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Biomedical subjects

D L Kent

Publications and source records attributed to D L Kent.

At least 19 recordsLinked to original sources
PubMed1999

MR contrast media in neuroimaging: a critical review of the literature.

BACKGROUND AND PURPOSE: MR contrast media are commonly used but do not have evidence-based guidelines for their application. This investigation seeks to define specific methodological problems in the MR contrast media literature and to suggest guidelines for an improved study design. METHODS: To evaluate the reported clinical efficacy of MR contrast media in neuroimaging, we performed a critical review of the literature. From 728 clinical studies retrieved via MEDLINE, we identified 108 articles that evaluated contrast media efficacy for a minimum of 20 patients per study. The articles were randomly assigned to four readers (a fifth reader reviewed all of the articles) who were blinded to article titles, authors, institutions, and journals of publication. The readers applied objective, well-established methodological criteria to assign each article a rating of A, B, C, or D. RESULTS: One hundred one of 108 articles received a D rating, six received a C rating, and one received a B rating. In general, the Methods sections of the evaluated articles did not contain details that would allow the reader to calculate reliable measures of diagnostic accuracy, such as sensitivity and specificity. Specifically, a common problem was failure to establish and uniformly apply an acceptable standard of reference. In addition, images were not always interpreted independently from the reference standard. Radiologists and clinicians need to determine the applicability of any published study to their own practices. Unfortunately, the studies we reviewed commonly lacked clear descriptions of patient demographics, the spectrum of symptomatology, and the procedure for assembling the study cohort. Finally, small sample sizes with inadequate controls were presented in almost all of the articles. CONCLUSION: Although MR contrast media are widely used and play an essential role in lesion detection and confidence of interpretation, no rigorous studies exist to establish valid sensitivity and specificity estimates for their application. On the basis of this review, we herein describe basic methods to document improvements in technology. Such studies are essential to devise measures of diagnostic accuracy, which can form the basis for further studies that will assess diagnostic and therapeutic impact and, ultimately, patient outcomes.

Cohort Studies↗
PubMed1994

Designing studies of diagnostic tests for low back pain or radiculopathy.

New diagnostic tests for the evaluation of patients with low back pain are constantly emerging, but are often not completely evaluated before they become used. Many published studies have a number of biases that tend to exaggerate the estimated accuracy of a diagnostic test. Several key study design features should be considered in such studies: independent comparison of the diagnostic test results with an appropriate "gold standard"; blinded assessment of the new test and the gold standard or competing tests; the reproducibility of interpretation of the test being examined; and the sensitivity and specificity of the test for the final gold standard diagnosis. In addition, evaluations of test accuracy should include patients with a wide spectrum of illness from mild to severe, and the study setting and patient characteristics should be described in detail. Finally, the contribution of a diagnostic test to the overall validity of a full group or sequence of tests should be considered, and, ideally, the effect of the test on actual patient outcomes should be determined.

Evaluation Studies as Topic↗
PubMed1994

The clinical efficacy of magnetic resonance imaging in neuroimaging.

PURPOSE: To assess the clinical efficacy of magnetic resonance imaging (MRI) for neuroimaging and to provide guidelines for clinical practice. STUDY SELECTION: After a comprehensive literature search, studies of the diagnostic accuracy of MRI alone or compared with other tests and of any impact on therapeutic choices or patient outcomes were reviewed by independent readers, followed by discussion to reach consensus conclusions. DATA EXTRACTION: Of 3125 citations retrieved, 156 studies with original data could be rated according to methodologic criteria for study design. One article contributed grade A quality information about diagnostic accuracy, 28 were graded B or C, and 113 were graded D. One randomized trial and 2 comparison studies contributed grade B or C information about the impact on therapeutic choices. Only 2 studies surveyed health status before and after magnetic resonance scanning. RESULTS: For most abnormalities, the sensitivity of MRI is equal to or better than competing technologies. Magnetic resonance imaging shows greater contrast and detail than computed tomography (CT) but also shows more clinically silent abnormalities or incidental findings. A few studies found a modest impact on therapeutic choices but no impact on quality of life or disability. Costs for MRI are high. Computed tomography is sufficient for initial diagnosis of most mass lesions or intracranial hemorrhages requiring immediate intervention. Magnetic resonance imaging is more accurate in the temporal lobes, posterior fossa, brainstem, and spinal cord. For lumbar radiculopathy, MRI and plain spinal CT are as accurate as post-myelographic CT and are less invasive. The role of magnetic resonance angiography for carotid artery stenosis is being studied. CONCLUSIONS: Although suggestions for appropriate use of MRI in clinical practice can be made, the supporting evidence in published studies is weak. Firm guidelines for appropriate use of MRI should be based on further clinical research using more rigorous methods.

Angiography↗
PubMed1994

A computerized intervention to improve timing of outpatient follow-up: a multicenter randomized trial in patients treated with warfarin. National Consortium of Anticoagulation Clinics.

OBJECTIVE: To evaluate a computerized scheduling model that employs nonlinear optimization to recommend optimal follow-up intervals for patients taking warfarin. DESIGN: Randomized trial. SETTING: 5 anticoagulation clinics. PATIENTS/PARTICIPANTS: 620 patients expected to receive warfarin for > or = 6 weeks. INTERVENTIONS: Computer-generated recommendations for scheduling the next visit were presented to or withheld from practitioners. MEASUREMENTS AND MAIN RESULTS: The main outcome measures were the follow-up interval scheduled by the provider, the interval at which the patient actually returned to clinic, and the quality of anticoagulation control (computed as the absolute difference between the measured and target prothrombin times [PTRs] or international normalized ratios [INRs]). Follow-up intervals scheduled for the patients whose practitioners received computer-generated recommendations were significantly longer than those for control patients (mean, 4.4 vs 3.5 weeks, p < 0.001), despite the fact that the practitioners modified the suggested return interval by > 1 week on 40% of the visits. The interval at which the intervention group actually returned to clinic was also longer (mean, 4.4 vs 4.1 weeks, p < 0.05), even though the control patients tended to return at longer intervals than were scheduled by their practitioners. Control of anticoagulation was nearly the same among experimental and control patients. Life-threatening complications occurred in the care of three experimental patients and one control patient, while other serious complications occurred in the care of 16 experimental patients and 17 control patients. CONCLUSIONS: Recommendations based on nonlinear optimization prompted clinicians to schedule less frequent follow-up for patients taking warfarin, with no deterioration in anticoagulation control. This approach to scheduling can potentially reduce utilization while maintaining quality of care for patients who require long-term monitoring.

Appointments and Schedules↗
PubMed1994

Toward a peer review process for medical decision analysis models.

This paper presents a framework for a peer review process for medical decision analysis models. This framework is based on the collective experience of the members of the Inter-PORT Decision Modeling work group, a team of decision analysis experts comprising members from each of the Patient Outcomes Research Teams (PORTs), sponsored by the Agency for Health Care Policy and Research. Important general principles of correct model structure include choice of model type, perspective of the analysis, choice of utility scheme and identification of strategies that should be included and events that should be modeled. In addition, a set of rules for correct decision model structure may help to identify common errors. Although not necessarily exhaustive, this scheme provides an approach by which a reviewer may judge the adequacy of a decision model presented for publication or as the basis for a health policy.

Decision Support Techniques↗
PubMed1993

Variation in the rate of cervical spine surgery in Washington State.

Lack of consensus about the treatment of low back pain is reflected by wide regional variations in lumbar spine surgery rates. Neck pain may be as common as low back pain, but there has been no similar evaluation of regional variation for the surgical treatment of neck pain. This report examines the geographic variation and temporal trends in the rate of cervical spine surgery in Washington state from 1986 through 1989. Using diagnosis and procedure codes from the International Classification of Diseases (ICD-9 CM), the authors retrospectively identified cervical spine surgery cases from a statewide hospital discharge registry for Washington. After excluding cases associated with trauma, infection, or malignancy, 5,173 incident cervical spine surgery cases were analyzed. Cervical spine surgery was performed at approximately 25% the rate of lumbar spine surgery, and from 1986 to 1989, the age- and gender-adjusted rate increased 20%. Small area analysis demonstrated a sevenfold variation among counties in the rate of cervical spine surgery (P < 0.001), with variation of fourfold to 13-fold for specific surgical procedures. These data demonstrate that cervical spine surgery for neck pain is an increasingly common procedure with wide geographic variability. Rational treatment of neck pain requires further definition of indications for cervical spine surgery, preferably based on firm data concerning the outcomes of surgical and nonsurgical care.

Cervical Vertebrae↗
PubMed1993

Prognosis of mechanically ventilated patients.

In this Department of Veterans Affairs cooperative study, we examined predictors of in-hospital and 1-year mortality of 612 mechanically ventilated patients from 6 medical intensive care units in a retrospective cohort design. The outcome variable was vital status at hospital discharge and after 1 year. The results showed that 97% of patients were men, the mean age was 63 +/- 11 years (SD), and hospital mortality was 64% (95% confidence interval, 60% to 68%). Within the next year, an additional 38% of hospital survivors died, for a total 1-year mortality of 77% (95% confidence interval, 73% to 80%). Hospital and 1-year mortality, respectively, for patients older than 70 years was 76% and 94%, for those with serum albumin levels below 20 grams per liter it was 92% and 96%, for those with an Acute Physiology and Chronic Health Evaluation II (APACHE II) score greater than 35 it was 91% and 98%, and for patients who were being mechanically ventilated after cardiopulmonary resuscitation it was 86% and 90%. The mortality ratio (actual mortality versus APACHE II-predicted mortality) was 1.15. Conclusions are that patient age, APACHE II score, serum albumin levels, or the use of cardiopulmonary resuscitation may identify a subset of mechanically ventilated veterans for whom mechanical ventilation provides little or no benefit.

Aged↗
PubMed1992

Disease, level of impact, and quality of research methods. Three dimensions of clinical efficacy assessment applied to magnetic resonance imaging.

Assessment of the clinical efficacy of diagnostic imaging technologies frequently involves reviews of published research. Reports may be classified in three dimensions; by disease, by type of assessment, and by the quality of research methods. The disease dimension describes the condition or conditions shown by an imaging technique. The assessment dimension spans five levels: technical capacity, diagnostic accuracy, diagnostic impacts, therapeutic impacts, and patient outcome impacts. The methods quality dimension can be expressed as four levels: excellent, good, fair or poor. An important interaction exists: the level of efficacy addressed by a research project dictates which methodologic procedures are important. For example, randomization is important only when a research report addresses the levels of therapeutic and patient outcome impacts. The authors suggest that classification of studies according to the three preceding dimensions maps the breadth (across diseases), depth (across levels of clinical efficacy), and quality of the assessment of complex imaging technologies. Such a map should help participants in technology assessment define the progress they have made. The classification strategy as applied to the clinical efficacy assessment of magnetic resonance imaging (MRI) for neuroradiology is illustrated.

Humans↗
PubMed1992

Diagnosis of lumbar spinal stenosis in adults: a metaanalysis of the accuracy of CT, MR, and myelography.

We undertook a literature synthesis of CT, MR, and myelographic studies to evaluate what is known about the diagnostic accuracy of these imaging tests for the diagnosis of lumbar spinal stenosis in adults without prior surgery. From 116 possibly relevant studies, we reviewed 14 articles that included cases of spinal stenosis with a reference standard other than the imaging tests of interest. Of the studies we reviewed, two involved only MR, nine only CT, and three used both; six studies included myelography. Rating categories of A, B, C, or D were assigned for the quality of research methods used to estimate diagnostic accuracy. All studies received either a C or D rating. Common methodologic problems were failure to assemble a representative cohort for study, small sample size, and failure to maintain independence between image readings and reference standards. Sensitivity ranged from 0.81 to 0.97 for MR, from 0.70 to 1.0 for CT, and from 0.67 to 0.78 myelography. Studies varied greatly in case selection, definition of test and disease categories, and geographic locale, so no pooled estimates could be derived. In asymptomatic patients, abnormal findings appeared on CT or MR in 4-28% of cases and were more common in the elderly. Published studies of the value of CT and MR for the diagnosis of lumbar stenosis lack methodologic rigor and do not permit strong conclusions about the relative diagnostic accuracies of these procedures. For the present, the choice between MR or CT depends on issues such as costs, reimbursements, access to equipment, skill of radiologists, and patient safety. Better studies will be needed to document claims for improvements in imaging accuracy as MR technologies evolve. These studies should emphasize larger sample sizes, more attention to research designs that avoid methodologic biases, and the contribution of imaging diagnoses to ultimate clinical outcome.

Evaluation Studies as Topic↗
PubMed1992

A prospective study of Staphylococcus aureus nasal colonization and intravenous therapy-related phlebitis.

BACKGROUND: Intravenous (IV) therapy-associated phlebitis is common, but its causes are ill defined. Some cases may be related to bacterial colonization of the skin surrounding the IV catheter, especially by Staphylococcus aureus. This prospective study examined the association of phlebitis with anterior nares S aureus carriage, as well as with other potential risk factors. METHODS: Selected demographic and clinical data and a nares culture were collected from patients on designated wards by us and from the IV therapy team at the time of initial IV catheter placement. Patients were followed up for signs and symptoms of phlebitis for the duration of the initial catheter's use and for up to two additional IV placements. Potential risk factors were compared for patients who developed phlebitis and those who did not by the Cox multivariate proportional hazards model. RESULTS: During 10 weeks, 273 men with a total of 416 catheter placements had fully evaluable data. Phlebitis occurred during 13.7% of the catheter placements. Nasal cultures yielded S aureus from 14.3% of the patients, but none of the IV team nurses. Surprisingly, S aureus nasal colonization was related (at borderline statistical significance) to a reduction in phlebitis risk. Location of the patient on a surgical ward, the presence of infection at any site, and a larger-gauge catheter were each significant independent risk factors for phlebitis. The highest risk of phlebitis appeared to have been within 12 to 24 hours of catheter placement. CONCLUSIONS: The primary finding of this study was that nasal colonization with S aureus did not increase the risk of developing IV catheter-associated phlebitis. Our rate of IV catheter-associated phlebitis was similar to that in other studies, but the factors predisposing to phlebitis differed somewhat from those in previous studies.

Catheterization, Peripheral↗
PubMed1992

The basics of decision analysis.

Historically, decision analysis (DA) arose from economics, psychology, and statistics. Medical and dental applications have developed over the past two decades. While decision psychology explores how people make their decisions, the DA process involves construction of a model and development of insights into the strengths and uncertainties about recommendations derived from analysis of model outputs. Uncertainties are represented as probabilities and values are assigned to desirable or adverse outcomes according to preferences expressed by the decision maker. The model unifies probabilities and values by calculation of the expected value for each decision choice. The decision maker can improve his or her insight into uncertainties in the model by conducting sensitivity analyses, and can take action based on this improved insight. The DA process is illustrated using the decision to take or skip influenza vaccination. People's decision making behavior for this problem has also been analyzed using methods from decision psychology. Distinctions between clinical DA and cost-effectiveness analysis are given, as are caveats about especially complicated subtopics in decision analysis for medical problems. In closing, opportunities for further study of decision analysis are presented.

Cost-Benefit Analysis↗
PubMed1991

Diagnostic accuracy and clinical utility of thermography for lumbar radiculopathy. A meta-analysis.

The role of thermography for diagnosing lumbar radiculopathy was evaluated by literature review and meta-analysis. From 81 relevant citations, 28 studies could be analyzed for diagnostic-accuracy data (sensitivity and specificity) and method. Diagnostic-accuracy data varied significantly between studies; therefore meaningful pooled summary statistics could not be reported. Twenty-seven studies had major methodologic flaws including biased test interpretations, faulty cohort assembly, poor clinical descriptions, and small sample size. The only study of reasonably high quality found no discriminant value for liquid-crystal thermography. The role of thermography remains unclear. Rigorous clinical research is required to establish its diagnostic accuracy and clinical utility. Thermography cannot be recommended currently for routine clinical use in evaluating low-back pain.

Back Pain↗
PubMed1990

Physician consent and researchers' access to patients.

Institutional review boards may require that researchers obtain permission from a patient's physician before initiating patient contact. We describe how this requirement affected a study of head injuries. Physicians denied study participation to 8% of 243 subjects; 9% of 126 physicians denied contact with at least one subject. Most physicians responded within ten days, although seven required more than a month to respond. Delays in reaching potential subjects compromise some clinical research protocols. Physicians may refuse permission for some patients, introducing selection biases. Our study did not detect such an effect, but investigators should be alert to such problems in their own research.

Adult↗
PubMed1989

The relevance of socioeconomic and health policy issues to clinical research. The case of MRI and neuroradiology.

Magnetic resonance imaging (MRI) is a high-cost, new technology with great potential for improving patient care. The lack of a coherent public policy for MRI, or its predecessor computed tomography (CT), has caused considerable problems. Lack of an enunciated public policy has led to inconsistent reimbursement and reimbursement levels that develop in haphazard ways. Furthermore, diffusion has been unpredictable and has led to geographical excesses and deficiencies. Technology assessments of MRI, although numerous, have used inconsistent criteria to rate MRI's clinical efficacy. The lack of methodologically sound studies of MRI severely hampered early evaluation. This article examines these problems and suggests that the medical profession take a stronger leadership role in developing policies for expensive, promising new diagnostic technologies. The profession should promote, demand, and perform rigorous clinical evaluations of new technologies, and help develop a consensus regarding the criteria for what constitutes a clinically valuable advance in diagnostic technology.

Costs and Cost Analysis↗
PubMed1988

Magnetic resonance imaging of the brain and spine. Is clinical efficacy established after the first decade?

STUDY OBJECTIVE: Evaluation of demonstrated clinical efficacy of magnetic resonance (MR) imaging in the central nervous system. DESIGN: Information synthesis of studies before January 1987. SETTING: Reports were classified by the level of clinical efficacy studied (technical capacity, diagnostic impacts, and therapeutic or patient outcome impacts) and were judged by the validity of their methods, especially avoidance of diagnosis review, test review, and work-up biases. MAIN RESULTS: Magnetic resonance imaging probably is superior to computed tomography for detection and characterization of posterior fossa lesions and spinal cord myelopathies, imaging in multiple sclerosis, detecting lesions in patients with refractory partial seizures, and detailed display for guiding complex therapy, as for brain tumors. In other diseases, the efficacy of MR imaging is similar to that of computed tomography (cerebrovascular, radiculopathy, and infection). Magnetic resonance imaging is less invasive than intrathecal or intravenous contrast-enhanced computed tomography and costs 20% to 300% more than computed tomography, although avoidance of hospital stays may offset some costs. Generally, the quality of MR images probably exceeds that of computed tomographic (CT) scans. However, published evidence does not show that the clinical efficacy of MR imaging is generally superior to that of existing imaging modalities such as computed tomography. Only six studies avoided major methodologic biases, and lower true-positive rates for MR imaging were reported in these studies than reported in multiply biased studies. Few studies of the potential of MR imaging for false-positive diagnosis have been done. CONCLUSIONS: Use of standards for quality of evidence leads to more conservative conclusions than those of reports describing the clinical potential of MR imaging. Some applications of MR imaging were confirmed by rigorous studies, whereas others were not well supported by reports free of methodologic biases. If the diagnostic alternative is invasive (for example, myelography and cisternography), MR imaging is preferred, but adequate diagnosis for many conditions (head trauma, simple stroke, and dementia) may not require the detail of an MR imaging study. In general, more rigorous clinical research studies are needed for new technologies such as MR imaging. Because the field of MR imaging is changing, review of its clinical efficacy will need to be revised frequently.

Adult↗