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Biomedical subjects

R Jaeschke

Publications and source records attributed to R Jaeschke.

At least 19 recordsLinked to original sources
PubMed1992

Measuring health status: what are the necessary measurement properties?

The different measurement properties necessary for instruments whose goal is to detect differences between subjects at a single point in time (discriminative instruments) and those whose goal is to detect longitudinal change within subjects (evaluative instruments) is becoming increasingly recognized. Up to now, requirements for evaluative instruments have been presented as reproducibility, validity, and responsiveness (i.e. the ability to detect change over time). An alternative conceptualization would characterize any instrument as requiring two crucial measurement properties. One is validity, the other a high ratio of signal to noise. For discriminative instruments, the signal to noise ratio can be summarized in a reliability coefficient; for evaluative instruments, in a responsiveness index or coefficient. This formulation can simplify and clarify the understanding and teaching of issues in health status measurement.

Epidemiologic Methods↗
PubMed1992

Evaluation of impairment of health related quality of life in asthma: development of a questionnaire for use in clinical trials.

BACKGROUND: In the past only physiological and clinical outcomes have been used to assess the effect of asthma interventions and the effect of the intervention on the lives of the patients has not been determined. The objective of this study was to assess health related impairment of quality of life in adult asthmatic patients and to develop a questionnaire for measuring quality of life in clinical trials in asthma. METHODS: Impairment of quality of life in adults with asthma was evaluated from structured interviews in which patients were asked to identify the parts of their daily lives affected by asthma. On the basis of these results, an asthma quality of life questionnaire was developed in an interviewer and self administered form and tested for comprehension and acceptability. A total of 150 adults with asthma and with a wide range of airway hyperresponsiveness were enrolled from previous clinical trials, local asthma clinics, and notices in the media. RESULTS: Areas of quality of life impairment included symptoms classically associated with asthma, responses to environmental stimuli, the need to avoid these stimuli, limitation of activities, and emotional dysfunction. Areas of impairment were similar across strata of airway hyperresponsiveness, age, and treatment requirements and between sexes, thus allowing a single questionnaire suitable for all adults with asthma to be developed. The questionnaire contains 32 items and takes 5-10 minutes to administer; in the pretesting it was shown to be acceptable to a wide range of patients. CONCLUSIONS: The questionnaire includes areas of quality of life impairment that are important to adult asthmatic patients. It has been designed to be responsive to within subject change and therefore may be used as a measure of outcome in clinical trials in asthma.

Adolescent↗
PubMed1991

Mechanism of bronchodilator effect in chronic airflow limitation.

OBJECTIVE: To examine the mechanisms through which two bronchodilators (theophylline and salbutamol) influence dyspnea during daily activities. METHODS: Twenty-four patients with chronic airflow limitation participated in a multiple crossover, randomized, placebo-controlled trial. The effect of theophylline and salbutamol, alone or combined, on pulmonary function and dyspnea during daily activities was examined. Correlations of changes in forced expiratory volume in 1 second (FEV1) and maximum expiratory pressures (MIPs) (independent variables) and changes in dyspnea score during daily activities (dependent variable) were also examined. RESULTS: The two drugs proved to be beneficial the effects in general were additive rather than synergistic. The drugs improved the FEV1; theophylline significantly improved the MIPs. The correlation between the changes in FEV1 and those in dyspnea score, after adjustment for the changes in MIPs, was 0.55 (p less than 0.001). The correlation between the changes in MIPs and those in dyspnea score, after adjustment for the changes in FEV1, was 0.39 (p less than 0.001). CONCLUSIONS: Changes in airway calibre and in respiratory muscle strength play an independent and important role in dyspnea during daily activities in patients with chronic airflow limitation. Changes in airway calibre may be of greater importance.

Activities of Daily Living↗
PubMed1991

Interpreting changes in quality-of-life score in N of 1 randomized trials.

To provide additional evidence regarding the plausible range of the differences in health-related quality of life (HRQL) questionnaire scores within which the minimal important difference (MID) falls, we reviewed the results of 32 randomized controlled trials in individual subjects (N of 1 RCTs) with chronic diseases. These trials had been conducted to establish whether a patient was obtaining more good than harm from a medication. Each N of 1 RCT included a series of pairs of treatment periods, one period on active drug, and one on placebo or alternative drug. We examined the relationship between small (MID), medium, and large differences between periods within pairs, as indicated by Global Ratings and differences between these same periods according to HRQL questionnaires. The results showed a mean difference of 0.29 points per question in HRQL questionnaire scores corresponded to the MID. Differences of approximately 0.66 points per question corresponded to a moderate difference as ranked by the Global Rating; difference of about 1.09 points per question represented marked difference.

Drug Therapy↗
PubMed1991

Clinical usefulness of n-of-1 randomized controlled trials in patients with nonreversible chronic airflow limitation.

To determine if n-of-1 randomized controlled trials (n-of-1 RCT) are useful in the care of patients with nonreversible chronic airflow limitation (CAL). Individual trials had a double-blind, randomized, multiple crossover design. Patients with CAL were recruited from several respirology practices. For each individual trial the main outcome measure was a symptom questionnaire; peak flow measurements were used as a secondary measure. Physicians' plans of management (before and after trials) and confidence in the plans were determined. The proportion of trials that provided a definite clinical or statistical answer was established. Patients were followed, and long-term adherence to decisions based on n-of-1 RCT was examined. A total of 26 n-of-1 RCT in patients with CAL were attempted; 18 of these (69%) were completed. After 17 (94%) of the completed trials clinicians expressed a high degree of confidence in their management plans, confidence that was not, in any case, present before the trial. After 8 n-of-1 RCT (44% of all completed, or 31% of all trials) clinicians decided to stop the drug, which would otherwise have been continued indefinitely. In all 17 of the clinically definite n-of-1 RCT, the management decision that followed the trial was still being adhered to 40 months (on average) after completion of the trial. The results support the feasibility and usefulness of n-of-1 RCT in respirology practice.

Double-Blind Method↗
PubMed1991

Clinical usefulness of amitriptyline in fibromyalgia: the results of 23 N-of-1 randomized controlled trials.

Twenty-three double blind, randomized, multiple crossover trials (N-of-1 RCT) of amitriptyline were conducted in patients with fibromyalgia. The benefit of amitriptyline was assessed using a symptom questionnaire and count of tender points. To assess the usefulness of the method, the proportion of trials that provided a definite answer was examined. Completing the trial resulted in reaching a high degree of confidence in the final management decision in 74% of trials. In 35% of trials, results led to discontinuation of the drug which otherwise would have been continued indefinitely. The drug benefit, if present, was evident within first 2 weeks of therapy. We concluded that these results support the feasibility and usefulness of N-of-1 RCT in rheumatology practice.

Adult↗
PubMed1990

The n-of-1 randomized controlled trial: clinical usefulness. Our three-year experience.

OBJECTIVE: To review the feasibility and effectiveness of n-of-1 randomized controlled trials (n-of-1 trials) in clinical practice. DESIGN: Individual trials were double-blind, randomized, multiple crossover trials. The impact of n-of-1 trials was determined by eliciting physicians' plans of management and confidence in those plans before and after each trial. SETTING: Referral service doing n-of-1 trials at the requests of community and academic physicians. OBJECT of ANALYSIS: All trials were planned, started, and completed by the n-of-1 service. MEASURES OF OUTCOME: The proportion of planned n-of-1 trials that were completed and the proportion that provided a definite clinical or statistical answer. A definite clinical answer was achieved if an n-of-1 trial resulted in a high level of physician's confidence in the management plan. Specific criteria were developed for classifying an n-of-1 trial as providing a definite statistical answer. MAIN RESULTS: Seventy-three n-of-1 trials were planned in various clinical situations. Of 70 n-of-1 trials begun, 57 were completed. The reasons for not completing n-of-1 trials were patients' or physicians' noncompliance or patients' concurrent illness. Of 57 n-of-1 trials completed, 50 provided a definite clinical or statistical answer. In 15 trials (39% of trials in which appropriate data were available), the results prompted physicians to change their "prior to the trial" plan of management (in 11 trials, the physicians stopped the drug therapy that they had planned to continue indefinitely). CONCLUSION: We interpret the results as supporting the feasibility and usefulness of n-of-1 trials in clinical practice.

Adult↗
PubMed1990

To what extent do congestive heart failure patients in sinus rhythm benefit from digoxin therapy? A systematic overview and meta-analysis.

PURPOSE: To reappraise the effectiveness of digoxin for the treatment of congestive heart failure (CHF) in patients with sinus rhythm in light of data from recently published randomized controlled trials and to quantitatively assess its usefulness. STUDY IDENTIFICATION: Computerized searches of the MEDLINE database were performed, and the reference list of each retrieved article was reviewed. STUDY SELECTION: Review of more than 360 citations and the reference lists of 19 review articles and 61 potentially relevant articles revealed seven double-blind randomized controlled trials that were included in this overview. DATA EXTRACTION: Study quality was assessed and descriptive information concerning the study populations, the specific interventions, and clinically relevant outcome measurements was extracted. RESULTS OF DATA SYNTHESIS: The common odds ratio for CHF deterioration while receiving digoxin versus placebo was 0.28, with a 95% confidence interval of 0.16 to 0.49. Predictors of digoxin benefit included presence of a third heart sound and the severity and duration of CHF. CONCLUSION: Data from seven trials of high methodologic quality suggest that, on average, one out of nine patients with CHF and sinus rhythm derive a clinically important benefit from digoxin (with a 95% confidence interval of 1/33 to 1/5).

Digoxin↗
PubMed1990

N of 1 randomized trials for investigating new drugs.

Presently, in the process of new drug development, large sample parallel group randomized trials are often begun without the detailed knowledge of optimal dose, most responsive patient group, and optimal outcomes which would be desirable. We propose that randomized trials in individual subjects (N of 1 RCTs) could be used to elucidate these issues at an early stage of drug development. In appropriate conditions N of 1 RCTs can be used to define the rapidity with which a drug begins and ceases its clinical action, the likely range of the optimal drug dose, and the optimal outcomes on which subsequent trials should focus. N of 1 RCTs can also generate initial estimates of the proportion of patients who respond to a new agent and for determining sample size, inclusion criteria, and dosage regimen(s) for subsequent parallel group trials. We provide an example of 14 N of 1 RCTs of amitriptyline in fibrositis that illustrate the ways in which N of 1 RCTs can elucidate these issues. The multiple uses of N of 1 RCTs suggest that the method has immense potential for use in the early phases of drug development programs.

Amitriptyline↗
PubMed1990

A comparison of seven-point and visual analogue scales. Data from a randomized trial.

Many controlled trials rely on subjective measures of symptoms or quality of life as primary outcomes. The relative merits of different response options for these instruments is an important issue. Therefore, we compared the responsiveness and validity of seven-point versus visual analogue scales (VAS) in a questionnaire measuring quality of life in chronic heart failure in a double-masked crossover trial of digoxin versus placebo. The VAS and seven-point scale versions of the questionnaire were administered to 20 patients during 7 weeks on digoxin and 7 weeks on placebo. The order of administration of the questionnaires was determined by random allocation. The ability of the two methods to distinguish digoxin and placebo, and their correlation with other measures, were comparable. We conclude that the two methods of presenting response options show comparable responsiveness and validity in a randomized trial setting. The ease of administration and interpretation of the seven-point scale recommend its use.

Humans↗
PubMed1990

Randomized trials in the study of antihypertensive drugs.

Heterogeneity in response to antihypertensive drugs can be addressed by randomized trials in individual subjects. In such a trial a patient receives pairs of treatment periods (one period of each pair active drug, one matched placebo, in random order); patient and clinician are blinded to allocation, and treatment targets are monitored. These trials can optimize antihypertensive therapy in clinical practice and facilitate the investigation of new drugs and the study of pathophysiology. Such trials also have potential in helping decide whether common, nonspecific symptoms reported by patients are really drug related.

Antihypertensive Agents↗
PubMed1989

Why different trials on digitalis give conflicting data.

Taking a careful look at each of the outcomes measured in randomized, controlled trials of digoxin suggest that discrepancies in results may be more apparent than real. Digoxin does work, but clinically important benefit is restricted to a relatively small proportion of congestive heart failure (CHF) patients. The play of chance, the dose of digoxin used, and the severity of heart failure in patients enrolled in the studies are other factors that may explain the variability in results that were observed. A systematic examination of the sort undertaken here is likely to help resolve apparent difference in outcomes of clinical trials of new (and old) therapies in CHF patients.

Digoxin↗
PubMed1989

Measurement of health status. Ascertaining the minimal clinically important difference.

In recent years quality of life instruments have been featured as primary outcomes in many randomized trials. One of the challenges facing the investigator using such measures is determining the significance of any differences observed, and communicating that significance to clinicians who will be applying the trial results. We have developed an approach to elucidating the significance of changes in score in quality of life instruments by comparing them to global ratings of change. Using this approach we have established a plausible range within which the minimal clinically important difference (MCID) falls. In three studies in which instruments measuring dyspnea, fatigue, and emotional function in patients with chronic heart and lung disease were applied the MCID was represented by mean change in score of approximately 0.5 per item, when responses were presented on a seven point Likert scale. Furthermore, we have established ranges for changes in questionnaire scores that correspond to moderate and large changes in the domains of interest. This information will be useful in interpreting questionnaire scores, both in individuals and in groups of patients participating in controlled trials, and in the planning of new trials.

Activities of Daily Living↗
PubMed1989

Research methods for obtaining primary evidence.

The use of new therapeutic and diagnostic technologies has become commonplace in modern medical practice. To avoid both clinical disappointment and the waste of money, health, and lives, the introduction of these technologies will have to be based on evidence that these technologies will do more good than harm. The evidence supporting their use should be derived using research methods designed to deal with placebo effects, confounders, and biases. Some of these methods, and the rationale for their use, are discussed in this article. Although the value of evidence derived from randomized controlled trials is stressed, the importance of reviewing critically the methodological details of such trials and interpreting their results with caution is emphasized. The benefits and risks of relying on case-control and cohort studies are reviewed.

Bias↗