LUNG FUNCTION IN CHILDREN WITH AND WITHOUT SICKLE CELL ANAEMIA AT THE LAGOS STATE UNIVERSITY TEACHING HOSPITAL

Abstract

Sickle cell anaemia (SCA) is a chronic disorder with multi-systemic manifestations. The burden
of the disease is highest in sub-Saharan West Africa, especially Nigeria, where approximately
4.2 million people are believed to be living with the disorder. Although much is known about the
clinical presentation and complications of the disease, studies on lung function in children with
sickle cell anaemia have not received enough attention. The study was therefore conducted to
determine the pattern of lung function abnormality, if any, in children with sickle cell anaemia.
A prospective, cross-sectional study was conducted between 15TH March 2011 and 17th June
2011 involving 200 children aged five to twelve years, 100 each with genotype SS and AA.
Measurements taken included height, sitting height, weight, arm span, chest circumference and
body mass index. Pulmonary function indices like peak expiratory flow rate (PEFR), forced vital
capacity (FVC) and forced expiratory volume in one second (FEV1) were measured using One
Flow Spirometer (Clement Clerk International, England) while FEV1% was derived from the
values of FVC and FEV1.
Mean weight (26.71kg), sitting height (65.48cm), arm span (131.58cm) and body mass index
(15.68kg/m2) of controls were significantly higher than corresponding figures for HbSS subjects
(23.64kg, 63.72cm, of 126.45cm and 14.64gk/m2 respectively): p < 0.05 in each case. Also,
mean lung function test indices were lower in HbSS subjects (PEFR: 214.95 L/min Vs 230.30
L/min, FVC: 1.52 L Vs 1.71 L, and FEV1: 1.30 L Vs 1.48 L, p < 0.05 in each case). However,
with regard to FEV1%, the mean values 86.94% for AA was higher than 85.75% for SS subjects
but the difference was not significant (p = 0.08).
A total of six HbSS subjects were identified with obstructive lung disease giving a prevalence of
6% while none were found among controls. The prevalence was highest among subjects in the
lower socio-economic strata at 7.8% of obstructive lung disease in comparison to 4.5% and 3.9%,
of middle and upper socio-economic strata respectively. The prevalence of obstructive lung
disease also increased with age with the highest prevalence of 13.6% in age group 11 to 12 years.
Also, the 11.1% prevalence of obstructive lung abnormality among those with family size of five
or more was higher than 5.5% observed in those with family size less than five suggesting that
overcrowding may influence the prevalence of obstructive lung disease. HbSS subjects who had
been hospitalized up to three times in the past had a 19.0% prevalence of obstructive lung
disease in comparison to 2.5% among those with lower number of hospitalizations. With regard
to restrictive lung abnormality, an overall 5% prevalence (five subjects) rate was recorded among
subjects. The highest prevalence of 8.0% was found in lower socio-economic strata while the
upper and middle strata had prevalence of 4.2% and 3.9% respectively. The prevalence of
restrictive lung abnormality was also higher in older subjects: 10% in children aged ≥ nine years
compared to 3.3% in the seven to eight years age group. Family size greater than five was
associated with higher prevalence of 11.1% compared to 4.4% with smaller family size. Also,
higher prevalence of 23.8% was observed among those with three or more admissions related to
respiratory problems. No case of restrictive lung abnormality was identified in those with fewer
admissions.
There was a strong positive correlation between pulmonary function variables and
anthropometric parameters such as standing height, sitting height, arm span, chest circumference
and weight (range of “r” between 0.694 to 0.939) while a weak positive correlation was observed
in the case of BMI (range of “r” between 0.415 to 0.482).
Multiple regression analyses with pulmonary function indices as the outcome variable of interest
and anthropometry (height, weight and age) as independent variables showed that combination
of height and age had the highest coefficient of determination (R2 = 0.844 and 0.824), as well as
the lowest standard error of the estimate (SEE) of 0.173 and 0.211 for the prediction of FVC
among female and male controls respectively. The use of other possible anthropometric
combinations resulted in lower R2 range and higher SEE range. In the same manner, height and
age had the highest R2 of 0.848 and 0.837, as well as the lowest SEE of 0.173 and 0.175 for the
prediction of FEV1 among male and female controls respectively. The PEFR prediction was also
highest with the use of height and age with R2 of 783 and 761, as well as SEE of 28.222 and
26.118 for male and female controls respectively. The predicted values were used in
determining the pattern of lung function abnormality among HbSS subjects.
In conclusion, children with sickle cell anaemia have reduced pulmonary function compared to
their AA counterparts. Therefore, there is a need for routine pulmonary function study among
children with sickle cell anaemia during follow up clinic visit for early detection of pulmonary
function abnormality. This is particularly important because the use of bronchodilators has been
found to reduce the frequency of acute chest syndrome thereby reducing the rate of deterioration
of lung function.

LUNG FUNCTION IN CHILDREN WITH AND WITHOUT SICKLE CELL ANAEMIA AT THE LAGOS STATE UNIVERSITY TEACHING HOSPITAL