Showing papers by "Gordon H. Guyatt published in 1995"

Users' Guides to the Medical Literature: IX. A Method for Grading Health Care Recommendations

Abstract: THE ULTIMATE PURPOSE of applied health research is to improve health care. Summarizing the literature to adduce recommendations for clinical practice is an important part of the process. Recently, the health sciences community has reduced the bias and imprecision of traditional literature summaries and their associated recommendations through the development of rigorous criteria for both literature overviews 1-3 and practice guidelines. 4,5 Even when recommendations come from such rigorous approaches, however, it is important to differentiate between those based on weak vs strong evidence. Recommendations based on inadequate evidence often require reversal when sufficient data become available, 6 while timely implementation of recommendations based on strong evidence can save lives. 6 In this article, we suggest an approach to classifying strength of recommendations. We direct our discussion primarily at clinicians who make treatment recommendations that they hope their colleagues will follow. However, we believe that any clinician who attends to

How to Use an Article About Therapy or Prevention

Abstract: You are working as an internal medicine resident in a rheumatology rotation and are seeing a 19 year-old woman who has had systemic lupus erythematosus diagnosed on the basis of a characteristic skin rash, arthritis, and renal disease. A renal biopsy has shown diffuse proliferative nephritis. A year ago, her creatinine was 140 micromoles/litre, six months ago 180, and in a blood sample taken a week before this clinic visit, 220. Over the last year she has been taking prednisone, and over the last six months, cyclophosphamide, both in appropriate doses.

Users' Guides to the Medical Literature: VIII. How to Use Clinical Practice Guidelines A. Are the Recommendations Valid?

Abstract: CLINICAL SCENARIO You are relieved to find that the last patient in your busy primary care clinic is a previously well 48-year-old woman with acute dysuria. There has been no polydipsia, fever, or hematuria; the physical examination reveals suprapubic tenderness; and urinalysis shows pyuria but no casts. You arrange cultures and antibiotic treatment for a lower urinary tract infection. On her way out the door, your patient observes that her friend has just started taking "female hormones," and she wonders whether she should too. Her menstrual periods stopped 6 months ago and she has never had cervical, ovarian, uterine, breast, or cardiovascular problems, but her mother had a mastectomy at age 57 for postmenopausal breast cancer. You give the same general advice you have offered similar patients in the past, but suggest that the matter be discussed at greater length when she returns after completing the antibiotic treatment. Later, as

Determinants in Canadian health care workers of the decision to withdraw life support from the critically ill

Abstract: Objective. —To examine the attitudes of health care workers regarding the withdrawal of life support. Design. —Cross-sectional survey. Participants. —Attending staff, house staff, and intensive care unit (ICU) nurses in 37 Canadian university-affiliated hospitals. Main Outcome Measures. —Health care workers' ratings of the importance of 17 factors considered in the decision to withdraw life support, and their ratings of five levels of care ranging from comfort measures to intensive care in two of 12 different clinical scenarios. Results. —We surveyed 1361 respondents (149 of 167 potentially eligible ICU attending staff, 142 of 173 ICU house staff, and 1070 of 1455 ICU nurses, with response rates of 89%, 82% and 74%, respectively). The most important factors were likelihood of surviving the current episode, likelihood of long-term survival, premorbid cognitive function, and age of the patient. In choosing the level of care for the patient scenarios, the same option was chosen by more than 50% of respondents in only one of 12 scenarios; opposite extremes of care were chosen by more than 10% of the respondents in eight of 12 scenarios. Respondent characteristics affecting choices included the number of years since graduation, the city and province in which they worked, the number of beds in their ICU, and their assessment of the likelihood that they would withdraw life support in comparison with their colleagues (P Conclusions. —While ICU health care workers consistently identify a number of patient factors as important in decisions to withdraw care, there is extreme variability, which may be explained in part by the values of individual health care providers. (JAMA. 1995;273:703-708)

Enteral nutrition in the critically ill patient : a prospective survey

Abstract: ObjectivesTo describe current enteral nutrition-prescribing practices for critically ill patients, and to identify factors associated with initiation of, and tolerance to, enteral nutrition.DesignA prospective, cohort study.SettingTwo tertiary care medical-surgical intensive care units (ICU) in Onta

Users' Guides to the Medical Literature: VIII. How to Use Clinical Practice Guidelines B. What Are the Recommendations and Will They Help You in Caring for Your Patients?

Abstract: CLINICAL SCENARIO At the conclusion of our first article on practice guidelines 1 in this series, we left you examining the full text of a practice guideline 2 that could help you marshal a convincing response to a colleague who disagrees with your approach to hormone replacement therapy (HRT) in postmenopausal women. Later that day, chatting with another colleague, you mention the disagreement. He shrugs, and avows, "It's entirely a matter of personal preference, the evidence doesn't support either of you." You return to the guideline, looking for how particular recommendations may be justified and adapted to your patient's circumstances. WHAT ARE THE RECOMMENDATIONS? Are Practical, Clinically Important, Recommendations Made? To be useful, recommendations should give practical, unambiguous advice about a specific health problem. For guidelines about managing health conditions, you should determine if the intent is to prevent, screen for, diagnose, treat, or palliate the disorder. For guidelines about

Quality of life in asthma clinical trials: comparison of salmeterol and salbutamol.

Abstract: Most clinical trials in asthma have focused on outcomes that are primarily of importance to the clinician. Very few have assessed whether patients feel better and can function better in day-to-day activities. The aim of this study was to compare the effects of salmeterol (50 micrograms twice daily), salbutamol (200 micrograms four times a day), and placebo on asthma-specific quality of life and to relate the findings to conventional clinical asthma outcomes. The study was a 12-wk multicenter, double blind, randomized, placebo-controlled crossover trial with each trial medication taken for 4 wk. The subjects were 140 adults with mild to moderate asthma enrolled from 14 respiratory clinics across Canada. Outcome measures were: (1) the Asthma Quality of Life Questionnaire and spirometry at the end of each treatment period; and (2) daily asthma symptoms, morning and evening peak expiratory flow rates (PEFRs), and rescue salbutamol use during the last 14 d of each treatment period. Asthma-specific quality of life, both overall and for the individual domains (activity limitation, symptoms, emotional function, and exposure to environmental stimuli) was better with salmeterol than with placebo (p < 0.0001), and better with salmeterol than with salbutamol (p < 0.001). In both comparisons, differences were not only statistically significant, but most were also clinically important. There were moderate correlations between change in quality of life and change in clinical outcomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Users' Guides to the Medical Literature: VII. How to Use a Clinical Decision Analysis B. What Are the Results and Will They Help Me in Caring for My Patients?

Abstract: YOU RECALL from the first of our two articles concerning clinical decision analysis1that your patient is a middle-aged man with heart failure from an idiopathic dilated cardiomyopathy. You are trying to decide whether to recommend anticoagulation with warfarin to prevent systemic or pulmonary thromboembolism. Your literature search showed that no randomized clinical trials of warfarin for this use have been published. The search did discover a clinical decision analysis,2and in the first article, we showed you how to evaluate its validity. In this article, we will show you how to interpret the results and generalizability of a clinical decision analysis (Table). As shown in the Figure, decision trees are displayed graphically, oriented from left to right, with the decision to be analyzed on the left, the compared strategies in the center, and the clinical outcomes on the right. The square box, termed a "decision node," represents

Basic statistics for clinicians: 2. Interpreting study results: confidence intervals

Abstract: In the second of four articles, the authors discuss the "estimation" approach to interpreting study results. Whereas, in hypothesis testing, study results lead the reader to reject or accept a null hypothesis, in estimation the reader can assess whether a result is strong or weak, definitive or not. A confidence interval, based on the observed result and the size of the sample, is calculated. It provides a range of probabilities within which the true probability would lie 95% or 90% of the time, depending on the precision desired. It also provides a way of determining whether the sample is large enough to make the trial definitive. If the lower boundary of a confidence interval is above the threshold considered clinically significant, then the trial is positive and definitive, if the lower boundary is somewhat below the threshold, the trial is positive, but studies with larger samples are needed. Similarly, if the upper boundary of a confidence interval is below the threshold considered significant, the trial is negative and definitive. However, a negative result with a confidence interval that crosses the threshold means that trials with larger samples are needed to make a definitive determination of clinical importance.

Basic statistics for clinicians: 1. Hypothesis testing

Abstract: In the first of a series of four articles the authors explain the statistical concepts of hypothesis testing and p values. In many clinical trials investigators test a null hypothesis that there is no difference between a new treatment and a placebo or between two treatments. The result of a single experiment will almost always show some difference between the experimental and the control groups. Is the difference due to chance, or is it large enough to reject the null hypothesis and conclude that there is a true difference in treatment effects? Statistical tests yield a p value: the probability that the experiment would show a difference as great or greater than that observed if the null hypothesis were true. By convention, p values of less than 0.05 are considered statistically significant, and investigators conclude that there is a real difference. However, the smaller the sample size, the greater the chance of erroneously concluding that the experimental treatment does not differ from the control--in statistical terms, the power of the test may be inadequate. Tests of several outcomes from one set of data may lead to an erroneous conclusion that an outcome is significant if the joint probability of the outcomes is not taken into account. Hypothesis testing has limitations, which will be discussed in the next article in the series.

Basic statistics for clinicians: 3. Assessing the effects of treatment: measures of association.

Abstract: In the third of a series of four articles the authors show the calculation of measures of association and discuss their usefulness in clinical decision making. From the rates of death or other "events" in experimental and control groups in a clinical trial, we can calculate the relative risk (RR) of the event after the experimental treatment, expressed as a percentage of the risk without such treatment. The absolute risk reduction (ARR) is the difference in the risk of an event between the groups. The relative risk reduction is the percentage of the baseline risk (the risk of an event in the control patients) removed as a result of therapy. The odds ratio (OR), which is the measure of choice in case-control studies, gives the ratio of the odds of an event in the experimental group to those in the control group. The OR and the RR provide limited information in reporting the results of prospective trials because they do not reflect changes in the baseline risk. The ARR and the number needed to treat, which tells the clinician how many patients need to be treated to prevent one event, reflect both the baseline risk and the relative risk reduction. If the timing of events is important--to determine whether treatment extends life, for example--survival curves are used to show when events occur over time.

A taxonomy of health status instruments.

Abstract: Clinicians and policymakers are recognizing the importance of measuring health related quality of life (HRQL) to inform patient management and policy decisions. Self or interviewer administered questionnaires can be used to measure cross sectional differences in quality of life between patients at a point in time (discriminative instruments) or longitudinal changes in HRQL within patients over time (evaluative instruments). Both discriminative and evaluative instruments must be valid (really measuring what they are supposed to measure) and have a high ratio of signal to noise (reliability and responsiveness, respectively). Reliable discriminative instruments are able to reproducibly differentiate between persons. Responsive evaluative measures are able to detect important changes in HRQL over time, even if those changes are small. HRQL should be interpretable--that is, clinicians and policymakers must be able to identify differences in scores that correspond to trivial, small, moderate, and large differences. Two basic approaches to quality of life measurement are available: generic instruments that attempt to provide a summary of health related quality of life; and specific instruments that focus on problems associated with individual disease states, patient groups, or areas of function. Generic instruments include health profiles and instruments that generate health utilities. The approaches are not mutually exclusive. Each approach has its strengths and weaknesses and may be suitable under different circumstances. Investigations in HRQL have led to instruments suitable for detecting minimally important effects in clinical trials, measuring the health of populations, and for providing information for policy decisions.

Determinants in Canadian Health Care Workers of the Decision to Withdraw Life Support from the Critically Ill

Abstract: OBJECTIVE To examine the attitudes of health care workers regarding the withdrawal of life support. DESIGN Cross-sectional survey. PARTICIPANTS Attending staff, house staff, and intensive care unit (ICU) nurses in 37 Canadian university-affiliated hospitals. MAIN OUTCOME MEASURES Health care workers' ratings of the importance of 17 factors considered in the decision to withdraw life support, and their ratings of five levels of care ranging from comfort measures to intensive care in two of 12 different clinical scenarios. RESULTS We surveyed 1361 respondents (149 of 167 potentially eligible ICU attending staff, 142 of 173 ICU house staff, and 1070 of 1455 ICU nurses, with response rates of 89%, 82% and 74%, respectively). The most important factors were likelihood of surviving the current episode, likelihood of long-term survival, premorbid cognitive function, and age of the patient. In choosing the level of care for the patient scenarios, the same option was chosen by more than 50% of respondents in only one of 12 scenarios; opposite extremes of care were chosen by more than 10% of the respondents in eight of 12 scenarios. Respondent characteristics affecting choices included the number of years since graduation, the city and province in which they worked, the number of beds in their ICU, and their assessment of the likelihood that they would withdraw life support in comparison with their colleagues (P < .001 for all comparisons). CONCLUSIONS While ICU health care workers consistently identify a number of patient factors as important in decisions to withdraw care, there is extreme variability, which may be explained in part by the values of individual health care providers.

Basic statistics for clinicians: 4. Correlation and regression

Abstract: Correlation and regression help us to understand the relation between variables and to predict patients' status in regard to a particular variable of interest. Correlation examines the strength of the relation between two variables, neither of which is considered the variable one is trying to predict (the target variable). Regression analysis examines the ability of one or more factors, called independent variables, to predict a patient's status in regard to the target or dependent variable. Independent and dependent variables may be continuous (taking a wide range of values) or binary (dichotomous, yielding yes-or-no results). Regression models can be used to construct clinical prediction rules that help to guide clinical decisions. In considering regression and correlation, clinicians should pay more attention to the magnitude of the correlation or the predictive power of the regression than to whether the relation is statistically significant.

Profile of mood states and cardiac rehabilitation after acute myocardial infarction.

Abstract: Following an acute myocardial infarction, evaluation of a patient's own perceptions of health, including mood state, provides useful information about the efficacy of rehabilitation when data are available for patients randomized to both control and intervention. Data are presented on the Profile of Mood States (POMS) in 187 patients, with mild to moderate scores for Spielberger state anxiety and/or Beck depression, who were randomized within 6 wk of acute myocardial infarction to usual care or to brief cardiac rehabilitation lasting 8 wk and who were followed-up during the 12 months following the acute event. Repeated measures multivariate analysis of covariance identified significant main as well as time effects in POMS scores over 12 months. Repeated measures analysis of variance over the 12 months demonstrated significant improvement for both depression and anxiety in both groups. At 8 wk, improvement was greater in the rehabilitation patients than usual care patients but only in the tension-anxiety, depression-dejection and vigor-activity dimensions of POMS and only in anxiety in those patients with above mean anxiety scores. Overall, rehabilitation and control patients showed similar and significant improvements in anxiety, depression and in mood states over the duration of the 12-month trial.

Discrimination and abuse experienced by general internists in Canada.

Abstract: OBJECTIVE: To identify the frequency of psychological and emotional abuse, gender discrimination, verbal sexual harassment, physical sexual harassment, physical assault, and homophobia experienced by general internists. DESIGN: Cross-sectional survey. SETTING: Canadian general internal medicine practices. RESULTS: The overall response rate was 70.6% (984/1,393); the 501 respondents who classified themselves as general internists were studied. Three-fourths of the internists experienced psychological and emotional abuse at the hands of patients, and 38% of the women and 26% of the men experienced physical assault by patients. The majority of the female internists experienced gender discrimination by patients (67%) and by physician peers (56%). Forty-five percent of the women experienced verbal sexual harassment by patients, and 22% experienced physical sexual harassment by patients. The male internists experienced verbal sexual harassment from nurses slightly more often than the female internists did (19% vs 13%, p>0.05). Verbal sexual harassment by male colleagues was reported by 35% of the female internists, and physical sexual harassment was reported by 11%. Approximately 40% of general internists reported homophobic remarks by both health care team members and patients. CONCLUSIONS: Abuse, discrimination, and homophobia are prevalent in the internal medicine workplace. A direct, progressive, multidisciplinary approach is necessary to label and address these problems.

Quality of life in cystic fibrosis.

Abstract: Cystic fibrosis is a chronic, multisystem genetic disease with a wide variability in clinical severity. In recent years, advances in therapy have led to improved patient survival into adulthood. New treatments are rapidly being developed and require evaluation to determine their efficacy. The measurement of health-related quality of life in cystic fibrosis provides additional information about the impact of this disease that cannot be obtained by physiological tests such as pulmonary function. An instrument to measure health-related quality of life is especially useful as an outcome measure for clinical trials. To date, only a few general quality-of-life (QOL) measures have been used in people with cystic fibrosis. There has been some demonstration of validity in 2 measures (the Quality of Well-Being Scale and the Functional Status Index) but the responsiveness of these instruments in this population has not been established. A cystic fibrosis-specific QOL instrument would be valuable as an outcome measure because of its potential for increased responsiveness, but no published measures exist as yet.

Traducción española y validación de un cuestionario de calidad de vida en pacientes con enfermedad pulmonar obstructiva crónica

Abstract: The Chronic Respiratory Disease Questionnaire (CRDQ), proposed by Guyatt et al, is a specific instrument used to assess quality of life in patients with chronic obstructive pulmonary disease (COPD). Our aim was to translate the questionnaire and validate it so that it could then be used as a measurement instrument in programs of respiratory rehabilitation. Sixty-five patients with COPD who were candidates for breathing therapy were enrolled in the study. Mean age was 64 +/- 7 years and all had severe air flow limitation, with FEV1 33 +/- 13% over reference values but not respiratory failure (pO2 70 +/- 10 mmHg). The questionnaire was subjected to a process of translation/back translation and disagreements over wording were discussed by a panel of bilingual speakers and the author himself. The validation process involved the following steps: 1) a comprehension study with a group of 5 patients, which revealed no special difficulties; 2) analysis of internal consistency or reliability by way of Crombach's alpha coefficient, which gave and overall score of 0.92 and area scores of 0.51 for dyspnea, 0.8 for fatigue, 0.86 for emotional factors and 0.84 for disease control, and 3) analysis of correlation between various lung function parameters and exercise test results (6 min of increasing effort and a stationary cycle), which showed weak but statistically significant correlations that were comparable to those found by the author of the original CRDQ.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Trials in Cognitively Impaired Older Adults: Home versus Clinic Assessments

Abstract: OBJECTIVE: To compare the reliability of instruments used in clinical trials involving cognitively impaired older adults when the instruments are administered in-home rather than in-clinic and to compare withdrawal rates is these two groups DESIGN: This study was part of a larger n-of-1 clinical trial to investigate the efficacy and safety of a MAO/A inhibitor (Brofaromine) in patients with Alzheimer's disease Participants were initially assessed at the clinic (baseline) and then randomly allocated to in-home or in-clinic assessments for the remainder of the trial The baseline and second assessment (performed before initiation of the treatment) were used for the reliability analysis Withdrawal rates were examined over the course of the 6-month trial SETTING: Assessments took place at a geriatric clinic in an urban university teaching hospital and at residences of some of the patients PARTICIPANTS: Forty-six Alzheimer's disease patients participated in the study, of which, 22 were randomized to in-home assessments and 24 to in-clinic assessments MEASUREMENTS: Test-retest reliability was measured for all five instruments used in the study and was based on the first two assessments Sample size requirements, based on within-group variance, were calculated Withdrawal rates were obtained for the total duration of the trial RESULTS: Test-retest reliability of the instruments, as determined by intraclass correlations, was good in both groups but favored in-clinic for all but one instrument (range: 047–090 for in-home vs 057–092 for in-clinic) Sample size requirements based on reliability assessment data were found to be larger for some instruments when administered in-home Only four in-home patients withdrew before completion of the study, compared with eight in-clinic patients CONCLUSION: The results suggest the in-home assessments in cognitively impaired older adults may result in lower withdrawal rates but may necessitate larger sample sizes to offset larger test-retest variability

Inadequacy of intravenous heparin therapy in the initial management of venous thromboembolism

Abstract: To determine the adequacy of initial anticoagulation by intravenous heparin for patients who have deep venous thrombosis (DVT), and the factors that influence delayed anticoagulation, independent, duplicate chart review of 63 consecutive patients who had venography-proven DVT was conducted. Adequate heparinization (AH) was defined as an activated partial thromboplastin time (PTT) of more than 1.5 times the normal laboratory control. The proportions of patients achieving AH within 24 hours and 48 hours of initial heparin bolus were 46% and 62%, respectively. Patients who weighed more were less likely to achieve AH (p<0.05), while patients receiving care from the thromboembolism service were more likely to achieve AH (p<0.05). Low initial infusion rate was strongly but not significantly predictive of inadequate anti-coagulation (p=0.06). The mean heparin bolus and initial infusion rates were significantly lower than those suggested in the literature (p<0.01). The AH rates were comparable to historical controls but suboptimal compared with the rates of 66% at 24 hours and 81% at 48 hours reported in association with heparin nomogram use (p<0.05). A heparin nomogram is likely to achieve consistently higher rates of adequate heparinization.