DISCUSSION
There are only a limited number of studies, which focused on environmental allergens, although the relevant literature reported the importance of environmental factors on the variability in lung function of the patients with CF.6,23 Previous studies suggested that the prevalence of atopy in patients with CF was similar to the general population.24,25 The ISAAC (The International Study of Asthma and Allergies in Childhood) Phase II study, which was conducted in Izmir, the prevalence of susceptibility to at least one aeroallergen was 8.8% in 2112 school-age children based on the SPT results.26 In the present study, there was atopy in 33.3% of our patients with CF. This is indicative of the fact that the allergen susceptibility in children with CF is higher compared to the healthy children in Turkish society. Furthermore, it was suggested that environmental factors were more important regarding the prevalence of atopy compared to the genetic differences.6 In the present study, there was no difference between the presence of atopy and CFTR gene mutations.
The patients susceptible to allergens had higher Total IgE levels, higher rates of eosinophilia, and higher rates of ICS and SABA use. There was no difference by bacterial colonization, FEV1predicted value, bronchiectasis, BMI, and MSK scores between SPT positive and negative groups. Nevertheless, the prevalence of bronchiectasis was higher and MSK scores were lower in patients susceptible to AF. Patients with Pa colonization had a higher rate of positive SPT results compared to non-colonized patients, with manifest AF susceptibility. Nevertheless, there was no difference by Sa colonization. This may suggest that certain infectious agents are associated with atopy.
A study, which investigated 55 patients with CF in the adult population associated the presence of atopy in CF with rhinitis symptoms.27 However, the present study did not identify any correlation between presence of atopy and AR. Based on the results of the study, we suggest that the effect of AR on CF clinical findings is not remarkable.
There was susceptibility to fungi (19.6%) followed by pollen (15.7%), while the most prevalent was the AF susceptibility. It was reported that 35% of children with CF had susceptibility to AF, 25% to grass pollen, and 13% to house dust mites.8 Relevant studies suggested the association between susceptibility to AF and severe lung disease.1,3,6,28 ABPA is defined as a clinical picture that may result in chronic lung disease due to a sudden hypersensitivity reaction to AF.20 It was reported that 31-59% of the patients with CF were susceptible to AF and approximately 1-10% of those patients had ABPA.1,3 In the present study, there were clinical findings suggesting ABPA in 3 patients susceptible to AF. There was susceptibility to fungi in one case and to pollen in another case. Although we had a small number of patients, we considered that additional allergen susceptibility might have an effect on the occurrence of ABPA. Relevant literature reported that atopy was an important risk factor for the occurrence of ABPA and ABPA was more prevalent in SPT positive individuals with CF, who were susceptible to at least one aeroallergen other than AF.1,3
It was also reported that all the pulmonary function parameters, including forced expiratory volume in 1 second (FEV1), were lower in patients with ABPA, infected with Pa, and in atopic individuals with CF.5 Certain studies suggested that the effect of atopy on respiratory function was insignificant.25 In the present study, there was no significant difference between the FEV1 predicted value and positive SPT results, eosinophilia, and ICS use. Whereas, the FEV1 predictive value was significantly lower in patients with bacterial colonization, bronchiectasis, and lower BMI. Therefore, we considered that atopy had little effect on the respiratory function in patients with CF. Nevertheless, the prevalence of bacterial colonization and bronchiectasis was higher and MSK scores were lower in our patients susceptible to AF. Therefore, we suggest that AF is considered in patients with CF with severe clinical prognosis.
It is difficult to prove comorbid asthma in patients with CF. However, the term ”CF asthma” was introduced for the patients with CF with airway obstruction attacks responsive to bronchodilators, personal atopy evidence, and eosinophilia. It was even suggested that the above definition represented a different phenotype.29,30While certain studies argued that higher Total IgE levels and eosinophilia might support the CF and asthma combination, other studies disagreed.3,25,31 The Total IgE and eosinophil levels were higher in our atopic CF patients. Nevertheless, we were able to detect early reversibility in a very few patients by means of spirometry.
Relevant studies in the literature reported that 88.2% of the patients with CF used some sort of inhaled bronchodilator.29The rate of ICS prescription was reported as 10% in France, 12% in Germany, and 36% in the United Kingdom.32 Although the ICS use is frequent in patients with CF, relevant studies found inconsistent results as regards the effects of ICS use on FEV1.33-35 The rate of ICS use was 39.2% in our patients. The prevalence of positive SPT results significantly higher in patients using ICS compared to those who did not use ICS, and the Total IgE levels were significantly higher. However, there was no difference by the FEV1 predicted values and MSK scores. Similarly, there was no significant difference by FEV1 predicted value and MSK score between atopic and nonatopic groups using ICS. Obviously, we believe that extensive studies are needed to assess the effectiveness of and requirement for ICS treatment in CF cases.
A Turkish study, which investigated 54 patients with CF, reported that the mean MSK scores of the patients aged between 6 and 22 years was 71±18.7, where the mean BMI was 17.8±3.57. Furthermore, it was demonstrated that there was a strong positive correlation between FEV1 and MSK score (r=0.778, p<0.01).15 Another study reported that there was a weak correlation between the pulmonary function and BMI in children with CF (r = 0.52, p <0.001).36
The mean MSK score of our patients was 72.54±11.50, where the mean BMI was 17.47±3.09. The patients’ MSK scores were moderately correlated with FEV1 predicted value and weakly correlated with BMI. Furthermore, the FEV1 predicted values were moderately correlated with BMI.
Our study is based on the data collected from our clinic; the number of patients is limited and does not represent the total population of the patients with CF.
In conclusion; the importance of aeroallergens, which constitute an important risk factor for asthma and account for a different phenotype, is unclear as regards CF. Although the same may cause a new phenotype of CF, their effect on prognosis seem unremarkable, except for the mold allergens. Nevertheless, the relationship between CF and atopy should be closely observed for the fact that atopy in patients with CF may mediate the occurrence of ABPA. Furthermore, the individuals susceptible to AF should be closely monitored for bacterial colonization, bronchiectasis, ABPA, and poor clinical outcomes, regardless of other aeroallergens. Identification of the population, in which the ICS treatment aimed to prevent pulmonary exacerbation in CF may prove to be effective, may prevent unnecessary drug use. Extensive studies to investigate this topic will be useful.