title: Value of measuring diurnal peak flow variability in the recognition of asthma: a study in general practice.
abstract: In this study we analysed the value of measuring diurnal peak flow variability (DPV) in general practice for diagnosing asthma or chronic obstructive pulmonary disease (COPD). One hundred and eighty-two subjects, aged 18-75 yrs, with undiagnosed asthma or COPD, presenting with a persistent cough recorded a peak flow diary twice daily for 2 weeks. A diagnosis of asthma or COPD was based on the recurrence of airway symptoms in the past year accompanied by spirometric measurements and a provocative dose of methacholine causing a 20% fall in forced expiratory volume in one second. DPV was expressed as amplitude percentage highest of the day. Cut-off values of 15% and 20% (DPV15%, DPV20%) were employed and the number of days that these values were reached, was assessed. The influence of age, sex and pack-years smoking on DPV was analysed by logistic regression. The a priori probability to have asthma (n=69) or COPD (n=12) was 45% (81/182) and increased to >70% with a DPV20% for at least 3, and a DPV15% for at least 4 days. Scoring formulas for asthma (DPV15% (number of days present) + 4 (if female sex)) and for asthma and COPD combined (8x DPV15% (number of days present) + 24 (if female sex) + pack-years smoking) predicted which subjects were at risk for having asthma (or COPD). Simple formulas based on the number of days with diurnal peak flow variability at 15%, female sex and pack-years can predict which patients with persistent cough are likely to have asthma or chronic obstructive pulmonary disease.
authors.affiliation: Dept of General Practice, Leiden University Medical Centre, The Netherlands.
authors.forename: H A
authors.initials: HA
authors.lastname: Thiadens
authors.forename: G H
authors.initials: GH
authors.lastname: De Bock
authors.forename: F W
authors.initials: FW
authors.lastname: Dekker
authors.forename: J A
authors.initials: JA
authors.lastname: Huysman
authors.forename: J C
authors.initials: JC
authors.lastname: Van Houwelingen
authors.forename: M P
authors.initials: MP
authors.lastname: Springer
authors.forename: D S
authors.initials: DS
authors.lastname: Postma
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D002940:Circadian Rhythm; D003371:Cough / Q000503:physiopathology*; D003937:Diagnosis, Differential; D005194:Family Practice; D005260:Female; D006801:Humans; D016015:Logistic Models; D008173:Lung Diseases, Obstructive / Q000175:diagnosis* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate; D011336:Probability; D012680:Sensitivity and Specificity