Academic Detailing as a Health Information Technology Implementation Method: Supporting the Design and Implementation of an Emergency Department-Based Clinical Decision Support Tool to Prevent Future Falls

BACKGROUND

Clinical decision support (CDS) tools that incorporate machine learning-derived content have the potential to transform clinical care by augmenting clinicians' expertise. To realize this potential, such tools must be designed to fit the dynamic work systems of the clinicians who use them. We propose the use of academic detailing-personal visits to clinicians by an expert in a specific health IT tool-as a method for both ensuring the correct understanding of that tool and its evidence base and identifying factors influencing the tool's implementation.

OBJECTIVE

This study aimed to assess academic detailing as a method for simultaneously ensuring the correct understanding of an emergency department-based CDS tool to prevent future falls and identifying factors impacting clinicians' use of the tool through an analysis of the resultant qualitative data.

METHODS

Previously, our team designed a CDS tool to identify patients aged 65 years and older who are at the highest risk of future falls and prompt an interruptive alert to clinicians, suggesting the patient be referred to a mobility and falls clinic for an evidence-based preventative intervention. We conducted 10-minute academic detailing interviews (n=16) with resident emergency medicine physicians and advanced practice providers who had encountered our CDS tool in practice. We conducted an inductive, team-based content analysis to identify factors that influenced clinicians' use of the CDS tool.

RESULTS

The following categories of factors that impacted clinicians' use of the CDS were identified: (1) aspects of the CDS tool's design (2) clinicians' understanding (or misunderstanding) of the CDS or referral process, (3) the busy nature of the emergency department environment, (4) clinicians' perceptions of the patient and their associated fall risk, and (5) the opacity of the referral process. Additionally, clinician education was done to address any misconceptions about the CDS tool or referral process, for example, demonstrating how simple it is to place a referral via the CDS and clarifying which clinic the referral goes to.

CONCLUSIONS

Our study demonstrates the use of academic detailing for supporting the implementation of health information technologies, allowing us to identify factors that impacted clinicians' use of the CDS while concurrently educating clinicians to ensure the correct understanding of the CDS tool and intervention. Thus, academic detailing can inform both real-time adjustments of a tool's implementation, for example, refinement of the language used to introduce the tool, and larger scale redesign of the CDS tool to better fit the dynamic work environment of clinicians.

Older Adult Patients and Care Partners as Knowledge Brokers in Fragmented Health Care

OBJECTIVE

To describe older adult patients' and care partners' knowledge broker roles during emergency department (ED) visits.

BACKGROUND

Older adult patients are vulnerable to communication and coordination challenges during an ED visit, which can be exacerbated by the time and resource constrained ED environment. Yet, as a constant throughout the patient journey, patients and care partners can act as an information conduit, or knowledge broker, between fragmented care systems to attain high-quality, safe care.

METHODS

Participants included 14 older adult patients (≥ 65 years old) and their care partners (e.g., spouse, adult child) who presented to the ED after having experienced a fall. Human factors researchers collected observation data from patients, care partners and clinician interactions during the patient's ED visit. We used an inductive content analysis to determine the role of patients and care partners as knowledge brokers.

RESULTS

We found that patients and care partners act as knowledge brokers by providing information about diagnostic testing, medications, the patient's health history, and care accommodations at the disposition location. Patients and care partners filled the role of knowledge broker proactively (i.e. offer information) and reactively (i.e. are asked to provide information by clinicians or staff), within-ED work system and across work systems (e.g., between the ED and hospital), and in anticipation of future knowledge brokering.

CONCLUSION

Patients and care partners, acting as knowledge brokers, often fill gaps in communication and participate in care coordination that assists in mitigating health care fragmentation.

Dashboarding to Monitor Machine-Learning-Based Clinical Decision Support Interventions

BACKGROUND

 Existing monitoring of machine-learning-based clinical decision support (ML-CDS) is focused predominantly on the ML outputs and accuracy thereof. Improving patient care requires not only accurate algorithms but also systems of care that enable the output of these algorithms to drive specific actions by care teams, necessitating expanding their monitoring.

OBJECTIVES

 In this case report, we describe the creation of a dashboard that allows the intervention development team and operational stakeholders to govern and identify potential issues that may require corrective action by bridging the monitoring gap between model outputs and patient outcomes.

METHODS

 We used an iterative development process to build a dashboard to monitor the performance of our intervention in the broader context of the care system.

RESULTS

 Our investigation of best practices elsewhere, iterative design, and expert consultation led us to anchor our dashboard on alluvial charts and control charts. Both the development process and the dashboard itself illuminated areas to improve the broader intervention.

CONCLUSION

 We propose that monitoring ML-CDS algorithms with regular dashboards that allow both a context-level view of the system and a drilled down view of specific components is a critical part of implementing these algorithms to ensure that these tools function appropriately within the broader care system.

Human Factors Engineering for the Pediatric Hospitalist

As pediatrics hospitalists, we care for a diverse population of hospitalized children with increasing acuity and complexity in large, multidisciplinary medical teams. In this Method/ology paper, we summarize how human factors engineering (HFE) can provide a framework and tools to help us understand and improve our complex care processes and resulting outcomes. First, we define and discuss the 3 domains of HFE (ie, physical, cognitive, and organizational) and offer examples of HFE's application to pediatric hospital medicine. Next, we highlight an HFE-based framework, the Systems Engineering for Patient Safety model, which conceptualizes how our work system shapes health care processes and outcomes. We provide tools for leveraging this model to better understand the context in which our work is done, which, consequently, informs how we design our systems and processes to improve the quality and safety of care. Finally, we outline the basics of human-centered design and highlight a case study of a project completed in a pediatric hospital setting focused on making rounds more family-centered. In addition, we provide resources for those interested in learning more about HFE.

Effectiveness of an Emergency Department-Based Machine Learning Clinical Decision Support Tool to Prevent Outpatient Falls Among Older Adults: Protocol for a Quasi-Experimental Study

BACKGROUND

Emergency department (ED) providers are important collaborators in preventing falls for older adults because they are often the first health care providers to see a patient after a fall and because at-home falls are often preceded by previous ED visits. Previous work has shown that ED referrals to falls interventions can reduce the risk of an at-home fall by 38%. Screening patients at risk for a fall can be time-consuming and difficult to implement in the ED setting. Machine learning (ML) and clinical decision support (CDS) offer the potential of automating the screening process. However, it remains unclear whether automation of screening and referrals can reduce the risk of future falls among older patients.

OBJECTIVE

The goal of this paper is to describe a research protocol for evaluating the effectiveness of an automated screening and referral intervention. These findings will inform ongoing discussions about the use of ML and artificial intelligence to augment medical decision-making.

METHODS

To assess the effectiveness of our program for patients receiving the falls risk intervention, our primary analysis will be to obtain referral completion rates at 3 different EDs. We will use a quasi-experimental design known as a sharp regression discontinuity with regard to intent-to-treat, since the intervention is administered to patients whose risk score falls above a threshold. A conditional logistic regression model will be built to describe 6-month fall risk at each site as a function of the intervention, patient demographics, and risk score. The odds ratio of a return visit for a fall and the 95% CI will be estimated by comparing those identified as high risk by the ML-based CDS (ML-CDS) and those who were not but had a similar risk profile.

RESULTS

The ML-CDS tool under study has been implemented at 2 of the 3 EDs in our study. As of April 2023, a total of 1326 patient encounters have been flagged for providers, and 339 unique patients have been referred to the mobility and falls clinic. To date, 15% (45/339) of patients have scheduled an appointment with the clinic.

CONCLUSIONS

This study seeks to quantify the impact of an ML-CDS intervention on patient behavior and outcomes. Our end-to-end data set allows for a more meaningful analysis of patient outcomes than other studies focused on interim outcomes, and our multisite implementation plan will demonstrate applicability to a broad population and the possibility to adapt the intervention to other EDs and achieve similar results. Our statistical methodology, regression discontinuity design, allows for causal inference from observational data and a staggered implementation strategy allows for the identification of secular trends that could affect causal associations and allow mitigation as necessary.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05810064; https://www.clinicaltrials.gov/study/NCT05810064.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/48128.

Satisfaction of Older Patients With Emergency Department Care: Psychometric Properties and Construct Validity of the Consumer Emergency Care Satisfaction Scale

BACKGROUND

Patient satisfaction is an important indicator of quality of care, but its measurement remains challenging. The Consumer Emergency Care Satisfaction Scale (CECSS) was developed to measure patient satisfaction in the emergency department (ED). Although this is a valid and reliable tool, several aspects of the CECSS need to be improved, including the definition, dimension, and scoring of scales.

PURPOSE

The purpose of this study was to examine the construct validity of the CECSS and make suggestions on how to improve the tool to measure overall satisfaction with ED care.

METHODS

We administered 2 surveys to older adults who presented with a fall to the ED and used electronic health record data to examine construct validity of the CECSS and ceiling effects.

RESULTS

Using several criteria, we improved construct validity of the CECSS, reduced ceiling effects, and standardized scoring.

CONCLUSION

We addressed several methodological issues with the CECSS and provided recommendations for improvement.

Evaluating the Usability of an Emergency Department After Visit Summary: Staged Heuristic Evaluation

BACKGROUND

Heuristic evaluations, while commonly used, may inadequately capture the severity of identified usability issues. In the domain of health care, usability issues can pose different levels of risk to patients. Incorporating diverse expertise (eg, clinical and patient) in the heuristic evaluation process can help assess and address potential negative impacts on patient safety that may otherwise go unnoticed. One document that should be highly usable for patients-with the potential to prevent adverse outcomes-is the after visit summary (AVS). The AVS is the document given to a patient upon discharge from the emergency department (ED), which contains instructions on how to manage symptoms, medications, and follow-up care.

OBJECTIVE

This study aims to assess a multistage method for integrating diverse expertise (ie, clinical, an older adult care partner, and health IT) with human factors engineering (HFE) expertise in the usability evaluation of the patient-facing ED AVS.

METHODS

We conducted a three-staged heuristic evaluation of an ED AVS using heuristics developed for use in evaluating patient-facing documentation. In stage 1, HFE experts reviewed the AVS to identify usability issues. In stage 2, 6 experts of varying expertise (ie, emergency medicine physicians, ED nurses, geriatricians, transitional care nurses, and an older adult care partner) rated each previously identified usability issue on its potential impact on patient comprehension and patient safety. Finally, in stage 3, an IT expert reviewed each usability issue to identify the likelihood of successfully addressing the issue.

RESULTS

In stage 1, we identified 60 usability issues that violated a total of 108 heuristics. In stage 2, 18 additional usability issues that violated 27 heuristics were identified by the study experts. Impact ratings ranged from all experts rating the issue as "no impact" to 5 out of 6 experts rating the issue as having a "large negative impact." On average, the older adult care partner representative rated usability issues as being more significant more of the time. In stage 3, 31 usability issues were rated by an IT professional as "impossible to address," 21 as "maybe," and 24 as "can be addressed."

CONCLUSIONS

Integrating diverse expertise when evaluating usability is important when patient safety is at stake. The non-HFE experts, included in stage 2 of our evaluation, identified 23% (18/78) of all the usability issues and, depending on their expertise, rated those issues as having differing impacts on patient comprehension and safety. Our findings suggest that, to conduct a comprehensive heuristic evaluation, expertise from all the contexts in which the AVS is used must be considered. Combining those findings with ratings from an IT expert, usability issues can be strategically addressed through redesign. Thus, a 3-staged heuristic evaluation method offers a framework for integrating context-specific expertise efficiently, while providing practical insights to guide human-centered design.

What makes a home? Designing home personas to represent the homes of families caring for children with medical complexity

Personas are widely recognized as valuable design tools for communicating dimensions of individuals, yet they often lack critical contextual factors. For those people managing chronic health conditions, the home is a critical context of their patient work system (PWS). We propose the development of 'home personas' to convey essential aspects of the home context to those tasked with designing technologies and interventions to fit it. We used an iterative, multi-stakeholder design process to design 'home personas' for a model population, families caring for children with medical complexity. Each of the four resultant home personas-Multi-level, Customized, Ranch, and Rental-has a unique home layout, pain points, and are described on three dimensions that emerged from the data. This study builds on a foundation of work in the emerging field of Patient Ergonomics, describing a mechanism for distilling rich descriptions of the PWS into brief yet informative design tools.

Caregiver perceptions of in-home COVID-19 testing for children with medical complexity: a qualitative study

BACKGROUND

In-home direct antigen rapid testing (DART) plays a major role in COVID-19 mitigation and policy. However, perceptions of DART within high-risk, intellectually impaired child populations are unknown. This lack of research could negatively influence DART uptake and utility among those who stand to benefit most from DART. The purpose of this study was to describe caregivers' perceptions of an in-home COVID-19 DART regimen in children with medical complexity, including the benefits and limitations of DART use.

METHODS

This qualitative study was a subproject of the NIH Rapid Acceleration of Diagnostics Underserved Populations research program at the University of Wisconsin. We combined survey data and the thematic analysis of semi-structured interview data to understand caregivers' perceptions of in-home COVID-19 testing and motivators to perform testing. Caregivers of children with medical complexity were recruited from the Pediatric Complex Care Program at the University of Wisconsin (PCCP). Data were collected between May and August 2021.

RESULTS

Among n = 20 caregivers, 16/20 (80%) of their children had neurologic conditions and 12/20 (60%) used home oxygen. Survey data revealed that the largest caregiver motivators to test their child were to get early treatment if positive (18/20 [90%] of respondents agreed) and to let the child's school know if the child was safe to attend (17/20 [85%] agreed). Demotivators to testing included that the child could still get COVID-19 later (7/20 [35%] agreed), and the need for officials to reach out to close contacts (6/20 [30%] agreed). From interview data, four overarching themes described perceptions of in-home COVID-19 testing: Caregivers perceived DART on a spectrum of 1) benign to traumatic and 2) simple to complex. Caregivers varied in the 3) extent to which DART contributed to their peace of mind and 4) implications of test results for their child.

CONCLUSIONS

Although participants often described DART as easy to administer and contributing to peace of mind, they also faced critical challenges and limitations using DART. Future research should investigate how to minimize the complexity of DART within high-risk populations, while leveraging DART to facilitate safe school attendance for children with medical complexity and reduce caregiver burden.

Feasibility Testing of Tubes@HOME: A Mobile Application to Support Family-Delivered Enteral Care

BACKGROUND

Assistance from medical devices is common for children with medical complexity (CMC) but introduces caregiving challenges. We tested the feasibility of "Tubes@HOME," a mobile application supporting CMC family-delivered care using enteral care as a model.

METHODS

Caregivers of CMC with enteral tubes participated in a 30-day feasibility study of Tubes@HOME November 2020 through January 2021. Tubes@HOME was available on mobile devices and designed to support collaborative care and tracking over time. Key features include child profile, caregiving network management, care routines, feedback loop, and action plans. Care routines delineated nutrition, medication, and procedural tasks needed for the child: frequencies, completions, and reminders. Metadata summarized feature use among users. Feasibility was evaluated with postuse questionnaires and interviews. Measures of Tubes@HOME's usability and usefulness included the NASA Task Load Index (TLX), System Usability Scale (SUS), and Acceptability and Use of Technology Questionnaire (AUTQ).

RESULTS

Among n = 30 children, there were 30 primary (eg, parent) and n = 22 nonprimary caregivers using Tubes@HOME. Children had a median (IQR) 10 (5.5-13) care routines created. For care routines created, 93% were marked complete at least once during the study period, with participants engaging with routines throughout study weeks 2 to 4. Results (mean [SD]) indicated low mental workload (TLX) 30.9 (12.2), good usability (SUS) 75.4 (14.7), and above-average usefulness (AUTQ) 4.0 (0.7) associated with Tubes@HOME, respectively. Interviews contextualized usefulness and suggested improvements.

CONCLUSIONS

Longitudinal use of Tubes@HOME among caregiving networks appeared feasible. Efficacy testing is needed, and outcomes could include reliability of care delivered in home and community.

Priorities for Safer In-Person School for Children With Medical Complexity During COVID-19

OBJECTIVES

To establish statewide consensus priorities for safer in-person school for children with medical complexity (CMC) during the coronavirus disease 2019 (COVID-19) pandemic using a rapid, replicable, and transparent priority-setting method.

METHODS

We adapted the Child Health and Nutrition Research Initiative Method, which allows for crowdsourcing ideas from diverse stakeholders and engages technical experts in prioritizing these ideas using predefined scoring criteria. Crowdsourcing surveys solicited ideas from CMC families, school staff, clinicians and administrators through statewide distribution groups/listservs using the prompt: "It is safe for children with complex health issues and those around them (families, teachers, classmates, etc.) to go to school in-person during the COVID-19 pandemic if/when…" Ideas were aggregated and synthesized into a unique list of candidate priorities. Thirty-four experts then scored each candidate priority against 5 criteria (equity, impact on COVID-19, practicality, sustainability, and cost) using a 5-point Likert scale. Scores were weighted and predefined thresholds applied to identify consensus priorities.

RESULTS

From May to June 2021, 460 stakeholders contributed 1166 ideas resulting in 87 candidate priorities. After applying weighted expert scores, 10 consensus CMC-specific priorities exceeded predetermined thresholds. These priorities centered on integrating COVID-19 safety and respiratory action planning into individualized education plans, educating school communities about CMC's unique COVID-19 risks, using medical equipment safely, maintaining curricular flexibility, ensuring masking and vaccination, assigning seats during transportation, and availability of testing and medical staff at school.

CONCLUSIONS

Priorities for CMC, identified by statewide stakeholders, complement and extend existing recommendations. These priorities can guide implementation efforts to support safer in-person education for CMC.

Disparate perspectives: Exploring healthcare professionals' misaligned mental models of older adults' transitions of care between the emergency department and skilled nursing facility

Care transitions that occur across healthcare system boundaries represent a unique challenge for maintaining high quality care and patient safety, as these systems are typically not aligned to perform the care transition process. We explored healthcare professionals' mental models of older adults' transitions between the emergency department (ED) and skilled nursing facility (SNF). We conducted a thematic analysis of interviews with ED and SNF healthcare professionals and identified three themes: 1) ED and SNF healthcare professionals had misaligned mental models regarding communication processes and tools used during care transitions, 2) ED and SNF healthcare professionals had misaligned mental models regarding healthcare system capability, and 3) Misalignments led to individual and organizational consequences. Overall, we found that SNF and ED healthcare professionals are part of the same process but have different perceptions of the process. Future work must take steps to redesign and realign these distinct work systems such that those involved conceptualize themselves as part of a joint process.

Medical Device Workarounds in Providing Care for Children With Medical Complexity in the Home

OBJECTIVES

Children with medical complexity (CMC) are commonly assisted by medical devices, which family caregivers are responsible for managing and troubleshooting in the home. Optimizing device use by maximizing the benefits and minimizing the complications is a critical goal for CMC but is relatively unexplored. In this study, we sought to identify and describe workarounds families have developed to optimize medical device use for their needs.

METHODS

We conducted 30 contextual inquiry interviews with families of CMC in homes. Interviews were recorded, transcribed, and analyzed for barriers and workarounds specific to medical device usage through a directed content analysis. We used observation notes and photographs to confirm and elaborate on interview findings.

RESULTS

We identified 4 barriers to using medical devices in the home: (1) the quantity and type of devices allotted do not meet family needs, (2) the device is not designed to be used in locations families require, (3) device use is physically or organizationally disruptive to the home, and (4) the device is not designed to fit the user. We also identified 11 categories of workarounds to the barriers.

CONCLUSIONS

Families face many barriers in using medical devices to care for CMC. Our findings offer rich narrative and photographic data revealing the ways in which caregivers work around these barriers. Future researchers should explore the downstream effects of these ubiquitous, necessary workarounds on CMC outcomes toward developing interventions that optimize device use for families.

Codesign and Usability Testing of a Mobile Application to Support Family-Delivered Enteral Tube Care

BACKGROUND

Enteral tubes are prevalent among children with medical complexity (CMC), and complications can lead to costly health care use. Our objective was to design and test the usability of a mobile application (app) to support family-delivered enteral tube care.

METHODS

Human-centered design methods (affinity diagramming, persona development, and software development) were applied with family caregivers of CMC to develop a prototype. During 3 waves of usability testing with design refinement between waves, screen capture software collected user-app interactions and inductive content analysis of narrative feedback identified areas for design improvement. The National Aeronautics and Space Administration Task Load Index and the System Usability Scale quantified mental workload and ease of use.

RESULTS

Design participants identified core app functions, including displaying care routines, reminders, tracking inventory and health data, caregiver communication, and troubleshooting. Usability testing participants were 80% non-Hispanic white, 28% lived in rural settings, and 20% had not completed high school. Median years providing enteral care was 2 (range 1-14). Design iterations improved app function, simplification, and user experience. The mean System Usability Scale score was 76, indicating above-average usability. National Aeronautics and Space Administration Task Load Index revealed low mental demand, frustration, and effort. All 14 participants reported that they would recommend the app, and that the app would help with organization, communication, and caregiver transitions.

CONCLUSIONS

Using a human-centered codesign process, we created a highly usable mobile application to support enteral tube caregiving at home. Future work involves evaluating the feasibility of longitudinal use and effectiveness in improving self-efficacy and reduce device complications.

A high-density SNP chip for genotyping great tit (Parus major) populations and its application to studying the genetic architecture of exploration behaviour

High-density SNP microarrays ("SNP chips") are a rapid, accurate and efficient method for genotyping several hundred thousand polymorphisms in large numbers of individuals. While SNP chips are routinely used in human genetics and in animal and plant breeding, they are less widely used in evolutionary and ecological research. In this article, we describe the development and application of a high-density Affymetrix Axiom chip with around 500,000 SNPs, designed to perform genomics studies of great tit (Parus major) populations. We demonstrate that the per-SNP genotype error rate is well below 1% and that the chip can also be used to identify structural or copy number variation. The chip is used to explore the genetic architecture of exploration behaviour (EB), a personality trait that has been widely studied in great tits and other species. No SNPs reached genomewide significance, including at DRD4, a candidate gene. However, EB is heritable and appears to have a polygenic architecture. Researchers developing similar SNP chips may note: (i) SNPs previously typed on alternative platforms are more likely to be converted to working assays; (ii) detecting SNPs by more than one pipeline, and in independent data sets, ensures a high proportion of working assays; (iii) allele frequency ascertainment bias is minimized by performing SNP discovery in individuals from multiple populations; and (iv) samples with the lowest call rates tend to also have the greatest genotyping error rates.

The limited role of myocardial fluorine-18 fluorodeoxyglucose imaging in candidates for cardiac transplantation: a planar imaging study

This study compares the incidence and extent of hibernating myocardium (defined by myocardial perfusion/metabolism mismatch) in 28 cardiac transplant candidates with ischaemic cardiomyopathy and in 16 other patients with coronary artery disease (CAD) undergoing viability assessment. It then reviews the impact of myocardial perfusion metabolism imaging on management decisions in the transplant candidates at 6 months after scintigraphy. Each patient underwent a planar myocardial thallium-201 and fluorine-18 fluorodeoxyglucose scan on a modified gamma camera. Perfusion/metabolism mismatch was sized semi-quantitatively and each patient was assigned a global mismatch score. Transplant candidates had a lower left ventricular ejection fraction (LVEF) (P < 0.0002) and extent of hibernation myocardium (lower global mismatch score: P = 0.005) than other CAD patients but the difference in respect of mismatch frequency (8/28 vs 9/16 patients) did not reach statistical significance. Transplant candidates with LVEF < 20% had a lower global mismatch score (P < 0.02) than those with an LVEF > or = 20%. Interestingly two of three other CAD patients with LVEF < 20% had a moderate mismatch. Follow-up studies revealed the lack of impact of metabolic imaging as none of the three transplant candidates who eventually underwent revascularisation had hibernating myocardium and transplantation was offered to one of only two candidates with more than one minor mismatch. Thus metabolic imaging in potential transplant candidates may be of limited value because of the very low extent of hibernating myocardium, particularly if LVEF is below 20% and where clinical decisions are often based on many other factors.

Planar cardiac F-18 fluorodeoxyglucose imaging with a conventional gamma camera

OBJECTIVE

To examine the potential of an adapted gamma camera to image cardiac uptake of the positron emitting glucose analogue fluorine-18 fluorodeoxyglucose (FDG).

DESIGN

Postprandial studies were performed in 19 patients (mean age, 56 +/- 9 years) with coronary disease and resting cardiac dysfunction who had undergone a routine clinical 7 min/view planar thallium-201 (Tl-201) stress reinjection or rest redistribution study. A glucose/insulin protocol was used and, an hour after FDG injection, 15-minute static planar myocardial images were acquired in the four views used for Tl-201 scanning.

RESULTS

The diagnostic quality of FDG images was at least as good as that of their Tl-201 counterparts, with less liver background in all but one FDG study. In the left anterior oblique 45 degrees view uncorrected global myocardial FDG and stress Tl-201 counts were similar, but the FDG study had significantly higher peak myocardial to background ratios.

CONCLUSION

Assessing regional cardiac FDG uptake and myocardial perfusion seems feasible with conventional gamma camera technology, providing a widely available and cost effective means of detecting hibernating myocardium. Similar equipment may appreciably reduce the need for positron emission tomography in a range of clinical conditions.

The relationship between development of lung inflammation and changes in bone marrow populations in guinea-pigs following inhaled antigen challenge

Sensitised guinea-pigs were exposed to aerosolised antigen. The resultant cellular infiltration into the lung was assessed in lung tissue and bronchoalveolar lavage fluid 6, 24, 72 h and 7 days later. An early neutrophil infiltration peaking at 6 h was succeeded by eosinophil migration which persisted for 7 days, at which time some of the eosinophils appeared immature. The lung eosinophilia was accompanied by an initial fall in eosinophilic cells in the bone marrow, followed by an increase in this population. Treatment with dexamethasone (25 mg/kg i.p.) given daily for 7 days after antigen challenge reduced the lung eosinophilia and observed bone marrow changes.

DNA sequence dependent binding modes of 4',6-diamidino-2-phenylindole (DAPI)

The interactions of DAPI with natural DNA and synthetic polymers have been investigated by hydrodynamic, DNase I footprinting, spectroscopic, binding, and kinetic methods. Footprinting results at low ratios (compound to base pair) are similar for DAPI and distamycin. At high ratios, however, GC regions are blocked from enzyme cleavage by DAPI but not by distamycin. Both poly[d(G-C)]2 and poly[d(A-T)]2 induce hypochromism and shifts of the DAPI absorption band to longer wavelengths, but the effects are larger with the GC polymer. NMR shifts of DAPI protons in the presence of excess AT and GC polymers are significantly different, upfield for GC and mixed small shifts for AT. The dissociation rate constants and effects of salt concentration on the rate constants are also quite different for the AT and the GC polymer complexes. The DAPI dissociation rate constant is larger with the GC polymer but is less sensitive to changes in salt concentration than with the AT complex. Binding of DAPI to the GC polymer and to poly[d(A-C)].poly[d(G-T)] exhibits slight negative cooperativity, characteristic of a neighbor-exclusion binding mode. DAPI binding to the AT polymer is unusually strong and exhibits significant positive cooperativity. DAPI has very different effects on the bleomycin-catalyzed cleavage of the AT and GC polymers, a strong inhibition with the AT polymer but enhanced cleavage with the GC polymer. All of these results are consistent with two totally different DNA binding modes for DAPI in regions containing consecutive AT base pairs versus regions containing GC or mixed GC and AT base pair sequences. The binding mode at AT sites has characteristics which are similar to those of the distamycin-AT complex, and all results are consistent with a cooperative, very strong minor groove binding mode. In GC and mixed-sequence regions the results are very similar to those observed with classical intercalators such as ethidium and indicate that DAPI intercalates in DNA sequences which do not contain at least three consecutive AT base pairs.

The interaction with DNA of unfused aromatic systems containing terminal piperazino substituents. Intercalation and groove-binding

A number of unfused tricyclic aromatic intercalators have shown excellent activity as amplifiers of the anticancer activity of the bleomycins and the 4',6-diphenylpyrimidines, 2a and 2b, with terminal basic functions (4-methylpiperazino groups) have been synthesized to test the structural requirements for amplifier-DNA interactions. The terminal piperazine rings are bulky, have limited flexibility, and are twisted out of the phenyl ring plane in both 2a and 2b. With 2a the pyrimidine is unsubstituted at position 5 and the conformation predicted by molecular mechanics calculations has a 25-30 degrees twist between the phenyl and pyrimidine ring planes. With 2b the 5-position is substituted with a methyl group and this causes a larger twist angle (50-60 degrees) between the phenyl and pyrimidine planes. These conformational variations lead to markedly different DNA interactions for 2a and 2b. Absorption, CD and NMR spectral, viscometric, flow dichroism and kinetics results indicate that 2a binds strongly to DNA by intercalation while 2b binds more weakly in a groove complex. The general structure and conformation of 2a, a slightly twisted, unfused-aromatic system with terminal piperazino groups is more similar to groove-binding agents such as Hoechst 33258 than to intercalators. The fact that 2a forms a strong intercalation complex with DNA is unusual but in agreement with studies on other amplifiers of anticancer drug action. Molecular modeling studies provide a second unusual feature of the 2a intercalation complex. While most well-characterized intercalators bind with their bulky and/or cationic substitutents in the DNA minor groove, the cationic piperazino groups of 2a are too large to bind in the minor groove in an intercalation complex but can form strong interactions with DNA in the major groove. The tricyclic aromatic ring system of 2a stacks well with adjacent base-pairs in the major-groove complex and the piperazino groups have good electrostatic and van der Waals interactions with the DNA backbone.

The interaction of unfused polyaromatic heterocycles with DNA: intercalation, groove-binding and bleomycin amplification

A number of unfused-aromatic cations have been found to bind to DNA by intercalation and to amplify the bleomycin catalysed cleavage of DNA. These molecules are more similar in structure to unfused minor-groove binding compounds such as netropsin and DAPI than to fused-ring intercalators such as proflavine. An analysis of DAPI interactions with specific sequence DNA polymers has indicated that the binding modes for the molecule are sequence dependent: minor groove binding in sequences of three or more AT base pairs and intercalation in mixed or pure GC base pair sequences. As with other unfused intercalators which bind with their cationic side chains in the major groove, the amidinium groups of DAPI are in the major groove in the GC intercalation complex. DAPI is, thus, a good bleomycin amplifier in GC sequences but its minor-groove binding mode in AT sequences leads to bleomycin inhibition.

Interaction of unfused tricyclic aromatic cations with DNA: a new class of intercalators

Unfused tricyclic aromatic ring systems 1-6 with one or two cationic side chains have been synthesized and their interactions with DNA and synthetic polymers probed with a variety of techniques. Molecular mechanics calculations indicate that the torsional angle between ring planes in the minimum energy conformation of the tricyclic molecules can range from 0 degree to as high as 50 degrees depending on the type of rings and substituents. Viscometric titrations with linear and supercoiled DNA, linear dichroism, and NMR studies indicated that all compounds with torsional angles of approximately 20 degrees or less bind to DNA by intercalation. The more highly twisted intercalators caused significant perturbation of DNA structure. Unfused intercalators with twist angles of approximately 20 degrees have reduced binding constants, suggesting that they could not form an optimum interaction with the DNA base pairs. Unfused intercalators with twist less than 20 degrees formed strong complexes with DNA. The structures of these unfused intercalators are more analogous to typical groove-binding molecules, and an analysis of their interaction with DNA provides a better understanding of the subtle differences between intercalation and groove-binding modes for aromatic cations. The results indicate that intercalation and groove-binding modes should be viewed as two potential wells on a continuous energy surface. The results also suggest design strategies for intercalators that can optimally complement DNA base pair propeller twist or that can induce bends in DNA at the intercalation site.