Relationship between total serum immunoglobulin E levels, fractional exhaled breath nitric oxide levels and absolute blood eosinophil counts in atopic and non-atopic asthma: a controlled comparative study

Objective : Asthma is a prevalent non-communicable disease both in low- and high-income countries, including Nepal. Total serum immunoglobulin E levels and peripheral blood absolute eosinophil counts are known inflammatory markers of asthma. Fractional exhaled nitric oxide measurement in breath has also been proposed as a non-invasive biomarker to assess eosinophilic airway inflammation. This study explores the correlation between these three variables with the intent that one may replace the other in resource-limited setups. Approach : This prospective controlled trial evaluated 314 subjects with and without asthma, with the asthma group sub-divided into atopic and non-atopic categories. Total serum immunoglobulin E level, absolute eosinophil count in peripheral blood and fractional exhaled nitric oxide level were measured in all categories. Results : The geometric mean of immunoglobulin E levels, absolute eosinophil count and fractional exhaled nitric oxide were 221.07 ± 774.55 IU/mL, 214 ± 360/uL and 37 ± 49 ppb in the asthma group and 59.13 ± 174.32 IU/mL, 164 ± 137/uL and 12 ± 21 ppb in the control group, respectively. Significantly higher levels were seen in the asthma group for total serum immunoglobulin E (p < 0.001), AEC (p = 0.002) and F E NO (p < 0.001) levels. Total serum immunoglobulin E levels, absolute eosinophil count and fractional exhaled nitric oxide were 436.79 ± 822.40 IU/mL, 269 ± 395/uL and 76 ± 52 ppb in atopic asthma group. Similarly, total serum immunoglobulin E levels, absolute eosinophil count and fractional exhaled nitric oxide were 131.17 ± 692.96 IU/mL, 182 ± 328/uL and 23 ± 22.5 ppb in non-atopic asthma group. Significantly higher levels were seen in all three variables: tIgE (p < 0.001), AEC (p = 0.008) and F E NO (p < 0.001). A moderate degree of positive correlation was identified between tIgE and F E NO 50 (Spearman’s rho = 0.461) and tIgE and AEC (Spearman’s rho = 0.315) with only small correlation between F E NO 50 and AEC (Spearman’s rho = 0.299). Significance : tIgE levels, F E NO 50 and AEC levels are higher in asthma, specifically in the atopic phenotype, as compared to normal. Total serum IgE levels have moderate correlation with F E NO 50 and AEC but F E NO 50 and AEC are weakly correlated.