Reproducibility of responsiveness to a standardized bronchial allergen provocation—R_t compared to FEV₁ as measurement of response to provocation

Abstract

Standardized bronehial allergen provoeation was performed twiee in nineteen extrinsic, well defined, stable asthmatic patients, with an interval of median 15 days (range 14-19) to study the reproducibility of the bronchial response. Smoking and medications were withheld prior to the provocation after a rigid scheme. Ten-fold increasing concentrations of allergen solution 0 9 ml were inhaled by tidal volume breathing for 5 min with intervals of 10 min. The bronchial response to inhaled allergen was determined by forced expiratory volume in the first sec (FEV|) and by total resistance to breathing (R,) determined by an opening interrupter method. The provocation was continued until an allergen concentration causing at least 20% decrease ofthe postsaline FEVi or a 40% increase in Rt was reached. A PC20-FEV1 and a PC40-R1 was calculated by interpolation on the log-dose-response curve. The reproducibility of PC20-FEV1 allergen was high with a 95% confidence interval (CI) for a single determination being the observed value ±0 83, ten-fold concentration difference, the intraelass correlation (IC) was 0 99 and the coefiicient of variation 8 46%. Concerning PC40-R1 a 95% CI for a single determination was calculated being the observed value +0 58, ten-fold concentration difi'erence, IC was 0 99 and the coefiicient of variation was 5 79%. No significant correlation was found between difi"erences in pre-challenge FEV, and R, values and the corresponding PC20-FEV1 and PC40-R1 values. Least square regression between PC20-FEV: and PC40-R1 was performed for the first and the second provocation (/'<0 05). We conclude that bronchial allergen challenge performed in stable asthmatics is highly reproducible and as such a valuable test in the diagnosis of allergic asthma when connected with anamnesis, skin-prick test and the level of specific immunoglobulin E in peripheral blood.

Comparison of airway conductance and FEV1 as measures of airway responsiveness to methacholine

“…A possible explanation to this finding is that the bronchial response in subjects with low sensitivity to methacholine mainly includes larger airways (reflected as Gaw‐change) whereas in subjects who are more responsive to methacholine smaller airways are involved (FEV 1 ‐changes). This is in good agreement with others who have expressed PD Gaw as the dose that yields 35% or 40% decrease in Gaw (Frølund et al ., 1987).…”

Specific inhalation challenge in the diagnosis of occupational asthma: consensus statement

“…Peak expiratory flow shows reproducibility and sensitivity that are similar to FEV1 [70], but this test is more dependent on muscular effort and has no benefit over FEV1 for use during supervised measurements in hospital [71]. Measurements of airway resistance or conductance by body plethysmography [65,[72][73][74] and respiratory resistance by the forced oscillation technique [75] are not affected by inspiratory manoeuvres and are not effort-dependent, but they are less reproducible and require more expensive equipment. Nevertheless, these parameters may be useful in subjects who are not able to perform reproducible spirometric manoeuvres and may provide useful complementary evidence of a significant bronchial response during SICs that produce equivocal changes in FEV1 [76].…”

Use of interrupter technique in assessment of bronchial responsiveness in normal subjects

“…The 10 day reproducibility of the PD 100 Rint, EI was investigated by randomly asking 39 subjects to come again after one week for a second examination. During the second visit we compared Rint, EI with FEV 1 as measurements of response to provocation, the latter determined 30 s after the assessment of Rint, EI [9,17]. At least two technically correct forced expiratory manoeuvres with an FEV 1 variation within ± 5% were received and the highest value was used for calculating the dose producing a 20% fall in FEV 1 (PD 20 FEV 1 ).…”