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School of Physical and Occupational Therapy, McGill University, 3654 Prom Sir-William-Osler, Hosmer House, Room #200, Montreal, QC, H3G 1Y5, CanadaTranslational Research in Respiratory Diseases Program, Research Institute of the McGill University Health Centre, 1001 Decarie Blvd, Block E, Montreal, QC, H4A 3J1, CanadaCentre for Health Outcomes Research and Evaluation (CORE), Research Institute of the McGill University Health Centre, 5252 Boul. de Maisonneuve Ouest, Room # 3E.01, Montreal, QC, H4A 3S5, Canada
Department of Physical Therapy, Universidade Federal dos Vales do Jequitinhonha e Mucuri-UFVJM, Campus JK, Rodovia MGT 367, Km 583, Nº 5000, Alto da Jacuba CEP: 39100-000, Diamantina, Minas Gerais, Brazil
Respiratory Epidemiology and Clinical Research Unit (RECRU), McGill University Health Centre, 5252 Boul. de Maisonneuve Ouest, Montreal, QC, H4A 3S5, CanadaTranslational Research in Respiratory Diseases Program, Research Institute of the McGill University Health Centre, 1001 Decarie Blvd, Block E, Montreal, QC, H4A 3J1, Canada
School of Physical and Occupational Therapy, McGill University, 3654 Prom Sir-William-Osler, Hosmer House, Room #200, Montreal, QC, H3G 1Y5, CanadaRespiratory Epidemiology and Clinical Research Unit (RECRU), McGill University Health Centre, 5252 Boul. de Maisonneuve Ouest, Montreal, QC, H4A 3S5, CanadaTranslational Research in Respiratory Diseases Program, Research Institute of the McGill University Health Centre, 1001 Decarie Blvd, Block E, Montreal, QC, H4A 3J1, CanadaCentre for Health Outcomes Research and Evaluation (CORE), Research Institute of the McGill University Health Centre, 5252 Boul. de Maisonneuve Ouest, Room # 3E.01, Montreal, QC, H4A 3S5, Canada
Physical function tests may provide prognosis information in COPD patients.
•
Few studies have studied the prognostic value of simple measures of physical function and muscle strength in relation to exacerbations, hospitalizations and mortality in individuals with COPD.
•
The studies available are of low quality.
•
More studies with better methodological quality are needed.
Abstract
Purpose
There has been an increased interest in simple measures of physical function and muscle strength that can be used in all clinical settings to assess individuals with chronic obstructive pulmonary disease (COPD) and predict their prognosis. The main objective was to examine the prognostic value of simple measures of physical function and muscle strength in relation to exacerbation, hospitalization and mortality in individuals with COPD.
Methods
Medline, EMBASE, Cochrane and Web of Science were searched. We included prospective observational studies that examined the prognostic value of simple performed-based tests or self-reported measures of physical function or muscle strength in relation to exacerbation, hospitalization and mortality in individuals with COPD.
Results
Seven articles met the inclusion criteria. The most commonly used tests were the handgrip strength (HGS) (n = 4) and 1-min sit-to-stand (STS) (n = 2). There were considerable variations in terms of characteristics of patients included, setting of recruitment, type of tests used, duration of follow-up and outcome measures of interest. The majority of the studies were classified as having “fair” or “poor” methodological quality.
Conclusions
There is a limited number of studies examining the prognostic value of simple measures of physical function and muscle strength in relation to exacerbations, hospitalizations and mortality in individuals with COPD. To date, the HGS and 1-min STS tests are the most studied tests and seem to be suitable for prognosis purposes in individuals with COPD. However, more studies with better methodological quality are needed to confirm these findings.
]. Although the primary pathophysiology of COPD is related to the damage in the lungs, patients with COPD experience secondary non-respiratory related effects of the disease such as lower and upper limb muscle dysfunction and reduced exercise capacity which contribute to functional limitations [
] in these individuals and can provide relevant information about their prognosis. For example, exercise capacity and quadriceps muscle strength have been shown to be among the strongest predictors of mortality in individuals with COPD [
An official American Thoracic Society/European Respiratory Society statement: update on limb muscle dysfunction in chronic obstructive pulmonary disease.
]. However, assessment of exercise capacity in the laboratory and/or field tests such as Six-Minute Walk Test (6MWT) and Incremental Shuttle Walk Test require trained staff, space and equipment which is rarely feasible in the outpatient clinics. Similarly, proper quadriceps muscle strength assessment requires expensive dynamometers and trained personnel which may not be readily available.
In recent years, there has been an increased interest in simple measures of physical function and muscle strength that can be used in all clinical settings to assess individuals with COPD and predict their prognosis [
Functional tests in chronic obstructive pulmonary disease, Part 1: clinical relevance and links to the international classification of functioning, disability, and health.
]. These “simpler” tests require less time for the professional and patient to conduct; some require less space; and some have potential suitability in more frail patients [
]. Many of these tests (e.g. the time up and go, sit-to-stand and grip strength tests) are already used and studied in older adults and have shown to be predictors of mortality and healthcare utilization in this population. Previous systematic reviews have described some simple functional exercise tests used in people with COPD and their psychometric properties [
]; however, no systematic review has focused on the prognostic value of these tests with respect to important clinical outcomes such as exacerbations, healthcare utilization and mortality.
The objective of this systematic review is to systematically review the literature on the prognostic value of simple measures of physical function and muscle strength in relation to exacerbations, hospitalizations and mortality in individuals with COPD.
2. Methods
2.1 Search strategy and data sources
A librarian performed electronic literature searches in three databases (Medline (Ovid), Embase (Ovid), Cochrane Library (Wiley) and Web of Science) from inception until November 16, 2016, with no limits or language restrictions. An updated search was performed by one investigator (DM) to include articles published to December 2018. The key terms used were related to COPD, physical function measures (both performance-based tests and self-reported measures), muscle strength and hospitalization, exacerbation or mortality. The terms were searched as text words in the Title/Abstract/Keywords as well as in the Subject Headings. The specific search terms and strategy are presented in Appendix A. While performing full-text screening, one investigator (WA) conducted hand searches of the reference list of the articles.
2.2 Inclusion criteria
We included prospective observational studies that, as primary or secondary objective, examined the performance of simple measures of overall physical function and muscle strength in predicting exacerbations, hospitalizations and mortality in patients with COPD or that examined the relationship of these tests with these outcomes.
We considered the term “overall physical function” according to the World Health Organization (WHO)'s International Classification of functioning, Disability and Health (ICF) definition [
] for functioning. We included measures that addressed the following ICF constructs: 1) activities (e.g. functioning evaluated in terms of performance-based measurement focused on limitations in specific activities); 2) measurements assessing participation (involvement in everyday life situations) [
Additionally, we defined “simple” performance-based physical function measures or muscle strength if: 1) the test does not require a specialized facility; 2) it takes a relatively short time to be performed (e.g. less than 10 min); 3) it can be performed in any setting (e.g. primary care, acute and/or rehabilitation hospital); and 4) it does not require a professional with specialized expertise. We considered studies that assessed mortality using true observations of all-cause deaths. We excluded self-reported measures that covered quality of life, symptoms, general health perception, emotional and social role functioning and studies that examined the associations of demographic data, symptoms, disease severity, lung function with exacerbation, hospitalization and mortality. We also excluded cross-sectional, pre-post studies, research letters, and congress abstracts.
2.3 Study selection and data extraction
One investigator (WA) reviewed the study titles and abstracts and two investigators (WA and TJF) reviewed the full texts of the articles independently to determine study eligibility. These two investigators met when the full-text screening was complete to resolve any discrepancy.
We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [
]. The review protocol was registered in the PROSPERO database (CRD42017059358). Two reviewers (WA and DM) performed the data extraction and tabulation using a standardized form. A second reviewer (VPL) double-checked the extracted data.
2.4 Quality assessment of the included studies
To assess the quality of the studies we used the modified Downs and Black [
The feasibility of creating a checklist for the assessment of the methodological quality both of randomised and non-randomised studies of health care interventions.
The feasibility of creating a checklist for the assessment of the methodological quality both of randomised and non-randomised studies of health care interventions.
] checklist has a total of 27 items but 6 items were considered as ‘not applicable’ because they are not relevant to non-RCTs. Therefore, the overall possible score was 22 (question 5 gives 2 points for yes). Two assessors (DM and a Research Associate) independently rated each study, and consensus discussion was used to resolve any disagreement. A third assessor (TJF) resolved any outstanding divergences.
3. Results
Fig. 1 shows the PRISMA flow diagram of the search with the number of papers identified, included and excluded (with reasons for exclusion). Seven studies met the inclusion criteria and their characteristics are presented in Table 1. There were considerable variations in terms of characteristics of patients included (e.g. age, stable vs on exacerbation), setting of recruitment, type of tests used, duration of follow-up and outcome measures of interest. The quality assessment of the included studies is presented in Table 2. The total scores ranged from 8 to 18 out of a possible maximum of 22 (average score was 14). No study was classified as “excellent”, three studies were classified as “good” [
Table 1Characteristics and main findings of the included studies.
Author, Year
Patient and study characteristics
Original objectives of the study
Type of Test
Which outcome of interest was included?
Main findings related to the objective of our systematic review
Mortality
Exacerbation
Hospitalization
Yohannes et al., 2002
COPD outpatients, clinically stable with no change in medication for 1 month and no hospital admission in the previous 6 weeks. N = 137 Age: 60–89 (range) FEV1: 0.89 ± 0.3 (Liters) Follow up: 2.5 years
To evaluate mortality predictors in elderly patients with COPD.
MRADL
Yes
No
No
MORTALITY: MRADL score found to be a predictor of mortality (OR = 0.87 (95% CI 0.80–0.97; P < 0.007). Lower MRADL score in those who died versus survivors (7.6 vs 14.0 (p < 0.0001))
Yohannes et al., 2005
Hospitalized AECOPD patients. Groups: Died (n = 36) versus those alive (n = 64). N = 100 Age: 60–89 (range) FEV1: 0.81 ± 0.3 (Liters) Follow up: 1 year
To examine mortality predictors in patients after AECOPD
MRADL
Yes
No
No
MORTALITY: On univariate logistic regression analysis, the MRADL was found to be a predictor of mortality (OR = 0.87 (95% CI 0.80–0.94); P = 0.0001). On multivariate logistic regression analysis MRADL was not a mortality predictor. MRADL score of <12 gave a sensitivity of 86%, specificity of 55%, positive predictive value of 88% and negative predictive value of 52% (in terms of mortality prediction).
Habraken et al., 2011
COPD patients in GOLD stage IV and age ≥60 years. Group Severity based on mean GARS scores at baseline: Low (n = 27), Intermediate (n = 25), High (n = 30). N = 82 Age: 69.4 ± 6.5 FEV1% predicted: 26 (20–28) Follow up: 5 years
To examine the development of health-related quality of life and functional status over time in COPD patients.
GARS
Yes
No
No
MORTALITY: There was a higher probability of survival in the low-severity subgroups. At the 2 year follow up, patients in the high-severity subgroup had a lower probability of survival (hazard ratio 0.53, 95% CI 0.38–0.75)) compared the probability of survival of the low-severity subgroup (0.70 (95% CI 0.55–0.90))
De Buyser et al., 2013
Ambulatory older men recruited from the population register of a semirural community. The subjects self-reported chronic diseases. Comorbidity status was categorized into cardiovascular disease (n = 111), COPD (n = 28) and diabetes mellitus (n = 25). N = 28 Age: 71–86 (all sample) FEV1% predicted: not reported Follow up: 184 months
To assess and compare the predictive value of physical function measurements for all-cause mortality in older men and to evaluate the Timed Up and Go test (TUG) as a predictor in subjects with underlying comorbidity.
HGS; 5STS test; TUG test
Yes
No
No
MORTALITY: Results of the functional tests: 5STS (15.7 ± 4.9 s); TUG test (13.6 ± 5.3 s); Grip strength (22.1 ± 9.6 Kg). Mortality risk doubled for every 8 s increase in time needed to perform TUG (age-adjusted HR per 8 s increase for TUG = 2.08, 95% CI 1.70–2.54, P < 0.001). ANCOVA further revealed shorter survival time for subjects with COPD (P = 0.006). The performance on TUG had NO influence on survival time in subjects with COPD (P = 0.202).
Puhan et al., 2013
Multicentre cohort study with COPD patients from primary care in Switzerland and the Netherlands. N = 409 Age: 67.3 ± 10 FEV1% predicted: not reported GOLD stage II = 63.8% GOLD stage III = 21.8% GOLD stage IV = 14.4% Follow up: 2 years
To assess the predictive performance of the 1-min sit-to-stand test (STS) and handgrip strength tests for mortality and exacerbations.
1-min STS and HGS tests
Yes
Yes
No
MORTALITY: 1-min STS test was strongly associated with mortality (adjusted HR per five more repetitions of 0.58, 95% CI 0.40–0.85; p = 0.004). Handgrip strength test was strongly associated with mortality (HR 0.84, 95% CI 0.72–1.00; p = 0.04). 1-min STS test alone was a stronger predictor of 2-year mortality (AUC 0.78), than Handgrip Strength (AUC 0.62). EXACERBATION: No association of the 1-min STS test or handgrip strength test with exacerbations was found.
Crook et al., 2017
COPD patients from primary care practices in Switzerland and Netherlands; 409 patients for the handgrip strength test and 371 patients for the 1-min STS test. N = 409 Age: 67.3 ± 10 FEV1% predicted: 58 (44–68) GOLD stages II to IV Follow up: 5 years
To assess the long-term (5-year) predictive performance of the 1-min STS and handgrip strength tests for mortality, health-related quality of life (HRQoL) and exacerbations in COPD patients.
1-min STS and HGS tests.
Yes
Yes
No
MORTALITY: 1-min STS test was strongly associated with long-term mortality (HR per 3 more repetitions: 0.81, 95% CI 0.65–0.86). Handgrip strength test was not statistically significantly associated with mortality. EXACERBATION: Neither the 1-min STS test nor handgrip strength test was associated with exacerbation.
Martinez et al., 2017
Cross sectional analysis from the COPDGene (Genetic Epidemiology of COPD Study) trial study. For the secondary objective the authors performed longitudinal analysis to verify the long-term associations of HGS with acute respiratory events. N = 272 Age: 64.7 ± 8 FEV1% predicted: 59 ± 22.5 GOLD 1–2 = 62% GOLD 3–4 = 38%
To test associations of handgrip strength test with pectoralis muscle area (PMA), subcutaneous adipose tissue (SAT), imaging characteristics, and lung function in smokers with COPD, and evaluate the cross-sectional and longitudinal associations of handgrip strength test with acute respiratory events.
HGS test
No
Yes
Yes
EXACERBATION: HGS was associated with exacerbation risk. An increment of 5% in the risk of exacerbations for each 1-kg decrement in handgrip strength (risk ratio 1.05; 95% CI 1.01–1.08), and there was a similar risk during follow-up (risk ratio, 1.04; 95% CI 1.01–1.07). Mean follow-up = 2.6 years HOSPITALIZATION: An increment of 6% in the risk of hospitalization for each 1- kg decrement in handgrip strength (risk ratio 1.06; 95% CI 1.01–1.12). Risk for severe events (those requiring emergency visits or hospital admission) during follow-up.
OR: odds ratio; HR: hazard ratio; 95% CI: 95% confidence interval; ANCOVA, analysis of covariance; AUC, area under the curve. FEV1: forced expiratory volume in 1 s; COPD: chronic obstructive pulmonary disease; AECOPD: acute exacerbation of COPD; MRADL: Manchester respiratory activities of daily living questionnaire; GOLD: Global Initiative for Chronic Obstructive Lung Disease; GARS: Groningen Activities for Daily Living Restriction Scale; HGS: handgrip strength; 5STS: Five-repetitions Sit-to-Stand Test; TUG: timed up and go test; 1-min STS: 1-min sit-to-stand test.
] (handgrip strength (HGS), 1-min sit-to-stand (1-min STS), 5 repetitions sit-to-stand (5STS) and Time Up and Go (TUG) tests) and three included self-reported measures [
] (Manchester respiratory activities of daily living (MRADL) and Groningen activities for daily living restriction scale (GARS) questionnaires). The handgrip strength (HGS) test was the only muscle strength test that was considered in the included studies. A brief description of these tests and main findings related to each test is shown in Table 3.
Table 3Description of the tests and main findings related to each test.
Performance-based tests
Description
Main findings
1-min Sit-To-Stand test (1-min STS)
The test is performed with a standard height (46 cm) chair without arm rests. The patient starts the test sitting on a chair and repeatedly stands up and sits down again during 1 min. The outcome is how many times patients perform this movement in 1 min. This test measures general lower limb strength and is a strong predictor of mortality in older adults.
Associated with 2-year mortality. Adjusted HR = 0.58 (95% CI 0.4–0.85; P = 0.004) per 5 more STS repetitions. Lower performance on the test in patients who had died at 2 year follow up than in patients who were still alive (11.8 rises vs 19.5) (Follow up: 2 years) [
]. Number of repetitions during the STS test was 18.9 ± 8.8. STS test results were lower for females compared with males (17.2 ± 7.4 vs 20.3 ± 9.5) (Follow up: 2 years) [
The patient starts the test sitting and repeatedly stands up and sits down five times as quickly as he/she can. Outcome is time (how long it takes for the patients to perform the five repetitions).
5STS was associated with all-cause mortality in ambulatory multimorbidity older men sample (n = 352). (HR 1.46, 95% CI 1.28–1.65, p < 0.001). Authors did not report COPD subgroup analysis (n = 28; not available data) (Follow up: 184 months) [
The patient starts the test sitting on chair and is asked to stand up, walk 4 m and come back and sit down again. The outcome is time (how long it takes for the patient to perform the task). This test measures mobility and balance.
ANCOVA analysis further revealed shorter survival time for subjects with COPD (P = 0.006). Performance on TUG had no influence on survival time in older men with COPD (P = 0.202) (Follow up: 184 months) [
The patient presses a dynamometer with the hand. It is a measure of overall body strength and a strong predictor of mortality in older adults and other clinical populations.
HGS test was strongly associated with mortality (adjusted HR 0.84, 95% CI 0.72–1.00; P = 0.04) (Follow up: 2 years) [
Manchester Respiratory Activities of Daily Living questionnaire (MRADL)
MRADL is a 21-item, self- reported questionnaire. It has four domains: Mobility (7 items), Kitchen activities (4 items), Domestic tasks (6 items), and Leisure activities (4 items). The MRADL is scored compositely in the range 0–21, with a score of 21 signifying no physical impairment.
MRADL was a good predictor of mortality at 2.5 year follow up (OR 0.87; 95% CI 0.80–0.97; P < 0.007) (univariate logistic regression analysis). But on multivariate logistic regression analysis, this finding was not confirmed [
]. At 1-year follow-up, the MRADL was found to be a predictor of mortality (OR 0.87 95% CI 0.80–0.94). However, in a multivariate logistic regression analysis this effect was not maintained. (AECOPD) [
Groningen Activities of daily living Restriction Scale (GARS)
The GARS measures ADL (personal care) as well as instrumental ADL (domestic activities). The total score has a range of 18–54. Higher scores indicate worse daily functioning in all domains.
At 2-year follow-up, high-severity subgroup based on the GARS had a lower probability of survival (hazard ratio 0.53, 95% CI 0.38–0.75) [
] demonstrated that the 1-min STS test was strongly associated with mortality at two-year follow up (adjusted hazard ratio (HR) per five more repetitions of 0.58, 95% CI 0.40–0.85; P = 0.004) and HGS was moderately associated with mortality (HR 0.84, 95% CI 0.72–1.00; P = 0.04). In addition, the authors showed that, 1-min STS test and HGS were substantially lower at baseline in patients who died compared to those who were alive at two-year follow up (11.8 versus 19.5 repetitions; 30.1 kg versus 36.4 kg, respectively). Crook et al. [
] followed up this same cohort for five years. Contrary to the first work, the authors did not observe statistically significantly association between HGS test and mortality. Only the 1-min STS test showed good long-term predictive (5 years) validity for mortality (HR per 3 more repetitions: 0.81, 95% CI 0.65–0.86).
] compared the predictive value of different physical function measures (HGS, 5STS and TUG tests) in 352 ambulatory older man. Subjects with COPD performed poorer on the all physical function measures than did healthy subjects. ANCOVA analysis further revealed shorter survival time for subjects with COPD (P = 0.006). Performance on TUG had no influence on survival time in older men with COPD (P = 0.202). The authors posited that the lack of predictive validity of the TUG in subjects with COPD was due to their small sample size.
Yohannes et al. conducted two prospective cohort studies with individuals suffering from COPD; activities of daily living (ADL) were assessed using the MRADL questionnaire [
]. The first study found that MRADL was a good predictor of mortality at 2.5 year follow up (Odds ratio (OR) 0.88, 95% CI 0.80–0.97). The second study included patients who had been hospitalized with an acute exacerbation of COPD (AECOPD). At 1-year follow-up, the MRADL was found to be a predictor of mortality in the study population (OR 0.87, 95% CI 0.80–0.94; univariate logistic regression analysis). However, in a multivariate logistic regression analysis this effect was not maintained.
] measured ADL using the GARS questionnaire in 82 COPD patients. The authors stratified the study population into severity subgroups according to the lowest, intermediate and highest tertile of the questionnaire. Higher scores indicated worse daily functioning in all domains. After 2 years follow up, the scores on the GARS declined gradually over time in the majority of patients. Patients in the high-severity subgroup had a lower probability of survival (hazard ratio 0.53, 95% CI 0.38–0.75) compared to low severity subgroup (hazard ratio 0.70, 95% CI 0.55–0.90) at the same time point.
3.2 Relationship to COPD exacerbation
Three articles examined the relationship of simple physical function or muscle strength measures to exacerbation. Puhan et al. [
] assessed in their studies the predictive performance of the 1-min STS and HGS tests for exacerbations at 2-year and 5-year follow up respectively but did not find any relationship to exacerbation [
] in a cross-sectional analysis of a cohort study, (n = 272) demonstrated that HGS test was associated with exacerbation risk, an increment of 5% in the risk of exacerbations for each 1-kg decrement in HGS test (risk ratio 1.05; 95% CI, 1.01–1.08). Even in their longitudinal analysis and after statistical adjustments, each additional kilogram decrement in HGS test was associated with higher relative risks of having any incident event during follow-up (mean 2.6 years) (risk ratio, 1.04; 95% CI, 1.01–1.07).
3.3 Relationship with COPD-related hospitalizations
] found that the risk for severe events (emergency room visits or hospital admissions) during follow-up period (mean 2.6 years) was higher per 1-kg decrement in HGS test (relative risk, 1.06; 95% CI, 1.01–1.12).
4. Discussion
This is the first study that has systematically reviewed information on the predictive validity of simple measures of physical function and muscle strength in relation to outcomes such as mortality, exacerbations and hospitalizations in patients with COPD. Few studies have examined the predictive validity of this type of tests. From the seven studies included in the review, six evaluated the relationship of these measures to mortality; three studies examined this relationship with exacerbations and only one study included the outcome hospitalization. Among the included studies, four used performance-based tests (the most common being the HGS test and 1-min STS) and three used self-reported questionnaires (the MRADL and GARS). The majority of the studies were classified as having “fair” or “poor” methodological quality.
Of the six studies that evaluated the relationship of our tests of interest to mortality, four of them showed that some of these tests are associated with either true observation of death or probability of survival. The tests included in these studies were the 1-min STS, 5STS, TUG, HGS tests and two self-reported questionnaires, the MRADL and GARS. The MRADL and GARS are self-reported questionnaires that evaluate the ability to perform ADL. Limitations in ADL (or disability) have been shown to be a predictor of mortality in different populations [
]. The MRADL and GARS questionnaires are easy and quick to be completed and could be used in any setting for prognostic purposes. However, the type of patients to which the questionnaires should be administered should be taken into consideration. Yohannes et al. published two studies examining the MRDAL questionnaire as a mortality predictor in two different populations and found contradictory results. The first study published in 2002 included outpatients with stable COPD and the authors demonstrated that the MRADL was a significant predictor of mortality in that population [
]. One of the main reasons for this divergent result may be that the disease severity as well as the management of these different populations influence their pattern of recovery and functional responses. Moreover, the studies that considered MRADL [
] included older patients (age ≥ 60 years) with GOLD (Global initiative for chronic obstructive lung disease) stage 4, thus the predictive validity of these questionnaires in younger patients who are at earlier stages of the disease is unknown.
The 1-min STS and HGS were shown, in two and three studies, respectively, to be strongly associated with mortality (average follow-up of 2 years) [
] followed a population for 5 years and demonstrated that only the 1-min STS test showed long-term predictive validity (5 years). The authors attributed the greater long-term predictive validity of the 1-min STS in relation to the HGS to the fact that the 1-min STS is more physically demanding (involves larger muscle groups) and thus more likely to estimate functional exercise performance which may reflect the patients’ overall health status.
The performance of the HGS in predicting exacerbations seems to be conflicting. Martinez et al. [
] attributed the lack of association in their studies to the small number of exacerbations that occurred during the study periods, probably because of the COPD severity (the majority of the patients in their cohort were GOLD stage 2). Moreover, the results of Martinez's study might have been overestimated since they recruited patients from a specialized outpatient clinic and relied on patients to report whether or not they had an exacerbation (while in Puhan's cohort, occurrence of exacerbation had to be medically confirmed and they recruited patients from primary care centres). In addition, Puhan's model of events during follow-up were adjusted for exacerbation history at enrollment.
Despite the conflicting results of the predictive validity of the HGS test in relation to exacerbation, there is strong data on its predictive validity in term of mortality and hospitalization and could be a great test to use for prognostication in many clinical settings. The HGS test requires an inexpensive hand-held dynamometer (approximately US$ 300; one time investment), is simple to perform by individuals of any age and a good option for patients who may not be able to conduct tests where walking or standing is required [
Is the 1-minute sit-to-stand test a good tool for the evaluation of the impact of pulmonary rehabilitation? Determination of the minimal important difference in COPD.
]. The disadvantage of the 1-min STS is that it may be difficult for patients with musculoskeletal or neurological conditions to perform. It also seems to have a floor effect (older or too debilitated patients may not be able to complete the test) [
] and there is limited evidence for its association with exacerbation and hospitalization in individuals with COPD. It is important to note that even though the HGS and 1-min STS tests seem to be promising tests to be used for prognosis purposes in patients with COPD, the data available are based on 3 and 2 studies, respectively.
The strength of this review is that it compiles, in a systematic manner, information on the predictive validity of simple measures of physical function and muscle strength in relation to exacerbation, hospitalization and mortality in individuals with COPD. Previous reviews had focused on the clinical value and psychometric properties of these tests [
Functional tests in chronic obstructive pulmonary disease, Part 1: clinical relevance and links to the international classification of functioning, disability, and health.
] but to the best of our knowledge, no review had compiled information on the prognostic value of these tests.
Our systematic review has some limitations. First, the main challenge was that the primary objective of the included studies was not necessarily related to the primary objective of our systematic review which made data extraction difficult. Other limitations were the high diversity of methodologies (patient characteristics, exposures, type of tests used and outcome measures) of the included studies which made it difficult for the authors to conduct a meta-analysis. Finally, the majority of the studies in this review (n = 4) were classified as having a “fair” or “poor” quality assessment according the Downs & Black checklist. The items that received low scores were related to external/internal validity and study's power demonstrating the low methodological quality of the included studies.
5. Conclusions
There is a limited number of studies examining the prognostic value of simple measures of physical function and muscle strength in relation to exacerbations, hospitalizations and mortality in individuals with COPD. To date, the HGS and 1-min STS tests are the most studied tests and seem to be suitable for prognosis purposes in individuals with COPD. However, more studies with better methodological quality are needed to confirm these findings. It remains unclear whether improvements in these physical function measures can translate into improvement in patient prognosis. Further studies addressing the short-term predictive validity of these tests (e.g. 30-day readmission to hospital) are also needed.
Financial support
None.
Author's contributions
WA and TJF conducted titles and abstracts review. DM and WA screened and accessed the data. All authors made substantial contributions to the interpretation of the data. DM and TJF wrote the paper. WA, VPL and JB critically revised the manuscript for important intellectual content. All authors approved the final version to be submitted for publication.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors would like to thank the research associate Dr Catherine Tansey for helping with the quality assessment of the studies.
List of abbreviations
COPD
Chronic Obstructive Disease
6MWT
Six-minute walk test
ICF
International Classification of functioning, Disability and Health
HGS
Handgrip strength test
STS
sit-to-stand
5STS
Five repetitions sit-to-stand
TUG
Time Up and Go
1-min STS
1-min sit-to-stand
GARS
Groningen activities for daily living restriction scale
MRADL
Manchester respiratory activities of daily living questionnaire
ADL
Activities of daily living
AECOPD
Acute exacerbation of chronic obstructive pulmonary
GOLD
Global Initiative for chronic obstructive lung disease
Appendix A. Electronic search strategy
Tabled
1
Terms Used
Variations of Terms to use when searching
Physical Function Measures
Performance Based Tests
•
Exercise Test/OR ((exercise* or physical activit* or performance or step* or stand* or walk* or strength* or function* or balance or grip or handgrip or sit or lift* or gait or stair or rise) adj3 (test* or measure* or score* or status or assess* or evaluat* or batter* or scale or subscale)).tw,kf.
Self-Reported Measures
•
exp Activities of Daily Living/or ((activit* adj2 (daily living or limit*)) or ADL or ADLs).tw,kf.
AND
•
exp “Surveys and Questionnaires"/or (assess* or tool* or evaluat* or test* or scale* or subscale* or score* or inventor* or questionnaire* or measure*).tw,kf.
•
(self-report* or PFP or PPT or “PFP-10″ or SPPB or “SF-36″).tw,kf.
An official American Thoracic Society/European Respiratory Society statement: update on limb muscle dysfunction in chronic obstructive pulmonary disease.
Functional tests in chronic obstructive pulmonary disease, Part 1: clinical relevance and links to the international classification of functioning, disability, and health.
The feasibility of creating a checklist for the assessment of the methodological quality both of randomised and non-randomised studies of health care interventions.
Is the 1-minute sit-to-stand test a good tool for the evaluation of the impact of pulmonary rehabilitation? Determination of the minimal important difference in COPD.
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