What kind of Asthmatic are you?
Mild Intermittent Asthma
- symptoms two or fewer times a week
- normal peak flow between flare-ups
- flare-ups brief, intensity varies
- nighttime symptoms that wake you two or fewer times a
- FEV1 or peak flow greater than or equal to
- peak flow varies less than 20% (the difference between
afternoon readings is less than 20%)
Mild Persistent Asthma
- symptoms more than two times a week but fewer than once a
- flare-ups may limit activity
- nighttime symptoms that wake you more than twice a
- FEV1 or peak flow greater than or equal to
- peak flow varies from 20% to 30% (the difference
between morning and afternoon readings is
between 20% and 30%)
Moderate Persistent Asthma
- symptoms daily; use of
- flare-ups two or more times a week that limit
- symptoms at night that wake you more than once a
- FEV1 or peak flow greater than 60% and less
than 80% predicted
- peak flow variability is greater than 30% (the
between morning and afternoon readings is more than
Severe Persistent Asthma
- symptoms constant and limit activity
- flare-ups frequent during day and night
- FEV1 or peak flow equal to or less than
- peak flow variability greater than 30% (the difference between
morning and afternoon readings is more than 30%)
Classifying asthma phenotypes based on Cluster Analysis :
Currently, there’s a push in the scientific community to come up with a better asthma classification system.
The National Asthma Education and Prevention Program and GINA (Global Initiative for Asthma) guidelines divide asthma severity based on lung function ( mainly FEV1), daytime and nocturnal symptoms, and frequency of rescue bronchodilator . There is increasing evidence however, that this approach does not reflect all the many complexities observed in populations with asthma and also does not reflect the heterogeneous characteristics of this disease. Identification of heterogeneity and classification of asthma by phenotypes provides a foundation from which to understand disease causality and ultimately to develop management approaches that lead to improved asthma control while avoiding adverse effects and decreasing the risk of serious asthma outcomes (e.g., exacerbations and loss of pulmonary function).
In that regard, SARP researchers ( including my personal pulmonologist, Dr Wenzel) through cluster analysis of the asthmatics who have participated in SARP, have now identified 5 distinct groups of asthmatics, and may have identified a 6th. It’s important to note, that this was not a population study, so we still have a long way to go, but I think we’re on the right path.
What Cluster do you belong in?
Fifteen percent of those tested are in this group. This cluster is characterized by younger, predominantly female subjects with childhood onset/atopic asthma and normal lung function. Forty percent of these subjects were receiving no controller medications, and those on asthma medications were most often on two or fewer controller therapies, with a combination of inhaled corticosteroids (ICS) and long-acting ?-agonists most frequently reported. HCU was infrequent in this group, with nearly 70% reporting no need for any urgent physician or emergency department visits, oral corticosteroid bursts, or hospitalizations in the past year. Despite a lack of exacerbations requiring urgent evaluation, 30 to 40% of Cluster 1 subjects reported daily symptoms and rescue bronchodilator use This group contains the youngest and potentially most active subjects, suggesting that symptoms may be primarily exercise related.
The largest group (44% of subjects), it consists of slightly older subjects, two-thirds female, with primarily childhood onset/atopic asthma. This group is distinguished by baseline prebronchodilator lung function that is relatively normal (65% with an FEV1 >80% predicted) or can be reversed to normal (>80% predicted) in nearly all of the subjects (94%). Medication use is more prevalent in this group, with fewer subjects not receiving controller medications (26%), a shift toward increased numbers of controllers (29% on three or more drugs), and higher doses of ICS (28% on high-dose ICS). HCU, asthma symptoms, and reported albuterol use were similar to those observed in Cluster 1, although Cluster 2 was treated with a greater number of asthma medications.
Is the smallest cluster (8% of subjects). It is markedly different from the other clusters and consists mainly of older women (mean age, 50 years; range, 34–68 years) with the highest body mass index [BMI] (58% with BMI >30) and late-onset asthma (all older than 23 years of age), who are less likely to be atopic (64%). Despite a shorter reported duration of asthma, subjects in this cluster have decreased baseline pulmonary function (71% with FEV1 <80% predicted), and only 64% are able to attain this benchmark after bronchodilators. These subjects report complicated medical regimens, with more than half describing treatment with three or more asthma drugs (one of which is frequently high-dose ICS) and 17% receiving regular systemic corticosteroids. Despite this increased reliance on medications, they report more HCU (especially the need for oral corticosteroid bursts) and daily asthma symptoms that approach levels reported by subjects in Clusters 4 and 5. Subjects in Cluster 3 report symptoms and HCU that appear to be out of proportion to their degree of airflow obstruction. This result suggests an important relationship between obesity, level of symptoms, and HCU in this group of subjects.
Clusters 4 and 5
The remaining 33% of subjects are grouped in Clusters 4 and 5. Nearly 70% of subjects in Cluster 4 and 80% of subjects in Cluster 5 fulfill the ATS workshop criteria for severe asthma. Subjects are equally divided between these two clusters, but Cluster 4 is characterized by equal representation of both genders and many subjects with childhood onset (72%) and atopic disease (83%), whereas Cluster 5 consists of more women (63%) with mainly later-onset disease (69% late onset) and less atopy (66%). Clusters 4 and 5 are characterized by a long duration of disease, with those in Cluster 5 having the longest duration. Clusters 4 and 5 differ in the level of baseline lung function and the magnitude of response to bronchodilators. Subjects in Cluster 4 have severe reductions in pulmonary function at baseline (mean FEV1 57% predicted), but 40% of subjects are able to reverse to the near normal range (>80% predicted) after six to eight puffs of albuterol. In contrast, subjects in Cluster 5 have the most severe airflow limitation at baseline (mean FEV1 43% predicted), and, despite some response to maximum bronchodilator testing, 94% of subjects remain with a FEV1 <80% predicted. In both clusters, lung function is abnormal despite the use of multiple asthma medications; 55 to 70% are receiving three or more asthma drugs, and 60 to 80% are on high–dose ICS with subjects in Cluster 5 treated more frequently with systemic corticosteroids (47%) than were subjects in Cluster 4 (39%). HCU was similar in both Clusters 4 and 5, with nearly half of subjects reporting three or more oral CS bursts and an additional 25% reporting inpatient hospitalization in the past year for a severe exacerbation. Nearly 40% of subjects in Clusters 4 and 5 report a history of a prior ICU admission for asthma in their lifetime. Not unexpectedly, 70% of subjects in these groups report daily symptoms and poor quality of life. A potential sixth cluster was a subset of Cluster 5 consisting of 31 subjects who showed a phenotype that was intermediate between Clusters 4 and 5. These individuals were somewhat younger, were more atopic, and showed more bronchodilator reversibility than the remaining 85 subjects in Cluster 5.