Abstract

Blood eosinophil counts (BEC) show moderate fluctuations over time but their long-term variability and clinical relevance in the general population remain unclear. We hypothesise a temporal variation of BEC over two visits (V1 and V2; 4.3±0.6?years) in the population-based Austrian LEAD study.

Adults (n=6932) were categorised by their BEC levels: consistently high (BECHIGH, ?210?cells·µL?1 at V1 and V2), consistently low-normal (BECLOW/NORMAL, <210?cells·µL?1 at V1 and V2), variably increasing (BECINCREASE, <210?cells·µL?1 at V1 and ?210?cells·µL?1 at V2) and variably decreasing (BECDECREASE, ?210?cells·µL?1 at V1 and <210?cells·µL?1 at V2). Associations with lung function and respiratory conditions were analysed.

Most individuals remain within their baseline BEC threshold (83.7% in BECLOW/NORMAL and 67.3% in BECHIGH). BEC variability exceeded the normal range (?30 to 60?cells·µL?1) BECINCREASE (+150?cells·µL?1) and BECDECREASE (?144?cells·µL?1) groups. BEC variability significantly affected lung function (?FEV1- BECDECREASE, 26.14 (95.75, 46.52) and BECINCREASE, ?21.58 (?38.41, ?4.75); and ?FVC- BECDECREASE, 28.74 (8.14, 49.34) and BECINCREASE, ?20.78 (?37.73, ?3.83)). BECHIGH individuals were most associated with respiratory symptoms.

BEC is not a static biomarker; longitudinal variability predicts changes in lung function. Current guidelines rely on single time-point BEC measurements, but our findings suggest that repeated assessments and the use of thresholds to determine normal BEC variability over time may better guide treatment decisions in high-risk patients.

Footnotes

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