Family Practice Advance Access originally published online on July 31, 2006
Family Practice 2006 23(6):674-681; doi:10.1093/fampra/cml041
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Can the Asthma Control Questionnaire be used to differentiate between patients with controlled and uncontrolled asthma symptoms? A pilot study
a Department of Family Medicine, Radboud University Nijmegen Medical Centre The Netherlands
b Division of Clinical Methods and Public Health, Department of Family Medicine, Academic Medical Centre, University of Amsterdam The Netherlands
Correspondence to Lotte van den Nieuwenhof, MD, Department of Family Medicine (117-HAG), Radboud University Medical Center Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands; Email: L.vandennieuwenhof{at}hag.umcn.nl
Received 19 October 2005; Revised 23 May 2006; Accepted 28 June 2006.
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Abstract |
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Background. A substantial number of adult patients with asthma are inadequately controlled despite the availability of effective asthma treatment. Patients and physicians seem to overestimate the level of asthma control.
Objective. The current study explores whether valid differentiation is possible between asthma patients with controlled and uncontrolled asthma symptoms, on the basis of the Asthma Control Questionnaire (ACQ).
Methods. In this multi-centre, cross-sectional study, patients were classified according to Global Initiative for Asthma criteria into levels of asthma symptom control based on a diary card registration. We defined Step 1 (‘well controlled’ asthma symptoms), Step 2 (‘moderately controlled’), Step 3 (‘poorly controlled’) and Step 4 (‘very poorly controlled’). These control steps were related with the sum score of the ACQ.
Results. From 108 asthma patients complete data were obtained. The Step 1 subgroup comprised 17 patients; Step 2, 12 patients; Step 3, 22 patients; and Step 4, 57 patients. Receiver Operating Characteristic curve analysis showed that the optimal ACQ sum score cut-off value to differentiate between Step 1 and Steps 2, 3 and 4 was three points (sensitivity: 84%, specificity: 76%). For Steps 1 and 2 versus Steps 3 and 4, this was four points (sensitivity: 77%, specificity: 59%). For Steps 1, 2 and 3 versus Step 4, this was six points (sensitivity: 70%, specificity: 74%).
Conclusion. Our results show that discrimination between asthma patients with controlled and uncontrolled asthma symptoms, based on the ACQ, is possible with a reasonable margin of test inaccuracy. Thus, the ACQ may be an important tool for health care professionals who aim to optimize the level of asthma control in their patient population.
Keywords. Asthma symptoms, control, detection, family practice, questionnaire.
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Introduction |
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Asthma is a common chronic respiratory disease with a prevalence of 5% of the world's population, and this prevalence is still rising.1,2 By achieving optimal control of asthma, the risk of life-threatening exacerbations and severe morbidity can be greatly reduced. Therefore, achieving respiratory symptom control is one of the main targets in the management of patients with asthma. The Global Initiative for Asthma (GINA) guidelines3 specify a number of goals for the long-term management of asthma. Among these are minimal chronic symptoms—including nocturnal symptoms—minimal need for as-required ß2-agonists and no limitations to daily activities. These treatment objectives are also pursued in (primary care) guidelines like the Dutch College of Family Physicians guideline for asthma.4
However, despite the availability of highly effective pharmacotherapy, poorly controlled asthma is reported in up to 70–95% of patients in Western Europe and the Asian-Pacific region.5,6 Among other factors, poor compliance and knowledge of asthma medication and poor adherence towards regular control visits are explanations for this suboptimal control.7,8 There are also indications that patients as well as physicians overestimate the level of asthma control.5,6 Therefore, a good and simple method to identify those asthma patients who are inadequately controlled would be welcome to support health care professionals in deciding which patients are particularly in need of their attention. Unfortunately, even though asthma control is of growing concern to clinicians and researchers, there is currently no gold standard to classify patients according to their level of asthma control. Because of this, the asthma severity classification in the GINA guideline3 is often used to define asthma control.9,10
In The Netherlands, all inhabitants are registered with a family physician (FP), and access to health care services is largely coordinated by the FP. As a consequence, the majority of Dutch patients with asthma are treated by FPs, so, particularly in family practice, an adequate method to detect patients with poor asthma control is very relevant. Because of the time restraints health care professionals generally have, patients with apparent poor asthma control could be prioritized for extra attention by their FP or other primary care professionals.
An increase of bronchial symptoms has been reported to be an essential part of true loss of asthma control,11 and several questionnaires have been developed to measure asthma symptoms.12,13 However, these questionnaires have been developed and used in selected patients and in specific settings—mostly in clinical studies—so there is a need to explore whether these instruments can be used in primary care to trace patients with uncontrolled asthma. Therefore, the aim of the current study was to explore whether FPs can differentiate between patients with controlled and uncontrolled asthma symptoms by using a short questionnaire that measures the level of asthma symptom control. The shortened version of the Asthma Control Questionnaire©(ACQ) developed by Juniper et al.13–15 was selected for this purpose. In particular, we wanted to investigate if an ACQ score cut-off value could be established in order to differentiate between patients with adequate and inadequate asthma symptom control.
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Methods |
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Design, subject recruitment and measurements
This pilot study was a multi-centre, cross-sectional study relating individuals' ACQ scores to their GINA symptom level.3 The study aimed to analyse data of 100 patients with different levels of asthma control. In order to recruit these patients, 333 asthma patients from 8 family practices were contacted, of whom 88 were willing to participate. An additional 25 asthma patients were recruited through a newspaper advertisement. Patients had to be aged between 18 and 45 years. A diagnosis of chronic obstructive pulmonary disease (COPD) and inability to communicate in the Dutch language were grounds for exclusion. The medical ethics review board of the Radboud University Nijmegen Medical Centre approved of the study.
Patients were sent a diary card and a questionnaire in which the ACQ and questions on smoking habits were integrated. In order to describe the average level of asthma symptom control of a patient, the diary card comprised a 4-week registration period. The diary card contained questions on the presence of daytime and nocturnal respiratory symptoms, impact of asthma symptoms on daily activities and use of asthma medication. Participants were instructed to fill in the diary card every day throughout the 4-week registration period.
The ACQ is a 7-item questionnaire that has been validated and has been used to measure the effects of asthma treatment in clinical studies.13 Patients recall their experiences during the previous week and respond to each question on a 7-point scale, which ranges from 0 (well controlled) to 6 (extremely poor controlled). Because of the use of the postal mailing procedure, we used a shortened version of the ACQ in which the final question about pulmonary function is omitted. Omission of this question does not influence the validity of the ACQ.14,15 The sum of the six remaining items was used to calculate a total ACQ score, which could range from 0–36. Participants were instructed to complete the questionnaire on the last day of their diary registration period. Participants returned their diary cards and questionnaires to the department of family practice of the Radboud University Nijmegen Medical Centre in a prepaid envelope.
Classification of asthma symptom control
We used the data obtained from the diary cards to classify patients into levels of asthma symptom control. In order to describe asthma symptom control we applied the asthma severity classification in the GINA guideline3 to classify (the frequency of) bronchial symptoms and use of rescue bronchodilator use. Patients were classified into one of four steps (Table 1) according to their frequency of (i) daytime asthma symptoms; (ii) nocturnal asthma symptoms; (iii) limitations of physical activities due to asthma; and (iv) daily use of short-acting ß2 agonists. Patients were classified into Step 1 (‘well controlled’ asthma symptoms), Step 2 (‘moderately controlled’), Step 3 (‘poorly controlled’) and Step 4 (‘very poorly controlled’). Because we used a postal mailing procedure for data collection, the lung function criteria that are included in the GINA classification (level of FEV1 and PEF) were not used in this classification. The process of categorizing patients into the consecutive GINA steps was started by looking at each of the four criteria separately. During this initial phase of the analysis it turned out that 85 patients (79%) reported frequencies for daytime symptoms, nocturnal symptoms, limitation of daily activities and short-acting ß2 agonist use that were not all consistent with one particular step. Only 23 patients (21%) in the study population complied with all four criteria according to one and the same step. Following the GINA guideline, the patient then was assigned to the highest level of severity of any one criterion. This was defined as the ‘stringent classification’. This stringent classification means, for instance, that a patient who complies with three criteria according to Step 1 and only one criterion according to Step 4 is categorized in the same step as is a patient who complies with all four criteria of Step 4. Therefore, we also formulated a less stringent classification, the ‘lenient classification’. In order to be categorized in Step 1, patients had to comply with all four criteria that appertain to Step 1. For Step 2, patients had to comply with Step 1 or Step 2 for three criteria, but were allowed to have one criterion in a higher step (either Step 3 or 4). For Step 3, patients had to comply with at least three of the criteria that appertain to Step 3 but did not have more than one criterion in Step 4. Step 4 subjects had to comply with all four criteria according to Step 4.
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Statistical analyses
Data analysis was performed with SPSS 12.0 for Windows. A series of Receiver Operating Characteristic (ROC) curves were created to determine the optimal ACQ cut-off values to distinguish (i) Step 1 patients from Steps 2, 3 and 4 patients; (ii) Steps 1 and 2 patients from Steps 3 and 4 patients; (iii) Steps 1, 2 and 3 patients from Step 4 patients for the stringent and lenient classifications. A cut-off point with a sensitivity of 0.80 and a specificity of 0.80 was considered the most appropriate cut-off value for the ACQ. For each ROC curve the area under the curve (AUC) and the accompanying 95% confidence interval (95% CI) was calculated. Differences between the various steps were analysed by Chi-square and one-way ANOVA (analysis of variance) testing.
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Results |
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Study population
A total of 113 patients with asthma participated in the study. Of all patients, 88 (78%) had been recruited by the FPs involved in the study and 25 through the newspaper advertisement. Valid diary cards were missing for five patients and ACQ scores were missing for two patients. Thus, data for further analysis were available for 108 patients. The mean age was 34.9 years (SD: 7.5), and 71 patients (65.7%) were females. In Table 2 the characteristics of the participating asthma patients are given for the stringent classification of asthma symptom control.
Classification of asthma control
According to the stringent classification, there were 17 patients (15.7%) with ‘well controlled asthma symptoms’ (Step 1), 12 patients (11.1%) with ‘moderately controlled asthma symptoms’ (Step 2), 22 patients (20.4%) with ‘poorly controlled asthma symptoms’ (Step 3) and 57 patients (52.8%) with ‘very poorly controlled asthma symptoms’ (Step 4) (Table 2). Using the lenient classification fewer patients were categorized as having poor asthma control: 17 patients (15.7%) were categorized in Step 1, 38 patients (35.2%) in Step 2, 47 patients (42.5%) in Step 3 and 6 patients (5.6%) in Step 4.
ACQ scores
For the total study population, the mean ACQ score was 6.8 points (95% CI: 5.7; 8.0). The ACQ scores of the stringent classification are shown in Table 2. As compared with the stringent classification, the Step 1 patients of the lenient classification had an identical mean ACQ score (1.6 points, 95% CI: 0.7; 2.4), Step 2 patients had a slightly lower ACQ score (4.1 points, 95% CI: 3.2; 5.0), whereas Steps 3 and 4 patients showed substantially higher ACQ scores (9.8 points, 95% CI: 8.1; 11.6, and 16.7 points, 95% CI: 9.0; 24.3, respectively). Again, one-way ANOVA testing showed that the differences in ACQ scores between the four steps were statistically significant (P < 0.001). The scatter plots in Fig. 1 show a considerable overlap in the ACQ scores of the patients in Steps 1 to 4 for the stringent as well as for the lenient classification.
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Optimal cut-off for ACQ values
Figure 2 shows—for the stringent classification—the ROC curves for the ACQ cut-off values to distinguish asthma patients in Step 1 from those in Steps 2, 3 and 4 (Fig. 2A), Steps 1 and 2 patients from Steps 3 and 4 patients (Fig. 2B), and Steps 1, 2 and 3 patients from Step 4 patients (Fig. 2C) and the accompanying sensitivities and 1- specificities (Tables 3, 4 and 5). Table 6 shows that for the stringent classification an ACQ cut-off score of
3 points best discriminated between patients with good (Step 1) and patients with moderate or worse asthma symptom control (Steps 2, 3, and 4). An ACQ score of 4 points distinguished between patients with good or moderate symptom control (Steps 1 and 2) and patients with (very) poor symptom control (Steps 3 and 4), whereas an ACQ score of 6 points best detected patients with very poor symptom control. Except for the differentiation between Step 1 and Steps 2 to 4, the ACQ cut-off values were higher when the lenient classification was used.
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Discussion |
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The aim of this pilot study was to explore whether it is possible for primary care physicians to differentiate between patients with controlled and uncontrolled asthma symptoms on the basis of the shortened version of the ACQ. A simple but valid method to make this differentiation would enable FPs to efficiently select those asthma patients who are in most need of their attention. The results of this exploratory study indicate that the ACQ may be a good and simple mailing tool to guide FPs in detecting patients with poor asthma symptom control in their practice.
In terms of demographics or illness severity our study population does probably not fully represent the family practice asthma population. For instance, women were over-represented, especially in the poorly and very poorly controlled subgroups. Also, we studied patients aged between 18 and 45 years. The upper age limit of 45 was chosen to exclude patients with COPD as much as possible, although assessing asthma control would obviously not have to be limited to this age group. In our view, the lack of external validity is only of limited relevance. Most important in this exploratory study was to include patients with different levels of asthma control in order to see whether the ACQ could discriminate between these different levels of asthma symptom control. However, a similar study in a larger cohort of asthma patients with a wider age range and a wide spectrum of levels of symptom control is needed to confirm our findings. From such research it could also become clear how relevant it is to check on medication non-compliance (which is a very common feature in patients with asthma)16 once a patient is identified as having suboptimal control. Further research in this field is certainly needed, as up until now we have not been able to trace other studies in which the actual identification of patients with poor asthma control in a primary care setting with the aid of simple methods has been investigated. Future studies should also take into account that improved asthma control might come at the price of adverse effects of the medication (i.e. inhaled corticosteroids) that is needed to achieve a higher level of control.
An objective way to screen for asthma symptom control is important because there is a discrepancy between asthma patients' self-reported level of control and the level of control that is measured objectively. Asthma patients tend to underestimate their asthma symptoms.6,7,17,18 Although we did not investigate this in the current study, there is evidence that better asthma control improves the overall health status of patients.9 Identification of patients with poorly controlled asthma would give practitioners the opportunity to raise the level of asthma control and, consequently, the health status in their practice population.
In order to be able to compare the results of studies on asthma control, it is important to have consensus on a definition of bronchial symptom control. Cockcroft and Swystun19 have reported that most of the criteria describing asthma severity also describe the lack of asthma control, but that asthma control and asthma severity are two different concepts. However, in the absence of an instrument to actually measure asthma control we used the criteria for disease severity of the widely accepted GINA guideline.3 The four steps of asthma symptom control we applied have previously been used by other investigators.5,6,17 We found the GINA criteria for asthma symptoms not to be mutually exclusive: a significant part (79%) of our study population could be allocated to more than one step at the same time. Following the GINA guideline the patient then has to be assigned to the highest level of severity of any one criterion (the ‘stringent' classification) meaning that a patient who has, for instance, three criteria indicating good asthma symptom control and just one criterion indicating poor control is ‘forced’ into the same category as a patient who has poor control according to all four criteria. This means that a larger proportion of patients will be categorized as having poor asthma symptom control. In the stringent classification, indeed a great part of patients (53%) are very poorly controlled (Step 4). In our lenient classification there was only a small number (6%) of patients with poorly controlled asthma symptoms (Step 4), which probably would be more compatible with a study in the primary care setting, as the Dutch asthma guideline advises patients with very poor asthma symptom control to be referred for further care by a respiratory physician.4 As a comparison, the Asthma Insights and Reality in Europe (AIRE) Study reported a proportion of 15 to 28% of all patients with asthma to suffer from uncontrolled asthma across seven countries in Western Europe.20
When using the more stringent classification we found lower cut-off values for the ACQ score to discriminate between asthma patients with decreasing levels of symptom control than with the lenient classification. Our stringent analysis showed that a cut-off value for the ACQ score of 3 points best discriminated patients with good asthma symptom control from patients with moderate or worse control. An ACQ score of 4 was the most suitable cut-off to select patients with (very) poor symptom control. And an ACQ score of 6 points was the most suitable cut-off to select patients with very poor symptom control. Although, as explained above, we need to be careful with the interpretation of these values because the study participants may not represent normal asthma population. The cut-off value for the ACQ score used is dependent upon what a FP wishes to achieve as well as on the time and manpower available. If the goal is to detect only the patients with poorly controlled asthma symptoms, the cut-off value of 6 points on the ACQ seems to be the most appropriate choice. If the FP wants to see all asthma patients with suboptimally controlled symptoms, a lower cut-off value on the ACQ (3) should be considered. Also, when using our cut-off values for individual patients it should be kept in mind that there was an overlap of ACQ scores between the step categories, with the exception of Step 1 and Step 4 patients in the lenient categorization.
Instead of using the mean ACQ score, which is commonly used, we used the sum score of the ACQ items, because calculation of the mean score complicates the application of the instrument in daily clinical practice. As long as there are no missing values among the six items—in our population this was the case for only 3.5% of patients—the interpretation is the same. The ACQ questionnaire had to be completed on the final day of the 4-week diary card observation period. Although diaries and questionnaires are commonly used research tools, there are shortcomings of this method. It has been reported that not all patients are perfectly compliant with completing questionnaires and diary cards.21 However, it seems unlikely that there has been a relevant dependency between the diary card recordings and the ACQ score: the ACQ items were part of a larger questionnaire that the participants completed on the final observation day; it seems unlikely that patients would take the trouble to trace the actual ACQ questions in the questionnaire and directly compare their responses with the previously recorded diary card entries.
In conclusion, the ACQ seems to be a helpful screening tool to distinguish asthma patients with good symptom control from patients with poor symptom control in an objective and feasible way. We found that it was possible to define a cut-off value for the ACQ score for this purpose. However, which cut-off value is most appropriate depends on the goals a health care professional has. When resources are limited, the goal might be to detect only patients with poorly controlled asthma symptoms, and an ACQ cut-off of 6 points would seem appropriate. If there are no restraints in time or manpower a more ambitious goal can be set, for instance, not to miss any asthma patients with a suboptimal level of symptom control. In that case an ACQ cut-off of 3 points seems apposite. This way of applying the ACQ may provide health care professionals with a good and effective starting point to actively detect patients with uncontrolled asthma symptoms in their practice, and to provide them with an important tool to optimize the level of asthma symptom control in their patient population.
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Acknowledgments |
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The authors like to thank Mrs Joke Grootens and Mr Aad Wissink for their assistance in the study logistics and data collection.
Funding: GlaxoSmithKline provided an unrestricted grant for this study.
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Notes |
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van den Nieuwenhof L , Schermer T, Eysink P, Halet E, Van Weel C, Bindels P and Bottema B. Can the Asthma Control Questionnaire be used to differentiate between patients with controlled and uncontrolled asthma symptoms? A pilot study. Family Practice 2006; 23: 674–681.
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References |
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1 National Heart, Lung and Blood Institute, Department of Health and Human Services National Institutes of Health. (1997) Guidelines for the diagnosis and management of asthma: expert panel report 2. (NIH publication No., Washington DC)97–4051.
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20 Vermeire PA, Rabe KF, Soriano JB, et al. (2002) Asthma control and differences in management practices across seven European countries. Respir Med 96:142–149.[CrossRef][ISI][Medline]
21 Stone AA, Shiffman S, Schwartz JE, et al. (2003) Patient compliance with paper, electronic diaries. Control Clin Trials 24:182–199.[CrossRef][ISI][Medline]
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