The Prevalence of Reversible Airflow Obstruction and/or Methacholine Hyperreactivity in Random Adult Asthma Patients Identified by Administrative Data

Abstract

Background. Asthma is a chronic inflammatory lung disease. It is commonly diagnosed and treated on the basis of clinical impression, although national guidelines recommend documenting reversible airflow obstruction. Objectives. Determine the frequency of reversible airflow obstruction, and/or methacholine hyperreactivity during 2003 in a well-characterized population with a low-risk asthma diagnosis during 2001. Methods. Of a total population of 7460 low-risk adult (18–64 years) asthma patients (no hospitalizations or emergency department visits; < 3 oral steroid courses; < 12 β-agonist canisters; and < 3 prescibers, all in prior 12 months) cared for by a large health care program, a random sample of 400 was recruited to undergo a diagnostic asthma evaluation. The evaluation included a physical examination, medical record review, questionnaires, allergy testing, spirometry for airflow obstruction and reversibility, and/or methacholine hyperreactivity. Results. Of the 400 randomly selected patients, 106 (26.5%) started and 82 (77.3%) completed the asthma evaluation. Evaluated subjects were predominately female (71%), middle-aged (mean 51.0 ± 11.0 years), diagnosed asthmatics for long duration (mean 22.1 ± 17.5 years), and nonsmokers (88.7%). Asthma was confirmed in 62.1% (51 of 82) based on a ΔFEV₁ 12% or greater after albuterol (n = 38), ΔFEV₁ 15% or greater after Advair® (n = 6), or a positive methacholine challenge (n = 7). Only 35 of 400 patients (8.7%) ever had reversibility measured in their medical record. Of these, only 12 (34.3%) had a ΔFEV₁ 12% or greater after albuterol. Reversibility was confirmed in all six who had asthma evaluations. Conclusions. More than one third of low-risk adult asthmatics cannot be confirmed to have asthma 2 years later. Spirometry that documented reversibility in the medical record accurately predicted asthma confirmation. Physicians should more widely perform spirometry with reversibility to establish the diagnosis of asthma as recommended by national asthma guidelines.

• administrative databases
• asthma diagnosis
• atopy
• reversiblen airflow obstruction
• HMO
• bronchial hyperreactivity
• methacholine hyperreactivity
• spirometry

Abbreviations
ACE:	=	Angiotensin Converting Enzyme
ACID:	=	Asthma Case Identification Database
BMI:	=	Body Mass Index
CHF:	=	Congestive Heart Failure
COPD:	=	Chronic Obstructive Pulmonary Disease
ED:	=	Emergency Department
GERD:	=	Gastroesophageal Reflux Disease
HEDIS®:	=	Health Plan Employer Data and Information Set
HMO:	=	Health Maintenance Organization
KP:	=	Kaiser Permanente
MC:	=	Methacholine Challenge