title: Predicted Values for Spirometry may Underestimate Long-Standing Asthma Severity.
abstract: BACKGROUND
  Asthma may show an accelerated lung function decline. Asthmatics, although having FEV1and FEV1/VC (and z-scores) higher than the lower limit of normality, may show a significant FEV1decline when compared to previous measurements. We assessed how many asymptomatic long-standing asthmatics (LSA) with normal lung function showed a significant FEV1decline when an older FEV1was taken as reference point.
  
  
  METHODS
  46 well-controlled LSA (age: 48.8±12.1; 23 females) with normal FEV1and FEV1/VC according to GLI2012 references (FEV1: 94.8±10.1%, z-score:-0.38±0.79; FEV1/VC: 79.3±5.2, z-score:-0.15±0.77) were selected. We considered FEV1decline, calculated by comparing the latest value to one at least five years older or to the highest predicted value measured at 21 years for females and 23 for males. A FEV1decline >15% or 30 ml/years was regarded as pathological.
  
  
  RESULTS
  When comparing the latest FEV1to an at least 5-year-older one (mean 8.1±1.4 years between 2 measurements), 14 subjects (30.4%) showed a FEV1decline <5% (mean: -2.2±2.6%), 19 (41.3%) had a FEV15-15% change (mean: -9.2±2.5%) and 13 (28.3%) a FEV1decrease>15% (mean: -18.3±2.4). Subjects with a FEV1decline>30 ml/year were 28 (60.8%). When using the highest predicted FEV1as reference point and declines were corrected by subtracting the physiological decrease, 6 (13%) patients showed a FEV1decline higher than 15%, whereas asthmatics with a FEV1loss>30 ml/year were 17 (37%).
  
  
  CONCLUSIONS
  FEV1decline calculation may show how severe asthma actually is, avoiding a bronchial obstruction underestimation and a possible under-treatment in lots of apparent "well-controlled" LSA with GLI2012-normal-range lung function values.
authors.affiliation: Unit of Pneumology, "Misericordia" Hospital, Grosseto, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Sposato
keywords: Asthma; FEV1 decline; Lung function; Reference values; Spirometry