Assessment of asthma control and lung function in asthmatic children in Sokoto, North Western Nigeria

INTRODUCTION

Asthma is estimated to affect about 339.4 million individuals of all ages worldwide.^[1] It remains the commonest cause of chronic ambulatory respiratory morbidity in the west African subregion.^[1,2] Although asthma affects all age groups, children suffer an undue twofold burden. First, they may be inherently exposed to genetic and environmental factors implicated in the etiology of asthma.^[2] Second, negative effects of the disease may retard their development and lead to limitation of their potentials as a result of school absenteeism, stigma, depression, and stunted growth.^[3] It also poses a major and detrimental health and economic burden on the individual, family, and government, hence the need for effective management. The goal of asthma management is to achieve and maintain asthma control, and improve quality of life.^[1]

The functional hallmark of asthma is a reversible airway obstruction and its detection is often required for the diagnosis of the disease.^[1]

The long-term goals of asthma management are to achieve good asthma symptom control and minimize future risk of asthma related mortality, exacerbations, persistent airflow limitation, and side effects of medication adverse outcomes.^[1]

Asthma control assesses the effectiveness of current therapy in a patient and the need for modification of therapy.^[1,4] Asthma symptom control is a good guide to reduce risk of exacerbations and improve lung function (LF).^[1]

LF using spirometry provides objective criteria in asthma diagnosis, follow-up, monitoring, and objective assessment of response to interventions.^[1] Spirometry confirms airflow limitation/obstruction with a reduced forced expiratory volume in the first second (FEV₁) and FEV₁/forced vital capacity (FVC) ratio. In general, a FEV₁/FVC ratio of <0.80 in adults, and <0.90 in children indicates a significant airflow obstruction.^[4] Reversibility is detected by a >12% and 200 ml increase in FEV₁ 15 min after inhaled short acting beta-2 agonist or 2–4 weeks trial of oral corticosteroids. The severity of obstruction is a known risk factor for exacerbations; therefore, functional monitoring is essential to achieve optimal control.^[1]

Studies have assessed asthma control using different conventional clinical assessment by standardized questionnaires and LF to establish the most appropriate measure for asthma evaluation and correlation between the two. However, there has been a disagreement and inconsistency between these reports.^[5-9]

MATERIALS AND METHODS

This was a hospital-based cross-sectional study conducted in UDUTH, Sokoto from October 2019 to January 2020.

Sample size was calculated and adjusted for finite population as follows:

Z_1-α/2 = Percentage point of the normal distribution corresponding to the required (two-sided) significance level (α) of 0.05 = 1.96.

Z^β= The value of the standard normal distribution cutting off probability β, which is 0.84 for 80% power.

σ = Standard deviation of variable under study.

D = Margin of error

A total of 60 subjects were enrolled aged 5–15 years by a systematic random sampling technique. Participants were enrolled from the Pediatric Pulmonology and Allergy clinic and Emergency Pediatric Unit of department of Pediatric, UDUTH, Sokoto with a diagnosis of childhood asthma based on GINA guideline. Patients with chronic respiratory or cardiac diseases such as pulmonary tuberculosis and congenital heart diseases were excluded from the study. History, examination, anthropometric measurements weight measured using seca digital weighing machine to the nearest 0.1 kg, height measured using seca stadiometer to the nearest 0.1 cm, body mass index (BMI) = weight (kg)/height (m²), and BMI percentile calculated as follows:

1. Underweight = <10^th percentile

2. Normal weight = 10^th–<85^th percentile

3. Overweight = 85^th–<95^th percentile

4. Obesity = >95^th percentile

were plotted on the growth chart accordingly.

The GINA classification^[10] asthma control assessment was administered and answered appropriately to asthmatic subjects and was categorized appropriately as follows:

1. Well controlled asthma - None of these symptoms

2. Partly controlled asthma - 1–2 of these symptoms

3. Poorly controlled asthma - 3–4 of these symptoms

Detailed spirometry was performed on all the children enrolled in the study to assess their LF according to American Thoracic Society guideline using BTL-08 Spiro Pro portable spirometer. The spirometer was calibrated daily and procedure done under ambient temperature, pressure and humidity. The procedure was explained and demonstrated to all the study participants. An incentive spirometer was used to encourage the participants while the subjects sat on a chair and instructions were given. The subjects were allowed two-three practice trial blows and 3 test blows for 4–6 s, the personal best (FVC, FEV₁, FEV₁/FVC, and peak expiratory flow rate [PEFR]) was recorded.

RESULTS

Sixty asthmatic children were enrolled, males accounted for 58.3% of the study population with M: F of 1.4:1. Thirty-three (55.0%) were aged <10 years while 55 (91.7%) of the participants were from the urban domicile with median age of the study population of 9.47 years (IQR 3.98 years), while normal weight accounted for 56.6% of the participants as shown in [Table 1].

DISCUSSION

The goal of asthma management is to achieve good control and improve quality of life. In this study, majority (50.0%) of the study participants had well-controlled asthma. Studies reported by Ayuk et al.^[11] and Omole et al.^[12] had similar findings with this study. Kuti and Omole^[13] reported a higher percentage of 83.7% of well-controlled asthma among Ilesa children. The high percentage of well controlled asthma in this study could be due to the good care given by the asthma specialist as it has been reported that asthma patients seen by specialists are more likely to have better management than those followed by non-specialists or general pediatrician.^[14,15] However, Kuti and Omole study attributed their findings to the fact that most of the children had mild intermittent asthma (82.7%).

However, Banjari et al.^[16] and Al Zahrani et al.^[17] had a contrasted report, with well-controlled asthma having lower percentages (16.0% and 12.0%, respectively) among Saudi Arabian asthmatic children. These studies used a different measurement tool of asthma control evaluation which was the Arabic validated version of ACT test for evaluation of asthma control. Whereas this study used GINA asthma control assessment which varies in evaluation of asthma symptom domain and scoring system which could account for the disparity noted. Studies that used ACT test as a measurement tool for asthma control evaluation have failed to match test scores to other objective measures of asthma control,^[18] while some studies found a significant disagreement between c-ACT and GINA and between c-ACT and pediatrician’s assessment of asthma control.^[19,20] In addition, discrepancies in environmental condition in that Saudi Arabia’s climate has many dust storms (which serve as trigger factor or environmental allergen exposure) and is more developed (which is associated with industrialization and air pollution with resultant poor air quality index) compared to Nigeria. These factors have been shown to play a major detrimental role in asthma control and could account for the low percentage of well-controlled asthma in their studies.^[21]

LF assessment with the use of spirometer is a reliable test for evaluating airway obstruction.^[1] Forced expiratory techniques are reliable for use in most children as young as 5−6 years of age.^[22,23] Thus, FEV₁ and FEV₁/FVC are sensitive markers to predict airway obstruction.^[22,23] Dissociation of asthma symptom reports with the degree of airflow obstruction has been noted and form part of written management plans, with LF monitoring to improve asthma control.^[24] LF results have reportedly changed management decisions in 15% of visits.^[22,23] Therefore, it is recommended that LF should be performed at each visit to improve asthma control and identify patients at risk for progressive loss of LF.^[10,23]

This study found no association between asthma control types and spirometry indices (FEV₁, FVC, FEV₁/FVC, and PEFR). This observation was also reported by these studies.^[25-27] This might reflect a disassociation between a patient’s asthma symptoms and their perception of those symptoms^[5,18,28] or a temporal delay between changes in symptoms and spirometric values.^[24]

Moreover, asthma symptoms and LF parameters represent and assess different domains of asthma and they correlate poorly over time in an individual, so both need to be monitored and evaluated differently to assess asthma control in clinical practice.^[29]

However, in contrast to this study, Sommanus et al.^[30] in a retrospective cohort study among 279 Thailand children reported significant positive correlations between c-ACT score and FEV₁ at enrollment. Lee et al.^[31] observed a significant correlation between FEV₁ and ACT scores among Korean children. This significant correlation probably was a result of the fact that the sample size was large (1000 participants) and it was cohort prospective study which followed up the subjects over time as contrasted to this study which had a cross sectional study at LF parameters and asthma control assessment.

Furthermore, the baseline level of asthma control of the study participants in this study differs from the aforementioned studies^[30,31] which may play an important factor that influences the correlation between the asthma control and LF. Extensive literature reviews^{[5,25-28,31-33]} to date on the relationship between asthma control and LF has had varied reports. This is not surprising as these studies differed with respect to study design, measurement tool used, sample design, sample size, methodology, and statistical analysis; thus, direct comparisons may not be justifiable and will lack objectivity. In addition, measurements of LF require a high degree of patient’s cooperation which may not be adequate in children, couple with the readings of a onetime measurement of the child’s LF status.^[34] This may not truly reflect the inherent variability of the disease; hence, the LF parameters are of questionable value to make a tentative conclusion.^[34]

Serial follow ups and monitoring of the LF measures are more reliable than a single reading which usually does not convey much meaning especially in a chronic variable disease such as asthma, more so that some studies^[35,36] have reported persistent abnormal LF or airway reversibility even among asthmatic children who were classified as controlled by GINA or c-ACT guideline. This highlights the need for periodic LF measurement and harmonization of methods of asthma control evaluation in clinical practice.

CONCLUSION AND RECOMMENDATIONS

There was no association between asthma control assessment and LF, Serial monitoring and measuring of LF in addition to uniformly agreed standardized assessment of asthma control is required to objectively evaluate asthma control in children. More studies are needed to determine longitudinal relationships between asthma control and LF.