Conformational states of TNFR1 as a molecular switch for receptor function

Tumor necrosis factor receptor 1 (TNFR1) is a transmembrane receptor that plays a key role in the regulation of the inflammatory pathway. While inhibition of TNFR1 has been the focus of many studies for the treatment of autoimmune diseases such as rheumatoid arthritis, activation of the receptor is important for the treatment of immunodeficiency diseases such as HIV and neurodegenerative diseases such as Alzheimer's disease where a boost in immune signaling is required. In addition, activation of other TNF receptors such as death receptor 5 or FAS receptor is important for cancer therapy. Here, we used a previously established TNFR1 fluorescence resonance energy transfer (FRET) biosensor together with a fluorescence lifetime technology as a high-throughput screening platform to identify a novel small molecule that activates TNFR1 by increasing inter-monomeric spacing in a ligand-independent manner. This shows that the conformational rearrangement of pre-ligand assembled receptor dimers can determine the activity of the receptor. By probing the interaction between the receptor and its downstream signaling molecule (TRADD) our findings support a new model of TNFR1 activation in which varying conformational states of the receptor act as a molecular switch in determining receptor function.

Results of report cards for patients with congestive heart failure depend on the method used to adjust for severity

BACKGROUND

The validity of outcome report cards may depend on the ways in which they are adjusted for risk.

OBJECTIVES

To compare the predictive ability of generic and disease-specific survival prediction models appropriate for use in patients with heart failure, to simulate outcome report cards by comparing survival across hospitals and adjusting for severity of illness using these models, and to assess the ways in which the results of these comparisons depend on the adjustment method.

DESIGN

Analysis of data from a prospective cohort study.

SETTING

A university hospital, a Veterans Affairs (VA) medical center, and a community hospital.

PATIENTS

Sequential patients presenting in the emergency department with acute congestive heart failure.

MEASUREMENTS

Unadjusted 30-day and 1-year mortality across hospitals and 30-day and 1-year mortality adjusted by using disease-specific survival prediction models (two sickness-at-admission models, the Cleveland Health Quality Choice model, the Congestive Heart Failure Mortality Time-Independent Predictive Instrument) and generic models (Acute Physiology and Chronic Health Evaluation [APACHE] II, APACHE III, the mortality prediction model, and the Chadson comorbidity index).

RESULTS

The community hospital's unadjusted 30-day survival rate (85.0%) and the VA medical center's unadjusted 1-year survival rate (60.9%) were significantly lower than corresponding rates at the university hospital (92.7% and 67.5%, respectively). No severity model had excellent ability to discriminate patients by survival rates (all areas under the receiver-operating characteristic curve < 0.73). Whether the VA medical center, the community hospital, both, or neither had worse survival rates on simulated report cards than the university hospital depended on the prediction model used for adjustment.

CONCLUSIONS

Results of simulated outcome report cards for survival in patients with congestive heart failure depend on the method used to adjust for severity.

The effect of anesthetic technique on postoperative outcomes in hip fracture repair

BACKGROUND

The impact of anesthetic choice on postoperative mortality and morbidity has not been determined with certainty.

METHODS

The authors evaluated the effect of type of anesthesia on postoperative mortality and morbidity in a retrospective cohort study of consecutive hip fracture patients, aged 60 yr or older, who underwent surgical repair at 20 US hospitals between 1983 and 1993. The primary outcome was defined as death within 30 days of the operative procedure. The secondary outcomes were postoperative 7-day mortality, postoperative myocardial infarction, postoperative pneumonia, postoperative congestive heart failure, and postoperative change in mental status. Numerous comorbid conditions were controlled for individually and by several comorbidity indices using logistic regression.

RESULTS

General anesthesia was used in 6,206 patients (65.8%) and regional anesthesia in 3,219 patients (3,078 spinal anesthesia and 141 epidural anesthesia). The 30-day mortality rate in the general anesthesia group was 4.4%, compared with 5.4% in the regional anesthesia group (unadjusted odds ratio = 0.80; 95% confidence interval = 0.66-0.97). However, the adjusted odds ratio for general anesthesia increased to 1.08 (0.84-1.38). The adjusted odds ratios for general anesthesia versus regional anesthesia for the 7-day mortality was 0.90 (0.59-1.39) and for postoperative morbidity outcomes were as follows: myocardial infarction: adjusted odds ratio = 1.17 (0.80-1.70); congestive heart failure: adjusted odds ratio = 1.04 (0.80-1.36); pneumonia: adjusted odds ratio = 1.21 (0.87-1.68); postoperative change in mental status: adjusted odds ratio = 1.08 (0.95-1.22).

CONCLUSIONS

The authors were unable to demonstrate that regional anesthesia was associated with better outcome than was general anesthesia in this large observational study of elderly patients with hip fracture. These results suggest that the type of anesthesia used should depend on factors other than any associated risks of mortality or morbidity.

How you look determines what you find: severity of illness and variation in blood transfusion for hip fracture

PURPOSE

Utilization report cards are commonly used to assess hospitals. However, in practice, they rarely account for differences in patient populations among hospitals. Our study questions were: (1) How does transfusion utilization for hip fracture patients vary among hospitals? (2) What patient characteristics are associated with transfusion and how do those characteristics vary among hospitals? (3) Is the apparent pattern of variation of utilization among hospitals altered by controlling for these patient characteristics?

SUBJECTS AND METHODS

We included consecutive hip fracture patients aged 60 years or older who underwent surgical repair between 1982 and 1993 in 19 hospitals from four states, excluding those who refused blood transfusion, had multiple trauma, metastatic cancer, multiple myeloma, an above the knee amputation, or were paraplegic or quadriplegic. The outcome of interest was postoperative blood transfusion. "Trigger hemoglobin" was the lowest hemoglobin recorded before transfusion or recorded at any time during the week before or after surgery for patients who were not transfused.

RESULTS

There was considerable variation in transfusion among hospitals postoperatively (range 31.2% to 54.0%, P = 0.001). Trigger hemoglobin also varied considerably among hospitals. In unadjusted analyses, four of nine teaching and two of nine nonteaching hospitals had postoperative transfusion rates significantly higher than the reference (teaching) hospital, while one nonteaching hospital had a lower rate. In an analysis controlling for trigger hemoglobin and multiple clinical variables, one of nine teaching and four of nine nonteaching hospitals had rates higher than the reference hospital, while four teaching hospitals and one nonteaching hospital had lower rates.

CONCLUSIONS

The apparent pattern of variation of transfusion among hospitals varies according to how one adjusts for relevant patient characteristics. Utilization report cards that fail to adjust for these characteristics may be misleading.

An international comparison of physicians' judgments of outcome rates of cardiac procedures and attitudes toward risk, uncertainty, justifiability, and regret

OBJECTIVE

Compare U.K. and U.S. physicians' judgments of population probabilities of important outcomes of invasive cardiac procedures; and values held by them about risk, uncertainty, regret, and justifiability relevant to utilization of cardiac treatments.

DESIGN

Cross-sectional study.

SETTING

University hospital and VA medical center in the United States; two teaching hospitals in the United Kingdom.

PARTICIPANTS

171 housestaff and attendings at U.S. teaching hospitals; 51 physician trainees and consultants at U.K. hospitals.

MEASURES

Judgments of probabilities of severe complications and deaths due to Swan-Ganz catheterization, cardiac catheterization, percutaneous transluminal coronary angioplasty (PTCA), and coronary artery bypass grafting (CABG); judgments of malpractice risks for case vignettes; Nightingale's risk-aversion instrument; Gerrity's reaction-to-uncertainty instrument; questions about need to justify decisions; responses to case vignettes regarding regret.

RESULTS

The U.S. physicians judged rates of two bad outcomes of cardiac procedures (complications due to cardiac catheterization; death due to CABG) to be significantly higher (p < or = 0.01) than did the U.K. physicians (U.S. medians, 5 and 3.5, respectively; U.K. medians 3 and 2). The median ratio of (risk of malpractice suit I error of omission)/(risk of suit I error of commission) judged by U.K. physicians, 3, was significantly (p=0.0006) higher than that judged by U.S. physicians, 1.5. The U.K. physicians were less often risk-seeking in the context of possible losses than the U.S. physicians (odds ratio for practicing in the U.K. as a predictor of risk seeking 0.3, p=0.003). The U.K. physicians had significantly more discomfort with uncertainty than did the U.S. physicians, as reflected by higher scores on the stress scale (U.K. median 48, U.S. 42, p=0.0001) and the reluctance-to-disclose-uncertainty scale (U.K. 40, U.S. 37, p < 0.0001) of the Gerrity instrument. There was no clear international difference in perceived need to justify decisions, or in regret.

CONCLUSIONS

The results were not clearly consistent with the uncertainty hypothesis that international practice variation is due to differences in judged rates of outcomes of therapy or with the imperfect-agency hypothesis that practice variation is due to differences in physicians' personal values. The causes and implications of practice variations remain unclear.

Perioperative blood transfusion and postoperative mortality

CONTEXT

The risks of blood transfusion have been studied extensively but the benefits and the hemoglobin concentration at which patients should receive a transfusion have not.

OBJECTIVE

To determine the effect of perioperative transfusion on 30- and 90-day postoperative mortality.

DESIGN

Retrospective cohort study.

SETTING

A total of 20 US hospitals between 1983 and 1993.

PARTICIPANTS

A total of 8787 consecutive hip fracture patients, aged 60 years or older, who underwent surgical repair.

MAIN OUTCOME MEASURES

Primary outcome was 30-day postoperative mortality; secondary outcome was 90-day postoperative mortality. The "trigger" hemoglobin level was defined as the lowest hemoglobin level prior to the first transfusion during the time period or, for patients in the nontranfused group, as the lowest hemoglobin level during the time period.

RESULTS

Overall 30-day mortality was 4.6% (n=402; 95% confidence interval [CI], 4.1%-5.0%); overall 90-day mortality was 9.0% (n=788; 95% CI, 8.4%-9.6%). A total of 42% of patients (n=3699) received a postoperative transfusion. Among patients with trigger hemoglobin levels between 80 and 100 g/L (8.0 and 10.0 g/dL), 55.6% received a transfusion, while 90.5% of patients with hemoglobin levels less than 80 g/L (8.0 g/dL) received postoperative transfusions. Postoperative transfusion did not influence 30- or 90-day mortality after adjusting for trigger hemoglobin level, cardiovascular disease, and other risk factors for death: for 30-day mortality, the adjusted odds ratio (OR) was 0.96 (95% CI, 0.74-1.26); for 90-day mortality, the adjusted hazard ratio was 1.08 (95% CI, 0.90-1.29). Similarly, 30-day mortality after surgery did not differ between those who received a preoperative transfusion and those who did not (adjusted OR, 1.23; 95% CI, 0.81-1.89).

CONCLUSIONS

Perioperative transfusion in patients with hemoglobin levels 80 g/L (8.0 g/dL) or higher did not appear to influence the risk of 30- or 90-day mortality in this elderly population. At hemoglobin concentrations of less than 80 g/L (8.0 g/dL), 90.5% of patients received a transfusion, precluding further analysis of the association of transfusion and mortality.

Telephone medical care administered by internal medicine residents: concerns of program directors and implications for residency training

The objective of this study was to determine the need for telephone medicine curricula and to help define important content for internal medicine residencies using scales that measure program director attitudes toward telephone medicine. Data were collected by surveying all 416 program directors of accredited internal medicine residencies in the United States. We applied factor analysis to develop reliable attitudinal scales and employed regression models to identify predictors of these attitudes. Response rate was 60%. Formal training for telephone medicine was available in only 6% of programs. The factor analysis showed three attitudinal concepts; all described marked program director discomfort with aspects of resident telephone prescription. Predictors of improved program director comfort included more frequent documentation of resident telephone calls, chart availability, and clear definition of resident roles pertaining to telephone interactions with patients (P < 0.02 for all predictor variables). These results identify a need for telephone curricula and suggest components that might alleviate program director discomfort with resident telephone practices.

Physicians' judgments of the risks of cardiac procedures. Differences between cardiologists and other internists

OBJECTIVES

The authors compared judgments of the population risks of invasive cardiac procedures made by cardiologists and other internal medicine physicians. Our main hypotheses were that cardiologists' judgments would differ from those made by the other physicians and that cardiologists' judgments would be more accurate than those of other physicians.

METHODS

This was a cross-sectional survey of senior staff and physician-trainees at two teaching hospitals affiliated with a US medical school, Emergency Department physicians at a community hospital in the same metropolitan area, and senior staff and trainees at two teaching hospitals affiliated with a UK school. Judgments of the risks of severe morbidity and death due to Swan-Ganz catheterization, cardiac catheterization, percutaneous coronary angioplasty, and coronary artery bypass grafting were assessed.

RESULTS

Nineteen cardiologists judged the risks of severe morbidity due to all procedures and the risks of death due to all procedures except coronary artery bypass grafting to be significantly lower than did the 78 other internists. Cardiologists more frequently made accurate judgments of the rates of morbidity and death due to cardiac catheterization than did the other internists; other internists more frequently made accurate judgments for the rates of morbidity due to Swan-Ganz catheterization.

CONCLUSIONS

Disagreements about the risks of procedures may arise from a paucity of published data, or from an over-supply of confusing data.

Physicians' survival predictions for patients with acute congestive heart failure

BACKGROUND

Current guidelines suggest that patients with low likelihoods of survival may be excluded from intensive care. Patients with new or exacerbated congestive heart failure are frequently but not inevitably admitted to critical care units.

OBJECTIVE

To assess how well physicians could predict the probability of survival for acutely ill patients with congestive heart failure, and in particular how well they could identify patients with small chances of survival.

METHODS

This was a prospective cohort study done in the emergency departments of a university hospital, a Veterans Affairs medical center, and a community hospital. The study population was consecutive adults for whom new or exacerbated congestive heart failure, diagnosed clinically, was a major reason for the emergency department visit. Physicians caring for the study patients in the emergency departments recorded their judgments of the numeric probability that each patient would survive for 90 days and for 1 year. The patients vital status at 90 days and 1 year was ascertained by multiple means, including interview, chart review, and review of hospital and state databases.

RESULTS

By calibration curve analysis, the physicians underestimated survival probability at both 90 days and 1 year, particularly for patients they judged to have the lowest probabilities of survival. Their predictions had modest discriminating ability (receiver operating characteristic curve areas, 0.66 [SE = 0.020] for 90 days; 0.63 [SE = 0.017] for 1 year). The physicians identified only 15 patients they judged to have a 90-day survival probability of 10% or less, whose survival rate was actually 33.3%.

CONCLUSIONS

Physicians have great difficulty predicting survival for patients with acute congestive heart failure and cannot identify patients with poor chances of survival. Current triage guidelines that suggest patients with poor chances of survival may be excluded from critical care may be impractical or harmful.

Telephone management training in internal medicine residencies: a national survey of program directors

BACKGROUND

Little is known about how internal medicine residents train for and practice telephone management. To address this deficiency, a national survey of program directors at accredited internal medicine training sites was conducted to evaluate residents' training for and practice of telephone medicine.

METHOD

A 43-item questionnaire was mailed in December 1993 to all program directors at the 416 accredited internal medicine training sites in the United States. A limited questionnaire, regarding the most essential training questions, was mailed to all non-responders.

RESULTS

The response rate was 60% (250) for the full questionnaire. Only 15 (6%) of the programs offered formal training in telephone management to their residents. This training usually consisted of single lectures (nine programs) or reading materials (seven programs). The respondents felt that formal training in telephone management was very important (155, 62%) and that such training should be a part of every internal medicine curriculum (150, 60%).

CONCLUSION

Few internal medicine programs offered training in telephone management. When training occurred, it was usually limited and informal. Most program directors felt that training was important and that current training efforts were unsatisfactory, emphasizing the need for curriculum development and implementation in telephone management.