Surveillance Case Definition For Asthma
I. MORTALITY AND HOSPITAL DISCHARGE CLASSIFICATION
There is no confirmed case classification for mortality and hospital discharge data. Health departments are encouraged to evaluate the accuracy of these sources.
death certificates/records listing the asthma diagnostic code (ICD-9 Code: 493; or ICD-10 Codes: J45, J46) as the underlying cause of death.
hospital records listing the asthma diagnostic code (ICD-9-CM Codes: 493.0- 493.9; ICD-10-CM Codes: J45.0-J45.9) as the primary diagnosis.
death certificates/records listing the asthma diagnostic code (ICD-9 Code: 493; or ICD-10 Codes: J45, J46) as a contributing cause of death.
hospital records listing the asthma diagnostic code (ICD-9-CM Codes: 493.0- 493.9;ICD-10-CM Codes: J45.0-J45.9) as a secondary diagnosis.
466(acute bronchitis and bronchiolitis), *** in children < 12 years***
491.20 and 491.21 (chronic bronchitis), *** in children < 12 years***
Additional ICD-9 codes that may be used to evaluate administrative data for misdiagnoses and to evaluate possible changes in diagnoses that could explain changes in asthma trends may include:
495 (extrinsic allergic alveolitis),
496 (chronic airway obstruction, not elsewhere classified),
508 (respiratory conditions due to other/unspecified external agents),
506.3 Other acute/subacute respiratory conditions due to fumes/vapors
506.9 unspecified respiratory conditions due to fumes and vapors
786 (symptoms involving respiratory system/other chest symptoms)
II. PREVALENCE CLASSIFICATION
There is no confirmed case classification for self-report. Health departments are encouraged to validate the accuracy of survey self-response data.
A positive response to the survey question, "Did a doctor (or other health professional) ever tell you (or any household member) that you (they) had asthma?"
A positive response to any of the following survey questions:
a) "Do you (or the household member) still have asthma?"
b) "Have you (or any household member) taken prescription medications for asthma (such as albuterol, inhaled steroids, cromolyn, theophylline, etc) during the past year?"
c) "Have you had a wheeze episode in the past year?"
Possible: A suspect case meets any of the following:
A positive response to survey question "Have you (or any household member) used over-the-counter medications for asthma during the past year?",
Positive response to survey question, "Have you (or any household member) experienced episodes of wheezing during the past year?
III. CLINICAL AND LABORATORY CLASSIFICATION
presence of wheezing lasting 2 or more consecutive days,
chronic cough that responds to bronchodilation that persists 3-6 weeks in the absence of allergic rhinitis or sinusitis,
nocturnal awakening with dyspnea, cough and/or wheezing in the absence of other medical conditions known to cause these symptoms (see Comments below).
Definitive Laboratory CriteriaPulmonary function testing (spirometry: FEV1, FVC) demonstrating a 12% increment after the patient inhales a short-acting bronchodilator;
a 20% decrement in FEV1 after a challenge by histamine, methacholine, exercise or cold air
20% diurnal variation in peak expiratory flow over 1 to 2 weeks
A confirmed case met any of the clinical symptoms at least 3 times during the past year AND at least one of the laboratory criteria.
A probable case meets any of the following:
In the absence of supporting laboratory criteria, presence of any of the clinical symptoms which have been reversed by physician treatment with asthma medications and have occurred at least 3 times during the past year.
In the absence of supporting clinical criteria, met at least one of the laboratory criteria during the past year.
In the absence of supporting laboratory or clinical criteria, taken medications in the past year that were prescribed by a physician for asthma.
Possible: A suspect case meets any of the following:
the presence of any of the following during the past year:
shortness of breath on exertion,
presence of wheezing or chronic cough in the absence of obvious respiratory infection
presence of increased nasal secretion, mucosal swelling, nasal polyps, or chronic sinusitis
hyper expansion of the thorax,
sounds of wheezing during normal breathing
prolonged phase of forced exhalation,
chest x ray showing hyper expansion,
FEV1 less than 80% of predicted value
COMMENT: This surveillance case definition may not be as useful in young children as in adults because it is more difficult to diagnose asthma in young children and there may be a reluctance to stigmatize young children with the diagnosis of asthma.
Recurrent episodes of cough and wheezing are frequently due to asthma. However, other causes of airway obstruction leading to wheeze exist (NIHNAEP 1997), such as:
In infants and children:
Upper airway diseases (allergic rhinitis and sinusitis); Obstructions involving small airways (foreign body in the trachea or bronchus, vocal cord dysfunction, vascular rings or laryngeal webs, laryngotracheomalacia, tracheal stenosis, or bronchostenosis, or enlarged lymph nodes or tumor); Obstructions involving small airways (viral bronchiolitis or obliterative bronchiolitis, cystic fibrosis, bronchopulmonary dysplasia, heart disease); Other causes (recurrent cough not due to asthma, aspiration from swallowing mechanism dysfunction or gastroesophageal reflux)
Chronic obstructive pulmonary disease (chronic bronchitis or emphysema); Congestive heart failure; Pulmonary embolism; Laryngeal dysfunction; Mechanism obstruction of the airways (benign and malignant tumors); Pulmonary infiltration with eosinophilia; Cough secondary to drugs; Vocal cord dysfunction.
National Heart, Lung, and Blood Institute. Global Initiative for Asthma. National Institutes of Health publication number 95-3659, Bethesda, MD, 1995.
National Asthma Education and Prevention Program. Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma.
National Institutes of Health publication number 97 -4051A Bethesda, MD, 1997.
It is recommend to combine the confirmed and probable cases for asthma case count.