Eosinophil markers in childhood asthma

Circadian variations in serum eosinophil cationic protein, and serum and urine eosinophil protein X

Biochemical evaluation of inflammation may be a useful adjunct to measures of pulmonary function and symptoms in children with asthma. However, little data have been provided to validate the markers in children. The aim of the present study was to assess circadian variations in serum eosinophil cationic protein (ECP), and serum and urine eosinophil protein X (EPX) in children. Five girls and two boys aged 10-14 years were studied. The first sample of urine consisted of urine collected from 24.00 hours the night before until 08.00 hours on the morning of the day of investigation. Thereafter urine was collected at 4-h intervals until 24.00 hours and in another 8-h interval from 24.00 to 08.00 hours. Blood samples for assessment of serum ECP and serum EPX were collected every 2 h during the 24 h. Statistically significant circadian variations in serum ECP (F=3.2, p=0.002), serum EPX (F=3.1, p=0.002) and in urine EPX/creatinine (F=5.4, p=0.003) were detected. The concentrations were higher during the night compared to daytime. Peak levels of serum ECP (mean [+/- SEM]) were found at 06.00 hours (16.3 [5.3] micro g/l), trough levels at 08.00 hours (3.9 [0.7] micro g/l) (p=0.01). Peak levels of serum EPX were seen at 06.00 (43.7 [9.5] micro g/l) with trough levels at 12.00 hours (22.0 [3.5] micro g/l) (p=0.01). Peak levels of urine EPX/creatinine occurred in urine collected from 24.00 to 08.00 hours (90.0 [27.7] micro g/mmol), trough levels in the 16.00-20.00 hours sample (29.7 [8.9] micro g/mmol) (p=0.02). Serum ECP, serum EPX and urine EPX exhibit a circadian variation in children with nocturnal and early morning peak levels. To avoid confounding influence from circadian variations in ECP and EPX in clinical studies blood or urine should be sampled at consistent times.

Asthma attack severity and urinary concentration of eosinophil X protein in children

OBJECTIVE

Determination of the urinary concentration of eosinophil protein X (U-EPX) may objectively predict the severity and activity of asthma in children.

METHODS

Concentrations of U-EPX in 80 non- atopic asthmatic children were compared with those in 25 healthy control children. The patients were studied during attacks and two weeks later. The severity of asthma attacks was determined according to a pre-existing score. U-EPX was measured by the specific radioimmunoassay technique (Pharmacia, Uppsala, Sweden). This measurement was correlated with the clinical and radiological investigations as well as with other variables such as blood oxygen saturation, peak expiratory rate and eosinophil count.

RESULTS

U-EPX concentrations were significantly higher in all asthmatic children during attacks (139.6 11.7 microg/mmol of creatinine) than those in the control group (35.3 6.2 microg/mmol of creatinine) (p < 0.001). Two weeks after resolution of the exacerbation, U-EPX significantly decreased (66.5 9.3 microg/mmol of creatinine) (p < 0.001). U-EPX concentrations were highest in patients with severe attacks (191.5 11.3 microg/mmol of creatinine) (p < 0.001). No statistically significant differences were found between mild (88.2 7.2 microg/mmol of creatinine) and moderate attacks (119.6 8.5 microg/mmol of creatinine). At the two-week follow-up, U-EPX concentrations in patients with mild or moderate attacks was similar to those in controls but were persistently elevated in the subgroup with severe attacks (103.8 9.4 microg/mmol of creatinine) (p < 0.001). No significant correlation was found between U-EPX concentrations and blood oxygen saturation, peak expiratory rate or eosinophil count.

CONCLUSION

A statistically significant correlation was found between U-EPX concentrations and the severity of attacks in asthmatic children. This substance could be useful in quantifying bronchial inflammation. This result could further be used as a marker of severity of disease exacerbation and would not only facilitate early diagnosis and staging of inflammatory and allergic disorders but would also allow therapy and interventions to be monitored.

Circadian variation of exhaled nitric oxide and urinary eosinophil protein X in asthmatic and healthy children

Asthmatic symptoms and the frequency of admissions to hospital because of acute asthma tend to increase in the early morning hours, and it is therefore possible that airway inflammation increases during the night. To elucidate the hypothetical circadian variation of airway inflammation, we measured concentrations of exhaled nitric oxide (FeNo), urinary eosinophil protein X excretion (EPX), and forced expiratory volume in the first second (FEV1) in 20 asthmatic and 6 nonatopic nonasthmatic children every 3 h during a 21-h period. Compared with control subjects, asthmatic subjects had higher FeNo (median, 22.7 versus 10.3 ppb, p = 0.016) and lower FEV1 % predicted (median, 91.0 versus 101.9%, p = 0.045), but did not differ significantly in EPX (median, 153.8 versus 148.7 microg/mmol creatinine, p = 0.83) at 7 AM. However, differences in gender and age do not allow direct comparisons between asthmatic and control children. FeNo and EPX demonstrated a cosinelike circadian rhythm (log FeNo, p = 0.0001; log EPX, p = 0.0001) with lowest levels at 7 PM and highest at 7 AM. This was also the case for FEV1 % (p = 0.01). No difference in the amplitude of circadian rhythm was observed between asthmatic and healthy control children for log FeNo (p = 0.35), log EPX (p = 0.57), and FEV1 % (p = 0.17). A stratified analysis showed a significant circadian rhythm in the control group for log FeNo (p = 0.014) and log EPX (p = 0.0001). Our results therefore suggest a circadian rhythm of inflammatory markers, which peaks in the early morning. Rhythmicity of EPX excretion and FeNo in healthy children suggests a physiologic mechanism; however, pathologic effects during the night might occur under conditions of asthma-specific inflammation.

Urinary eosinophil protein X in children with asthma: influence of atopy and airway infections

It has been suggested that urinary eosinophil protein X (U-EPX) can be used to monitor bronchial inflammation in childhood asthma. However, the influence of atopy and airway infections is not well elucidated. To determine the clinical value of measuring U-EPX in children with asthma and to evaluate the influence of atopy and airway infections, U-EPX was measured in 170 children with asthma (mean age 69 months, range 12-179 months), in 79 children with lower or upper respiratory tract infections (mean age 41 months, range 1-165 months), and in 64 controls. U-EPX was elevated in children with acute asthma (median 132 microg/mmol of creatinine, quartiles 77-195 microg/mmol of creatinine, n = 51, p <0.001) and chronic asthma (median 93 microg/mmol of creatinine; quartiles 46-149 microg/mmol of creatinine, n = 119, p <0.01) compared with controls (median 54 microg/mmol of creatinine, quartiles 40-89 microg/mmol of creatinine, n = 39). Atopic children had higher levels of U-EPX than non-atopics with acute asthma (median 155 microg/mmol of creatinine, quartiles 113-253 microg/mmol of creatinine, n = 27, vs. median 102 microg/mmol of creatinine, quartiles 56-168 microg/mmol of creatinine, n = 24, p <0.05), as well as with chronic asthma (median 110 microg/mmol of creatinine, quartiles 65-162 microg/mmol of creatinine, n = 63, vs. median 60 microg/mmol of creatinine, quartiles 39-123 microg/mmol of creatinine, n = 56, p <0.01). In chronic asthma, children without atopy had levels of U-EPX similar to values of controls; levels were similar in symptomatic and asymptomatic patients, and not influenced by treatment with inhaled corticosteroids. Moreover, U-EPX levels were higher in children with pneumonia (median 207 microg/mmol of creatinine, quartiles 111-280 microg/mmol of creatinine, n = 35, p <0.001), laryngitis (median 109 microg/mmol of creatinine, quartiles 65-161 microg/mmol of creatinine, n = 24, p <0.01), and rhinitis (median 172 microg/mmol of creatinine, quartiles 123-254 microg/mmol of creatinine, n = 19, p <0.001) than in controls (median 62 microg/mmol of creatinine, quartiles 41-93 microg/mmol of creatinine, n = 64). There was significant overlap among all groups of children with disease, as well as between children with disease and controls. Hence, U-EPX may reflect differences in eosinophil involvement and activation between children with atopic and non-atopic asthma, but the individual spread within groups and the influence of airway infections limits the clinical value of U-EPX in childhood asthma.