Submucosal ureteral calculi: a new entity?

We describe 3 patients with ureteral calculi who failed multiple extracorporeal shock wave lithotripsy treatments and whose stones could not be visualized by ureteroscopy despite radiological confirmation. We contend that these ureteral stones migrated submucosally and are refractory to the aforementioned treatment modalities. Each patient had a common presenting complaint of intermittent flank pain 5 years in duration, leading us to believe that long-standing stone impaction is a prerequisite for this entity. Our experience is reviewed.

Seeking and applying diagnostic information in a health care setting

Many studies have shown that people have difficulty judging the diagnostic value of conditional probability information with respect to one or more hypotheses. The present research addressed two aspects of performing the diagnostic task in a health care decision: (a) recognition of the information's importance, and (b) correct usage of that information. In experiment 1, health care providers, who are trained in, and regularly exposed, to conditional probabilities imparting diagnostic information, exhibited at least a rudimentary recognition of the need for this information in assessing diagnosticity. Experiment 2 indicated that health care and layperson subjects had difficulty in actually applying the information, however. This difficulty prompts a need for judgment aids and caution in using diagnostic information.

Near fatal puerperal fever due to Mycoplasma hominis

We describe a case of severe septicaemia caused by Mycoplasma hominis in a 23 year old patient following childbirth. She developed disseminated intravascular coagulation and acute respiratory distress syndrome which have not hitherto been described in association with septicaemia due to this organism. Investigation and treatment leading to full recovery is outlined.

The single-cutoff trap: implications for Bayesian analysis of stress electrocardiograms

Quantitative analysis of exercise electrocardiograms has been emphasized by many investigators. Specific problems have been found when a single cutoff is used to define a positive or a negative test: a single cutoff does not distinguish stress electrocardiography results that are slightly positive from those that are markedly positive. This may lead clinicians to underweigh strong evidence for or against coronary artery disease. This study evaluated clinicians' quantitative analysis of stress electrocardiograms. Two hundred and thirty-five physicians interpreted the results of mildly positive (1.2 mm ST-segment depression) and strongly positive (2.2 mm ST-segment depression) stress electrocardiograms. Their posttest probability estimates were too high for a mildly positive test (0.62 +/- 0.02 versus actual of 0.38; p less than 0.001) and too low for a strongly positive test (0.77 +/- 0.01 versus actual of 0.98; p less than 0.001). Physicians should understand decision aids and should use multiple rather than single cutoffs to interpret the results of stress electrocardiography.

Biochemical tests for pheochromocytoma: strategies in hypertensive patients

OBJECTIVE

To determine the optimal clinical strategy utilizing either 1) serum catecholamines, 2) urinary metanephrines, or 3) urinary vanillylmandelic acid measurements in the evaluation of hypertensive patients with suspected pheochromocytoma.

DESIGN

Prospective clinical determination of test-operating characteristics.

SETTING

Tertiary care university medical center.

PATIENTS/PARTICIPANTS

415 patients referred for evaluation of suspected pheochromocytoma.

INTERVENTIONS

All subjects had measurements of the three above-mentioned biochemical tests with the diagnosis of pheochromocytoma established by tissue confirmation.

RESULTS

All three biochemical tests were similar in sensitivity (0.70-0.75), specificity (0.90-0.95), and receiver operating characteristics. With an estimated disease prevalence of 5.9% in symptomatic hypertensive patients, the predictive value of any single negative test would be 98% in ruling out disease.

CONCLUSIONS

All three biochemical tests have similar performance characteristics and only a single test need be performed to exclude pheochromocytoma in most symptomatic hypertensive patients in a primary care population.

Bedside case presentations: why patients like them but learners don't

STUDY OBJECTIVE

To determine current attitudes of patients, medical students, housestaff, and clinical faculty toward bedside case presentations.

DESIGN

Survey using multiple-choice questionnaire and open comments for students, housestaff, and faculty, and a structured interview of patients.

SETTING

Major teaching hospitals on the campus of a midwestern medical school, staffed by full-time faculty.

PARTICIPANTS

136 medical students, 58 housestaff, 66 faculty, and 73 patients.

MEASUREMENTS AND MAIN RESULTS

85% of patients liked the case presentation discussion at the bedside, but 95% of both students and housestaff felt more comfortable with such discussion away from the patient. Attending faculty were about evenly divided in preference, with the younger staff preferring the conference room setting. Most patients (88%) opposed rounds in the hallway. Duration of rounds of one to two hours was felt desirable by most, but 50% of students preferred a duration of less than one hour. For length of new patient case presentation, 60% of learners again favored brevity, less than 5 minutes.

CONCLUSIONS

Bedside rounds are an opportunity to sharpen diagnostic skills and to demonstrate the art of medicine. They are undervalued by learners and younger faculty but appreciated by patients. The authors recommend that faculty improve bedside rounds by assessing team members' educational needs, by cultivating sensitivity and respect for the needs of all parties, and by assuring pertinence and brevity of bedside discussion.

The inexact use of Fisher's Exact Test in six major medical journals

We reviewed the use of Fisher's Exact Test in 71 articles published between 1983 and 1987 in six medical journals. Thirty-three of 56 selected articles did not specify use of a one- or two-tailed test, and 12 (36%) of these actually used the one-tailed test. Five (42%) of these 12 articles contained at least one table in which the standard significance level of P less than .05 was no longer met when a two-tailed analysis was run instead. Eleven (65%) of 17 articles with a statistical consultant compared with 10 (28%) of 36 articles without a consultant specified use of a one- or two-sided test. The use of Fisher's Exact Test without specification as a one- or two-tailed version may misrepresent the statistical significance of data. A uniform specification statement should be required for all manuscripts to correct such potential errors in interpretation.

Integrity of the blood-brain barrier in retinal xenografts is correlated with the immunological status of the host

The purpose of this study was to determine the immunological correlates of blood-brain barrier breakdown in retinal xenografts in rats by utilizing skin grafting to initiate a timed immune response to the transplanted neural tissue. Embryonic day 13-14 CD-1 mouse retinae were grafted into the brainstem parenchyma of neonatal Sprague-Dawley rats. In one group of animals a 100 mm2 CD-1 skin graft was placed on the flank 21 days after the initial neural transplant in order to provoke an immune response to the neural graft. Control animals received no skin graft. Animals were injected with horseradish peroxidase (HRP) in the femoral vein 2-8 days after skin grafting. Brains were processed for Nissl, HRP-tetramethylbenzidine, and anti-M-6, -lymphocyte, -macrophage, and -astrocyte antibodies. Experimental and control animals injected 2-4 days after skin grafting showed no leakage of reaction product in the grafted tissue. A small percentage (one of eight) of 5-day animals showed isolated, patchy leakage, but no evidence of rejection of the neural graft. At 6 days all of the grafts showed evidence of leakage, and 71% of these grafts showed infiltration of lymphocytes. By 7-8 days extensive leakage of HRP and widespread infiltration of lymphocytes and macrophages were clearly evident. The present study demonstrates that blood-brain barrier breakdown is correlated closely with the sequence of immunological rejection of the graft. While these results confirm that a barrier exists in healthy neural transplants, they suggest that immunological factors should be considered in cases in which grafts are not protected by an intact barrier.

Characterizing physicians' perceptions of ambiguity

Ambiguity, typically characterized as imprecision in judged probabilities is distinguishable from that uncertainty typically measured using probabilities. It reflects the inadequacy of a point probability judgement and the assumptions upon which it is based. Ambiguity influences both patients' and physicians' decisions, but it is unknown how decision makers conceptualize ambiguity. Toward this goal, properties of three ambiguity indicators were examined: a confidence rating, a plausible range, and an interquartile range. Board-certified internists and fourth-year medical students evaluated simulated cases of suspected coronary artery disease. Their judgements provided insights into the three ambiguity indicators. The distribution-based interquartile range was largely redundant with the plausible range, and was least adequate. The confidence rating was not equivalent to the plausible range, and appeared to best reflect the construct of ambiguity as it has been defined.

Epidemiology and interaction of risk factors in cardiovascular disease

Many patients seen in a primary care practice have multiple risk factors for cardiovascular disease. In evaluating these patients, it is important for primary care clinicians to understand the principles of multiple risk factor assessment. Although none of the large-scale randomized primary prevention trials have convincingly proven the benefits of multiple risk factor intervention, some practical guidelines reflecting the current state of information are presented.

Primacy effects in clinical judgments of contingency

In contingency judgment a primacy effect exists when a conclusion about the relationship between clinical variables is inordinately influenced by cases seen earlier rather than later in a presentation sequence. In this study, medical and nursing trainees evidenced this behavior in a hypothetical clinical judgment situation. The behavior was tied to an attention decrement explanation, by which inattention to the later-presented cases leads to inaccurate recall of the relative frequencies of observed cases, which in turn induces a misjudgment of a disease-finding contingency. An explicit intervention based on this hypothesis, forcing attention to later cases by warning that recall of the case frequencies would be required, was effective in reducing primacy effects among medical students. A related, but less explicit, intervention was also tried. This intervention did not significantly reduce primacy effects among nursing students, but was somewhat effective among general undergraduate students performing a non-clinical contingency judgment task.

Criteria for admitting patients with tricyclic antidepressant overdose

Several investigators have recently developed guidelines for determining which patients with tricyclic antidepressant overdose should be hospitalized. The width of the QRS complex on the ECG and several clinical parameters have been proposed to identify patients at risk for major complications. To validate these, we developed an algorithm and then applied it to 45 patients who had overdosed on tricyclic antidepressants. This algorithm correctly predicted which patients required admission, whether due to present or impending complications, and which patients could have been discharged without morbidity or mortality. We conclude that use of the modified algorithm can identify patients with tricyclic antidepressant overdose who can be safely discharged from the emergency department.

Do cardiologists have higher thresholds for recommending coronary arteriography than family physicians?

The purpose of this study was to use a new model of decision making to understand variability in physicians' utilization of diagnostic tests. We studied physicians' recommendations for coronary arteriography in hypothetical patients with chest pain by analyzing responses of 235 cardiologists and family physicians. Thresholds for testing were derived by obtaining estimates of the probability of disease and recommendations for coronary arteriography before and after an exercise test. We found that cardiologists compared with family practitioners had a significantly higher decision threshold and recommended coronary arteriography in fewer patients. These findings suggest that analyzing physicians' decision-making thresholds may be used to characterize differences in the practice behavior of groups of physicians.

Prediction rules for patients with suspected myocardial infarction. Applying guidelines in community hospitals

Several clinical prediction rules have been developed to assist physicians in managing intensive care resources for patients with suspected myocardial infarction. These guidelines, developed in university settings, attempt to identify patients at high or low risk for developing life-threatening complications or death. Since some prediction rules have not performed well when applied to different patient populations, we applied these rules to 397 patients with suspected myocardial infarction who were admitted to community hospital coronary care units. The relative risk of dying associated with an abnormal initial electrocardiogram declined from 17 in the academic center to 2.9 in the community hospital. In contrast, a guideline that uses data available after 24 hours of observation did segregate patients at higher and lower risk in both the community and academic hospitals. This study shows that clinical prediction rules that were developed in academic medical centers should be validated before applying them in community hospital settings.

Gene I products of cauliflower mosaic virus detected in extracts of infected tissue

The product of cauliflower mosaic virus (CaMV) gene I has been characterized from extracts of infected plants. Two size classes of this protein can be identified by the use of specific antiserum. The antiserum was induced against a chimeric protein produced in E. coli from a gene fusion between a fragment of the CaMV genome and the beta-galactosidase gene. A 36-kDa form of the gene I product is associated with virus particles. A 45-kDa form of this product was found only in the insoluble fraction of tissue homogenates. This insoluble fraction, the only fraction found to contain the product of viral gene VI, contains the virally induced inclusion bodies.

Propranolol for the treatment of the alcoholic hangover

Hangover following consumption of alcohol includes many disagreeable signs and symptoms that are suggestive of sympathetic overactivity. We performed a randomized, double-blind, crossover controlled study to assess the effect of beta blockade in preventing the symptoms of hangover. Ten subjects were randomized to receive 160 mg of a long-acting preparation of propranolol or a placebo and then participated in a controlled drinking situation. Patients were then evaluated for symptoms and signs of hangover. The results showed that although beta blockade was achieved, there was no clinically important reduction in symptoms of hangover. We conclude that propranolol does not prevent the symptoms of hangover.

Perceptions of ethical problems by nurses and doctors

To identify how nurses and physicians perceive ethical problems in clinical medicine, we conducted structured interviews with 26 nurses and 24 physicians who work in acute-care units. Both groups thought that they frequently encounter ethical problems, although there was significant variation within each group about how often members of each group perceived such problems. Members of the health-care team often disagreed about ethical decisions. Nurses often described conflicts with physicians, but physicians rarely recognized disagreements with nurses. Clinical ethicists need to be aware of this heterogeneous perception in order to communicate effectively about ethical problems.

Comparing aggregate estimates of derived thresholds for clinical decisions

Thresholds for medical decision making are the probabilities of disease at which clinicians choose to initiate testing or therapy. A descriptive analysis of clinicians' decision making can derive their test and test-treatment thresholds and has the potential to explain variations in test utilization. A previously described method summarizes thresholds for a group of clinicians by determining the range of probability which includes the maximum number of clinicians' individual thresholds. However, there is no statistical procedure to compare the summary measure of thresholds that is derived from the distribution of clinicians' thresholds. We describe two alternative methods of developing a summary measure of the thresholds for a group of clinicians. These alternative methods enable the analyst to apply standard statistical tests when analyzing the decision-making behavior of groups of clinicians. For the "Unweighted Mean of the Midpoints" method, confidence limits of means and standard t-tests can be used to compare different groups. For the "Weighted Mean of the Midpoints" method, a weighted standard error of the mean can be calculated to determine confidence intervals, and a weighted t-test or weighted regression can be used to compare weighted means of the midpoints of threshold ranges.

Propranolol for the treatment of the alcoholic hangover

Hangover following consumption of alcohol includes many disagreeable signs and symptoms that are suggestive of sympathetic overactivity. We performed a randomized, double-blind, crossover controlled study to assess the effect of beta blockade in preventing the symptoms of hangover. Ten subjects were randomized to receive 160 mg of a long-acting preparation of propranolol or a placebo and then participated in a controlled drinking situation. Patients were then evaluated for symptoms and signs of hangover. The results showed that although beta blockade was achieved, there was no clinically important reduction in symptoms of hangover. We conclude that propranolol does not prevent the symptoms of hangover.

Electromyographic biofeedback and physical therapy of the hemiplegic upper limb

A long-term, comparison-group outcome trial with a partial crossover design was carried out on the effects of electromyographic biofeedback (EMGBF) plus physiotherapy (PT) versus PT alone in the treatment of the hemiplegic upper limb in stroke patients who were at least six months beyond the onset of their disability. Both the experimental and the control groups benefited from their treatment, but EMGBF was shown to have an additional effect, both in the experimental patients, and in the control patients when they switched over to the experimental treatment condition.

Can physicians be rational about diagnostic tests?

Concerns about diagnostic test utilization have led to interest in the role of tests in clinical decision-making, and researchers have developed guidelines for interpreting the results of diagnostic tests using Bayesian probability revision and decision analysis. Although it acknowledges the importance of these quantitative models in medical education, this article identifies major obstacles that limit their application, demonstrating that " rational " decision-making may not be rational or optimal in clinical practice.

Naloxone-responsive hypotension in a patient with an ACTH-secreting tumor

We report a case in which hypotension was corrected by the administration of naloxone in a patient with an ACTH-secreting mediastinal tumor. According to previous reports, reversal of hypotension would not be expected in patients with suppressed central ACTH secretion. The implications of this patient's response on the possible mechanisms for naloxone's action in reversing septic shock are discussed.

Sample size nomograms for interpreting negative clinical studies

In recent years there has been increasing attention to the appropriate interpretation of a clinical study. One special concern has been the difficulty inherent in interpreting studies that were not statistically significant: Was the sample size sufficient to detect a clinically important effect if, in fact, it existed? This concern is further complicated because readers may have differing opinions of what size effect is clinically important. A pair of sample size nomograms has been developed, using common levels of statistical significance, to assist in this interpretation. The nomograms are intended to provide the clinician with a handy and easy-to-use reference for ascertaining whether an apparently negative study has a sample size adequate to detect reliably any difference between treatment groups that the clinician believes is clinically important. Examples are provided to show these principles and the use of the nomograms in interpreting negative studies.

A time-course analysis of attentional tuning of the auditory evoked response

This study examined the time course of attentional tuning of the N1 and P3 components of the auditory evoked potential. Human subjects were presented with two concurrent sequences of pure tone stimuli, one sequence delivered to each ear. They were instructed to listen to the tones in one ear and count randomly-embedded target stimuli, identified by pitch, while ignoring concurrent and physically equivalent stimuli in the other ear. Attention was then allocated to other ear-pitch combinations in subsequent runs. The rate of stimulation was rapid, an average of three stimuli per second per channel, to maximize N1 differences between channels. Evoked potentials were sampled at various times during each experimental run, to determine the time course of amplitude change in each auditory channel, as the subject tuned his neural response to the selected stimuli. The results indicated that N1 took 30-45 s to emerge as significantly larger in the attended channel, whereas P3 was instantly larger in the attended channel upon presenting the first rare stimulus of a run. The N1 effect disappeared for standard stimuli after about 7 min of stimulation, despite a continuously high rate of target identification. However, for the rare target stimuli, N1 and P3 remained at a higher level in the attended channel throughout the typical 15 min run. The study concludes that neural selectivity proceeds in a "top-down" manner, with the longer-latency P3 component showing a selective response sooner than N1. In addition, there is evidence that the selectivity of N1 tuning increases over time, with the continued focussing of attention.