Implementation of the I-PASS handoff program in diverse clinical environments: A multicenter prospective effectiveness implementation study

BACKGROUND

Handoff miscommunications are a leading source of medical errors. Harmful medical errors decreased in pediatric academic hospitals following implementation of the I-PASS handoff improvement program. However, implementation across specialties has not been assessed.

OBJECTIVE

To determine if I-PASS implementation across diverse settings would be associated with improvements in patient safety and communication.

DESIGN

Prospective Type 2 Hybrid effectiveness implementation study.

SETTINGS AND PARTICIPANTS

Residents from diverse specialties across 32 hospitals (12 community, 20 academic).

INTERVENTION

External teams provided longitudinal coaching over 18 months to facilitate implementation of an enhanced I-PASS program and monthly metric reviews.

MAIN OUTCOME AND MEASURES

Systematic surveillance surveys assessed rates of resident-reported adverse events. Validated direct observation tools measured verbal and written handoff quality.

RESULTS

2735 resident physicians and 760 faculty champions from multiple specialties (16 internal medicine, 13 pediatric, 3 other) participated. 1942 error surveillance reports were collected. Major and minor handoff-related reported adverse events decreased 47% following implementation, from 1.7 to 0.9 major events/person-year (p < .05) and 17.5 to 9.3 minor events/person-year (p < .001). Implementation was associated with increased inclusion of all five key handoff data elements in verbal (20% vs. 66%, p < .001, n = 4812) and written (10% vs. 74%, p < .001, n = 1787) handoffs, as well as increased frequency of handoffs with high quality verbal (39% vs. 81% p < .001) and written (29% vs. 78%, p < .001) patient summaries, verbal (29% vs. 78%, p < .001) and written (24% vs. 73%, p < .001) contingency plans, and verbal receiver syntheses (31% vs. 83%, p < .001). Improvement was similar across provider types (adult vs. pediatric) and settings (community vs. academic).

Capturing the Rest: Inpatient Mammography for Nonadherent Hospitalized Women

INTRODUCTION

More than a third of hospitalized women are overdue or nonadherent to breast cancer screening guidelines, and almost a third of them are also at high risk for developing breast cancer. The purpose of this study is to evaluate the feasibility of coordinating inpatient breast cancer screening mammography for these women before their discharge from the hospital.

METHODS

A prospective intervention study was conducted among 101 nonadherent women aged 50-74 years who were hospitalized to a general medicine service. Sociodemographic, reproductive history, family history of breast cancer, and medical comorbidities data were collected for all patients from January 2015 to October 2016. The data were analyzed in March 2018. Fisher's exact tests and unpaired t-tests were utilized to compare the characteristics of the study population.

RESULTS

Of the 101 women enrolled who were nonadherent to breast cancer screening recommendations, their mean age was 59.3 (SD=6) years, the mean 5-year Gail risk score was 1.63 (SD=0.69), and 29% of the women were African American. Almost 80% (n=79) underwent inpatient screening mammography. All women who underwent screening mammography during their inpatient stay were extremely satisfied with the experience. The convenience of having screening mammography while hospitalized was reported to be a major facilitator of completing the overdue screening. All nurses (100%) taking care of these women believed that this practice should become part of the standard of care, and most hospitalist physicians (66%) agreed that this practice is feasible.

CONCLUSIONS

This study shows that it is possible to coordinate mammography for hospitalized women who were overdue for screening and at high risk for developing breast cancer.

TRIAL REGISTRATION

This study is registered at www.clinicaltrials.gov NCT04164251.

Retrospective Quality Improvement Study of Insulin-Induced Hypoglycemia and Implementation of Hospital-Wide Initiatives

BACKGROUND

Hospitalized patients who are receiving antihyperglycemic agents are at increased risk for hypoglycemia. Inpatient hypoglycemia may lead to increased risk for morbidity, mortality, prolonged hospitalization, and readmission within 30 days of discharge, which in turn may lead to increased costs. Hospital-wide initiatives targeting hypoglycemia are known to be beneficial; however, their impact on patient care and economic measures in community nonteaching hospitals are unknown.

METHODS

This retrospective quality improvement study examined the effects of hospital-wide hypoglycemia initiatives on the rates of insulin-induced hypoglycemia in a community hospital setting from January 1, 2016, until September 30, 2019. The potential cost of care savings has been calculated.

RESULTS

Among 49 315 total patient days, 2682 days had an instance of hypoglycemia (5.4%). Mean ± SD hypoglycemic patient days/month was 59.6 ± 16.0. The frequency of hypoglycemia significantly decreased from 7.5% in January 2016 to 3.9% in September 2019 (P = .001). Patients with type 2 diabetes demonstrated a significant decrease in the frequency of hypoglycemia (7.4%-3.8%; P < .0001), while among patients with type 1 diabetes the frequency trended downwards but did not reach statistical significance (18.5%-18.0%; P = 0.08). Based on the reduction of hypoglycemia rates, the hospital had an estimated cost of care savings of $98 635 during the study period.

CONCLUSIONS

In a community hospital setting, implementation of hospital-wide initiatives targeting hypoglycemia resulted in a significant and sustainable decrease in the rate of insulin-induced hypoglycemia. These high-leverage risk reduction strategies may be translated into considerable cost savings and could be implemented at other community hospitals.

Retrospective study of inpatient diabetes management service, length of stay and 30-day readmission rate of patients with diabetes at a community hospital

Background: Hospitalized patients with diabetes are at risk of complications and longer length of stay (LOS). Inpatient Diabetes Management Services (IDMS) are known to be beneficial; however, their impact on patient care measures in community, non-teaching hospitals, is unknown.

Objectives: To evaluate whether co-managing patients with diabetes by the IDMS team reduces LOS and 30-day readmission rate (30DR).

Methods: This retrospective quality improvement cohort study analyzed LOS and 30DR among patients with diabetes admitted to a community hospital. The IDMS medical team consisted of an endocrinologist, nurse practitioner, and diabetes educator. The comparison group consisted of hospitalized patients with diabetes under standard care of attending physicians (mostly internal medicine-trained hospitalists). The relationship between study groups and outcome variables was assessed using Generalized Estimating Equation models.

Results: 4,654 patients with diabetes (70.8 ± 0.2 years old) were admitted between January 2016 and May 2017. The IDMS team co-managed 18.3% of patients, mostly with higher severity of illness scores (p < 0.0001). Mean LOS in patients co-managed by the IDMS team decreased by 27%. Median LOS decreased over time in the IDMS group (p = 0.046), while no significant decrease was seen in the comparison group. Mean 30DR in patients co-managed by the IDMS decreased by 10.71%. Median 30DR decreased among patients co-managed by the IDMS (p = 0.048).

Conclusions: In a community hospital setting, LOS and 30DR significantly decreased in patients co-managed by a specialized diabetes team. These changes may be translated into considerable cost savings.

Association of a Care Coordination Model With Health Care Costs and Utilization: The Johns Hopkins Community Health Partnership (J-CHiP)

IMPORTANCE

The Johns Hopkins Community Health Partnership was created to improve care coordination across the continuum in East Baltimore, Maryland.

OBJECTIVE

To determine whether the Johns Hopkins Community Health Partnership (J-CHiP) was associated with improved outcomes and lower spending.

DESIGN, SETTING, AND PARTICIPANTS

Nonrandomized acute care intervention (ACI) and community intervention (CI) Medicare and Medicaid participants were analyzed in a quality improvement study using difference-in-differences designs with propensity score-weighted and matched comparison groups. The study spanned 2012 to 2016 and took place in acute care hospitals, primary care clinics, skilled nursing facilities, and community-based organizations. The ACI analysis compared outcomes of participants in Medicare and Medicaid during their 90-day postacute episode with those of a propensity score-weighted preintervention group at Johns Hopkins Community Health Partnership hospitals and a concurrent comparison group drawn from similar Maryland hospitals. The CI analysis compared changes in outcomes of Medicare and Medicaid participants with those of a propensity score-matched comparison group of local residents.

INTERVENTIONS

The ACI bundle aimed to improve transition planning following discharge. The CI included enhanced care coordination and integrated behavioral support from local primary care sites in collaboration with community-based organizations.

MAIN OUTCOMES AND MEASURES

Utilization measures of hospital admissions, 30-day readmissions, and emergency department visits; quality of care measures of potentially avoidable hospitalizations, practitioner follow-up visits; and total cost of care (TCOC) for Medicare and Medicaid participants.

RESULTS

The CI group had 2154 Medicare beneficiaries (1320 [61.3%] female; mean age, 69.3 years) and 2532 Medicaid beneficiaries (1483 [67.3%] female; mean age, 55.1 years). For the CI group's Medicaid participants, aggregate TCOC reduction was $24.4 million, and reductions of hospitalizations, emergency department visits, 30-day readmissions, and avoidable hospitalizations were 33, 51, 36, and 7 per 1000 beneficiaries, respectively. The ACI group had 26 144 beneficiary-episodes for Medicare (13 726 [52.5%] female patients; mean patient age, 68.4 years) and 13 921 beneficiary-episodes for Medicaid (7392 [53.1%] female patients; mean patient age, 52.2 years). For the ACI group's Medicare participants, there was a significant reduction in aggregate TCOC of $29.2 million with increases in 90-day hospitalizations and 30-day readmissions of 11 and 14 per 1000 beneficiary-episodes, respectively, and reduction in practitioner follow-up visits of 41 and 29 per 1000 beneficiary-episodes for 7-day and 30-day visits, respectively. For the ACI group's Medicaid participants, there was a significant reduction in aggregate TCOC of $59.8 million and the 90-day emergency department visit rate decreased by 133 per 1000 episodes, but hospitalizations increased by 49 per 1000 episodes and practitioner follow-up visits decreased by 70 and 182 per 1000 episodes for 7-day and 30-day visits, respectively. In total, the CI and ACI were associated with $113.3 million in cost savings.

CONCLUSIONS AND RELEVANCE

A care coordination model consisting of complementary bundled interventions in an urban academic environment was associated with lower spending and improved health outcomes.

Implementation of a comprehensive program to improve coordination of care in an urban academic health care system

Purpose Academic healthcare systems face great challenges in coordinating services across a continuum of care that spans hospital, community providers, home and chronic care facilities. The Johns Hopkins Community Health Partnership (J-CHiP) was created to improve coordination of acute, sub-acute and ambulatory care for patients, and improve the health of high-risk patients in surrounding neighborhoods. The paper aims to discuss this issue. Design/methodology/approach J-CHiP targeted adults admitted to the Johns Hopkins Hospital and Johns Hopkins Bayview Medical Center, patients discharged to participating skilled nursing facilities (SNFs), and high-risk Medicare and Medicaid patients receiving primary care in eight nearby outpatient sites. The primary drivers of the program were redesigned acute care delivery, seamless transitions of care and deployment of community care teams. Findings Acute care interventions included risk screening, multidisciplinary care planning, pharmacist-driven medication management, patient/family education, communication with next provider and care coordination protocols for common conditions. Transition interventions included post-discharge health plans, hand-offs and follow-up with primary care providers, Transition Guides, a patient access line and collaboration with SNFs. Community interventions involved forming multidisciplinary care coordination teams, integrated behavioral care and new partnerships with community-based organizations. Originality/value This paper offers a detailed description of the design and implementation of a complex program to improve care coordination for high-risk patients in an urban setting. The case studies feature findings from each intervention that promoted patient engagement, strengthened collaboration with community-based organizations and improved coordination of care.

A Concise Tool for Measuring Care Coordination from the Provider's Perspective in the Hospital Setting

BACKGROUND

To support hospital efforts to improve coordination of care, a tool is needed to evaluate care coordination from the perspective of inpatient healthcare professionals.

OBJECTIVES

To develop a concise tool for assessing care coordination in hospital units from the perspective of healthcare professionals, and to assess the performance of the tool in measuring dimensions of care coordination in 2 hospitals after implementation of a care coordination initiative.

METHODS

We developed a survey consisting of 12 specific items and 1 global item to measure provider perceptions of care coordination across a variety of domains, including teamwork and communication, handoffs, transitions, and patient engagement. The questionnaire was distributed online between October 2015 and January 2016 to nurses, physicians, social workers, case managers, and other professionals in 2 tertiary care hospitals.

RESULTS

A total of 841 inpatient care professionals completed the survey (response rate = 56.6%). Among respondents, 590 (75%) were nurses and 37 (4.7%) were physicians. Exploratory factor analysis revealed 4 subscales: (1) Teamwork, (2) Patient Engagement, (3) Handoffs, and (4) Transitions (Cronbach's alpha 0.84-0.90). Scores were fairly consistent for 3 subscales but were lower for patient engagement. There were minor differences in scores by profession, department, and hospital.

CONCLUSIONS

The new tool measures 4 important aspects of inpatient care coordination with evidence for internal consistency and construct validity, indicating that the tool can be used in monitoring, evaluating, and planning care coordination activities in hospital settings.

Hospitalists and Their Impact on Quality, Patient Safety, and Satisfaction

The forces promoting the hospitalist model arose from the need for high-value care; therefore, improving quality and cost has been part of the hospitalist formula for success. The factors driving the rapid growth of generalist and subspecialty hospitalists include nationally mandated quality and safety measures, increasing age and complexity of the hospitalized patient, reduced residency duty hours, increased economic pressures to contain costs and reduce length of stay, and also primary care physicians, and specialists, relinquishing hospital privileges to focus on outpatient practices. Hospitalists are playing key roles in patient safety and quality as either leaders or practitioners in the field.

Introducing the Hospitalist Morale Index: A new tool that may be relevant for improving provider retention

OBJECTIVE

To develop a valid instrument to assess morale and explore the relationship between morale and intent to leave employment due to unhappiness.

PATIENTS AND METHODS

An expert panel identified 46 drivers of hospitalist morale. In May 2009, responders of our single-site pilot survey rated each driver in terms of current contentment and importance to their morale. With exploratory factor analysis, a 28-item/7-factor instrument emerged. In May 2011, the refined scale was distributed to 108 hospitalists from 2 academic and 3 community hospitals. Confirmatory factor analysis (CFA) was used for internal validation and refinement of the Hospitalist Morale Index. Importance ratings and contentment assessments were used to generate item scores, which were then combined to generate factor scores and personal morale scores. Results were used to validate the instrument and evaluate the relationship between hospitalist morale and intent to leave due to unhappiness.

RESULTS

The 2011 response rate was 86%. The final CFA resulted in a 5-factor and 5-stand-alone-item model. Personal morale scores were normally distributed (mean = 2.79, standard deviation = 0.58). For every categorical increase on a global question that assessed overall morale, personal morale scores rose 0.23 points (P < 0.001). Each 1-point increase in personal morale score was associated with an 85% decrease (odds ratio: 0.15, 95% confidence interval: 0.05-0.41, P < 0.001) in the odds of intending to leave because of unhappiness.

CONCLUSION

The Hospitalist Morale Index is a validated instrument that evaluates hospitalist morale across multiple dimensions of morale. The Hospitalist Morale Index may help program leaders monitor morale and develop customized and effective retention strategies. Journal of Hospital Medicine 2016;11:425-431. © 2016 Society of Hospital Medicine.

What do hospitalists think about inpatient mammography for hospitalized women who are overdue for their breast cancer screening?

BACKGROUND

A recent study showed that many hospitalized women are nonadherent with breast cancer screening recommendations, and that a majority of these women would be amenable to inpatient screening if it were offered.

OBJECTIVE

Explore hospitalists' views about the appropriateness of inpatient breast cancer screening and their concerns about related matters.

METHODS

A cross-sectional study was conducted among 4 hospitalist groups affiliated with Johns Hopkins Medical Institution. χ(2) and t-test statistics were used to identify hospitalist characteristics that were associated with being supportive of inpatient screening mammography.

RESULTS

The response rate was 92%. Sixty-two percent of respondents believed that hospitalists should not be involved in breast cancer screening. In response to clinical scenarios describing hospitalized women who were overdue for screening, only one-third of hospitalists said that they would order a screening mammogram. Lack of follow-up on screening mammography results was cited as the most common concern related to ordering the test.

CONCLUSIONS

Future studies are needed to evaluate the feasibility and potential barriers associated with inpatient screening mammography.

Hospitalists' ability to use hand-carried ultrasound for central venous pressure estimation after a brief training intervention: a pilot study

BACKGROUND

Access to hand-carried ultrasound technology for noncardiologists has increased significantly, yet development and evaluation of training programs are limited.

OBJECTIVE

We studied a focused program to teach hospitalists image acquisition of inferior vena cava (IVC) diameter and IVC collapsibility index with interpretation of estimated central venous pressure (CVP).

METHODS

Ten hospitalists completed an online educational module prior to attending a 1-day in-person training session that included directly supervised IVC imaging on volunteer subjects. In addition to making quantitative assessments, hospitalists were also asked to visually assess whether the IVC collapsed more than 50% during rapid inspiration or a sniff maneuver. Skills in image acquisition and interpretation were assessed immediately after training on volunteer patients and prerecorded images, and again on volunteer patients at least 6 weeks later.

RESULTS

Eight of 10 hospitalists acquired adequate IVC images and interpreted them correctly on 5 of the 5 volunteer subjects and interpreted all 10 prerecorded images correctly at the end of the 1-day training session. At 7.4 ± 0.7 weeks (range, 6.9-8.6 weeks) follow-up, 9 of 10 hospitalists accurately acquired and interpreted all IVC images in 5 of 5 volunteers. Hospitalists were also able to accurately determine whether the IVC collapsibility index was more than 50% by visual assessment in 180 of 198 attempts (91% of the time).

CONCLUSIONS

After a brief training program, hospitalists acquired adequate skills to perform and interpret hand-carried ultrasound IVC images and retained these skills in the near term. Though calculation of the IVC collapsibility index is more accurate, coupling a qualitative assessment with the IVC maximum diameter measurement may be acceptable in aiding bedside estimation of CVP.

Prevalence of asymptomatic left ventricular systolic dysfunction in at-risk medical inpatients

BACKGROUND

Asymptomatic left ventricular systolic dysfunction is an important risk factor for heart failure and death. Given the availability of patients, trained personnel, and equipment, the hospital is an ideal setting to identify and initiate treatment for left ventricular systolic dysfunction. The purpose of this study was to determine the prevalence of asymptomatic left ventricular systolic dysfunction in patients 45 years of age or older with at least one clinical heart failure risk factor admitted to a general medical service.

METHODS

Bedside, hand-carried echocardiography provided quantitative assessment of left ventricular systolic function in 217 medical inpatients 45 years of age or older who had at least one heart failure risk factor. Patients with known or suspected heart failure or with an assessment of left ventricular function in the past 5 years were excluded. We measured the prevalence of asymptomatic left ventricular systolic dysfunction, defined by left ventricular ejection fraction of 50% or lower, and its association with heart failure risk factors.

RESULTS

Of 207 patients with interpretable images, 11 (5.3%) had a left ventricular ejection fraction of 50% or lower. Patients with left ventricular systolic dysfunction had more heart failure risk factors than those without left ventricular systolic dysfunction (3.09±0.8 vs 2.5±1.0, P=.04). The total number of heart failure risk factors trended towards an association with a greater prevalence of asymptomatic left ventricular systolic dysfunction, but this did not reach significance (odds ratio 1.74; 95% confidence interval, 0.97-3.12, P=.06).

CONCLUSIONS

Asymptomatic left ventricular systolic dysfunction is present in about 1 of every 20 general medical inpatients with at least one risk factor for heart failure. Because treatment of asymptomatic left ventricular systolic dysfunction may reduce morbidity, further studies examining the costs and benefits of using hand-carried ultrasound to identify this important condition in general medical inpatients are warranted.

Improving interunit transitions of care between emergency physicians and hospital medicine physicians: a conceptual approach

Patient care transitions across specialties involve more complexity than those within the same specialty, yet the unique social and technical features remain underexplored. Further, little consensus exists among researchers and practitioners about strategies to improve interspecialty communication. This concept article addresses these gaps by focusing on the hand-off process between emergency and hospital medicine physicians. Sensitivity to cultural and operational differences and a common set of expectations pertaining to hand-off content will more effectively prepare the next provider to act safely and efficiently when caring for the patient. Through a consensus decision-making process of experienced and published authorities in health care transitions, including physicians in both specialties as well as in communication studies, the authors propose content and style principles clinicians may use to improve transition communication. With representation from both community and academic settings, similarities and differences between emergency medicine and internal medicine are highlighted to heighten appreciation of the values, attitudes, and goals of each specialty, particularly pertaining to communication. The authors also examine different communication media, social and cultural behaviors, and tools that practitioners use to share patient care information. Quality measures are proposed within the structure, process, and outcome framework for institutions seeking to evaluate and monitor improvement strategies in hand-off performance. Validation studies to determine if these suggested improvements in transition communication will result in improved patient outcomes will be necessary. By exploring the dynamics of transition communication between specialties and suggesting best practices, the authors hope to strengthen hand-off skills and contribute to improved continuity of care.

The Creating Incentives and Continuity Leading to Efficiency staffing model: a quality improvement initiative in hospital medicine

OBJECTIVE

To determine the effect of a hospitalist-developed, continuity-centered hospitalist staffing model on patient outcomes and resource use.

METHODS

The Creating Incentives and Continuity Leading to Efficiency (CICLE) staffing model was conceived by a group of hospitalists who sought to improve continuity of inpatient care. Using a retrospective, observational, pre-post study design, we compared patient-level data for all discharges from our hospitalist service from 6 months after implementation of the CICLE staffing model (September 1, 2009, through February 28, 2010; n=1585) with data from those same months in the prior year (September 1, 2008, through February 28, 2009; n=1808). We used the number of unique hospitalists who documented an encounter during the admission as a measure of continuity of care. Length of stay and hospital charges per admission constituted the measures of resource use.

RESULTS

The odds of having a single hospitalist for the entire hospitalization nearly doubled under the CICLE model (odds ratio, 1.87; 95% confidence interval, 1.60-2.2; P<.001). Mean length of stay decreased 7.5% (from 2.92 before to 2.70 days after initiation of the model; P<.001). Mean hospital charge per admission decreased 8.5% (from $7224.33 before to $6607.79 after initiation of the model; P<.001). Thirty-day readmission rates were not substantially affected by the CICLE model (15.0% before to 17.3% after initiation of the model; P=.08).

CONCLUSION

Improved continuity of care among hospitalists was associated with reductions in length of stay and lower health care costs. These benefits were realized without substantially affecting readmission rates. The staffing model can be achieved by reorganizing existing hospitalists and may not require the hiring of additional personnel. The CICLE staffing model is a viable option for hospitalist groups that are aiming to diminish resource use and improve quality of care.

Research in progress conference for hospitalists provides valuable peer mentoring

BACKGROUND

Many academic hospitalist units lack senior mentors. In such groups, peer mentoring may be valuable. To formalize collaboration, we instituted a research-in-progress conference at our institution, and this article describes the format and evaluation data.

METHODS

The research-in-progress sessions were held every 3 to 4 weeks and followed a specific format. Evaluation forms were completed after each of the 15 sessions during the 2009 academic year. Attendees and presenters completed surveys at the end of the sessions. The projects presented were tracked for successful academic outcomes, namely, publication in a peer-reviewed journal or presentation at a national meeting.

RESULTS

A mean of 9.6 persons were present at each session and completed the evaluations. All 15 presenters rated the climate of the sessions as extremely supportive, and 86% believed they were helpful in advancing their project. A total of 143 evaluations were completed by the attendees, 86% and 96% of whom found the sessions to be intellectually stimulating and to have satisfactorily kept them abreast of their colleagues' scholarly pursuits, respectively. To date, 10 of the 15 projects have translated into successful academic outcomes: 6 peer-reviewed publications and 4 other presentations presented at national meetings.

CONCLUSIONS

The research-in-progress conference has been well received and has resulted in academic productivity within our hospitalist division. It is likely that such a conference will be most valuable for groups with limited access to senior mentors.

Hospitalist physician leadership skills: perspectives from participants of a leadership conference

OBJECTIVE

To characterize how the use of behavioral contracts may serve to focus individuals' intentions to grow as leaders.

METHODS

Between 2007 and 2008, participants of the Society of Hospital Medicine Leadership Academy courses completed behavioral contracts to identify 4 action plans they wanted to implement based on things learned at the Academy. Contracts were independently coded by 2 investigators and compared for agreement. Content analysis identified several major themes that relate to professional growth as leaders. Follow-up surveys assessed fulfillment of personal goals.

RESULTS

The majority of respondents were male (84; 70.0%), and most were hospitalist leaders (76; 63.3%). Their median time practicing as hospitalists was 4 years, 14 (11.7%) were Assistant Professors, and 80 (66.7%) were in private practice. Eight themes emerged from the behavioral contracts, revealing ways in which participants wished to develop: improving communication and interpersonal relations; refining vision and goals for strategic planning; developing intrapersonal leadership; enhancing negotiation skills; committing to organizational change; understanding business drivers; establishing better metrics to assess performance; and strengthening interdepartmental relationships. At follow-up, all but 1 participant had achieved at least 1 of their personal goals.

CONCLUSIONS

Understanding the areas that hospitalist leaders identify as "learning edges" may inform the personal learning plans of those hoping to take on leadership roles in hospital medicine.

Pilot study comparing patients' valuation of health-care services with Medicare's relative value units

BACKGROUND AND AIMS

Physician reimbursement for services and thus income are largely determined by the Medicare Resource-Based Relative Value Scale. Patients' assessment of the value of physician services has never been considered in the calculation. This study sought to compare patients' valuation of health-care services to Medicare's relative value unit (RVU) assessments and to discover patients' perceptions about the relative differences in incomes across physician specialties.

DESIGN

Cross-sectional survey.

PARTICIPANTS AND SETTING

Individuals in select outpatient waiting areas at Johns Hopkins Bayview Medical Center.

METHODS

Data collection included the use of a visual analog 'value scale' wherein participants assigned value to 10 specific physician-dependent health-care services. Informants were also asked to estimate the annualized incomes of physicians in specialties related to the above-mentioned services. Comparisons of (i) the 'patient valuation RVUs' with actual Medicare RVUs, and (ii) patients' estimations of physician income with actual income were explored using t-tests.

OUTCOMES

Of the 206 eligible individuals, 186 (90%) agreed to participate. Participants assigned a significantly higher mean value to 7 of the 10 services compared with Medicare RVUs (P<0.001) and the range in values assigned by participants was much smaller than Medicare's (a factor of 2 vs. 22). With the exception of primary care, respondents estimated that physicians earn significantly less than their actual income (all P<0.001) and the differential across specialties was thought to be much smaller (estimate: $88,225, actual: $146,769).

CONCLUSION

In this pilot study, patients' estimations of the value health-care services were markedly different from the Medicare RVU system. Mechanisms for incorporating patients' valuation of services rendered by physicians may be warranted.

Hand-carried ultrasound performed by hospitalists: does it improve the cardiac physical examination?

OBJECTIVE

The traditional physical examination of the heart is relatively inaccurate. There is little information regarding whether cardiac hand-carried ultrasound performed by noncardiologists adds to the accuracy of physical examinations. The purpose of this study was to determine whether hand-carried ultrasound can add to the accuracy of hospitalists' cardiac physical examinations.

METHODS

During a focused training program in hand-carried echocardiography, 10 hospitalists performed cardiac examinations of 354 general medical inpatients first by physical examination and then by hand-carried ultrasound. Eligible inpatients included those for whom a conventional hospital echocardiogram was ordered. We measured how frequently the hospitalists' cardiac examination with or without hand-carried ultrasound matched or came within 1 scale level of an expert cardiologist's interpretation of the hospital echocardiogram.

RESULTS

Adding hand-carried ultrasound to the physical examination improved hospitalists' assessment of left ventricular function, cardiomegaly, and pericardial effusion. For left ventricular function, using hand-carried ultrasound increased the percentage of exact matches with the expert cardiologist's assessment from 46% to 59% (P=.005) and improved the percentage of within 1-level matches from 67% to 88% (P=.0001). The addition of hand-carried ultrasound failed to improve the assessments of aortic stenosis, aortic regurgitation, and mitral regurgitation.

CONCLUSION

Adding hand-carried ultrasound to physical examination increases the accuracy of hospitalists' assessment of left ventricular dysfunction, cardiomegaly, and pericardial effusion, and fails to improve assessment of valvular heart disease. The clinical benefit achieved by improved immediacy of this information has not been determined. An important limitation is that the study assessed only 1 level of training in hand-carried ultrasound.

Physician-teacher characteristics associated with learner-centered teaching skills

BACKGROUND

Academic institutions do not have a way to identify physician-teachers who are proficient in learner-centered teaching.

AIM

To identify physician characteristics associated with being highly learner-centered.

METHODS

A cohort of 363 physicians was surveyed. Measured items included personal characteristics, professional characteristics, teaching activities, self-assessed teaching proficiencies and behaviors, and scholarly activities. A learner-centeredness scale was developed using factor analysis. Logistic regression models were used to determine which characteristics were independently associated with scoring highly on the learner-centeredness scale.

RESULTS

Two hundred and ninety-nine physicians responded (82%) of whom 262 (88%) had taught medical learners in the prior 12 months. Six variables combined to form the learner-centeredness scale and the Cronbach Alpha of the scale was 0.73. The eight characteristics independently associated with high learner-centered scores for physician teachers were (i) proficiency in giving lectures or presentations (OR ;= ;5.1, 95% CI: 1.3-19.6), (ii) frequently helping learners identify resources to meet their own needs (OR ;= ;3.7, 95% CI: 1.3-10.3), (iii) proficiency in eliciting feedback from learners (OR ;= ;3.7, 95% CI: 1.7-8.5), (iv) frequently attempting to detect and discuss emotional responses of the learners (OR ;= ;2.9, 95% CI: 1.2-6.9), (v) frequently reflecting on the validity of feedback from the learners (OR ;= ;2.8, 95% CI: 1.1-7.4), (vi) frequently identifying available resources to meet the teacher's learning needs (OR ;= ;2.8, 95% CI: 1.1-7.2), (vii) having given an oral presentation related to education at a national/regional meeting (OR ;= ;2.6, 95% CI: 1.1-6.0), and (viii) frequently letting learners know how different situations affect the teacher (OR ;= ;2.5, 95% CI: 1.1-5.5).

CONCLUSIONS

The clinical competence and professional growth of medical learners can be most effectively facilitated by learner-centered educational methods. It may now be possible to identify medical educators who are more learner-centered in their teaching.

What motivates physicians throughout their careers in medicine?

Motivation provides direction and purpose in physicians' work, and motivating factors vary during different career stages. Motivation theories divide sources of motivation into those intrinsic to the work, such as the opportunity for self-expression and intellectual challenge, and those extrinsic to the work, such as salary and time. Although much attention has focused on minimizing negative extrinsic factors, the authors argue that career resilience requires that physicians reflect on and define the sources of their own intrinsic motivation. Opportunities to maximize self-awareness may allow physicians to structure their work in ways that maximize meaning and fulfillment over the long-term.

Hospitalist performance of cardiac hand-carried ultrasound after focused training

PURPOSE

Because the training that noncardiologists require to perform cardiac hand-carried ultrasound has not been defined, we studied how well hospitalists perform hand-carried echocardiography after limited training.

METHODS

Ten hospitalists completed a focused training program that included performing an average of 35 hand-carried echocardiograms. Hospitalists' echocardiograms were compared with gold-standard conventional echocardiograms, and hospitalists were compared with 5 certified echocardiography technicians in their ability to acquire, measure, and interpret hand-carried ultrasound images and with 6 senior cardiology fellows in their ability to interpret echocardiograms.

RESULTS

Echocardiography technicians had significantly higher performance scores for image acquisition, measurement, and interpretation than hospitalists. Senior cardiology fellows outperformed hospitalists in most aspects of image interpretation. For hospitalists, learning image acquisition was more difficult than image interpretation.

CONCLUSIONS

Hospitalists can learn aspects of hand-carried echocardiography, but after 35 training echocardiograms cannot replicate the quality of conventional echocardiography. Whether the lower performance skills are important will depend on the clinical context of hand-carried echocardiography performed by hospitalists.

Insufficient treatment of hypercholesterolemia among patients hospitalized with chest pain

BACKGROUND

Although morbidity and mortality from coronary artery disease can be improved with a variety of pharmacologic interventions, many patients remain undertreated.

HYPOTHESIS

This study sought to assess whether hospitalization for possible coronary artery disease would prompt initiation of appropriate lipid-lowering therapy.

METHODS

This prospective, observational study was conducted on consecutive patients with active chest pain admitted to the Emergency Department of the hospital for suspected myocardial ischemia. Elevated cholesterol, defined as low-density lipoprotein (LDL), was >100 mg/dl with a prior history or a new diagnosis of coronary artery disease, or an LDL >130 mg/dl without known coronary artery disease. Data were recorded at the time of admission, discharge, and at 4-month follow-up.

RESULTS

Of the patients with hyperlipidemia, 65% men and 55% women were on medication at the time of admission (p = 0.30), while at discharge, 79% men and 60% women were on treatment (p = 0.002), with similar rates of treatment at 4-month follow-up (p = 0.030). At discharge, two variables were independently associated with patients receiving lipid-lowering therapy: age > or =65 years (odds ratio = 2.3; 95% confidence interval 1.2-4.5) and male gender (2.7; 15-5.0).

CONCLUSIONS

In patients hospitalized with chest pain, particularly in women, the initiation of treatment of hyperlipidemia frequently does not happen. This oversight represents a lost opportunity for making an impact on the health of this population.

Residents' perceptions of professionalism in training and practice: barriers, promoters, and duty hour requirements

BACKGROUND

The Accreditation Council for Graduate Medical Education duty hour requirements may affect residents' understanding and practice of professionalism.

OBJECTIVE

We explored residents' perceptions about the current teaching and practice of professionalism in residency and the impact of duty hour requirements.

DESIGN

Anonymous cross-sectional survey.

PARTICIPANTS

Internal medicine, neurology, and family practice residents at 3 teaching hospitals (n=312).

MEASUREMENTS

Using Likert scales and open-ended questions, the questionnaire explored the following: residents' attitudes about the principles of professionalism, the current and their preferred methods for teaching professionalism, barriers or promoters of professionalism, and how implementation of duty hours has affected professionalism.

RESULTS

One hundred and sixty-nine residents (54%) responded. Residents rated most principles of professionalism as highly important to daily practice (91.4%, 95% confidence interval [CI] 90.0 to 92.7) and training (84.7%, 95% CI 83.0 to 86.4), but fewer rated them as highly easy to incorporate into daily practice (62.1%, 95% CI 59.9 to 64.3), particularly conflicts of interest (35.3%, 95% CI 28.0 to 42.7) and self-awareness (32.0%, 95% CI 24.9 to 39.1). Role-modeling was the teaching method most residents preferred. Barriers to practicing professionalism included time constraints, workload, and difficulties interacting with challenging patients. Promoters included role-modeling by faculty and colleagues and a culture of professionalism. Regarding duty hour limits, residents perceived less time to communicate with patients, continuity of care, and accountability toward their colleagues, but felt that limits improved professionalism by promoting resident well-being and teamwork.

CONCLUSIONS

Residents perceive challenges to incorporating professionalism into their daily practice. The duty hour implementation offers new challenges and opportunities for negotiating the principles of professionalism.

Residents' perceptions of professionalism in training and practice: barriers, promoters, and duty hour requirements

BACKGROUND

The Accreditation Council for Graduate Medical Education duty hour requirements may affect residents' understanding and practice of professionalism.

OBJECTIVE

We explored residents' perceptions about the current teaching and practice of professionalism in residency and the impact of duty hour requirements.

DESIGN

Anonymous cross-sectional survey.

PARTICIPANTS

Internal medicine, neurology, and family practice residents at 3 teaching hospitals (n=312).

MEASUREMENTS

Using Likert scales and open-ended questions, the questionnaire explored the following: residents' attitudes about the principles of professionalism, the current and their preferred methods for teaching professionalism, barriers or promoters of professionalism, and how implementation of duty hours has affected professionalism.

RESULTS

One hundred and sixty-nine residents (54%) responded. Residents rated most principles of professionalism as highly important to daily practice (91.4%, 95% confidence interval [CI] 90.0 to 92.7) and training (84.7%, 95% CI 83.0 to 86.4), but fewer rated them as highly easy to incorporate into daily practice (62.1%, 95% CI 59.9 to 64.3), particularly conflicts of interest (35.3%, 95% CI 28.0 to 42.7) and self-awareness (32.0%, 95% CI 24.9 to 39.1). Role-modeling was the teaching method most residents preferred. Barriers to practicing professionalism included time constraints, workload, and difficulties interacting with challenging patients. Promoters included role-modeling by faculty and colleagues and a culture of professionalism. Regarding duty hour limits, residents perceived less time to communicate with patients, continuity of care, and accountability toward their colleagues, but felt that limits improved professionalism by promoting resident well-being and teamwork.

CONCLUSIONS

Residents perceive challenges to incorporating professionalism into their daily practice. The duty hour implementation offers new challenges and opportunities for negotiating the principles of professionalism.

Female sex: a protective role in suspected myocardial ischemia

OBJECTIVE

Women are felt to have poor outcomes in coronary artery disease, largely on the basis of secondary observations in acute coronary syndrome trials. We sought to examine the neglected topic of sex differences in workup and outcomes in the general population presenting with chest pain.

METHODS

We examined 439 consecutive patients admitted via the emergency department with ongoing chest pain. Cardiac testing was defined as any cardiac catheterization or stress test. Positive testing was defined as a 70% or greater stenosis in an epicardial coronary artery on catheterization, or a positive stress test result. Follow-up was obtained via telephone contact at 4 months following discharge.

RESULTS

Further cardiac testing was deemed necessary in 68% (164/241) of women and 77% (153/198) of men (P=0.038). Among women undergoing further testing, only 21% (35/164) had positive tests, whereas 41% (62/153) of men had positive tests (P=0.002). At 4 months, women were less likely to have suffered the combined endpoint of subsequent myocardial infarction, revascularization, or death, than men (15 vs. 23%, P=0.027). Events were more likely to occur in patients who had further testing, and especially in those who had positive testing.

CONCLUSIONS

These data suggest that women admitted with chest pain are less likely to have active coronary artery disease, and much less likely to have poor outcomes at 4 months than men. This apparent 'gender protection' effect warrants further study.

Hospitalists and an innovative emergency department admission process

After treatment in an emergency department (ED), patients often wait several hours for hospital admission, resulting in dissatisfaction and increased wait times for both admitted and other ED patients. We implemented a new direct admission system based on telephone consultation between ED physicians and in-house hospitalists. We studied this system, measuring admission times, length of stay, and mortality. Postintervention, admission times averaged 18 minutes for transfer to the ward compared to 2.5 hours preintervention, while pre- and postintervention length of stay and mortality rates remained similar.

Prognostic usefulness of marginal troponin T elevation

Marginal elevations of troponin T among patients with chest pain are often considered to be insignificant. We sought to define the prognostic value of marginal troponin T elevations in patients presenting to the emergency department with suspected myocardial ischemia. Four hundred twenty-eight consecutive patients presenting to the emergency department with ongoing chest pain were evaluated, followed through their hospital course, and contacted for follow-up 4 months after discharge. Two hundred ninety-nine patients had undetectable troponin T levels (<0.01 microg/L), 76 had marginal troponin T elevations (0.01 to 0.09 microg/L), and 53 had frank troponin T elevations (> or =0.1 microg/L). Patients with either marginally or frank elevated troponin levels were older and more likely to be men, but did not differ from patients with undetectable troponin levels with regard to the prevalence of coronary artery disease risk factors, history of coronary disease, or race. While in the hospital, the undetectable and marginal troponin groups were referred for cardiac testing in equal proportions (58% and 59%, respectively), whereas 87% of the elevated group underwent further testing. After adjustment for possible confounders, a significantly increased rate of death/myocardial infarction/revascularization was observed in the marginal troponin group compared with the undetectable troponin group (p = 0.004). Marginal elevations of troponin T identified a currently underevaluated high-risk subgroup of patients with suspected myocardial ischemia who are more likely to have adverse clinical outcomes than those with undetectable troponin levels.

Chest pain relief by nitroglycerin does not predict active coronary artery disease

BACKGROUND

The belief that chest pain relief with nitroglycerin indicates the presence of active coronary artery disease is common. However, this hypothesis has not been tested.

OBJECTIVE

To define the diagnostic and prognostic value of chest pain relief with nitroglycerin.

DESIGN

Prospective observational cohort study.

SETTING

Urban community teaching hospital.

PATIENTS

459 consecutive patients with chest pain admitted through the emergency department who received nitroglycerin from emergency services personnel or an emergency department nurse. Follow-up was obtained by telephone contact at 4 months.

MEASUREMENTS

Chest pain relief was defined as a decrease of at least 50% in patients' self-reported pain within 5 minutes of the initial dose of sublingual or spray nitroglycerin. Active coronary artery disease was defined as any elevated serum enzyme levels, coronary angiography demonstrating a 70% or greater stenosis, or a positive exercise test result.

RESULTS

Nitroglycerin relieved chest pain in 39% of patients (181 of 459). In patients with active coronary artery disease as the likely cause of their chest pain, 35% (49 of 141) had chest pain relief with nitroglycerin. In contrast, in patients without active coronary artery disease, 41% (113 of 275) had chest pain relief (P > 0.2). Four-month clinical outcomes were similar in patients with or without chest pain relief with nitroglycerin (P > 0.2).

CONCLUSIONS

These data suggest that, in a general population admitted for chest pain, relief of pain after nitroglycerin treatment does not predict active coronary artery disease and should not be used to guide diagnosis.

One site fits both: a model for the ternary complex of folate + NADPH in R67 dihydrofolate reductase, a D2 symmetric enzyme

R67 dihydrofolate reductase (DHFR) is a novel enzyme that confers resistance to the antibiotic trimethoprim. The crystal structure of R67 DHFR displays a toroidal structure with a central active-site pore. This homotetrameric protein exhibits 222 symmetry, with only a few residues from each chain contributing to the active site, so related sites must be used to bind both substrate (dihydrofolate) and cofactor (NADPH) in the productive R67 DHFR.NADPH.dihydrofolate complex. Whereas the site of folate binding has been partially resolved crystallographically, an interesting question remains: how can the highly symmetrical active site also bind and orient NADPH for catalysis? To model this ternary complex, we employed DOCK and SLIDE, two methods for docking flexible ligands into proteins using quite different algorithms. The bound pteridine ring of folate (Fol I) from the crystal structure of R67 DHFR was used as the basis for docking the nicotinamide-ribose-Pi (NMN) moiety of NADPH. NMN was positioned by both DOCK and SLIDE on the opposite side of the pore from Fol I, where it interacts with Fol I at the pore's center. Numerous residues serve dual roles in binding. For example, Gln 67 from both the B and D subunits has several contacts with the pteridine ring, while the same residue from the A and C subunits has several contacts with the nicotinamide ring. The residues involved in dual roles are generally amphipathic, allowing them to make both hydrophobic and hydrophilic contacts with the ligands. The result is a 'hot spot' binding surface allowing the same residues to co-optimize the binding of two ligands, and orient them for catalysis.

Role of S65, Q67, I68, and Y69 residues in homotetrameric R67 dihydrofolate reductase

R67 dihydrofolate reductase (DHFR) shares no sequence or structural homology with chromosomal DHFRs. This enzyme arose recently in response to the clinical use of the antibacterial drug trimethoprim. R67 DHFR is a homotetramer possessing a single active site pore. A high-resolution crystal structure shows the homotetramer possesses exact 222 symmetry [Narayana, N., et al. (1995) Nat. Struct. Biol. 2, 1018-1025]. This symmetry dictates four symmetry-related binding sites must exist for each substrate as well as each cofactor. Isothermal titration calorimetry studies, however, indicate only two molecules bind: either two dihydrofolate molecules, two NADPH molecules, or one substrate and one cofactor [Bradrick, T. D., et al. (1996) Biochemistry 35, 11414-11424]. The latter is the productive ternary complex. To evaluate the role of S65, Q67, I68, and Y69 residues, located near the center of the active site pore, site-directed mutagenesis was performed. One mutation in the gene creates four mutations per active site pore which typically result in large cumulative effects. Steady state kinetic data indicate the mutants have altered K(m) values for both cofactor and substrate. For example, the Y69F R67 DHFR displays an 8-fold increase in the K(m) for dihydrofolate and a 20-fold increase in the K(m) for NADPH. Residues involved in ligand binding in R67 DHFR display very little, if any, specificity, consistent with their possessing dual roles in binding. These results support a model where R67 DHFR utilizes an unusual "hot spot" binding surface capable of binding both ligands and indicate this enzyme has adopted a novel yet simple approach to catalysis.

Interligand Overhauser effects in type II dihydrofolate reductase

R67 dihydrofolate reductase (DHFR) is a type II DHFR produced by bacteria as a resistance mechanism to the increased clinical use of the antibacterial drug trimethoprim. Type II DHFRs are not homologous in either sequence or structure with chromosomal DHFRs. The type II enzymes contain four identical subunits which form a homotetramer containing a single active site pore accessible from either end. Although the crystal structure of the complex of R67 DHFR with folate has been reported [Narayana et al. (1995) Nat. Struct. Biol. 2, 1018], the nature of the ternary complex which must form with substrate and cofactor is unclear. We have performed transferred NOE and interligand NOE (ILOE) studies to analyze the ternary complexes formed from NADP(+) and folate in order to probe the structure of the ternary complex. Consistent with previous studies of the binary complex formed from another type II DHFR, the ribonicotinamide bond of NADP(+) was found to adopt a syn conformation, while the adenosine moiety adopts an anti conformation. Large ILOE peaks connecting NADP(+) H4 and H5 with folate H9 protons are observed, while the absence of a large ILOE connecting NADP(+) H4 and H5 with folate H7 indicates that the relative orientation of the two ligands differs significantly from the orientation in the chromosomal enzyme. To obtain more detailed insight, we prepared and studied the folate analogue 2-deamino-2-methyl-5,8-dideazafolate (DMDDF) which contains additional protons in order to provide additional NOEs. For this analogue, the exchange characteristics of the corresponding ternary complex were considerably poorer, and it was necessary to utilize higher enzyme concentrations and higher temperature in order to obtain ILOE information. The results support a structure in which the NADP(+) and folate/DMDDF molecules extend in opposite directions parallel to the long axis of the pore, with the nicotinamide and pterin ring systems approximately stacked at the center. Such a structure leads to a ternary complex which is in many respects similar to the gas-phase theoretical calculations of the dihydrofolate-NADPH transition state by Andres et al. [(1996) Bioorg. Chem. 24, 10-18]. Analogous NMR studies performed on folate, DMDDF, and R67 DHFR indicate formation of a ternary complex in which two symmetry-related binding sites are occupied by folate and DMDDF.

Effects of single-tryptophan mutations on R67 dihydrofolate reductase

R67 dihydrofolate reductase (DHFR) is an R-plasmid-encoded enzyme that confers clinical resistance to the antibacterial drug trimethoprim. This enzyme shows no sequence or structural homology to the chromosomal DHFRs. The active form of the protein is a homotetramer possessing D(2) symmetry and a single active-site pore. Two tryptophans occur per monomer: W38 and its symmetry-related residues (W138, W238, and W338) occur at the dimer-dimer interfaces, while W45 and its symmetry-related partners (W145, W245, and W345) occur at the monomer-monomer interfaces. Two single-tryptophan mutant genes were constructed to determine the structural and functional consequences of four mutations per tetramer. The W45F mutant retains full enzyme activity and the fluorescence environment of the unmutated W38 residues clearly monitors ligand binding and a pH dependent tetramer right harpoon over left harpoon 2 dimers equilibrium. In contrast, four simultaneous W38F mutations at the dimer-dimer interfaces result in tetramer destabilization. The ensuing dimer is relatively inactive, as is dimeric wild-type R67 DHFR. A comparison of emission spectra indicates the fluorescent signal of wild-type R67 DHFR is dominated by the contribution from W38. Equilibrium unfolding/folding curves at pH 5.0, where all protein variants are dimeric, indicate the environment monitored by the W38 residue is slightly less stable than the environment monitored by the W45 residue.

A case of post-streptococcal reactive arthritis

Reactive arthritis is a term used to describe a sterile inflammatory arthritis occurring after a documented infection elsewhere in the body. Group A streptococcus is known to cause such an arthropathy in the setting of acute rheumatic fever. Friedberg first postulated that a reactive arthritis might occur in response to a streptococcal pharyngeal infection as a separate entity from rheumatic fever in the 1950s. Then, in the 1980s, other investigators began describing cases of reactive arthritis that were not characteristic of acute rheumatic fever based on certain observations and application of criteria. We present a patient whose clinical features are more consistent with post-streptococcal reactive arthritis than acute rheumatic fever.

A glutamine 67--> histidine mutation in homotetrameric R67 dihydrofolate reductase results in four mutations per single active site pore and causes substantial substrate and cofactor inhibition

R67 dihydrofolate reductase (DHFR) is a type II DHFR produced by bacteria as a resistance mechanism to increasing clinical use of the antibacterial drug trimethoprim. Type II DHFRs are not homologous in either sequence or structure with chromosomal DHFRs. The crystal structure of R67 DHFR shows a single active site pore that spans the length of the homotetramer. Related sites (due to a 222 symmetry element at the center of the pore) are used to bind ligands, i.e. each half of the pore can accommodate either the substrate, dihydrofolate (DHF), or the cofactor, NADPH, although DHF and NADPH are bound differently. To evaluate the role of glutamine 67 (and its symmetry-related Q167, Q267 and Q367 residues which occur at the center of the active site pore), a Q67H mutation was constructed. Binary binding of dihydrofolate (DHF; monitored by isothermal titration calorimetry) displays two identical sites with a Kd value of 0.04 microM, while binding of NADPH shows two sites possessing negative cooperativity with Kd values of 0.027 and 0.62 microM. A comparison of ligand binding in Q67H versus wild-type (wt) R67 DHFR indicates both ligands bind more tightly (80-6000-fold) and DHF binding in Q67H R67 DHFR no longer displays positive cooperativity as seen in wt R67 DHFR. Ternary complex binding in the Q67H mutant indicates a total of two ligands can bind per pore. Substantial substrate and cofactor inhibition are observed during catalysis, consistent with non-productive binding of either two DHF or two NADPH molecules in Q67H R67 DHFR. Because of the symmetry-related binding sites in the active site pore, the accumulation of potentially positive mutations in R67 DHFR is limited by the balance between tighter binding of ligands (and thus potentially increased catalytic efficiency) and inhibition that arises upon tighter binding of two identical ligands at symmetry-related sites.

Effects of insertions and deletions in a beta-bulge region of Escherichia coli dihydrofolate reductase

The role of a beta-bulge in Escherichia coli dihydrofolate reductase (DHFR) has been explored by a series of insertion and deletion mutations. Insertion of a seven amino acid sequence from a structurally equivalent 'beta-blowout' sequence from human DHFR destabilizes E. coli DHFR by 3.6 kcal/mol and decreases catalytic efficiency (kcat/K(m)) 34-fold. Deletion of F137, delta 137, the looped out residue in the bulge, also destabilizes E. coli DHFR by 2.8 kcal/mol but only decreases catalytic efficiency threefold. Concurrent deletion of F137 and mutation of, V136 to proline to try and maintain the strand twist associated with the beta-bulge decreases protein stability by 3.4 kcal/mol and decreases catalytic efficiency 84-fold. These insertion/deletion mutations were also constructed in a D27S DHFR background. The D27S mutation has been described previously and proposed to remove the catalytic acid from the active site. The delta 137 mutation partially suppresses the effect of the D27S mutation as it decreases the K(m) for substrate, dihydrofolate, twofold. Non-additive effects are observed for the insertion/deletion mutations in wild-type versus D27S DHFR backgrounds, consistent with structural changes.

Mechanistic studies of R67 dihydrofolate reductase. Effects of pH and an H62C mutation

R67 dihydrofolate reductase (DHFR) is encoded by an R-plasmid, and expression of this enzyme in bacteria confers resistance to the antibacterial drug, trimethoprim. This DHFR variant is not homologous in either sequence or structure with chromosomal DHFRs. The crystal structure of tetrameric R67 DHFR indicates a single active site pore that traverses the length of the molecule (Narayana, N., Matthews, D. A., Howell, E. E., and Xuong, N.-H. (1995) Nat. Struct. Biol. 2, 1018-1025). A pH profile of enzyme activity in R67 DHFR displays an acidic pKa that is protein concentration-dependent. This pKa describes dissociation of active tetramer into two relatively inactive dimers upon protonation of His-62 and the symmetry-related His-162, His-262, and His-362 residues at the dimer-dimer interfaces. Construction of an H62C mutation results in stabilization of the active tetramer via disulfide bond formation at the dimer-dimer interfaces. The oxidized, tetrameric form of H62C R67 DHFR is quite active at pH 7, and a pH profile displays increasing activity at low pH. These results indicate protonated dihydrofolate (pKa = 2.59) is the productive substrate and that R67 DHFR does not possess a proton donor.

Dynamics of trimethoprim bound to dihydrofolate reductase--a deuterium NMR study

We have employed deuterium NMR techniques to determine the dynamics of trimethoprim (TMP) in a binary complex with dihydrofolate reductase (DHFR) or in a ternary complex with DHFR and cofactor NADP+ in the fully hydrated state. TMP was deuterated at the following positions: (2',6'-D2)TMP, (3'-Ome-D3)TMP and (3',4'-Ome-D6)TMP. Dynamics of TMP were deduced from lineshape simulation and relaxation measurements of the deuterium NMR powder spectra of the three samples obtained at various temperatures. The results showed that in the polycrystalline state the TMP molecule is very rigid. The only detectable motion is the methyl group rotation at a rate of 10(10) s-1 at 25 degrees C, as determined from simulation of the partially relaxed powder patterns. When bound to DHFR a residual deuterium quadrupole splitting of 140 kHz was observed for (2',6'-D2)TMP at temperatures up to 30 degrees C, suggesting that the benzyl ring in the bound state is also very rigid. In contrast, in the binary complex with DHFR the methoxyl groups of TMP undergo librational motion of 10(7) s-1 about the C3-O bond at an amplitude of 54 degrees for the meta methoxyl group and about the C4-O bond at an amplitude of 70 degrees and similar rate for the para methoxyl group at 30 degrees C. The presence of the cofactor, NADP+, appears to tighten up the binding pocket such that the motion freedom of TMP is more restricted. The rigidity of TMP in a protein complex as revealed by our deuterium NMR results is in accord with the tight binding of TMP to DHFR.

Redesigning the quaternary structure of R67 dihydrofolate reductase. Creation of an active monomer from a tetrameric protein by quadruplication of the gene

R67 dihydrofolate reductase (DHFR) provides resistance to the antibacterial drug trimethoprim. This R-plasmid-encoded enzyme does not share any homology with chromosomal DHFR. A recent crystal structure of active, homotetrameric R67 DHFR (Narayana, N., Matthews, D. A., Howell, E. E., and Xuong, N.-H. (1995) Nat. Struct. Biol. 2, 1018-1025) indicates that a single active site pore traverses the length of the molecule. Since the center of the pore possesses exact 222 symmetry, site-directed mutagenesis of residues in the pore will produce four mutations/active site. To break this inevitable symmetry, four copies of the gene have been linked in frame to create an active monomer possessing the essential tertiary structure of native tetrameric R67 DHFR. The protein product, quadruple R67 DHFR, is 4 times the molecular mass of native R67 DHFR in SDS-polyacrylamide gel electrophoresis and is monomeric under nondenaturing conditions as measured by sedimentation equilibrium experiments. The catalytic activity of quadruple R67 DHFR is decreased only slightly when compared with native R67 DHFR. Folding of quadruple R67 DHFR is completely reversible at pH 5. However, at pH 8, folding is not fully reversible; this is likely due to a competition between productive intramolecular versus nonproductive intermolecular domain association. The production of a fully active, monomeric R67 DHFR variant will enable the design of more meaningful site-directed mutants where single substitutions per active site pore can be generated.

Unusual binding stoichiometries and cooperativity are observed during binary and ternary complex formation in the single active pore of R67 dihydrofolate reductase, a D2 symmetric protein

R67 dihydrofolate reductase (DHFR) is an R-plasmid-encoded enzyme that confers resistance to the antibacterial drug, trimethoprim. This DHFR variant is not homologous in either sequence or structure to chromosomal DHFRs. A recent crystal structure of the active tetrameric species describes a single active site pore that traverses the length of the protein (Narayana et al., 1995). Related sites (due to a 222 symmetry element at the center of the active site pore) are used for binding of ligands, i.e., each half-pore can accommodate either the substrate, dihydrofolate, or the cofactor, NADPH, although dihydrofolate and NADPH are bound differently. Ligand binding in R67 DHFR was evaluated using time-resolved fluorescence anisotropy and isothermal titration calorimetry techniques. Under binary complex conditions, two molecules of either NADPH, folate, dihydrofolate, or N10 propargyl-5,8-dideazafolate (CB3717) can be bound. Binding of NADPH displays negative cooperativity, binding of either folate or dihydrofolate shows positive cooperativity, and binding of CB3717 shows two identical sites. Any asymmetry introduced by binding of one ligand is proposed to induce the cooperativity associated with binding of the second ligand. Evaluation of ternary complex formation demonstrates that one molecule of folate binds to a 1:1 mixture of R67 DHFR+NADPH. These binding results indicate a maximum of two ligands bind in the pore. A mechanism describing catalysis is proposed that is consistent with the binding results.

A plasmid-encoded dihydrofolate reductase from trimethoprim-resistant bacteria has a novel D2-symmetric active site

Bacteria expressing R67-plasmid encoded dihydrofolate reductase (R67 DHFR) exhibit high-level resistance to the antibiotic trimethoprim. Native R67 DHFR is a 34,000 M(r) homotetramer which exists in equilibrium with an inactive dimeric form. The structure of native R67 DHFR has now been solved at 1.7 A resolution and is unrelated to that of chromosomal DHFR. Homotetrameric R67 DHFR has an unusual pore, 25 A in length, passing through the middle of the molecule. Two folate molecules bind asymmetrically within the pore indicating that the enzyme's active site consists of symmetry related binding surfaces from all four identical units.

Equilibrium folding studies of tetrameric R67 dihydrofolate reductase

R67 dihydrofolate reductase (DHFR) is an R-plasmid encoded enzyme that confers resistance to the antibacterial drug trimethoprim. This enzyme is not homologous in sequence or structure to chromosomal DHFRs. Equilibrium folding of tetrameric R67 DHFR was studied and found to be fully reversible. Formation of an inactive intermediate was assayed by loss of enzyme activity. Denaturation of the intermediate was monitored by concurrent changes in fluorescence and circular dichroism signals. Both transitions are protein concentration dependent. A simple model fitting these data is tetramer<==>2 dimers<==>4 unfolded monomers. No evidence for folded monomer was found. Global fitting of all the folding data yielded a delta GH2O of -9.63 kcal/mol for the initial transition and a delta GH2O of -12.35 kcal/mol for the second transition. In addition, thermal unfolding of tetrameric R67 DHFR was found to be reversible A folding intermediate also occurred during thermal unfolding as evidenced by the asymmetric endotherms and a delta Hcalorimetric/delta H(van't Hoff) ratio of 2.1.

Long-range structural effects in a second-site revertant of a mutant dihydrofolate reductase

X-ray crystal structures have been determined for a second-site revertant (Asp-27-->Ser, Phe-137-->Ser; D27S/F137S) and both component single-site mutants of Escherichia coli dihydrofolate reductase. The primary D27S mutation, located in the substrate binding pocket, greatly reduces catalytic activity as compared to the wild-type enzyme. The additional F137S mutation, which partially restores catalytic activity, is located on the surface of the molecule, well outside of the catalytic center and approximately 15 A from residue 27. Comparison of kinetic data for the single-site F137S mutant, specifically constructed as a control, and for the double-mutant enzymes indicates that the effects of the F137S and D27S mutations on catalysis are nonadditive. This result suggests that the second-site mutation might mediate its effects through a structural perturbation propagated along the polypeptide backbone. To investigate the mechanism by which the F137S substitution elevates the catalytic activity of D27S we have determined the structure of the D27S/F137S double mutant. We also present a rerefined structure for the original D27S mutant and a preliminary structural interpretation for the F137S single-site mutant. We find that while either single mutant shows little more than a simple side-chain substitution, the double mutant undergoes an extended structural perturbation, which is propagated between these two widely separated sites via the helix alpha B.

Artificial duplication of the R67 dihydrofolate reductase gene to create protein asymmetry. Effects on protein activity and folding

R67 dihydrofolate reductase (DHFR), encoded by an R plasmid, provides resistance to the antibacterial drug trimethoprim. This enzyme does not exhibit any structural or sequence homologies with chromosomal DHFR. A recent crystal structure of tetrameric R67 DHFR (D. Matthews, X. Nguyen-huu, and N. Narayana, personal communication) shows a single pore traversing the length of the molecule. Numerous physical and kinetic experiments suggest the pore is the active site. Since the center of the pore possesses exact 222 symmetry, mutagenesis of residues designed to explore substrate binding will probably also affect cofactor binding. As a first step in breaking this inevitable symmetry in R67 DHFR, the gene has been duplicated. The protein product, R67 DHFRdouble, is twice the molecular mass of native R67 DHFR and is fully active with kcat = 1.2 s-1, Km(NADPH) = 2.7 microM and Km(dihydrofolate) = 6.3 microM. Equilibrium unfolding studies in guanidine-HCl indicate R67 DHFRdouble is more stable than native R67 DHFR at physically reasonable protein concentrations. Microcalorimetry studies show native R67 DHFR undergoes fully reversible thermal unfolding. Unfolding can be described by a two-state process since a ratio of delta Hcalorimetric to delta Hvan't Hoff equals 0.96. In contrast, thermal unfolding of R67 DHFRdouble is not fully reversible and possesses an oligomerization component introduced by the gene duplication event.

How do mutations at phenylalanine-153 and isoleucine-155 partially suppress the effects of the aspartate-27-->serine mutation in Escherichia coli dihydrofolate reductase?

Several second-site suppressors of the D27S lesion in Escherichia coli dihydrofolate reductase (DHFR) have been identified. The activity of the primary mutant, D27S DHRF, was found to be greatly decreased at pH 7.0, consistent with aspartic acid-27 being critically involved in proton donation during catalysis. Partial suppressors of the D27S mutation have been selected by their ability to confer an increased resistance to trimethoprim upon host E. coli; the suppressors have been identified as F153S or I155N substitutions. D27S+F153S and D27S+I155N DHFRs display 2-3-fold increases in kcat over D27S DHFR values, but only the F153S mutation decreases the Km for dihydrofolate by a factor of 2. Neither double mutant approaches wild-type DHFR activity. Unexpectedly, Phe153 and Ile155 occur on the surface of the protein and are approximately 8 and 14 A distant from the active site. Ile155 is a member of a beta-bulge. A previously identified suppressing mutation, F137S, occurs nearby and is also a member of the same beta-bulge [Howell et al. (1990) Biochemistry 29, 8561-8569]. Clustering of these three second-site mutations indicates this area of the structure may be important in protein function. Conformational changes due to the presence of these suppressing mutations are likely as the F153S and I155N mutations do not affect hydride-transfer rates upon introduction in wild-type DHFR and alterations in circular dichroism spectra are associated with the double-mutant DHFRs.