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Background. Broncho-obstructive syndrome (BOS), particularly, its recurrent course in young children, is an important question of modern pediatrics. The burdened allergic history, manifestations of atopy are traditionally considered as risk factors for recurrent episodes of BOS, which, however, are not present in all cases. Recently, the possible role of vitamin D (VD) in susceptibility to recurrent episodes of BOS is discussed due to its anti-infective effect that is provided by activating immune mechanisms. Thus, purpose of the research was to study VD level and peculiarities of interferon gamma (INF-g) and interleukin (IL) 4 production in the blood serum of young children with recurrent episodes of BOS. Materials and methods. 120 children aged 6 months to 3 years with a clinical diagnosis of acute obstructive bronchitis (J20) were examined, they were divided into two groups (group I — 60 patients with episodic BOS, group II — 60 children with recurrent BOS). The control group consisted of 30 clinically healthy children from 6 months to 3 years old. All patients were evaluated for anamnestic data, including the level of insolation, the severity of BOS according to a 12-point scoring scale, general clinical examination, pulse oximetry, and the asthma predictive index (API) was calculated. Laboratory studies included determination of 25-hydroxyvitamin-D (25(OH)D) concentration in the blood serum on days 2 and 3 of the disease using an electrochemiluminescence method on the Cobas e411 analyzer (serial number 1041-24, manufactured by Roche Diagnostics GmbH, Germany), serum concentrations of IFN-g, IL-4 by enzyme-linked immunosorbent assay method using IFA-Best sets (manufactured by Vector-Best, Russian Federation) and total calcium (Ca) according to the generally accepted method. Nonparametric statistical criteria were used in the analysis of the obtained data. The difference between the compared indicators was considered to be significant at a rate of p < 0.05. Results. Most patients with a recurrent course of the disease (56.7 %) had 4 episodes of BOS in the last 12 months. The analysis of anamnestic parameters, including the allergic history, did not reveal any significant differences between groups (p > 0.05). API was negative in 78.3 % of patients of group II. The severe course of BOS was observed among children of group II two times more often than in group I (23.3 and 10.0 %, respectively, c2 = 4.50, p = 0.034). The mean of 25(OH)D in the blood serum in children of group I was 33.0 (28.19; 41.97) ng/ml and group II — 13.68 (7.96; 19.51) ng/ml (p < 0.001). The level of VD in 75 % of children in group II was considered as deficiency while in group I this indicator was 6.6 % (c2 = 57.98, p < 0.001). The inverse correlation was found between VD level and the incidence (r = 0.27, p = 0.002) and severity of BOS (r = 0.24, p = 0.008). The level of total Ca in the blood serum in both groups was within the normal range. The mean level of IFN-g in children of group I was 22.69 (8.98; 41.44) pg/ml and in group II — 21.08 (8.57; 37.03) pg/ml, both of which were higher than in the control group (12.18 (5.31; 12.92) pg/ml (p = 0.016 for both parameters). We revealed that the study groups differed by the level of VD supplementation, which was 60 % in group I and only 5 % in children of group II (p < 0.001). The mean serum level of IL-4 in group I was significantly higher in comparison to the corresponding parameters of group II and control group (p = 0.012 according to the Mann-Whitney U test for both indicators). The inverse correlation between the incidence of BOS and IFN-g level in the blood was found in children of group I (r = –0.45, p < 0.001), and between severity of BOS and the serum IL-4 concentration — in group II (r = –0.28, р = 0.030). Direct correlation between IL-4 and IFN-g (r = 0.41, p < 0.001) was revealed in patients with recurrent BOS. No correlation between VD and immunological indicators was found. Conclusions. BOS has predominantly viral etiology in young children. The severe course of the disease is more common in children with recurrent episodes of BOS although most of them have negative asthma predictive index. In 3/4 of patients with recurrent BOS, the level of VD is within the deficiency level. VD inversely correlates with severity and the incidence of BOS episodes. Vitamin D level in young children mostly depends on level of its supplementation. The course of BOS in young children is accompanied by increasing serum level of IFN-g in the acute period of the disease regardless of the incidence of BOS episodes in the past medical history. Study groups do not differ from each other in the blood serum levels of IL-4 while in the presence of recurrent episodes, this indicator is directly correlated with IFN-g. Thus, IFN-g and IL-4 do not significantly affect the incidence and severity of BOS in young children, as opposed to vitamin D, which might be considered as a predictor of the severe course of BOS and development of its recurrent episodes.

Background. Diseases of the respiratory tract, including broncho-obstructive syndrome (BOS), are common pathology in childhood. It is known that the incidence and severity of respiratory diseases correlates with the level of vitamin D (VD), which deficiency may contribute to the deve­lopment of recurrent episodes of BOS in young children along with other risk factors, such as eosinophilia, family and individual allergy history. Materials and methods. 120 children aged 6 months to 3 years with the diagnosis of acute obstructive bronchitis were examined (I group — 60 children with episodic BOS, group II — 60 children with recurrent BOS). All children were evaluated for anamnesis, general clinical examination with assessment of severity of BOS according to the Seattle Children’s respiratory scoring tool. Laboratory studies included estimation of 25-hydroxyvitamin-D (25(OH)D) concentration in the blood serum using an electrochemiluminescence method on the Cobas e411 analyzer (serial number 1041-24, manufacturer Roche Diagnostics GmbH, Germany) and total calcium concentration in the blood serum according to the generally accepted methodology. Non-parametric statistical criteria were used for the analysis of the obtained data. The difference between compared indicators was considered as statistically significant at a rate of p < 0.05. Results. In children with recurrent BOS, unlike children with episodic one, the level of VD supplementation was significantly lower (p