Evidence Report/Technology Assessment: Number 8
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Under its Evidence-based Practice Program, the Agency for Health Care Policy and Research (AHCPR) is developing scientific information for other agencies and organizations on which to base clinical guidelines, performance measures, and other quality improvement tools. Contractor institutions review all relevant scientific literature on assigned clinical care topics and produce evidence reports and technology assessments, conduct research on methodologies and the effectiveness of their implementation, and participate in technical assistance activities.
Overview / Reporting the Evidence / Methodology / Findings / Future Research / Availability of Full Report
This study was conducted by ECRI investigators to evaluate methods for diagnosing and treating swallowing disorders (dysphagia) in older Americans. The study had two primary goals: first, to examine the efficacy and clinical value of methods for diagnosing and treating swallowing disorders in older Americans with neurologic disorders; and second, to suggest important directions for future dysphagia research.
For the first goal, ECRI investigators concentrated on the broad area of speech-language pathology and, more specifically, on the diagnostic and treatment methodologies associated with the services provided by speech-language pathologists, focusing on oropharyngeal dysphagia and not esophageal dysphagia.
The available evidence further defined the scope of this study. The ECRI investigators originally attempted to address all of the neurologic disorders that affect older Americans and that commonly cause dysphagia. However, because most cases of dysphagia occur in stroke patients, most of the published data have focused on stroke victims. Thus, the focus of this report is on the diagnosis and treatment of dysphagia in a patient population that contains some patients who may spontaneously recover their swallowing function, and not on patients with neurodegenerative diseases whose swallowing function may progressively worsen.
For the second goal of the report, investigators present their recommendations for conducting a clinical trial. To help strengthen their recommendations, they comment throughout the report on the strengths and weaknesses of available studies. In this comparative approach, two major themes become apparent.
The first theme is that in many studies on diagnostic tests for dysphagia, there is a relationship between diagnosis and treatment that makes it impossible to distinguish between the true and false positive results of these tests in terms of predicting risk for pneumonia (by detection of aspiration). The only ethical way to compare diagnostic tests is to compare the patient outcomes of prevention of pneumonia following diagnosis and treatment, not the sensitivities and specificities for detection of pneumonia risk. In such comparisons of pneumonia outcomes, it must be ensured that patients given different diagnostic tests receive similar treatment.
The second theme is based on statistical power. Virtually all of the studies that attempted to compare the efficacy of diagnostic tests or treatments were too small. In general, they contained no more than 150 patients each—when 10 times this number is needed to obtain statistically significant differences.
Patients with dysphagia are often at increased risk for developing other medical conditions. For example, oropharyngeal dysphagia can be quite serious if it results in leakage of food, drink, or oral secretions into the lungs (aspiration) and can lead to aspiration pneumonia (sometimes fatal for older Americans). Patients with dysphagia also may be unable to eat and drink enough to maintain their own body weight. Malnutrition and/or dehydration may result, weakening the immune system and leaving patients, particularly older Americans, susceptible to other illnesses.
Information on the incidence and prevalence of dysphagia is scarce. Using calculations based on existing data, ECRI investigators estimated that approximately 300,000 to 600,000 people each year are affected by dysphagia resulting from neurologic disorders, and approximately 51,000 of these cases are from neurologic disorders other than stroke. Based on data from the stroke literature, it is estimated that approximately 43 to 54 percent of stroke patients with dysphagia experience aspiration, approximately 37 percent of these patients will develop pneumonia, and 3.8 percent of these patients will die of pneumonia if they are not part of a dysphagia diagnosis and treatment program. Also, up to 48 percent of all acute-care stroke patients with dysphagia will experience malnutrition.
Formal diagnosis of oropharyngeal dysphagia is usually carried out using a full bedside exam or videofluoroscopy (also called the modified barium swallow, or MBS), but other diagnostic methods are available, including several variants of fiberoptic endoscopy. Common treatments include both noninvasive therapies (such as diet modification and swallow therapy) and invasive therapies, such as percutaneous endoscopic gastrostomy (PEG). PEG is the most common invasive intervention for neurogenic oropharyngeal dysphagia, and is often used when dysphagia and aspiration are serious enough to be life threatening.
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Reporting the Evidence
Four key questions are addressed in the full report:
- How does diagnosis of dysphagia or aspiration affect the subsequent course of treatment and outcomes?
- What are the appropriate indications for having patients diagnosed using a full bedside exam, the modified barium swallow, fiberoptic endoscopy, or another instrumented exam?
- Is there any evidence that one diagnostic technology provides more useful information than another?
- When is noninvasive swallow therapy appropriate? Does it work particularly well or particularly poorly in any particular patient population? What can the evidence tell us about this therapy? Are feeding tubes useful, or a last resort that might be avoided for some patients by dysphagia diagnosis and therapy?
Considerable effort was devoted to determining the relative efficacy of different diagnostic tests. Of primary interest in the assessment were the efficacies of the commonly used instrumented and noninstrumented technologies. Instrumented tests include the videofluoroscopic swallow study (VFSS), and its primary variant, the modified barium swallow (MBS). Investigators in dysphagia research consider the MBS the "gold standard" against which to compare new diagnostic technologies. Also, of particular interest were two newer technologies: the fiberoptic endoscopic exam of swallowing (FEES), and the fiberoptic endoscopic exam of swallowing with sensory testing (FEESST).
The noninstrumented diagnostic test of primary interest is the full bedside exam (BSE), a formal, structured test that often incorporates a questionnaire, noninvasive oral-pharyngeal physical examination, and functional swallowing tests. There are many variants of this diagnostic test, which sometimes is only a simple water swallow test. To avoid confusion of this exam with a preliminary bedside exam, which also has many variants, investigators refer to the formal, structured exam as the full bedside exam.
The focus of analysis of these diagnostic tests, which is dictated by the preponderance of the literature, is on their ability to predict aspiration and aspiration pneumonia. The investigators were, however, interested in all patient outcomes, including mortality and any morbidity directly associated with dysphagia or aspiration.
Investigators focused primarily on noninvasive treatments; however, minimally invasive therapy (i.e., percutaneous endoscopic gastrostomy [PEG]), was also considered because some patients may have severe dysphagia that precludes oral feeding. There are two basic categories of noninvasive treatment—swallow therapy and diet modification. Within the category of swallow therapy, there are three basic subcategories: compensatory techniques (that teach the patient postural maneuvers to compensate for swallowing difficulty; indirect swallow therapy (which teaches the patient exercises to strengthen impaired or weakened muscles); and direct swallow therapy (in which patients are taught exercises to perform during the swallow). Diet modification, individualized to the patient's needs, is sometimes used if the patient aspirates only certain substances while swallowing.
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Twenty-three electronic databases were used to retrieve clinical trials for analysis, along with review articles to gauge current opinion in the field. The databases used included Cancerlit, CATLINE, Current Contents, DIRLINE, MEDLINE, and HealthSTAR (for a complete listing of the electronic databases, see the full report).
The search strategies employed a large number of free-text keywords, as well as controlled vocabulary terms, under the following categories: Diagnostic Modalities, Disorder, Epidemiology, Etiology, Treatment, and Miscellaneous.
In addition, World Wide Web searches were conducted using various search engines. Searches focused on the areas of dysphagia, aging, neurologic disorders, and pneumonia. Twenty-three Web pages were accessed for this project.
Hand searches of journal and nonjournal literature included searching Current Contents—Clinical Medicine on a weekly basis as well as more than 1,600 journals and supplements. In addition, investigators conducted a hand search of the Cumulated Index Medicus for the terms deglutition, deglutition disorders, speech therapy, and speech disorders. Nonjournal publications and conference proceedings from professional organizations, private agencies, and government agencies were also screened.
Other mechanisms. Other mechanisms used to retrieve additional information included review of bibliographies/reference lists from peer-reviewed journals and literature produced by local government agencies, private organizations, educational facilities, corporations, etc., that do not commonly appear in the published peer-reviewed journal literature. Published and unpublished information was also solicited from a panel of experts in the field.
Information retrieved. The use of these search methodologies, as well as personal communications from several technical experts, resulted in the identification of 4,485 journal articles, book chapters, manuscripts, monographs, Web pages, personal communications, and other miscellaneous items. Two primary analysts blinded from each other independently reviewed the titles and abstracts of all electronic search results, and ordered articles using the following inclusion criteria.
- Ten or more subjects.
- Human studies.
- In vivo studies.
- English language studies.
A total of 1,808 articles were retrieved, including 1,467 clinical trials, 183 review articles, and material from 9 World Wide Web sites. In addition, the investigators obtained 32 unpublished articles and 28 personal communications.
They adopted a flexible scheme for assessing the quality of the literature, which consists of several types of study designs. Among these designs were randomized controlled trials (RCTs), historical prospective case series, case controlled studies, and case series. In general, they considered data from RCTs to be more reliable than data from other study designs, and considered data from historical prospective case series to be of the second highest level of reliability. They did not, however, rigidly adhere to this scheme because some RCTs and some case studies had flaws serious enough to render the results unreliable.
Because of the scarcity of controlled trials on the effectiveness of dysphagia diagnosis and treatment programs or of treatment per se, a standard meta-analysis that used improvement in patient outcomes as the dependent variable was not possible. Nevertheless, the analytical approach used throughout this evidence report is heavily quantitative. (For details on statistical and meta-analyses performed, see the full report. The appendices and supplemental analyses provided in the evidence report contain many other original calculations.)
The need to perform a substantial number of original calculations is a reflection of the relatively poor reporting and poor quality of the literature related to this evidence report. Without these original calculations, it would have been difficult to reach meaningful conclusions. Investigators recognized, however, that their attempt to come to conclusions based on studies of relatively poor design is uncommon. However, it must also be recognized that many of today's pressing health care questions must be answered in the absence of strong evidence, and that failure to do so imposes serious limitations on the practical applications of evidence-based medicine.
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These findings are applicable only to acute-care stroke patients.
Findings Related to Question Number 1
How does diagnosis of dysphagia or aspiration affect the subsequent course of treatment and outcomes?
- Current evidence suggests that a systematic program of diagnosis and treatment of dysphagia in an acute stroke management plan may yield dramatic reductions in pneumonia rates. Because these data are derived from historically controlled studies rather than randomized controlled trials, the exact magnitude of this reduction in pneumonia is difficult to determine. However, because the effects observed in these studies are substantial, it would be imprudent to ignore them, and these results must be taken as evidence of efficacy of these programs.
- Despite the sparse available data, it seems prudent to include dysphagia-specific management with formal diagnosis and treatment as part of the standard protocol of stroke management in the acute care setting. Also, these programs appear to have a minimal potential to harm patients.
Findings Related to Question Number 2
What are the appropriate indications for having patients diagnosed using a full bedside exam, modified barium swallow, fiberoptic endoscopy, or another instrumented exam?
- The risk for developing aspiration pneumonia cannot be accurately predicted from any single clinical sign or symptom. There is a clear-cut need to optimize a brief initial exam that accurately detects patients with possible unsafe swallows, and who therefore need more extensive testing. An optimum combination of signs and symptoms for such an initial test has not been determined, and further research is needed.
Findings Related to Question Number 3
Is there any evidence that one diagnostic technology provides more useful information than another?
- Neither videofluoroscopy nor fiberoptic endoscopy can serve as a perfect "gold standard" for detection of aspiration, because each yields false negative and false positive results. Without a third, better reference standard, these two methods to detect aspiration cannot be compared.
- Full bedside exams can have sensitivities for aspiration near 80 percent—with specificities near 70 percent. Epidemiologic evidence indicates that about half of the patients with dysphagia who aspirate do so silently (without a cough). These two points, taken with the very low pneumonia rates observed in dysphagia management programs that used full bedside exams, indicate that these exams are capable of detecting most aspiration, even silent aspiration.
- The ability of the full bedside exam to detect silent aspiration should be optimized in future research. Whether it can be conclusively stated that an optimized full bedside exam can entirely replace imaging exams such as videofluoroscopy and fiberoptic endoscopy depends partly on the degree to which the bedside exam is optimized, and partly on the additional benefit that results from the direct internal visual information provided by the imaging exams.
- The studies that attempted to predict pneumonia from the results of a diagnostic test were distorted by intervening treatment that prevented some pneumonia from occurring. This distortion cannot be circumvented by withholding treatment, because this would be unethical. This means that the only ethical method of comparing various diagnostic tests is to conduct controlled trials that measure the combined effects of diagnosis and treatment on the rate of pneumonia and/or other patient outcomes.
- Another reason why current studies do not conclusively show the superiority of any diagnostic test is because they are too small.
- The differences in the ability of various diagnostic tests to predict pneumonia are likely to be small because the two studies using bedside exams were so successful (nearly all pneumonia was prevented). It is difficult to obtain a statistically significant improvement on their results.
- Currently available data do not allow one to determine the degree to which (or even whether) the use of videofluoroscopy or other instrumented exams leads to lower pneumonia rates than does the full bedside exam. However, it is entirely reasonable to expect that their use might lead to lower pneumonia rates because instrumented exams provide more information than the full bedside exam. Research on this issue is needed.
- Because there are no data that satisfactorily compare the abilities of the full bedside exam and videofluoroscopy to prevent pneumonia, ECRI investigators constructed two clinical value models to address this issue. These models assume that patients will receive a preliminary bedside assessment, and that one result of this assessment is that no more than 39 percent of patients will be referred for further evaluation. The clinical value analysis suggests that dysphagia diagnosis and treatment programs that use the bedside exam would either save money or have very little net cost if they reduced pneumonia rates by amounts similar to those obtained in certain published studies.
- Some evidence suggests that dysphagia patients who aspirate have about a 50 percent greater risk of developing aspiration pneumonia than dysphagia patients who do not aspirate during videofluoroscopy exams. However, since other patient characteristics may play equal or greater roles in causing pneumonia, aspiration should not be considered a definitive marker for the patient outcomes of pneumonia.
- Large randomized controlled trials measuring patient outcomes such as aspiration pneumonia, malnutrition, dehydration, and quality of life are needed to determine the comparative effectiveness of the various dysphagia diagnostic and treatment methods. These trials should enroll patients in reasonably homogeneous disease groups, or stratify patients into appropriate subsets. The full report includes detailed suggestions for such studies, along with some estimates of the number of patients needed.
Findings Related to Question Number 4
When is noninvasive swallow therapy appropriate? Does it work particularly well or particularly poorly in any particular patient population? What can the evidence tell us about this therapy? Are feeding tubes useful or a last resort that might be avoided for some patients by dysphagia diagnosis and therapy?
- Most study designs used in the evaluation of noninvasive therapy have made it impossible to assess the effectiveness of individual treatments.
- The results of a single RCT supported the use of a soft mechanical diet over a pureed diet for preventing aspiration pneumonia in stroke patients with dysphagia who had a history of aspiration pneumonia.
- A single RCT reported inconclusive results about the effect of treatment intensity level on patient outcomes. The statistical power of this trial may have been too low to detect the appropriate differences.
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Research in the areas of diagnosis and treatment of dysphagia in neurologic patients has thus far largely focused on stroke patients, who comprise the largest proportion of patients with dysphagia, and has mostly been conducted as case reports and small case series. Only a few randomized trials have been attempted, and a few additional studies included historical controls. Future research is needed on all aspects of dysphagia, and some suggestions for study design and methodology are outlined below.
- Results from patients whose dysphagia is caused by different diseases, disorders, or conditions should not be combined. When they are combined, it is probable that the results of a study will be influenced as much, if not more, by patient characteristics as by treatment.
- Patient outcomes should be analyzed by stage of disease. For example, combining results obtained from patients soon after a stroke and results obtained from patients weeks or months after a stroke is not appropriate. Here, too, patient characteristics can have an undue influence on the overall results of a study.
- Case series provide extremely limited information. Randomized controlled trials are preferable but, where they are not ethical, controlled studies of other design should be employed. Randomization of patients to receive diagnosis by different methods is ethical because no single diagnostic has yet been proven superior to any other. This is not necessarily the case in the treatment of dysphagia, where randomizing patients to an untreated group may be unethical. If a control group is deemed unethical, the comparison group should be a similar patient population receiving a different treatment or different level of treatment.
- Studies should focus on assessing overall dysphagia management programs because of the difficulty of separating diagnosis and treatment in this field.
- Researchers should specify the kind of pneumonia that they are studying. Results from patients with aspiration pneumonia should be reported separately from results from patients with pneumonia due to other causes (understanding, however, that the distinction between these two diagnoses is generally a hypothesis, rather than a certainty, due to difficulty in ascertaining the etiology of pneumonia).
- More study of whether dysphagia causes malnutrition and/or dehydration is required. If such a causal relationship is confirmed, investigators should begin to report these measures as outcomes.
- Researchers need to report the specific causes of patient mortality to make it clear whether a patient died from complications due to dysphagia or from the primary disease.
- Additional information on the quality of life of patients with dysphagia, and on the degree to which treatment of dysphagia improves quality of life, is needed. Quality of life should be measured using standard methods.
- Studies on feeding tube efficacy should separately report results obtained in patients with dysphagia, and not combine such results with feeding tubes placed for other reasons.
- Patients should be followed for longer times than those used in available studies. Followup times should be standardized within any give study so that all patients are followed for approximately the same length of time.
- Investigators comparing two diagnostic methodologies should ensure that patients in different groups do not receive different treatment, or comparisons between the two are no longer useful.
Because of the shortcomings in available research, a multi-armed, randomized trial to evaluate the efficacy of different dysphagia management programs is needed. The primary outcome of this trial should be aspiration pneumonia rates, but other outcomes, such as those related to malnutrition and dehydration, should also be measured. The trial can consist of two to four groups, but for the purposes of illustration, it will be described here as if it consisted of four.
In this trial, the control group would consist of patients randomized to receive a full bedside examination alone; the three experimental groups would consist of patients randomized to receive the full bedside examination plus one of three possible instrumented examinations. Readers of the instrumented examinations would be blinded to the results of the bedside exam. The results of the bedside exam would be used to determine whether combinations of signs and symptoms predicted aspiration pneumonia and other outcomes. Treatment choices in the group that received only the bedside exam and in the groups that received the instrumented exams would be appropriately based on each of these exams.
The results of this trial could be extended using decision analysis and clinical value analysis. Only if data from such a trial are available will it be possible to conclude definitively whether one exam is superior to another in reducing the incidence of aspiration pneumonia and/or other adverse outcomes.
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Availability of the Full Report
The full evidence report from which this summary was taken was prepared by ECRI, an AHCPR Evidence-based Practice Center located in Plymouth Meeting, Pennsylvania. The report was developed under contract No. 290-97-0020.
The Evidence Report is available online at the National Library of Medicine Bookshelf. Print copies are no longer available.
AHCPR Publication Number 99-E023
Current as of March 1999