The aim of this study is to determine and compare serum cytokine levels of six different severe asthma inflammatory phenotypes differentiated by their atopy, peripheral eosinophilia and/or chronic rhinosinusitis and/or nasal polyposis status.

A prospective observational study of 90 adults diagnosed with severe asthma and on regular follow-up and 15 control subjects will be investigated. Stable (controlled or partly-controlled) status (of all) and exacerbated-status (if any) serum cytokine levels [IL-4, IL-5, IL-10, IL-13, IL-25, IL-33, thymic stromal lymphopoietin (TSLP), IL-17A, periostin) will be evaluated. Also nasopharyngeal brush samples will be obtained for respiratory tract panel work-up with PCR in exacerbated patients. Effect of viral infections' on cytokine response in different inflammatory phenotypes will be evaluated.](streamdown:incomplete-link)

Inclusion Criteria (for disease groups):

1. Patients diagnosed with severe asthma and followed-up at least 6 months at our clinic
2. Asthma that can only be complete or partly controlled with Global Initiative for Asthma (GINA) 4-5 treatment
3. Asthmatics that are eligible for the defined phenotypes
4. At least one perennial allergen sensitivity for the atopic groups

Inclusion Criteria (for control group):

1. Non-asthmatics (without clinical and pulmonary function test evidence)
2. Non-atopics (proved by skin prick tests)
3. Serum eosinophil count <300/cells

Exclusion Criteria (for disease groups):

1. <18 year-old

2. Smoking history within the last 1 year prior to the study

3. Asthmatics with inadequate inhaler technique and/or adherence problems

4. Comorbidities: malignancy history, connective tissue disorders, rheumatological disorders, hyperthyroidism, coronary heart diseases, diabetes mellitus, active hepatic diseases, akut kidney injury, any autoimmune diseases

5. Organ transplantation history

6. Pregnancy

7. Other pulmonary problems: chronic obstructive pulmonary disease (COPD), bronchiectasis, interstitial lung diseases, pulmonary thromboemboli

8. During stable period investigation

   1. Asthma control test <20
   2. Upper respiratory tract infections within 1 month before admission
   3. Exacerbation and/or systemic steroid use within 1 month before admission

9. Atopic patients that only have seasonal allergen sensitivity

Inclusion Criteria (for control group):

1. <18 year-old
2. Smoking history within the last 1 year prior to the study
3. Asthmatics with inadequate inhaler technique and/or adherence problems
4. Comorbidities: malignancy history, connective tissue disorders, rheumatological disorders, hyperthyroidism, coronary heart diseases, diabetes mellitus, active hepatic diseases, akut kidney injury, any autoimmune diseases
5. Organ transplantation history
6. Pregnancy
7. Other pulmonary problems: COPD, bronchiectasis, interstitial lung diseases, pulmonary thromboemboli
8. Without consent

Asthmatic groups will be selected from the Erciyes University Allergy Clinic admisisons.

Control group wil be selected from the Erciyes University Allergy Clinic admisisons and from the volunteers.