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* From MEDTAP International (Dr. Leidy and Ms. Schmier), Bethesda, MD; University of Nebraska Medical Center (Dr. Rennard), Omaha, NE; and AstraZeneca (Dr. Goldman and Ms. Jones), Wilmington, DE.
Correspondence to: Nancy Kline Leidy, PhD, Center for Health Outcomes Research, MEDTAP International, Inc., 7101 Wisconsin Ave, Suite 600, Bethesda, MD 20814; e-mail: leidy{at}medtap.com
| Abstract |
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Objective: To develop empirically based guidelines for interpreting mean changes in symptom scores using the Breathlessness, Cough, and Sputum Scale (BCSS).
Methods: Analyses were performed on data from three multinational trials (n = 2,971). Mean changes in BCSS score with treatment were examined by physician and patient ratings of treatment efficacy, juxtaposed with percentage change in symptoms, statistical effect size (ES),
FEV1, and change in St. George Respiratory Questionnaire (SGRQ) score. BCSS scores during an exacerbation were examined relative to changes in peak expiratory flow and rescue medication use.
Results: Mean baseline BCSS total score was 5.2 ± 2 (± SD); 90% of scores were between 2 and 9. Highly efficacious treatment (n = 257; physician rating) was associated with a
BCSS total score of - 1.3 ± 1.8, representing a 24% improvement (ES = 0.7), and corresponding to a 10% improvement in FEV1 and
SGRQ score total of - 10.3 ± 13.8. Similar changes in BCSS score were observed during recovery from an exacerbation (n = 713; - 1.3 ± 1.8). Mean change with moderately efficacious treatment (n = 965) was - 0.7 ± 1.8, a 13% improvement (ES = 0.3) corresponding to
SGRQ total score of - 6.8 ± 12.6. Mildly efficacious treatment (n = 891) was associated with a change of - 0.35, a 7% improvement (ES = 0.18), with a
FEV1 <1% and
SGRQ total score of - 2.6 ± 11.7.
Conclusions: Patient-reported daily symptom data are sensitive to change and useful for both observational studies and controlled clinical trials of patients with COPD. A mean
BCSS total score > 1.0 represents substantial symptomatic improvement, changes of approximately 0.6 can be interpreted as moderate, and changes of 0.3 can be considered small.
Key Words: bronchitis clinical trials COPD cough dyspnea emphysema exacerbation health-related quality of life instrument patient-reported outcome sputum St. George Respiratory Questionnaire symptoms
| Introduction |
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There are relatively few instruments to assess the severity of respiratory symptoms and symptom outcomes in the COPD population within the context of a clinical trial. The Baseline Dyspnea Index/Transition Dyspnea Index,5 modified Medical Research Council Dyspnea Scale,6 Oxygen Cost Diagram,7 and Borg Scale8 have been used to evaluate breathlessness but do not address cough or sputum. The length and 3-month recall period of the chronic lung disease severity index9 is not conducive to evaluating treatment outcomes in controlled clinical trials. Condition-specific health-related quality of life (HRQL) measures, such as the St. George Respiratory Questionnaire (SGRQ)10 or the Chronic Respiratory Questionnaire,11 were not designed to assess symptom severity per se, but rather the impact of symptoms on daily functioning and well-being. None of these measures prospectively assess the severity or variability of symptoms day to day. In fact, as of this date, there are no published, validated (reliable, valid, responsive) measures to assess day-to-day symptom severity in COPD.
The Breathlessness, Cough, and Sputum Scale (BCSS) was developed to meet the need for a precise, easy-to-use instrument for tracking the severity of respiratory symptoms and evaluating efficacy of treatment in clinical trials of patients with COPD. Designed as part of a daily diary, subjects are asked to assess and record the severity of three symptoms of COPD: breathlessness, cough, and sputum. The diary format of the BCSS enables investigators, and potentially clinicians, to assess symptom variability, including the variance associated with acute exacerbations, and to evaluate the trajectory of symptom severity over time in this patient population. The symptoms of breathlessness, cough, and sputum have been identified as cardinal symptoms of COPD in various consensus statements,1 2 3 4 and are those most likely to be affected by pharmacotherapy designed to ameliorate and control respiratory symptoms in this population.
The BCSS is a brief, three-item, patient-reported outcome measure in which each of the three symptoms assessed by the measure is represented by a single item (see Appendix). Patients are asked to evaluate each symptom/item on a 5-point Likert-type scale, ranging from 0 to 4, with higher scores indicating a more severe manifestation of the symptom. A daily total score is expressed as the sum of three item scores, with a range of 0 to 12. For greater precision as a clinical trial outcome, weekly and period (eg, baseline, treatment, follow-up) scores can be computed by aggregating daily scores over time.
Results of a previous investigation12
provided evidence that the BCSS is a reliable and valid measure of symptom severity. Item and total scale scores were found to be internally consistent (Cronbach
= 0.70 daily; 0.95 to 0.99 over time) and reproducible under stable conditions, in this case, a situation in which both the physician and patient agreed that the treatment produced no change or was mildly effective. Intraclass correlation coefficients for item and total scores ranged from 0.74 to 0.78. Values for both indicators of reliability exceeded the guideline of 0.70 for group-level analyses.13
The study also provided evidence of the concurrent, convergent, divergent, and discriminant validity of the BCSS.
The previous investigation12 also indicated the instrument is responsive to change, with preliminary tests suggesting a mean decline of 1 point on the BCSS total scale signifies a substantial reduction in symptom severity. Mean score changes considered small (minimal) to moderate and changes observed during the course of an acute exacerbation of COPD have not yet been determined. The purpose of this study was to evaluate the magnitude of mean change scores observed in the BCSS under various scenarios and develop empirically based guidelines for interpreting results of clinical trials and observational or naturalistic studies in which this instrument is used.
| Materials and Methods |
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Study Subjects
All patients were between 35 years and 80 years of age with a history of COPD
2 years, a smoking history, and a percentage of predicted FEV1 between 20% and 70%. Exclusion criteria included a complicating comorbid condition or need for domiciliary oxygen.15
Measures
In these trials, the BCSS was administered as a daily diary, yielding multiple assessments over time for each subject. Consistent with its use in clinical trials14
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and the validation study,12
daily scores for each patient were aggregated over the baseline period and again over the final 4 weeks of treatment, defined by the end of study or study discontinuation. Unless otherwise specified, change scores reflect the difference between these two values. In addition to the BCSS, physician and patient ratings of treatment efficacy at the end of the study, FEV1, SGRQ scores, evening peak flow (PEF) [available in two of the three studies], rescue medication use, and physician-determined severity of the first exacerbation during the study period were used in the analyses.
Physician and patient ratings of treatment efficacy were appraised on a 5-point scale, from "highly effective" to "made condition worse." The SGRQ is a widely-used, condition-specific measure of health status or HRQL.10 Scores range from 0 to 100, with higher scores indicating poorer health status. Guidelines for interpretation suggest changes in the SGRQ total score of ± 4 points are clinically meaningful, ± 8 are considered moderate, while ± 12 are interpreted as a large change in health status.16
For the subgroup of patients experiencing at least one exacerbation during the study period, symptom severity (BCSS), PEF, and rescue medication use prior to, during, and immediately following the first exacerbation were examined for the subgroup as a whole and by physician-defined severity of exacerbation (mild, moderate, severe). COPD exacerbations were defined as worsening symptoms of COPD requiring drug therapy in addition to study drug, rescue medication, and doses of concomitant COPD medications.14
Analytical Approach
Analyses were performed across treatment groups using aggregated data from the three clinical trials. A triangulation approach was used, where mean score changes on the BCSS were examined in light of mean changes observed in related, commonly used clinical parameters and statistical indicators of magnitude. The following clinical parameters were used in this study: patient and physician ratings of treatment efficacy, FEV1, SGRQ score, presence of an exacerbation, and PEF and rescue medication use during an exacerbation. Percentage change and effect size (ES) served as statistical indicators.
The analytical procedures were as follows. First, three different methods were used to stratify the data into five groups based on ratings of treatment efficacy: highly effective, moderately effective, mildly effective, not effective, and condition made worse. The three rating methods were physician rating of treatment efficacy, patient rating of treatment efficacy, and convergence of physician and patient ratings, that is, the subgroup of patients for whom both the physician and the patient agreed on their ratings of treatment efficacy. The purpose of this procedure was to provide insight into the magnitude of BCSS score changes associated with various levels of treatment efficacy as perceived by physicians and patients. Although the stratification process reduced the effective sample size from the 3,643 randomized patients to 2,971 patients, due to the availability of ratings data as well as complete data on all clinical parameters, the relatively large sample sizes in four of the five efficacy subgroups (n = 195 to n = 1,063) engendered confidence in the stability of the parameter estimates. Results for the subgroup of patients rated "worse" should be considered preliminary due to relatively small sample sizes (n = 24 to n = 62).
Because this study was designed to develop interpretation guidelines, ie, to assign meaning to change scores rather than to test the statistical significance of change, only one series of statistical tests was performed at this step in the analyses. Paired t tests were used to confirm that any changes in BCSS score observed in the smaller, "not effective" groups were not significantly different from zero. The statistical significance of change observed in the remaining groups was not relevant to the purposes of this study.
Second, the mean BCSS total and item change scores, stratified by level of treatment efficacy using the three methods outlined above, were juxtaposed with percentage change in symptom severity, statistical ES,
FEV1, and
SGRQ score. ES estimates were computed by subtracting the baseline mean value (MB) from the treatment mean value (MT) and dividing by the baseline variance in BCSS score (
B) [ES = MT - MB/
B], and were interpreted as follows: values at or near 0.10 were considered small, values at or near 0.30 were regarded as moderate, and values near or > 0.50 were interpreted as large.17
Changes in SGRQ score were evaluated in light of recommended guidelines for the measure as outlined above.16
Percentage change and
FEV1 provided further clinical context for the interpretation of changes in BCSS score.
Finally, to further evaluate the meaning associated with
BCSS scores under conditions of known change in the patients clinical condition, scores during the 7 days preceding a physician-documented exacerbation, the first 7 days of the exacerbation, and the first 7 days following medically confirmed resolution were also examined. First, mean daily scores were computed across patients and exhibited graphically, to note the daily patterns of symptom change during this period. Mean values were then computed for each of the three time periods, consistent with the principal of data aggregation over time used in clinical trials. These mean values were then juxtaposed with data on percentage
BCSS score, ES, and available data on PEF and rescue medication use during these time periods. The BCSS was also tested for sensitivity to change under this clinical condition using repeated-measures analyses of variance. PEF and rescue medication use were subjected to the same statistical tests to confirm that the three parameters were all moving in the same direction, ie, reflected expected changes in the clinical condition of these patients. Finally, Spearman rank-correlation coefficients (rs) were used to evaluate the consistency of patient ranking based on the magnitude of changes in BCSS score, PEF, and rescue medication use during exacerbations.
| Results |
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BCSS total score > - 1.0, which corresponded to > 20% improvement in symptoms and an ES > 0.60, exceeding the 0.50 value considered large. Highly effective treatment was also associated with a
SGRQ total score greater than the 8-point change regarded as a moderate change in health status, and an 8 to 10% improvement in FEV1. For patients in whom treatment was considered moderately efficacious, a mean
BCSS total score of at least - 0.60 was observed, corresponding to > 10% improvement in symptoms and an ES of at least 0.30, considered moderate. Mean
SGRQ total score exceeded the 4-point guideline for meaningful improvement in health status, while FEV1 improved by approximately 5%. Finally, mean
BCSS total score associated with treatment considered mildly effective was approximately - 0.35, representing a 6 to 7% improvement in symptoms and an ES nearing 0.20, larger than the 0.10 regarded as small. In this case, mean
SGRQ score was less than the 4-point guideline for minimal change, with no change in FEV1. Mean BCSS total score did not change in the subgroup of patients for whom the treatment was considered ineffective (t = - 0.12, p = 0.90 for physician rating of treatment efficacy; t = - 1.89, p = 0.06 for patient rating of treatment efficacy; and t = - 1.47, p = 0.14, for the subgroup of patients and physicians who concurred on their efficacy ratings).
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FEV1 and
SGRQ score are provided in Table 2
. Mean daily BCSS total scores over time for the exacerbation period by severity of exacerbation are shown in Figure 1 . Mean values for each of the three arbitrarily defined phases of exacerbation and mean change over time are shown in Table 4 . As expected, there were significant time and severity-by-time interaction effects for the BCSS total score (p < 0.0001). Rescue medication use also showed a significant time (p < 0.0001) and severity-by-time interaction (p < 0.001).
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BCSS scores for periods of symptomatic decline (1.24, 24% deterioration) and recovery (- 1.28, 20% improvement) were similar to those observed with highly effective treatment. PEF data (n = 448) showed a 4% decline and 5% improvement during deterioration and recovery, respectively. As one might expect, the most remarkable symptomatic improvements were seen in patients recovering from a severe exacerbation, where a mean
BCSS total score of - 1.81 was observed (n = 99), with a parallel (24%) decline in rescue medication use (n = 69). The individual item scores deteriorated an average of 0.31 ± 0.60 for breathlessness, 0.50 ± 0.73 for cough, and 0.43 ± 0.68 points for sputum; with recovery, scores improved by - 0.39 ± 0.66, - 0.49 ± 0.75, and - 0.39 ± 0.70 for the three symptoms, respectively.
There was a statistically significant correspondence between
BCSS score and change in both PEF and rescue medication use during the course of the exacerbation (p < 0.0001). As peak flow declined, BCSS total score increased (symptoms became more severe; rs = 0.51). Correlations between PEF and the three symptoms comprising the BCSS were - 0.44, - 0.46, and - 0.45 for breathlessness, cough, and sputum, respectively. Similarly, as BCSS scores increased, there was a concomitant increase in rescue medication use (rs = 0.37 for the total score; rs = 0.40, rs = 0.30, and rs = 0.27 for breathlessness, cough, and sputum, respectively). During the recovery period, BCSS scores (symptoms) improved as PEF improved (rs = 0.47 for the total score; rs = - 0.45, rs = - 0.34, and rs = - 0.36 for breathlessness, cough, and sputum, respectively) and rescue medication use declined (rs = 0.39 for the total score; rs = 0.40, rs = 0.29, and rs = 0.29 for breathlessness, cough, and sputum, respectively).
| Discussion |
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BCSS scores were examined in light of two objective clinical measures commonly used to evaluate treatment success under these conditions (PEF and rescue medication use), as well as the statistical indicators of magnitude. It is important to note that this study was a secondary analysis of an existing data set, rather than a prospective study of change. In order to fully utilize the available data without bias, a comprehensive statistical analysis plan was developed by investigators who did not develop the instrument and who were blind to the data at the time the plan was written (N.K.L., J.S.). These investigators performed the analyses independently and according to the prespecified, a priori analysis plan. All results were examined and critiqued by clinical investigators (S.I.R., M.G.), who also assisted in the interpretation and presentation of results. Thus, every step possible was taken to minimize bias.
The results of this secondary analysis suggests that a mean improvement in BCSS total score with treatment approaching or exceeding 1 point represents a substantial improvement in symptoms in the COPD population. This value corresponded to ratings by both physicians and patients that the treatment was highly efficacious. The corresponding mean
SGRQ total score exceeded the guideline of 8 points considered a large improvement in health status, indicating this level of symptom relief was accompanied by substantial improvements in patient functioning and well-being. Symptomatic improvements > 1 point were also observed during recovery from acute exacerbations of COPD, and were accompanied by improvements in PEF and a reduction in rescue medication use. Together, these results indicate mean changes > 1 point on the BCSS total score represent a relatively dramatic improvement in symptoms for patients with COPD. That is not to say that further improvement would not be possible or desirable, but rather that treatment leading to a group-level mean change of
1 point on the BCSS total score corresponds to substantial symptomatic relief in this population.
Mean improvements in BCSS total score of - 0.60 to - 0.70 were observed in patients for whom treatment was considered moderately effective. This change was associated with smaller yet substantial percentage improvements in symptoms, along with clinically meaningful changes in health status or HRQL. Once again, patients experienced sufficient symptomatic relief to also realize meaningful, though less dramatic, improvements in daily function and well-being. Together, these results suggest that a mean
BCSS total score of or near 0.60 can be interpreted as a moderate-to-large symptomatic improvement from both clinical and empirical perspectives.
A mean
BCSS total score of - 0.30 to - 0.40 accompanied treatment considered mildly efficacious and corresponded to 6 to 7% improvement in symptoms and negligible change in HRQL. However, results from interviews with COPD patients conducted as part of a cognitive debriefing study for the BCSS suggest patients can perceive and appreciate a small improvement in symptoms, regardless of any concomitant improvement in day-to-day activities (data not shown). One could argue, therefore, that a
BCSS total score > 0.30 to 0.35, though small, represents clinically meaningful symptomatic relief to patients with COPD.
Mean BCSS values of - 0.01 to - 0.12 were observed in patients for whom treatment was perceived, by physicians and patients, as ineffective. No changes in pulmonary function or health status were observed in this group. These results attest to the reproducibility of the BCSS under conditions of clinical stability. They also cast doubt on the clinical significance of any treatment in which a mean
BCSS total score of < 0.20 is observed.
Interpretation of individual items comprising the BCSS requires further quantitative and qualitative study of symptom-specific change. However, based on the results of this and previous studies,12 mean change scores of 0.25 to 0.50 on breathlessness, 0.15 to 0.40 on cough, and 0.10 to 0.30 on sputum could be interpreted as moderate-to-large changes, with the descending values across the three symptoms consistent with the dominance of breathlessness in the selection and evaluation of treatment in this population. These values are proposed as a basis for further clinical and qualitative investigation.
Results of this study also substantiate the need for observational and qualitative studies of the pattern and meaning associated with day-to-day symptom variability and the predictive value of increasing scores over time in patients with COPD. The current study showed a progressive increase in symptoms prior to medical confirmation of an exacerbation, implying a delay in seeking treatment. Unfortunately, this waiting period impedes timely intervention for acute exacerbations to reduce the severity and duration of the exacerbation.18 The tendency for patients to tolerate increasing symptoms may also contribute to the underreporting of exacerbations described by Seemungal and colleagues.19 20 Daily monitoring of the key symptoms of COPD may be a useful clinical tool for helping patients track the status of their disease, detect subtle yet clinically meaningful increases in symptom severity, modify their treatment or seek care, and initiate early treatment of a developing exacerbation.
Consensus documents and new guidelines for the classification, treatment, and management of COPD1 suggest symptom management should play a primary role in the treatment of stable disease. In this context, the evaluation of new treatments requires a robust quantitative method for symptom assessment. The current study indicates daily patient reports of symptom severity, using instruments such as the BCSS, are sensitive to the effects of treatment in this population, and could therefore be used to assess therapeutic interventions.
Current guidelines also recognize exacerbations as therapeutic targets in COPD. Several therapies have been suggested to decrease exacerbation frequency, severity, or duration21 22 23 24 25 ; these studies have been hampered, however, by a lack of consensus on the definition for both exacerbation events and severity. A recent consensus panel26 suggested tying exacerbation definition and severity assessment to health-care utilization. While operationally convenient and relevant for health economic analyses, variations in health-care delivery systems complicate the generalizability of results obtained from studies using such definitions. Since COPD exacerbations are characterized by symptomatic worsening, an instrument such as the BCSS that provides simple and robust quantification of symptoms that can be repeated on a daily basis, may prove particularly valuable for evaluating exacerbations in patients with COPD.
In summary, the purpose of this study was to establish guidelines for interpreting mean change scores in clinical trials in which the BCSS is used to evaluate symptomatic improvement in patients with COPD. A triangulation approach was used, in which changes in BCSS scores were evaluated in light of changes observed in familiar clinical and statistical indicators of improvement in this population. Based on this evaluation, a mean improvement of
1.0 on the BCSS total score is an indication that, on average, patients in a given treatment group experienced dramatic symptomatic relief with treatment; changes of - 0.60 to - 0.70 represent moderate-to-large symptomatic improvement; and mean changes at or near - 0.35 indicate the treatment under evaluation provides small, but clinically meaningful symptom relief. It is doubtful that treatment with a group-level mean change < - 0.20 offers meaningful symptomatic benefit. A prospective study with a prior hypotheses addressing change in BCSS scores and other clinical indicators of improvement, along with qualitative interviews with patients and clinicians concerning the magnitude of symptomatic change with treatment, would be needed to further this tool for clinical research. Nonetheless, these results provide evidence that patient-reported diary card data can be sensitive to change in patients with COPD and may serve as valuable tools for both clinical research and as an assessment of the effect of medical and therapeutic interventions in such patients.
| Appendix |
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Please complete in the evening (prior to going to bed): Please enter day (Monday, Tuesday, etc.):
Please record the date (day/month):
How much difficulty did you have breathing today?
How was your cough today?
How much trouble was your sputum today?
For permission to use this instrument, contact Dr. Mitchell Goldman at mitchell.goldman@astrazeneca.com
| Footnotes |
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B = baseline variance in Breathlessness, Cough, and Sputum Scale score; PEF = peak expiratory flow; SGRQ = St. George Respiratory Questionnaire This study was supported by AstraZeneca Pharmaceuticals LP.
Dr. Jones and Dr. Goldman are employees of AstraZeneca.
Dr. Rennard has received research grant support, honoraria for speaking, and fees for consultancy from AstraZeneca. Neither he nor his family have any ownership position in AstraZeneca.
Received for publication October 15, 2002. Accepted for publication July 23, 2003.
| References |
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