- Email: [email protected]
Symptom Measurement
rules, rates of VAP will plummet but overall mortality will not change. In fact, we will likely see research explode in a newly discovered syndrome: infectious tracheobronchitis in patients receiving mechanical ventilation. Additionally, although the intent of the CMS efforts is noble-to improve care-the fear of retribution will potentially motivate clinicians to inaction whenever a new case of VAP is suspected. Because clinicians will now have an incentive to err on the side of abeyance, the critical opportunity for early appropriate therapy will likely be missed more regularly and clinical outcomes may actually worsen. When it comes to VAP, sloth and gluttony rule the ICU. Strict adherence to evidence-based practices is presently the exception as opposed to the rule. Accordingly, our efforts need to concentrate on those areas likely to have the greatest effect: education, prevention, early and accurate dagnosis, and appropriate empiric therapy. If we are not executing these fundamental strategies correctly within the present system, what will be our motivation in the future? VAP outcomes will potentially be worsened by adding pride, lust, wrath, greed, and envy into the existing toxic milieu.
Lee E. Morrow, MD, MSc, FCCP Omaha, N E Andrew F. Shorr, MD, MPH, FCCP Washington, DC Dr. Morrow is Associate Professor of Medicine, Pulmonary, Critical Care and Sleep Medicine, Creighton University Medical Center. Dr. Shorr is Associate Professor of Medicine, Pulmonary and Critical Care Medicine Service, Washington Hospital Center, Georgetown Universig , , , The authors have no con icts of interests to disclose regarding this editorial. Reproduction of this article is rohibited without written permission froin the American College orchest Physicians (www.chestjournal. org/misc/re rints shtml) Corre.spon&nce to: Andrea F. Shorr, MD, MPH, FCCP, Rooin 2A-380, Washington Hos ital Center, 110 lming S t N W , Washington, DC 2001 0; e-mai~a~horr~dnanu2il,co,li DOI: 10.1378/chest.08-0860
REFERENCES 1 Kollef MH. What is ventilator-associatedpneumonia and why is it important? Respir Care 200.5; 50:714-721 2 Federal Register Part 11, Medicare Program. Proposed changes to the hospital inpatient prospective payment systems and fiscal year 2008 rates: proposed rule, 42 CFR parts 411, 412, 413, and 489. Bethesda, MD: Department of Health and Human Services, Centers for Medicare and Medicaid Services, 2007 3 Kollef KE, Schramm G, Wills A, et al. Predictors of 30-day mortality and hospital costs in patients with ventilatorassociated pneumonia attributed to potentially antibioticresistant Gram-negative bacteria. Chest 2008; 134:281-287 4 Iregui M , Ward S, Sherman G, et al. Clinical importance of delays in the initiation of appropriate antibiotic treatment for ventilator-associated pneumonia. Chest 2002; 122362268 5 Chastre J. Antibiotic prescribing for ventilator-associated
226
pneumonia: get it right from the beginning hut he able to rapidly deescalate. Intensive Care Med 2005; 31:1463-
1465 6 National Nosocomial Infections Surveillance (NNIS) system report: data summary from January 1992 through June 2004, issued October 2004. Am J Infect Control 2004; 32:470-48.5
Symptom Measurement he article by Polley et all in this issue of CHEST T ( s e e page 295) illustrates the use of symptom questionnaires to quantify cough and gain a better understanding about its relationship to the underlying diseases. Its findings are predicated on the validity of the instruments that were used. Laboratory measurements and biomarkers of disease have turned medicine from a profession that was solely shlled based to one that is founded on solid science. However, the ultimate outcome of treatment is to improve clinical outcomes. These are things that are identified by the patients themselves: symptoms, wellbeing, and ability to perform daily tasks and function as healthy people do.2 Laboratory measurements of disease severity are only markers of outcome. Indeed many may be surrogate markers (ie, markers of other markers), for example diffusion capacity of the lung for carbon monoxide as a marker for CT lung densitometry as a marker of emphysema. An observer cannot estimate symptoms. They are subjective and experienced only by the patient. The term subjective has a pejorative connotation in medicine. It suggests that the way the patient feels and thinks will influence his or her estimation. Most damningly, it implies unreliability, lack of rigor, not verifiable. So, the patient’s estimate of his or her symptoms is not reliable. If he or she cannot be trusted to make the measurement, no one can. Therefore, symptoms are therefore not scientifically quantifiable. Let us step back from this nihilism and think through the issues. It is true that mood state and personality can influence how we judge things. A healthy adult, having been awake all night with a fretful child, judges the world differently in the morning than after a good night’s sleep. Previous experience of a symptom may influence current estimates3 But, despite all of those factors, in clinical practice we all ask our patients to quantify symptoms and make management decisions based on those apparently unscientific and unreliable assessments. The science of converting people’s answers to questions into valid numbers developed in education, and moved into medicine about 40 years ago. Editorials
However, the first clinical quantification scale in pulmonary medicine is older than that. The British Medical Research Council Dyspnoea Scale was developed half a century ago by experienced clinicians, without any modern psychometric tools. It only got two things wrong: first it is not actually a dyspnea scale because it measures disability due to breathlessness, and second it asks about two different activity imitations in one question. These things aside, it has stood the test of time although it was only properly tested some 40 years after it was developed.4 The science of developing reliable and responsive questionnaires is now sophisticated and rigorous and continues to develop. Most recently, mathematical modeling techniques have been applied to questionnaire development and testing to ensure that the instrument has reliable measurement properties and behaves like a ruler: the same distance between two points means the same difference in severity, regardless of where they lie along the scale. For a more extensive explanation of this important methodology, see the online supplement to Meguro et al? This method of questionnaire development to some extent supersedes those used in the development of those questionnaires but does not render them invalid. The term validity is often associated with a range of jargon terms in this context to describe different aspects of testing whether an instrument truly and reliably measures what it purports to do. Many of the methods were developed because the construct being measured was abstract (eg, “intelligence” or “mood). There were no external references against which to compare the new instrument. The process of validating instruments is continuous, as illustrated in this article, which provides important new validation data about two existing cough questionnaires but also tells us more about cough and its interrelationships. The two cough questionnaires correlated well with each other (convergent validity). It is also reassuring to see that the severity of cough in coughers was the same across disease groups, but the health of the patients measured with a generic instrument was different (divergent validity). It was equally reassuring to see that cough did not correlate with FEV,; why should it? Having got these validation steps out of the way, it is then interesting to see that some
www.chestjournal.org
components of cough are more important in some conditions than others, and that the influence of cough on overall quality of life may differ between diseases. However the numbers of patients are small, and these observations deserve further testing. Symptom measurement by well-designed questionnaires has taught us a lot and can change perceptions. Health status measurement has shown us just how important are COPD exacerbations6.7True, no questionnaire is perfect and most can be improved,s but let us not forget that FEV, is affected by at least two entirely separate mechanisms, but that has not hindered its adoption as a measurement of immense value.
Paul W. Jones, M D , PhD London, U K Dr. Jones is Professor of Respiratory Medicine, Cardiac and Vascular Science, St. George’s, University of London, London SW17 ORE, UK. Reproduction of this article is rohibited without written permission from the American College orchest Physicians (www.chestjoumal. org/misc/re rints shtml) Corre,spon&nce io; Paul W. ]ones, MD, PhD, Respiratory Med-
icine, Cardiac and Vascular Science, St. George’s, University of London, London SWl7 ORE, UK; e-mail: [email protected] DOI: 10.1378/chest.08-0916
REFERENCES 1 Polley L, Yainan N, Heaney L, et al. Impact of cough across
2
3
4
5
6
7
different chronic respiratory diseases: comparison of two cough-specific health-related quality of life questionnaires. Chest 2008; 134:295302 Jones PW, Augusti AA. Outcomes and markers in the assessment of COPD. Eur Respir J 2006; 27522-832 Wilson RC, Oldfield WLG, Jones PW. Effect of residence at altitude on the perception of breathlessness on return to sea level in normal subjects. Clin Sci 1993; 84:159-167 Bestall JC, Paul EA, Garrod R, et al. Usefulness of the Medical Research Council (MRC) dyspnoea scale as a measure of disability in patients with chronic obstructive pulmonary disease. Thorax 1999; 54~581-586 Meguro M , Barley EA, Spencer S, et al, Development and validation of an improved COPD-specific version of the St George’s Respiratory Questionnare. Chest 2007; 132: 456-463 Seeinungal TAR, Donaldson GC, Paul EA, et al. Effect of exacerbation on quality of life in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1998; 157~1418-1422 Spencer S, Jones PW. Time course of recovery of health status following an infective exacerbation of chronic bronchitis. Thorax 2003; 58:589-593
CHEST I 134 I 2 I AUGUST, 2008
227
Lee E. Morrow, MD, MSc, FCCP Omaha, N E Andrew F. Shorr, MD, MPH, FCCP Washington, DC Dr. Morrow is Associate Professor of Medicine, Pulmonary, Critical Care and Sleep Medicine, Creighton University Medical Center. Dr. Shorr is Associate Professor of Medicine, Pulmonary and Critical Care Medicine Service, Washington Hospital Center, Georgetown Universig , , , The authors have no con icts of interests to disclose regarding this editorial. Reproduction of this article is rohibited without written permission froin the American College orchest Physicians (www.chestjournal. org/misc/re rints shtml) Corre.spon&nce to: Andrea F. Shorr, MD, MPH, FCCP, Rooin 2A-380, Washington Hos ital Center, 110 lming S t N W , Washington, DC 2001 0; e-mai~a~horr~dnanu2il,co,li DOI: 10.1378/chest.08-0860
REFERENCES 1 Kollef MH. What is ventilator-associatedpneumonia and why is it important? Respir Care 200.5; 50:714-721 2 Federal Register Part 11, Medicare Program. Proposed changes to the hospital inpatient prospective payment systems and fiscal year 2008 rates: proposed rule, 42 CFR parts 411, 412, 413, and 489. Bethesda, MD: Department of Health and Human Services, Centers for Medicare and Medicaid Services, 2007 3 Kollef KE, Schramm G, Wills A, et al. Predictors of 30-day mortality and hospital costs in patients with ventilatorassociated pneumonia attributed to potentially antibioticresistant Gram-negative bacteria. Chest 2008; 134:281-287 4 Iregui M , Ward S, Sherman G, et al. Clinical importance of delays in the initiation of appropriate antibiotic treatment for ventilator-associated pneumonia. Chest 2002; 122362268 5 Chastre J. Antibiotic prescribing for ventilator-associated
226
pneumonia: get it right from the beginning hut he able to rapidly deescalate. Intensive Care Med 2005; 31:1463-
1465 6 National Nosocomial Infections Surveillance (NNIS) system report: data summary from January 1992 through June 2004, issued October 2004. Am J Infect Control 2004; 32:470-48.5
Symptom Measurement he article by Polley et all in this issue of CHEST T ( s e e page 295) illustrates the use of symptom questionnaires to quantify cough and gain a better understanding about its relationship to the underlying diseases. Its findings are predicated on the validity of the instruments that were used. Laboratory measurements and biomarkers of disease have turned medicine from a profession that was solely shlled based to one that is founded on solid science. However, the ultimate outcome of treatment is to improve clinical outcomes. These are things that are identified by the patients themselves: symptoms, wellbeing, and ability to perform daily tasks and function as healthy people do.2 Laboratory measurements of disease severity are only markers of outcome. Indeed many may be surrogate markers (ie, markers of other markers), for example diffusion capacity of the lung for carbon monoxide as a marker for CT lung densitometry as a marker of emphysema. An observer cannot estimate symptoms. They are subjective and experienced only by the patient. The term subjective has a pejorative connotation in medicine. It suggests that the way the patient feels and thinks will influence his or her estimation. Most damningly, it implies unreliability, lack of rigor, not verifiable. So, the patient’s estimate of his or her symptoms is not reliable. If he or she cannot be trusted to make the measurement, no one can. Therefore, symptoms are therefore not scientifically quantifiable. Let us step back from this nihilism and think through the issues. It is true that mood state and personality can influence how we judge things. A healthy adult, having been awake all night with a fretful child, judges the world differently in the morning than after a good night’s sleep. Previous experience of a symptom may influence current estimates3 But, despite all of those factors, in clinical practice we all ask our patients to quantify symptoms and make management decisions based on those apparently unscientific and unreliable assessments. The science of converting people’s answers to questions into valid numbers developed in education, and moved into medicine about 40 years ago. Editorials
However, the first clinical quantification scale in pulmonary medicine is older than that. The British Medical Research Council Dyspnoea Scale was developed half a century ago by experienced clinicians, without any modern psychometric tools. It only got two things wrong: first it is not actually a dyspnea scale because it measures disability due to breathlessness, and second it asks about two different activity imitations in one question. These things aside, it has stood the test of time although it was only properly tested some 40 years after it was developed.4 The science of developing reliable and responsive questionnaires is now sophisticated and rigorous and continues to develop. Most recently, mathematical modeling techniques have been applied to questionnaire development and testing to ensure that the instrument has reliable measurement properties and behaves like a ruler: the same distance between two points means the same difference in severity, regardless of where they lie along the scale. For a more extensive explanation of this important methodology, see the online supplement to Meguro et al? This method of questionnaire development to some extent supersedes those used in the development of those questionnaires but does not render them invalid. The term validity is often associated with a range of jargon terms in this context to describe different aspects of testing whether an instrument truly and reliably measures what it purports to do. Many of the methods were developed because the construct being measured was abstract (eg, “intelligence” or “mood). There were no external references against which to compare the new instrument. The process of validating instruments is continuous, as illustrated in this article, which provides important new validation data about two existing cough questionnaires but also tells us more about cough and its interrelationships. The two cough questionnaires correlated well with each other (convergent validity). It is also reassuring to see that the severity of cough in coughers was the same across disease groups, but the health of the patients measured with a generic instrument was different (divergent validity). It was equally reassuring to see that cough did not correlate with FEV,; why should it? Having got these validation steps out of the way, it is then interesting to see that some
www.chestjournal.org
components of cough are more important in some conditions than others, and that the influence of cough on overall quality of life may differ between diseases. However the numbers of patients are small, and these observations deserve further testing. Symptom measurement by well-designed questionnaires has taught us a lot and can change perceptions. Health status measurement has shown us just how important are COPD exacerbations6.7True, no questionnaire is perfect and most can be improved,s but let us not forget that FEV, is affected by at least two entirely separate mechanisms, but that has not hindered its adoption as a measurement of immense value.
Paul W. Jones, M D , PhD London, U K Dr. Jones is Professor of Respiratory Medicine, Cardiac and Vascular Science, St. George’s, University of London, London SW17 ORE, UK. Reproduction of this article is rohibited without written permission from the American College orchest Physicians (www.chestjoumal. org/misc/re rints shtml) Corre,spon&nce io; Paul W. ]ones, MD, PhD, Respiratory Med-
icine, Cardiac and Vascular Science, St. George’s, University of London, London SWl7 ORE, UK; e-mail: [email protected] DOI: 10.1378/chest.08-0916
REFERENCES 1 Polley L, Yainan N, Heaney L, et al. Impact of cough across
2
3
4
5
6
7
different chronic respiratory diseases: comparison of two cough-specific health-related quality of life questionnaires. Chest 2008; 134:295302 Jones PW, Augusti AA. Outcomes and markers in the assessment of COPD. Eur Respir J 2006; 27522-832 Wilson RC, Oldfield WLG, Jones PW. Effect of residence at altitude on the perception of breathlessness on return to sea level in normal subjects. Clin Sci 1993; 84:159-167 Bestall JC, Paul EA, Garrod R, et al. Usefulness of the Medical Research Council (MRC) dyspnoea scale as a measure of disability in patients with chronic obstructive pulmonary disease. Thorax 1999; 54~581-586 Meguro M , Barley EA, Spencer S, et al, Development and validation of an improved COPD-specific version of the St George’s Respiratory Questionnare. Chest 2007; 132: 456-463 Seeinungal TAR, Donaldson GC, Paul EA, et al. Effect of exacerbation on quality of life in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1998; 157~1418-1422 Spencer S, Jones PW. Time course of recovery of health status following an infective exacerbation of chronic bronchitis. Thorax 2003; 58:589-593
CHEST I 134 I 2 I AUGUST, 2008
227