Nigerian Journal of Paediatrics 2011;38(4):165 - 169

ORIGINAL

Obasa TO

Glucose 6 phosphate dehydrogenase

Mokuolu OA

levels in babies delivered at the University

Ojuawo A

of Ilorin teaching hospital.

Received: 10th September 2011

Abstract Background: Glucose-

babies with normal enzyme levels

Accepted: 13th October 2011

6-phosphate dehydrogenase

were significantly higher than in

deficiency, an X-linked recessive

male babies with normal enzyme

Obasa TO

( )

disorder, is the most common

levels (5.72 + 2.45 U/gHb versus

Mokuolu OA, Ojuawo A

enzymopathy producing disease

4.99 + 2.3 U/gHb, p = 0.002).

Department of Paediatrics

in humans.It is known to cause

Enzyme levels in babies with G6PD

University of Ilorin Teaching

severe neonatal

deficiency was comparable in both

Hospital, Nigeria

hyperbilirubinaemia.

males and females (2.05 ± 0.60

240001

Aims and Objectives: To determine

u/gHb in females and 2.1 + 0.66

E-mail: drtopeobasa@gmail.com

G6PD levels in babies delivered at

U/gHb in males, p = 0.66). The

Tel: +2348034988894

the University of Ilorin Teaching

prevalence of G6PD deficiency was

H o s p i t a l

w i t h

a

v i e w

t o

comparable among males and

determining the prevalence of

females (p = 0.81 , χ = 0.06, RR =

2

G6PD deficiency.

1 . 0 2 ,

C I = 0 . 9 0 < R R < 1 . 1 5 ,

Methods: Samples of cord blood

OR=1.04).

were collected at delivery, from

Conclusion:

There is a high

933 babies who met set criteria.

prevalence of G6PD deficiency in

Blood was assayed for G6PD

babies delivered at the University of

levels using a quantitative in vitro

Ilorin Teaching Hospital, and the

test (RANDOX©).

enzyme deficiency appears to occur

Results: A total of 348 (37.3%) of

equally among the sexes.

the 933 tested subjects had G6PD

deficiency with enzyme activity of

Key words: Glucose-6-phosphate,

≤ 2.8U/gHb. Glucose 6 Phosphate

neonates, cord blood

Dehydrogenase levels in female

Introduction

been sent by this presentation. While many other

body cells have other mechanisms of generating

Glucose-6-phosphate dehydrogenase (G-6-PD) is an

NADPH, the red blood cells rely completely on G-6-

enzyme in the hexose monophosphate shunt that

PD activity because it is the only source of NADPH

that protects the cell against oxidative stress.

2

catalyses the oxidation of glucose-6-phoshate to 6-

phosphogluconate. This is the rate limiting step of

the pathway. Concomitantly, Nicotinamide Adenide

Glucose-6-phosphate dehydrogenase (G-6-PD)

Dinucleotide Phosphate (NADP ) is reduced to

+

deficiency is the most common disease producing

NADPH. The NADPH, a required co-factor in

1

enzymopathy in humans. It is inherited as an X

many biosynthetic reactions, maintains glutathione

linked recessive disorder. It affects about 400 million

people worldwide. The highest prevalence rates

3

in its reduced form. Reduced glutathione acts as a

scavenger for free radicals, and thus helps reduce

occur in persons of African, Asian, Mediterranean or

Semitic descent.

4

oxidized haemoglobin to free haemoglobin;

Specific prevalence rates

worldwide range from 3.9% in India 12.8% in the

5

otherwise oxidized haemoglobin will precipitate as

Heinze bodies. The message of haemolysis has NOT

166

USA and 50% in the Middle East. In Nigeria, an

6

7

Data Analysis

estimated 21% of the male population is said to have

15

G-6-PD deficiency.

8

In neonates, the prevalence

This was done using EPI-info version 6 software.

among jaundiced babies range from 30.9% - 50%in

Association between categorical variables were

Nigeria.

9-12

tested using Chi-square test. Relationship between a

continuous variable and dependent variable were

G-6-PD deficiency causes a clinical spectrum of

tested using the Student t test or ANOVA as

illness which includes a purely asymptomatic state,

appropriate.

acute haemolytic episodes (from drugs , infections,

ingestion of fava beans, diabetes mellitus), chronic

For all statistical analysis, p <0.05 was considered

haemolysis (hereditary non-spherocytic haemolytic

significant.

anaemia), and neonatal jaundice.

13

Few studies have been conducted, in this part of the

world in this part of the world, to determine the G6PD

Results

status of the newborn prior to the onset of jaundice.

Study Population

This study was aimed to determine the G6PD enzyme

level in newborn babies prior to the onset of jaundice,

The study was conducted over a 10 month period

and to relate these enzyme levels to the baby's

during which 4591 babies were delivered at the

gender/sex.

University of Ilorin Teaching Hospital. They

comprised 2525 males and 2066 females with a male

to female ratio of 1.1:1. The gestational age of the

babies ranged from 26 weeks to 44 weeks, with a

Methods

mean GAof 39 + 3.9 weeks. Birth weight ranged from

Patients and Treatment

7005450g with a mean of 3892 ± 1148g. Atotal of 933

babies had samples for G6PD assay collected during

This cross sectional prospective study was performed

this study.

at the maternity unit of the University of Ilorin

Teaching Hospital, which is located in the North

Table 1 shows the baseline characteristics of study

Central region of Nigeria. Ethical approval was

subjects. There were 903 (96.8%) singleton deliveries

obtained from the institutions' Ethical Review

and 15 (3.2%) sets of twins. Babies delivered at term

Committee of the institution. Average yearly

constituted 79.9% of the study population, while

deliveries range from 4500

5000 babies, with

preterm babies made up 20.1% of the study

virtually all babies being of WestAfrican descent.

population. The male to female ratio was 1.3:1.

Alternately delivered newborn babies whose mothers

Table1: Baseline Characteristics of study subjects

gave consent were recruited into the study. Exclusion

Enrolled

criteria included babies whose gestational age was

Variables

greater than 42 weeks, babies with severe birth

(%)

asphyxia, and those with congenital abnormalities.

Type of Delivery

Singleton

903 (96.8)

Blood from the placental end of the cord was drawn

Twins

15 (3.2)

and G6PD levels were assayed using an in vitro

Gestational age (GA)

diagnostic kit manufactured by RANDOX

©

Preterm

187 (20.1%)

Laboratories Limited (Ardmore Diamond Road,

Term

764 (79.9%)

Crumlin, Co.Antrim, United Kingdom, BT 294 QY.

Gender

Male

514 (55.1)

Laboratory Methods

Female

419 (44.9)

Male : Female

1.3:1

For G6PD assay, 2ml of blood drawn from the

placental end of the cord was collected into EDTA

Figures in brackets are percentages of 933

containing bottles after delivery. Enzyme level was

assayed using a quantitative in vitro test

(RANDOX©). Its principle is based on reduction of

NADP+ by G6PD present in red blood cells. The

NADPH generated fluoresces under UV light at a

wave length of 340nm. Enzyme activity is determined

by the rate of absorbance change. Red blood cell

G6PD value of ≥ 2.9 U/gHb was regarded as normal.

14

167

Table 2 shows the distribution according to mean birth

And 2.05 + 0.60 U/gHb in females, p = 0.66). (Table 4)

weight and gestational age. The gestational age (GA)

of the babies studied ranged from 26 to 42 weeks with

Table 4: Glucose-6-Phosphate Dehydrogenase levels

a mean GA of 38 + 2.7 weeks. Birth weights ranged

in normal and deficient neonates according to sex

from 800 - 5050g, with a mean of 2866.9 ± 710g

grammes.

Classificati

Mean

(N)

F

P

on

Table 2: Mean birth weight in relation to gestational

Normal

age

Male

4.99 + 2.3

320

Gestational Age

Number

Mean birth

Female

U/gHb

265

9.39

0.002

(weeks)

(%)

weight (gm)

5.7 + 2.45

U/gHb

26 – 29

18 (1.9)

1107.5 + 370

Deficient

30 – 33

68 (7.3)

1565.2 + 252

Male

2.1 + 0.66

194

Female

U/gHb

154

0.32

0.6

34 – 36

101 (10.8)

2282.4 + 476

2.05 + 0.60

37 – 40

653 (69.9)

3099.7 + 509

U/gHb

41 – 42

93 (10)

3217.3 ± 626

Total

933

2866.9 ± 710

Female

χ

2

Male (%)

P

(%)

Glucose -6-Phosphate Dehydrogenase Levels in the

Normal

320

265

Subjects

Deficient

194 (37.7)

154

0.06

0.81

(36.8)

Glucose-6-Phosphate Dehydrogenase levels that

were ≥ 2.9U/gHb were regarded as normal, while

values ≤ 2.8U/gHb were regarded as deficient.

14

Stratification of G6PD levels into various ranges

Discussion

Table 3: Relative proportion of G6PD values

The overall prevalence of G6PD deficiency as shown

G6PD values (U/gHb)

Number (t=933)

in the study was 37.3% in the neonatal population. In

other words, about four out of every 10 babies born at

= 1

26 (2.8%)

the teaching hospital was G6PD deficient. The

2

86 (9.2%)

method used in enzyme assay in this study was

2 -2.8

236 (25.3%)

quantitative enzyme assay, rather than qualitative

2.9 - 7.2

457 (49%)

(fluorescent spot). The fluorescence spot test is based

7.3 - 10

94 (10.1%)

on the visual evaluation of fluoresced reduced

>10

34 (3.6%)

NADPH when activated by ultraviolet light so that,

the sample is considered G6PD enzyme “ deficient ”

when they do not fluorescence, and “ normal ” when

Three hundred and forty-eight babies (37.3% of 933)

they fluorescence.

14

Studies have shown that false

were found to be G6PD deficient, thereby giving a

negative results may occur, with the use of the

hospital based prevalence of 37.3%. They comprised

fluorescent spot test, in heterozygote females and in

194 males (37.7% of male population) males and 154

h o m o z y g o t e

m a l e s

f o l l o w i n g

a n

a c u t e

haemolysis.

14,16,17

females (36.8% of female population) females (p =

In one study involving known

0.81 ,

χ

2

= 0.06 RR = 1.02, CI=0.90<RR<1.15,

female heterozygotes, G6PD deficiency was

OR=1.04).

diagnosed in 53% of these females by the use of

enzyme assay, but in only 7.5% of these females with

the use of the fluorescence spot test. This (florescent

14

The overall mean G6PD value was 4.1 + 2.48 U/gHb

(range 0.87 13.0 U/gHb). Among those with normal

spot test) was the method used in enzyme assay in

G6PD values, males had a mean G6PD value of 4.99 +

studies done in Nigeria thus, the prevalence rate in this

2.3 U/gHb and females 5.7 + 2.45 U/gHb. Thus,

study is at a variance with rates determined by other

normal females had a mean G6PD value that was

workers viz, 20.5%, 20.6%, and 35.3%.

18

19

20

significantly higher than that of normal males (p =

0.002).

Additionally, the babies recruited into these studies

already had jaundice.

18,19,20

Enzyme levels assayed

Enzyme levels in babies with G6PD deficiency was

during an acute haemolytic event will likely

about equal in both sexes (2.1 + 0.66 U/gHb in males

168

demonstrate enzyme activity in reticulocytes and

homozygous.

29

Because of random X chromosome

13

neocytes.

21

In the enzyme variant responsible for

inactivation by Lyonization the heterozygote female

deficiency in the West African sub-region, GdA ,

- 22

has two red cell populations: one G6PD deficient, and

enzyme activity wanes as the cells age so that

the other G6PD normal. In most instances, the

neocytes have near normal enzyme activity.

23

Thus,

heterozygote female still has normal enzyme activity

earlier studies conducted in this region would have

but, the total G6PD activity of the heterozygote

underestimated the level of enzyme deficiency in

female can range from near normal to near

neonates.

15

deficient.

13,15

It has also been postulated that in

geographic areas where G6PD deficiency is very

Studies, in this environment, where G6PD enzyme

common, female newborns might be homozygous for

was assayed prior to the onset of jaundice are few, and

the trait, thus behaving like the hemizygous G6PD

deficient male newborn.

15

hence a relative dearth of information on either the

A DNA analysis, which

incidence or prevalence rate of the enzyme

would have served as a tie-breaker, was beyond the

deficiency. In one study where enzyme activity was

24

financial scope of this study.

assayed from cord blood samples,

24

the prevalence

rate of G6PD deficiency did not appear to be the aim

Overall, enzyme levels in normal females were

of the researchers. Other studies in which G6PD

clearly higher than the levels in normal males. This

enzyme assays were determined at birth reveal

finding can, however, not be explained. The gene for

prevalence rates of 12.8% in the African-American

6

the G6PD enzyme is located on the X chromosome

population in the US, 7.6% in Malaysia, and 3.2%

14

25

and so, because the female is doubly endowed, she

in Iran. The link between G6PD deficiency and

should demonstrate higher enzyme levels. However,

malaria is well documented,

15,19,22

and with malaria

because of the influence of Lyonization

13

enzyme

being holoendemic in Nigeria a higher prevalence of

levels in the female should not be appreciably higher

the enzyme deficiency is to be expected.

26

Luzzatto

27

than in males. This will serve as grounds for further

in his work discovered that 22% of Nigerian adult

research.

males, and 3 - 4% of female homzygotes were G6PD

deficient.

In view of the high prevalence of G6PD deficiency in

this region, newborn screening programmes should

A similar proportion of females and males, in this

be instituted to aid in the early diagnosis and

study, were found to be enzyme deficient (χ = 0.06, p

2

preemptive care of babies with this condition.

= 0.81, RR = 1.02, CI=0.90<RR<1.15, OR=1.04). In

The major limitations of this study were our inability

another study done on neonates with jaundice, using a

to carry out DNA analysis on the sample drawn from

quantitative assessment of enzyme activity, 58% of

female neonates (financial and technological

females and 50.3% of males in the study population

constraints), and the low number of early preterm

were found to be G6PD deficient.

28

The cut off for

neonates recruited.

enzyme deficiency used in that study were levels that

were 40% of normal adult values (8.83 ±

1.59eU/gHb). This finding is contrary to what would

be expected of an X-linked disorder. It would

Acknowledgement

naturally be expected that the enzyme deficiency

would occur more in males because they carry only

Our thanks go to the nursing staff of the labour ward

one X chromosome. The females are however in the

UITH. We are also grateful to Dr. Olanrewaju of the

unique position to have 3 genotypes: normal

Department of Haematology and Mr. Akinyinka of

homozygous, heterozygous and deficient

the Department of Chemical Pathology for their help

with analyzing the samples.

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