Responsiveness of Three Instruments to Assess Self-Reported Functional Status in Patients with COPD

Abstract

The study aimed to compare the responsiveness of three instruments to assess self-reported changes in functional status after exercise training in patients with COPD: Pulmonary Functional Status and Dyspnea Questionnaire –modified version (PFSDQ-M), London Chest Activity of Daily Living (LCADL) and Medical Research Council scale (MRC). Twenty-two patients (11 female, 66[62-71] years, FEV₁ 42[33-61]%predicted) participated in a 3-month high-intensity exercise program. The three instruments were applied pre- and post-program, as well as assessment of lung function, muscle strength, exercise capacity (6-minute walking test, 6MWT) and quality of life (St. George's Respiratory Questionnaire, SGRQ). SGRQ, 6MWT and quadriceps femoris, biceps and triceps brachialis strength improved significantly after the program (p < 0.05 for all). Training also yielded significant improvement in the LCADL total score and self-care, domestic and leisure domains and in the PFSDQ-M ‘change in activities’ domain, with no improvement in the MRC (p = 0.11). Calculation of effects sizes also indicated higher responsiveness in the LCADL than the other instruments. There were no significant correlations between changes in the three instruments and changes in lung function, SGRQ or 6MWT. In conclusion, PFSDQ-M's ‘change in activity’ domain and specially the LCADL (to a higher extent) showed responsiveness to detect changes in functional status after three months of high-intensity exercise training in patients with COPD, whereas the MRC scale did not. In this population, the improvement in functional status was not related with improvement in exercise capacity, lung function or quality of life.

Keywords: :

• Chronic Obstructive Pulmonary Disease
• activities of daily living
• functional status
• questionnaires
• responsiveness

INTRODUCTION

Chronic Obstructive Pulmonary Disease (COPD) is characterized by airway obstruction that is not fully reversible and systemic consequences that contribute to disease severity (1). As a result, dyspnea and fatigue are important symptoms in patients with COPD. Due to these symptoms, patients are subject to an impaired ability to perform activities of daily living (ADL), which can also be defined as a functional status impairment (2). This reduction in functional status is linked to deconditioning and consequent increase in dyspnea and fatigue, featuring a vicious circle or downward spiral (3). Additionally, functional status has been described as a strong predictor of survival in advanced stages of COPD (4). Therefore, a proper assessment of functional status in patients with COPD is relevant to the correct characterization and treatment approach of these patients.

According to the currently available literature, specific questionnaires stand out as the more common method to assess functional status. Questionnaires are low cost instruments and often of easy application, making them a useful tool both in clinical practice and scientific research. Among the instruments used for the self-reported assessment of ADL performance in patients with COPD, three are noteworthy for their frequent use: the Modified Pulmonary Functional Status and Dyspnea Questionnaire (PFSDQ-M)(5), which assesses the intensity of dyspnea and fatigue during ADL, and also evaluates changes in ADL performance comparing before and after the development of symptoms; the London Chest Activity of Daily Living (LCADL) scale (6), which is shorter and grades how intensely dyspnea impairs the performance of various ADL; and the Medical Research Council (MRC) scale (7), which is even shorter and allows patients to indicate the impact of dyspnea on their mobility during daily life. Although the reliability, internal consistency and criterion-validity of the three instruments have been demonstrated (8,9), a detailed comparative investigation of these instruments’ responsiveness to a physical training program in patients with COPD has never been performed.

Therefore, this study was aimed primarily at comparing the responsiveness of PFSDQ-M, LCADL and MRC to detect subjective changes in functional status after three months of high-intensity exercise training in patients with COPD. Secondarily, it aimed to study the relationship between eventual improvement in the ability to perform ADL and changes in pulmonary function, functional exercise capacity, muscle strength and health-related quality of life after the training program.

MATERIALS AND METHODS

Study design

Twenty-two patients with COPD performed the following assessments at baseline and after the training program: assessment of ADL performance using the three instruments applied in random order (PFSDQ-M, LCADL and MRC), lung function (spirometry), exercise capacity (6-minute walking test, 6MWT), muscle strength (one repetition maximum test) and health-related quality of life (St. George's Respiratory Questionnaire [SGRQ]).

The diagnosis of COPD was confirmed according to internationally accepted criteria (Global Initiative for Chronic Obstructive Lung Disease [GOLD])(1). In addition to the diagnosis of COPD, other inclusion criteria were: 1) stable condition, with no exacerbations or infections within the last three months, 2) no severe or unstable heart disease, and 3) no other pathological conditions which could impair the ADL performance, such as cerebro-vascular, orthopedic or rheumatic disease. Exclusion criteria were: 1) severe acute exacerbation during the rehabilitation program, requiring hospitalization and training program discontinuation; and 2) inability to understand or cooperate with the application of the questionnaires and other assessment methods. The study was approved by the Ethics in Research Committee of the Universidade Estadual de Londrina (HU-UEL), and data were collected from February 2007 to November 2008. All patients gave written consent prior to participation in the study.

Modified Pulmonary Functional Status and Dyspnea Questionnaire (PFSDQ-M)(5,8)

The PFSDQ-M is composed of three domains: the degree to which dyspnea and fatigue influence ADL (5 general and 10 specific items for each domain) and change in ADL related to the onset of the disease (10 specific items). The patient reports to which degree dyspnea and fatigue affect the 10 specific ADL items, choosing for each activity a value from 0 to 10: 0 (none), 1-3 (mild), 4-6 (moderate), 7-9 (severe) and 10 (very severe). In the third domain the patient reports the degree of change in ADL related to the onset of disease, choosing for each activity a value from 0 to 10: 0 (as active as always in relation to this activity), 1-3 (small change), 4-6 (moderate change), 7-9 (extreme change) and 10 (do not perform this activity). A sub-score is calculated, ranging from 0 to 100 for each of the three domains (dyspnea, fatigue and change in ADL) and an overall score is obtained by summing the scores of the three domains, totalizing a value ranging from 0 to 300. A higher value on the scale indicates greater ADL limitation. The five general issues in the dyspnea and fatigue domains are informative and qualitative, and their responses are not accounted for in the questionnaire score.

London Chest Activity of Daily Living Scale (LCADL)(6,9)

The LCADL contains 15 activities commonly performed in daily life, divided into four domains: Self-care (4 items), Domestic (6 items), Physical Activity (2 items) and Leisure (3 items). The patient reports how much dyspnea interferes with these 15 activities choosing for each activity a value from 0 to 5, as follows: 0 (I do not do this), 1 (I have no shortness of breath doing this), 2 (I have a slight shortness of breath), 3 (I have a great shortness of breath), 4 (I no longer do this) and 5 (I need help doing this or someone to do it for me). A sub-score is calculated for each domain, and an overall score (ranging from 0 to 75) is obtained by the sum of the four domains sub-scores, with higher values indicating greater ADL limitation.

Medical Research Council Scale (MRC)(7,8)

The MRC scale is comprised of only five options, and the patient chooses amongst them the option which corresponds to the degree that dyspnea impairs their mobility in daily life. The 5 options are: 1 (only suffers from shortness of breath during vigorous exercise), 2 (suffers from shortness of breath when hurrying or walking up a slight ramp), 3 (walk more slowly than people of the same age because of breathlessness or have to stop to breath even when walking slowly), 4 (stops to breath after walking less than 100 meters or after a few minutes) and 5 (feels so much shortness of breath that does not leave home anymore, or while changing clothes).

Due to the high prevalence of illiteracy typically observed in the population attending the public health system served by the HU-UEL (Table 1), an interview application format (i.e., reading the questions for all patients) was the application method for all subjects in order to avoid bias. The interviewer was the same for pre- and post-treatment.

Table 1  Characterization of the 22 patients with COPD included in the study

Age (years)	66 ± 07
Gender (M/F)	11/11
BMI (kg/m^2)	27 ± 6
Literate (Yes/No)	17/5
FEV1 (% pred)	43 ± 14
FVC (% pred)	68 ± 17
FEV1/FVC	50±14
GOLD (I/II/III/IV)	0/8/10/4
6MWT (m)	445 ± 81
6MWT (% pred)	76 ± 11

Data described as mean ± standard deviation. M = male; F = female; BMI = body mass index; FEV₁ = forced expiratory volume in the first second; FVC = forced vital capacity; GOLD = Global Initiative for Chronic Obstructive Lung Disease; 6MWT = 6 minute walking test.

Additional assessments

Lung function assessment (spirometry) was performed according to the Pulmonary Function Test Guidelines of the Brazilian Society of Pulmonology and Tisiology (10). The equipment used was the Pony Graphics (Cosmed, Italy), and normal values were those of Pereira et al. (11).

The 6MWT was carried out according to International standards (12) in a 30-meter corridor. Two tests were performed with at least a 30 minutes interval, and the highest value was used for analysis. The normal values were those of Troosters et al. (13). The 6MWT was included in this study as it has recently been described as the best clinical predictor of the level of daily physical activity measured by a motion sensor in patients with COPD (14).

The St. George's Respiratory Questionnaire (SGRQ) (15), already validated in Portuguese (16) was specifically designed for patients with COPD and covers aspects of quality of life related to three domains: symptoms, activity and the psychosocial impact the respiratory disease has on the patient. Each domain has a minimum score of 0 and a maximum of 662.5, 1209.1, and 2117.8, respectively; the values of each answer are added together with the total expressed as the percentage achieved by the patient out of the maximum score. A total score based on the results of three domains is also calculated, with a maximum of 3989.4, and the total score is often expressed as the percentage achieved by the patient out of this score.

The one repetition maximum test (1RM) was performed for muscle strength assessment. The test was based on the protocol proposed by Brown and Weir (17) and is defined as the highest workload that can be moved once over a specific range of motion and with proper execution (without compensation)(18). The test aims at achieving the maximum load with which the individual can perform a single repetition of a specific standardized exercise. The muscle groups assessed were: knee extensors, elbow flexors and extensors. Firstly, patients were instructed on which muscle groups would be assessed, on how to perform the test and on important information such as placement, compensation, and test ending. Movements (knee extension, elbow flexion and extension) were requested during pursed lips expiration, in order to avoid Valsalva maneuver or increasing dyspnea, which could bias the assessment.

Training program

The 12-week training program consisted of 1-h training sessions, which patients attended three times per week. Circuit training including cycling, walking and strength training for the quadriceps, biceps and triceps muscle groups was performed based on a protocol previously published in the literature (19). For ergometry cycling, the training intensity was initially set at 60% of the initial maximal work rate; for treadmill walking, at 75% of the average walking speed during the baseline 6MWT; and for strength training, at 70% of the baseline 1RM. Physiotherapists increased patients’ work rates and/or exercise duration/repetitions on a weekly basis, guided by a pre-determined schedule and driven by the patients’ perception of their symptoms (Borg-symptom scores). A Borg score of 4–6 for dyspnea was set as a target (20). Close supervision was provided during training, with a ratio of one physiotherapist for every four patients.

Table 2  Comparison between the different domains of PFSDQ-M, LCADL, MRC scale and SGRQ questionnaires, for the responsiveness analysis after a 3-month high intensity exercise training program in patients with COPD

Questionnaire	Domains	Before Treatment	After Treatment	p-value
PFSDQ-M	Dyspnea	16[10–40]	10[4–32]	0.07
	Fatigue	18[9–34]	13[4–29]	0.27
	Change in ADL	29[13–37]	19[4–40]	0.04
LCADL	Self-Care	6[5–9]	4[4–6]	0.001
	Domestic	8[4–9]	5[3–9]	0.005
	Physical Activity	4[3–5]	3[3–4]	0.10
	Leisure	4[4–6]	3[3–5]	0.001
	Total	20[16–28]	17[14–23]	0.0004
MRC		3[2–4]	2[2–4]	0.11
SGRQ	Symptoms	59[34–72]	43[28–59]	0.049
	Physical Activity	66[48–84]	51[23–64]	0.0009
	Impact	42[29–89]	24[10–41]	0.0008
	Total	53[41–65]	34[24–49]	0.0003

Data are described as median [interquartile range].

PFSDQ-M = Modified Pulmonary Functional Status and Dyspnea Questionnaire; ADL = activities of daily living; LCADL = London Chest Activity of Daily Living Scale; MRC = Medical Research Council scale; SGRQ = Saint George Respiratory Questionnaire.

Statistical analysis

Statistical analysis was performed using the GraphPad Prism® 3.0 statistical package. Non-parametric statistics were used due to the relatively small sample size and the ordinal nature of the data. For the analysis of the questionnaires’ responsiveness to the training program, the Wilcoxon test was used. Effect size, standardized response mean and standard error of measurement were calculated for each domain of the three questionnaires. Correlations were studied by the Spearman coefficient. Statistical significance was determined as p < 0.05.

RESULTS

The enrolled patients were characterized on average by moderate to severe airflow obstruction, as well as a slightly decreased functional exercise capacity (Table 1). After the training protocol there was significant improvement in the LCADL self-care, domestic and leisure domains and LCADL total score, as well as in the PFSDQ-M change in ADL component (p < 0.05 for all). There was a trend for improvement in the PFSDQ-M dyspnea domain (p = 0.07) (Table 2). There was no significant improvement in the MRC scale (p = 0.11) (Table 2). Analysis of the effect size, standardized response mean and standard error of measurement (Table 3) confirmed that the LCADL showed more pronounced responsiveness in comparison to the other instruments, with most of its domains presenting effect size around or even above 0.50, suggesting a moderate change.

Table 3  Comparison between the different domains of PFSDQ-M, LCADL and MRC scale concerning different aspects of the responsiveness analysis after a high intensity exercise program (n = 22)

	Effect Size	Standardized Response Mean	Standard Error of Measurement
PFSDQ-M
Dyspnea	0.26	0.43	2.82
Fatigue	0.16	0.27	3.15
Change in ADL	0.33	0.48	3.19
LCADL
Self-care	0.60	0.75	0.40
Domestic	0.26	0.73	0.50
Physical Activity	0.43	0.40	0.24
Leisure	0.61	0.81	0.21
Total	0.45	0.91	1.03
MRC	0.36	0.39	0.22

PFSDQ-M = Modified Pulmonary Functional Status and Dyspnea Questionnaire; ADL = activities of daily living; LCADL = London Chest Activity of Daily Living Scale; MRC = Medical T Council scale.

There was also significant improvement in all domains and the total score of the SGRQ (p < 0.05 for all) (Table 2), in the 6MWT (76 ± 11 to 85 ± 13% predicted, (p < 0.0001) and in the muscle strength of elbow flexors and extensors (10 ± 4 to 15 ± 4 kg; 12 ± 3 to 16 ± 4 kg, respectively; p < 0.0001 for both) and knee extensors (12 ± 5 to 17 ± 6 kg, p < 0.0001).

Changes in ADL assessed by the three instruments did not correlate with changes in 6MWT, lung function or in the SGRQ. Post-training change in knee extensors muscle strength was weakly correlated with changes in the self-care domain and total score of the LCADL, dyspnea, fatigue and change in ADL domains of the PFSDQ-M and the MRC scale (r = 0.43, 0.43, 0.58, 0.45, 0.48 and 0.51, respectively, p < 0.05 for all). Furthermore, LCADL's physical activity and leisure domains and total score also correlated with post-training changes in elbow extensors strength (r = 0.50, 0.55, 0.44, respectively, p < 0.04 for all).

DISCUSSION

The present study showed that the LCADL and PFSDQ-M instruments are sensitive to detect changes in functional status after 3 months of high-intensity training in patients with COPD, and that this improvement in functional status was not correlated with improvement in the exercise capacity and quality of life in this population. The weak correlations between changes in functional status and muscle strength are unlikely to imply in any practical clinical implication.

A recent study by Costi et al. (21) also showed the responsiveness of the LCADL to a high-intensity training program. Furthermore, Trappenburg et al. (22) also showed a somewhat larger improvement in the PFSDQ-M's ‘change in activity’ in comparison to the other two domains of the questionnaire, what was also observed in the present study. This might be due to the PFSDQ-M's ‘change in activity’ domain better reflecting the functional status itself than the dyspnea and fatigue domains.

Different studies have reported significant cross-sectional correlations between functional status, 6MWT and quality of life, both concerning the LCADL (23,24) and the PFSDQ-M(8,25). The presence of longitudinal correlations between those outcomes, however, has not been yet studied in depth, although Garrod et al. (26) showed a weak but significant relationship between changes in the LCADL and changes in quality of life.

However, the present study shows that changes in functional status after exercise training are not necessarily correlated to changes in 6MWT and quality of life. Functional status, exercise capacity and quality of life are different domains that represent different aspects of the disease's impact on the patients, and therefore their longitudinal relationship after rehabilitation might depend on various reasons such as the level of baseline airway obstruction, dyspnea, fatigue, exercise capacity, adaptation to change, anxiety and depression in the studied sample and the characteristics of the exercise training protocol, among others. Therefore, the absence of correlation between changes in these outcomes after exercise training does not contradict the fact that these functional status instruments are responsive from the patient's point of view, since they are reporting to have improved their performance in daily tasks, regardless of the improvement in exercise capacity or quality of life in a broader sense.

Tables 2 and 3 showed that the LCADL total score was responsive to the 3-month high-intensity exercise program, as well as most of its domains (specially the self-care and leisure domains). On the other hand, results also showed that responsiveness of the PFSDQ-M to the protocol was more modest and mainly linked to the ‘change in ADL’ domain. For these reasons, the present study suggests that the LCADL is responsive to a higher extent in comparison to the PFSDQ-M.

The MRC scale was not responsive after training despite showing improvement (i.e., reduction) in its median value (Table 2). Pasqua et al. (27) performed a similar study (including a similar sample size) and showed significant improvement in the MRC scale. Similarly, other studies (28–30) showed significant improvement in the MRC scale after treatment. Furthermore, a number of studies (31–34) divided the patients according to the MRC grading scale to verify whether the response to treatment depended on the score reported at baseline.

These studies had conflicting results: for instance, Wedzicha et al. (31) showed that the effects of exercise training in patients with COPD may depend on the initial dyspnea severity, that is, patients with moderate dyspnea (MRC 3 and 4) showed greater improvement after training. On the other hand, Evans et al. (32) showed that the benefits of pulmonary rehabilitation are equal for those with lower or higher MRC score. A possible explanation for these discrepant results is that the training protocol was different between these two studies: Wedzicha et al. (31) used the same exercise training program for all individuals, whereas Evans et al. (32) used individual exercise prescription, which made the training “proportional” to each patient according to his/her limitation.

This last approach resembles the present protocol, and for this reason the results of our training program might have been optimized among all individuals, what does not indicate the presence of a relationship between the magnitude of improvement in outcomes after pulmonary rehabilitation and baseline MRC scores. We hypothesized that the MRC score was not responsive to exercise training in the present study probably due to the restricted scale's point scheme (1 to 5). Small and simple questionnaires may demonstrate higher reliability, but in return may also demonstrate lower sensitivity (35).

One may point out that changes in score after exercise training should be interpreted differently in the MRC (since it is a simple Likert 5-point scale) in contrast to the other two instruments, which have a higher scoring system. However, when analyzing effect sizes and standardized response means (Table 3), the MRC scale has also shown inferior results in comparison to the other two instruments, which reinforces the findings observed when analyzing the scales’ changes in score after the intervention. Furthermore, it is worthwhile to clarify that this study does not focus mainly on comparing the instruments, but rather in describing the specific responsiveness of each one of them.

In conclusion, PFSDQ-M's ‘change in activity’ domain and specially the LCADL (to a higher extent) showed responsiveness to detect changes in functional status after three months of high-intensity exercise training in patients with COPD, whereas the MRC scale did not. In this population, the improvement in functional status was not related with improvement in exercise capacity, lung function or quality of life.

DECLARATION OF INTEREST

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.