This cross-sectional study was done by using simple random sampling technique, jointly in the Department of Respiratory Medicine and Department of Physiology, Government Medical College, Haldwani, Uttarakhand, India during the period from October 2015 to January 2017. After obtaining approval from the institutional ethics committee (274/GMC/IEC/2015) and written informed consent, a total 429 patients of both sexes age above 18 years, who attended the OPD of Respiratory Medicine in designated three days (Monday, Wednesday and Friday) of every week and diagnosed as asthma by the physician were enrolled in the study. But, only 125 patients met our inclusion criteria.

Inclusion Criteria: Patients who met our operational definition of asthma were included.

Definitions: Current asthma was defined as a physician-diagnosed asthma in combination with at least one of the following [2]:

Subjects were defined as having ARC based on positive history of cold and congestion with seasonal aggravation. Patients of current asthma were divided into Allergic asthma (which have current asthma with ARC) and Nonallergic asthma (which have current asthma without ARC). Current smokers were defined as those who smoked even once or twice a day in last 12 months, while ex-smokers were defined as those who quitted smoking ≥12 months ago. Nonsmokers were defined as those who never smoked.

Exclusion criteria: Patients associated with tuberculosis, diseases like worm infestations, atopic skin disease and other allergic diseases, cardiac problems, renal failure, diabetes mellitus, hypertension, pulmonary fibrosis and neuromuscular diseases were excluded.

All the analysis was done on standard software (Microsoft Excel 2016 and SPSS 16.0 version). One-way ANOVA followed by Tukey HSD post-hoc analysis and Chi-square was done. Descriptive statistics like mean and standard deviation have been used. Level of statistical significance was set at p-value <0.05.

Total 429 patients were diagnosed asthma by the physician but only 125 patients met our inclusion criteria, rest 304 patients were excluded. The prevalence of allergic asthma was as observed in 79 patients (63.2%), in comparison to nonallergic asthma in 46 patients (36.8%). The allergic asthma among male patients were more prevalent than females (54:25) while no such gender difference was seen in nonallergic group. The prevalence of allergic asthma were more common among the patients who were working in allergic prone environment (74.6%), while the prevalence of nonallergic asthma were common in patients who were working in nonallergic prone environment (72%). Smoking showed declining trend of prevalence among current smoker, ex-smoker and nonsmoker in both the groups [Table/Fig-1].

As the severity of airway obstruction increased, FEV₁ decreased significantly (p<0.001) in allergic group of asthma as well as in nonallergic group of asthma. On applying, Tukey HSD post-hoc test, difference between groups (mild, moderate and severe) from each other was found to be statistically significant (p<0.001) [Table/Fig-2].

The prevalence of patients who are suffering from mild and severe grade is highest in comparison to moderate grade in both the study groups [Table/Fig-3].

There is significant increase in eosinophil count as the severity of airway obstruction increases in allergic group and no significant changes in other counts. Post-hoc test showed the statistically significant difference (p<0.001) between mild and severe group with more increase in severe one. Also, difference between moderate and severe groups was found to be statistically significant (p=0.001) with more increase in severe group [Table/Fig-4].

In nonallergic group over-all there was a significant increase in neutrophil count (0.044) but in moderate to severe lung impairment increasing trend was observed while in mild lung impairment absolute neutrophil count was more in comparison to moderate. Post-hoc test showed the statistically significant difference between mild and moderate group [Table/Fig-5] and there was an increasing trend of eosinophil count as the severity of airway obstruction increased. There were no significant changes in other counts.

The prevalence of allergic asthma was more (63.2%), in comparison to nonallergic asthma (36.8%). It was more prevalent among males (54%), who were suffering from allergic asthma and had working history in allergic prone environments like in paper mill, forest, wall painters and daily wage based laborers etc., [Table/Fig-1]. Pakkasela J et al., also reported that among the 445 physician-diagnosed asthma patients 52% were classified as allergic and 48% as nonallergic [17]. Similar findings i.e., increase in prevalence of allergic asthma were reported by Beckman H et al., Chandrika D., in their study [2,18]. In terms of severity, maximum patients presented with mild and severe grade of asthma. A similar study conducted by Ashem ND et al., also observed that the maximum asthma patients presented with mild severity [19]. The high prevalence of severe grade in our study, was may be due to lack of awareness towards asthma in common people. The prevalence of current smoker, ex-smoker and non smoker was 62%, 25% and 13% respectively in allergic group while in nonallergic group it was 52%, 35% and 13%, respectively. This was in conformity with the study conducted by Willemse BWM et al., [20]. It is now well established that smoking cessation improves the accelerated decline in forced expiratory volume in one second (FEV1), which strongly indicates that smoking cessation positively influence inflammatory processes in the lungs [20].

The present study found significantly higher eosinophil count (≥300 mm³) in allergic asthma group and the count increased as the severity of airways obstruction increased. Similar findings were also observed in a study conducted by Ashem ND et al., and Horn BR et al., Th2 lymphocytes plays important role in the development of eosinophilic allergic asthma [19,21]. It was well known fact that aeroallergen were an important cause of allergic asthma. These aeroallergen contain trace amounts of lipopolysaccharides. Therefore, when they penetrate into the airway epithelium, they activate the Toll-Like Receptor (TLR). Activation of TLR induces synthesis of cytokines mediated by Th2 lymphocyte. These cytokines stimulate the maturation and recruitments of eosinophils [22]. The present study found a significantly higher neutrophil count in nonallergic asthma patients. Similar finding was reported in a study conducted by Gibson PG et al., [23]. The nonallergic asthma was associated with a neutrophil influx and activation, which may be mediated by IL-8 secretion [23]. Cigarette smoking was associated with bronchial neutrophilia and corticosteroid insensitivity [24,25]. Other reasons of high neutrophil count in increased severity may be the use of steroids for treatment as severity of functional lung impairment increases. Steroids cause an increase in neutrophil count by accelerating release from bone marrow and decreasing its migration out of circulation.

Since, the preferred method to estimate prevalence trends requires continuous dedicated repeated survey of large random samples in the same area, within the same age span and with the same validated methods, were costly and time-consuming [26]. So this type of cross-sectional study can contribute towards the establishment of prevalence trend. This study also justify that peripheral blood leukocyte count can be used as a biological marker to differentiate allergic asthma from nonallergic asthma in setting of limited infrastructure.

However, finding of this study may not be generalised as this study was done in one tertiary institute with small sample size, covering one region of the state. Further studies are needed from different parts to establish the trend of current asthma as well as studies which establish peripheral blood leukocyte count as a biological marker.

Present study shows that prevalence of allergic asthma was more in comparison to the nonallergic type and it was more common in males than females. Further, it was found that allergic asthma was associated with a significant rise in blood eosinophil count while nonallergic asthma was associated with significant increase in blood neutrophil count. This finding in our study suggest that blood leukocyte count (eosinophil vs neutrophil) can be used as a biological marker, to differentiate the allergic asthma from nonallergic asthma type, and to start the presumptive treatment, for particular asthma. It will reduce the long term complications of asthma and improves the QOL.