Prognosing a severe course of asthma in children following the study of endothelial function
Article Category: Original Papers
Published Online: Oct 11, 2019
Page range: 68 - 74
DOI: https://doi.org/10.2478/pneum-2019-0014
Keywords
© 2019 Amanda et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.
Across the globe, respiratory allergies afect almost 700 million people, and about 330 million cases are affected by asthma (2, 3, 4). The increase in the prevalence of asthma in all age groups, the increase in the number of severe and resistant to the treatment forms of disease, and the “debut” of the disease at an early age explain the interest in this problem of modern medical society (5,6). Untimely diagnosis of asthma leads to significant restrictions in various aspects of human life and can cause disability (7). To prevent the development of severe forms of the disease, there is a need to predict asthma progression.
From the point of view of pathophysiological process, asthma is considered as chronic inflammation of the respiratory tract, regulated by various cellular elements and inflammatory mediators (8). The development of chronic inflammation of the bronchopulmonary system is due in no small part to vascular and endothelial factors (9).
The cascade of inflammatory reactions is determined by the activation of the endothelium, which expresses on its surface molecules of intercellular adhesion (in particular, sVCAM-1), resulting in the processes of migration of efector cells and tissue infiltration and vascular inflammation (10,11). Endothelium damage leads to impairment of its normal function. First of all, the synthesis of NO decreases, and therefore the ability of blood vessels to relax is inhibited (12, 13, 14).
Chronic inflammation in asthma is not limited to the respiratory tract but is systemic in nature. Microvascular changes are one of the components of respiratory tract remodeling. Consequently, it can be assumed that the degree of endothelial dysfunction may be associated with the severity of the disease (15,16).
It is believed that thorough determination of vascular and endothelial factors in the development of chronic inflammatory process of the bronchopulmonary system may be one of the perspective directions of further scientific study of the mechanisms of development, formation, and progression of asthma (9).
Thus, in our study, we aimed to evaluate the endothelial function in children with asthma in remission and the prognosis of severe asthma.
The study involved examination of 91 children with persistent asthma in the remission period (50 boys and 41 girls), aged 6–17 years. The diagnosis was based on GINA 2017 recommendations. The Asthma Control Questionnaire (ACQ) (17) was also used to determine asthma control. The inclusion criteria were (1) signed informed consent to participate in the study given by the parents and children aged from 12 to 17 years, (2) established diagnosis of persistent asthma, and (3) absence of symptoms of bronchial obstruction for 4 weeks. Exclusion criteria were (1) presence of congenital anomalies of the respiratory system, (2) cystic fibrosis, (3) pneumonia and other acute and chronic inflammatory diseases, and (4) patients who received anti-leukotriene drugs and systemic corticosteroids over the past 4 weeks. Depending on the severity of asthma, children were divided into three groups: Group 1 included patients with mild persistent course of asthma (
The pulmonary function test (PFT) and spirometry was performed using the SpiroCom computerized spirometer “KhAImedica.”
The examination was conducted in the morning after 12 h of night sleep. For 48 h before the study, the children did not use coffee, vasoactive agents, and did not engage into physical activity.
Venous blood (2 ml) was taken before meals and centrifuged at 2000 rpm for 10 min. Serum in the lower portion of the test tube was stored at -30°C until the assessment. The collected blood samples were analyzed to determine the serum level of the soluble vascular molecule of intercellular adhesion-1 (sVCAM-1) by immunoassay assay using human sVCAM-1 platinum ELISA (eBioscience, Bender MedSystems GmbH, Austria, BMS232) and also to determine the concentration of stable nitrogen oxide metabolites (NO2 + NO3) spectrophotometrically using Griess reagent.
The function of the endothelium was evaluated using the ultrasound digital ultrasound diagnostic complex “Ultima PA” using a 10–15 MHz sensor. The examination was carried out in a silent purpose-built room maintained at a constant temperature of 22–24°C in the supine position after 10 min of rest. Endothelium-dependent dilatation of the brachial artery [according to Celermajer et al., (1992)] was determined, and a percentage increase in the diameter of the brachial artery (FMD%) was calculated. FMD% is considered normal if the increase in the diameter of the brachial artery after occlusion is more than 10% of the initial one (18). The ultrasonography was used to study the thickness of the intima-media complex of the common carotid artery (IMC CCA) using the method of Pignoli, 1986 (19).
The protocol of this study was in accordance with the ethical guidelines of the Helsinki Declaration of 1975 and was approved by the Ethics Committee of Kharkiv National Medical University.
The study was performed with minimal psychological distress on the part of patients. Patients and their parents were fully informed about the methods and amount of research.
The verification of the distribution according to the Gauss law was carried out with the help of the Shapiro–Wilk test. The arithmetic mean and the standard deviation from the mean (SD) were considered as characteristics of the group for signs with distribution corresponding to the Gauss law. For non-Gaussian distribution, the median (Me), interquartile velocity (Lq, lower quartile; Uq, upper quartile) were determined. Comparing the indices characterized by comparison by more than two points, the Kruskal–Wallis (KW) test was used, and differences were considered probable in the context of the Bonferroni amendment.
Nonparametric Mann–Whitney
The procedure of multiple logistic regression analysis was performed in order to find out what factors should be taken into account in prognosis of the severe course of asthma.
Logistic regression models were fitted using a maximum likelihood estimation and adjusted for all potential and measured confounders including age, sex, duration of the disease, the presence of concomitant allergic disorder, positive family allergic history, recurrent respiratory diseases, duration of asthma, serum Ig level, PFT indices, endothelial function indices (serum levels of sVCAM-1, NO2 + NO3, IMC CCA thickness, FMD%) in the two groups, and we also performed a sensitivity analysis using propensity score matching.
The quality of the elaborated model was tested using the percent concordant (PC). This figure is equal to the fraction of observations that were correctly reclassified into separate subgroups of the dependent index using the logistic regression equation. The closer this indicator to 100%, the higher the quality of the resulting model is.
Mathematically, the logistic regression model is represented as the dependence of the logarithm of the chance of the onset of the predicted event (logit) on the linear combination of factor variables.
where
The construction of the logistic regression model was carried out by the method of stepwise exclusion of prognostic factors with the definition of the minimum set of predictors by the estimation of Nagelkerke square.
Results were considered statistically significant at
There was no significant diference in sex and age in all groups (
General characteristics of children with persistent BA
| Group 1 | Group 2 | Group 3 | ||
|---|---|---|---|---|
| Age, years | 10.78 ± 3.62 | 10.75 ± 2.83 | 10.94 ± 3.14 | |
| mean ± SD | ||||
| Girls/boys | 22/18 | 18/16 | 7/10 | |
| Duration of the disease (years) | 3 (1; 4) | 5 (2; 7) | 9 (6; 11) | |
| Median (IQR) | ||||
| Concomitant allergic disorders | 22 (55%) | 16 (47%) | 14 (82%) | |
| Positive family allergic history | 27 (68%) | 20 (59%) | 16 (94%) | |
| Recurrent respiratory diseases | 11 (28%) | 21 (62%) | 15 (88%) | |
| PFT | 94.0 (85.0; 100.5) | 85.5 (80.0; 91.0) | 81.0 (79.0; 86.0) | |
| FEV,% 1 | 87.0 (80.0; 94.5) | 92.0 (86.0; 97.0) | 79.0 (70.0; 85.0) | |
| FEF,% 25 | 87.5 (81.0; 95.5) | 91.0 (85.0; 96.0) | 82.0 (77.0; 87.0) | |
| FEF50,% | 88.5 (82.0; 95.0) | 86.0 (81.0; 92.0) | 84.0 (79.0; 89.0) | |
| FEF75,% | ||||
| IgE, IU/ml | 456.1 (248.0; 698.0) | 577.0 (180.1; 812.3) | 249.3 (65.7; 440.6) | |
| Blood serum | ||||
| Median (IQR) | ||||
| ACQ | 0.14 (0.11–0.19) | 0.34 (0.24–0.41) | 0.60 (0.44–0.86) | |
Assessment of family allergic history showed that in the majority (68% [62/91],
Evaluation of hereditary allergic diseases showed that the most frequent cases of positive family allergic history was found in children with severe disorders (
Risk factors for severe asthma
| Variables | RR | 95% CI | χ2 | |
|---|---|---|---|---|
| Positive family allergic history | 7.1 | 1.991–51.025 | 6.078 | |
| Recurrent respiratory diseases | 8.9 | 2.249–35.555 | 11.206 | |
| Concomitant allergic diseases | 3.5 | 1.080–11.343 | 5.425 |
Group 2 and 3 children were found to have recurrent respiratory diseases more frequently than Group 1 children. The statistical processing showed a relation between the severity of asthma and recurrent respiratory disorders (Table 2) and the risk of severe asthma in these patients was 8.9 times higher.
The study also showed a relation between the severity of asthma in children and associated allergic disorders (Table 2). Children with concomitant allergic disorders were found to have a high RR of developing severe course of asthma (3.5 times higher).
Further statistical processing implied a dispersion analysis of KW statistical characteristics of endothelial function parameters (Table 3). It showed that criterion
Statistical characteristics of endothelial function in children with BA in the remission period (Me [Lq; Uq])
| Children with BA | ||||
|---|---|---|---|---|
| Indices | Group 1 ( | Group 2 ( | Group 3 ( | Control group ( |
| sVCAM-1, mmol/l | 885.42 (800.57;990.47) | 1150.43 (990.37;1280.77) | 1500.18 (1300.32;1700.25) | 730.01 (690.63;790.19) |
| MW | ||||
| NO2+NO3, mcmol/l | 35.47 (32.00; 42.01) | 28.73 (25.23; 34.48) | 26.18 (22.57; 32.42) | 41.19 (38.22; 43.23) |
| MW | ||||
| FMD% | 11.27 (8.28; 13.33) | 10.12 (8.88; 11.76) | 8.33 (6.45; 8.82) | 23.33 (17.07; 27.77) |
| MW | ||||
| IMC CCA thickness, mm | 0.8 (0.8; 0.9) | 1.0 (0.8; 1.1) | 1.1 (1.1; 1.2) | 0.6 (0.5; 0.7) |
| MW | ||||
The study showed that the factors that should be taken into account during the prediction of the development of severe asthma were related to the positive family allergic history, the level of sVCAM-1 in serum, IMC CCA thickness, and serum NO2 + NO3 levels (Table 4).
Statistical characteristics of the multiple logistic regression of factors potentially able to have an impact on the development of severe bronchial asthma in children
| Coeficient | Standard coefficient | p | |
|---|---|---|---|
| Constant | 0.633 | - | |
| Positive family allergic history | 0.359 | 0.383 | <0.001 |
| sVCAM-1 | 0.00063 | 0.250 | <0.001 |
| IMC CCA thickness | 0.477 | 0.160 | <0.001 |
| NO2+NO3 | 0.0147 | 0.186 | <0.001 |
According to the results of the analysis, a multiple regression equation was created:
We have determined that the severe course of asthma to a significant extent depends on a high level of sensitization, as well as the impact of respiratory infections, which enhance the premorbid biological defect.
Asthma is known to be an allergic disorder (2), and therefore the presence of positive family allergic history and concomitant allergic conditions is also an unfavorable factor in the development and persistence of sensitization of the organism, as reflected in our study. Most of the children, especially those with severe asthma, have these symptoms. The greatest duration of the disease is established in patients with severe asthma, which can confirm the logic of the course of the pathological process. As for atopy, we have not identified a reliable diference in the level of IgE blood serum compared it in diferent groups. There are also no correlations between IgE levels with the severity of the course of asthma. This may indicate more complex mechanisms for the formation of the pathological process.
Our findings, such as the endothelium abnormalities in children with asthma in the remission period, may indicate significant violations of the functional state of the endothelium of the vessels as early as in the mild course of the disease and also speak in favor of the formation of persistent violations, which remain even beyond the activity of the disease. Thus, it is possible to assume continuation of the inflammatory process in the endothelium.
Inflammation leads to the activation of endothelial cells, which are active participants and regulators of the inflammatory process by expressing intercellular adhesion molecules (11). It further contributes to increased vascular permeability (10,11).
Secondary to activated inflammatory and immune mediators due to cytokine production, the immune system undergoes adhesion of leukocytes to the endothelium, and then their transendothelial migration (20,21). There is hypertrophy and hyperplasia of the endothelium, both due to inflammatory changes and due to oxidative stress, which leads to thickening of intima and media, and consequently to ongoing violations of adequate functional activity of the endothelium. These changes are reflected in the enlargement of the IMC vessels, which is shown in this study.
At this stage, the function of the endothelium is actively studied in various pathological conditions, both in children and in adults (22, 23, 24). The regulation of vascular tone is due to the balanced formation and release of vasodilator and vasoconstrictor substances (25). One of the major vascular tone regulators is nitric oxide, which is continuously formed from l-arginine by endothelial NO-synthetase and has a pronounced vasodilating effect. Moreover, NO exhibits antioxidant and bronchodilator effects, suppresses the aggregation and adhesion of platelets, has antiprotective properties, and participates in endothelial-leukocyte interactions and migration of monocytes (26,27).
Such factors as inflammation, hypoxia, and oxidative stress disrupt the normal functioning of the vascular endothelium. These circumstances imply an imbalance of vasoconstrictive and vasodilating substances. NO synthesis reduces, and therefore the ability of vessels to suppress the relaxation (28,29) is suppressed. This leads to the development of various pathological reactions (30,31). The decrease in the level of vasodilating substances and the deterioration of elastic-vascular properties of blood vessels in children with asthma shown in our study confirms endothelial dysfunction and agrees with other studies.
Persistent changes in the endothelium in the future may contribute to the formation of different pathologies, not only of the lungs but also of other systems, in particular cardiovascular, and lead to the development of severe complications (32, 33, 34).
According to our findings, not only inflammation and oxidative stress cause changes in the vascular wall but also processes that occur in the endothelium of the vessels can lead to a deterioration of the course of the inflammatory process, forming a vicious circle.
All the children with asthma were found to have endothelial dysfunction. The degree of endothelial function disruption depends on the severity of asthma. The most significant changes were recorded in children with severe asthma. During the study, factors that should be taken into account when predicting a severe course of bronchial asthma were identified, such as positive family allergic history, serum levels of sVCAM-1 and NO2 + NO3, and IMC CCA thickness. With the use of these criteria, an algorithm for the prognosis of asthma is created, which may contribute to early and reliable prediction of the course of bronchial asthma in children.