; in addition to other red blood cell indices, similarly, Hb FSC and FAS pattern supports a diagnosis of HbSC and HbAS, respectively.
Data were analysed using the Statistical Package for the Social Sciences version 20 (IBM-SPSS, Armonk, NY, USA), and results were presented using frequency tables. Categorical data were summarised using proportion (percentage), while quantitative data were summarised using mean, standard deviation (SD), median and range. Chi-square and Fisher's exact (where appropriate) tests were used to determine the association between sex and Hb phenotype and also between ethnicity and Hb phenotype. The level of significance was set at 0.05.
Ethical clearance for the study was obtained from the Ethics Committee of the National Hospital Abuja while informed consent was obtained from parents of each baby. The certificate of ethical clearance is attached to the manuscript: date of approval 1st June 2015 and approval number NHA/EC/009/2015.
| Results|| |
As shown in [Table 1], 311 babies aged 0–28 days were recruited. One hundred and seventy-three (55.6%) were male while 138 (44.4%) were female. The mean (SD) age at recruitment was 38.5 ± 49.7 h. While 95 (30.6%) were Igbos, Yoruba and Hausa/Fulani ethnic groups constituted 53 (17%) and 32 (10.3%), respectively, other minor ethnic groups which were over five in number accounted for 131 (42.1%) babies. Three hundred and seven (98.7%) of the mothers were married, 247 (79.4%) had tertiary education and 43 (13.8%), 5 (1.6%) and 16 (5.1%) had secondary, primary and 'no formal' education, respectively. Most of the parents (293, 94.2%) were in the upper socioeconomic class. There were 196 (63.0%) term babies and 115 (37.0%) preterm babies. Thirty-seven (11.9%) babies were products of multiple gestations.
Distribution of haemoglobin phenotypes
As shown in [Table 2], majority (236; 75.9%) of the phenotypes were FA (normal phenotype) while 63 (20.3%), 6 (1.9%) and 4 (1.3%) were FAS, FS and FAC, respectively (abnormal phenotypes). HbA variants were present in only 2 (0.6%) of the babies.
Associations between sex, ethnicity and haemoglobin phenotypes
As shown in [Table 3], females were more likely to have FA and FAC than males: 108 (78.3%) versus 130 (75.1%) and 3 (2.2%) versus 1 (0.6%), respectively. On the other hand, males were more likely to have FAS (36, 20.8%) than females (27, 19.6%). All the babies with FS phenotype (6, 3.5%) were males. The frequency of normal Hb phenotype was highest among the Yoruba ethnic group (45, 84.9%), followed by Hausa/Fulani (28, 81.3%) and Igbos (64, 67.4%). Similarly, the Yoruba ethnic group was most likely to have FAC; 2 (3.8%) compared with the other major ethnic groups, as shown in [Table 3]. The Igbos were most likely to have FAS 27 (28.4%), followed by the group of minor (other) ethnic groups (25, 19.1%), Hausa/Fulani 5 (15.6%), while the Yoruba were least likely 6 (11.3%). Similarly, the Igbos were most likely to have FS (3, 3.3%), followed by the minor (other) ethnic groups (3, 2.3%). The FS phenotype was not found among the Yoruba and Hausa/Fulani ethnic groups.
| Discussion|| |
This study has demonstrated the pattern and prevalence of Hb phenotypes among babies delivered at the National Hospital Abuja. The prevalence of the various phenotypes is as follows: FA (75.9%), FAS (20.3%), FS (1.9%), FAC (1.3%) and HbA variants (0.6%). These findings are comparable to reports from previous studies conducted in different parts of Nigeria.
The prevalence of normal adult Hb phenotype FA in this study is only slightly higher than those obtained in two earlier separate newborn studies by Inusa et al, Odunvbun et al(75.3%) from the northern and southern regions of the country, respectively. This finding is also not remarkably different from results of adult studies in Nigeria including those of Abdulrahaman et al. from Sokoto (70.0%) and Idowu et al. from Lagos (73.1%). This implies that the prevalence of normal Hb phenotype in the country has not changed significantly over the years. However, studies from some other African countries showed a higher prevalence of the FA phenotype compared with the present report: 77.3% reported by Mcgann et al. from Luanda in Angola and 96.2% and 81.6% reported by Ohene-Frempong et al. and Tshilolo et al. from Ghana and Democratic Republic of Congo, respectively. Prevalence rates of FA are even much higher in European and Asian countries. For instance, Bradakdjian-Michael et al. from France reported a prevalence of 99.96%, while Streetly et al. from England reported 98.45% and Italia et al. from India found a prevalence of 86.6%. The low prevalence of FA observed in our study compared to the various African studies,,, could be explained by the higher proportion of abnormal phenotypes (FAS and FS) in the study which is also consistent with reports from many other Nigerian studies.
The prevalence of FAS (20.3%) in our study is lower than the 23.3% reported by Abdulrahaman et al. and 24.5% by Idowu et al. The difference in the study population and the screening methods used may account for the dissimilarity between our own study and these two other studies; our study population were neonates while the other studies were mainly on adults. The relative prevalence of FAS expectedly increases with age because of the high mortality associated with the FS phenotype in childhood. Furthermore, the present study used HPLC which is able to pick specific phenotypes as against Hb electrophoresis used in the other studies.
Our study reported higher values of FAS phenotypes compared to reports from England (1.2%) by Streetly et al., France (2.4%) by Bradakdjian-Michael et al. and Columbia in the USA (4.5%) by Bradford et al. The high prevalence of FAS (which is the determinant of the SCD), as documented in this study, has been attributed to the climatic, ethnic and ancestral peculiarities of the black race. The high temperature and humidity which characterise most countries in sub-Saharan Africa are believed to promote malaria endemicity which perpetuates the sickle cell carrier state., SCD is said to have originated from black Africa, and its presence in those European countries and the USA is made possible by emigration. It is, therefore, not surprising that Nigeria with the largest population of black people in the world will have the largest number of sickle cell carriers.
The prevalence of 1.9% for FS found in this study is lower than some of the findings from other parts of the country.,,, The most striking of these is 4.75% reported by Abdulrahaman et al. in Sokoto in the north-western part of the country. This is not surprising because consanguinity is a common practice in the predominant ethnic group in the north-western city of Sokoto, a practice often associated with a high prevalence of inherited autosomal recessive disorders such as SCD. However, the prevalence is higher than what was reported from two other studies conducted predominantly among adult population from Nigeria by Akhigbe et al. (0.54%) and Umoh et al.,(1.5%) from Ogbomosho and Uyo, respectively. This is not unexpected given the high mortality in children with HbSS resulting in few survivors among adults in settings such as Nigeria where there are no routine newborn screening and other interventions needed to reduce mortality from the disease.,,,
The prevalence of FAC (1.3%) is similar to what was documented by Odunvbun et al. (1.1%) in Benin City from Southern Nigeria. Other reports among the adult population from Nigeria were variable, for example, Akhigbe et al. reported the highest rate of 5.25% from Ogbomosho in South-Western Nigeria. Akinyanju had reported that this phenotype was more prevalent among the Yoruba ethnic group in South-Western Nigeria, and this has been attributed to their historical linkage and proximity to Ghana which has the highest prevalence of the phenotype in the world. Surprisingly, this study did not encounter any baby with FSC, even though Nigeria is reported to be among the countries within the West African region with the largest burden of the phenotype.
The prevalence of HbA variants (0.6%) found in this study was higher than the value 0.25% obtained from a multicentre newborn screening from Northern Nigeria. These relatively insignificant Hb variants could not be categorised into specific Hb phenotypes by the screening methods and their clinical significance is not readily discernible.
Similar to the report of Abdulrahaman et al. from Sokoto in Northern Nigeria, this study found a significant association between sex and Hb phenotypes (P = 0.003). However, the gender-related pattern in our study was different from that of the previous study. There were more males with FS in both studies, whereas FAS (20.8%) was more prevalent in males in this study in contrast to the earlier study where FAS was more prevalent in females. Our study also showed female preponderance for FAC (2.2%). No possible explanation could be proffered for this sex predilection.
This study demonstrated a significant association between ethnicity and Hb phenotypes (P = 0.047). The prevalence of FAC was higher among the Yoruba (3.8%) and Hausa-Fulani (3.1%) ethnic groups, while FAS and FS were found to be more among the Igbos (28.4%) and other ethnic groups in Nigeria (19.1%). This is consistent with several reports in the literature.,, Akinyanju had reported a high rate of FAC phenotype among the Yoruba ethnic group in Nigeria. Similar findings of ethnic associations have also been reported in other parts of the world such as Abu Dhabi among the indigenous Arabs (1.1%) and in India among the Warli tribe (22.9%). Although no other Nigerian study has reported that the Igbo ethnic group has the highest incidence of FS as shown in this study, it is possibly due to the fact that Igbo constituted the largest ethnic group in our study population. It could also be an evolution resulting from increased intertribal marriages. This may form the subject of subsequent studies.
| Conclusion and Recommendation|| |
Our study has demonstrated the persistence of a wide spectrum of abnormal Hb phenotypes in Nigeria, and these phenotypes can easily be detected at birth using HPLC. This justifies a recommendation for routine neonatal screening for SCD in Nigeria.
This was a hospital-based study and may not accurately reflect the true prevalence of the various Hb phenotypes in the general population among newborns.
We wish to acknowledge Professor Obaro SK, Mrs Olanipekun G and the entire staff of International Foundation against Infectious Disease in Nigeria (IFAIN) laboratory for their immense contribution towards the successful completion of this study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]