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Circadian variations in serum eosinophil cationic protein, and serum and urine eosinophil protein X
1Children's Clinic Randers, Randers, Department of Paediatrics, Denmark. o.d.wolthers@dadlnet.dk
Insights
Biochemical markers for asthma, eosinophil cationic protein (ECP) and eosinophil protein X (EPX), show significant daily variations in children. Levels are highest at night and in the early morning, necessitating consistent sampling times for accurate clinical studies.
Area of Science:
- Pediatric Allergy and Immunology
- Biochemical Markers of Inflammation
- Circadian Biology
Background:
- Biochemical markers of inflammation are valuable adjuncts for assessing childhood asthma.
- Limited data exist on the validation of these markers, such as eosinophil cationic protein (ECP) and eosinophil protein X (EPX), in pediatric populations.
- Understanding diurnal variations is crucial for accurate interpretation of these markers.
Purpose of the Study:
- To investigate circadian variations in serum eosinophil cationic protein (ECP) and serum and urine eosinophil protein X (EPX) in children.
- To establish the timing of peak and trough levels for these inflammatory markers in a pediatric cohort.
Main Methods:
- A study involving seven children (five girls, two boys) aged 10-14 years.
- Blood samples for serum ECP and EPX were collected every 2 hours over a 24-hour period.
- Urine samples were collected at timed intervals throughout the 24-hour period for EPX/creatinine analysis.
Main Results:
- Statistically significant circadian variations were detected in serum ECP, serum EPX, and urine EPX/creatinine.
- Concentrations of all measured markers were significantly higher during nighttime and early morning hours compared to daytime.
- Peak serum ECP levels were observed at 06:00, peak serum EPX at 06:00, and peak urine EPX/creatinine in samples collected overnight (24:00-08:00).
Conclusions:
- Serum ECP, serum EPX, and urine EPX exhibit significant circadian variation in children, with nocturnal and early morning peaks.
- To mitigate confounding effects of diurnal variation, blood and urine samples for ECP and EPX assessment should be collected at consistent times in clinical studies.
- These findings support the potential utility of ECP and EPX as biomarkers in pediatric asthma management, provided sampling timing is standardized.
Abstract:
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.