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 FNO (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 FNO (p < 0.001). A moderate degree of positive correlation was identified between tIgE and FNO (Spearman's rho = 0.461) and tIgE and AEC (Spearman's rho = 0.315) with only small correlation between FNO and AEC (Spearman's rho = 0.299).

SIGNIFICANCE

tIgE levels, FNO and AEC levels are higher in asthma, specifically in the atopic phenotype, as compared to normal. Total serum IgE levels have moderate correlation with FNO and AEC but FNO and AEC are weakly correlated.