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D Dunn

Publications and source records attributed to D Dunn.

At least 127 records · Page 7Linked to original sources
PubMed1988

Resource-based relative values. An overview.

Studies have been conducted over the past decade to develop a Resource-Based Relative Value Scale (RBRVS) for physicians' services. Policymakers view an RBRVS as a potential tool to pay physicians. The Physician Payment Review Commission, under a congressional mandate, has endorsed the general concept of a fee schedule based on resource costs for physician payment under Medicare. In this overview article, we present the policy context in which the RBRVS may play a role and describe the approach taken to develop this scale, specifically consultation with clinicians, researchers, and insurers and data gathering, including a national survey of physicians. We discuss underlying elements that are necessary to constructing an RBRVS, each of which is described more fully in subsequent articles: measuring the work (intraservice work) of performing medical services and procedures, estimating preservice and postservice work, comparing work across specialties, measuring practice costs, extrapolating from surveyed services, and establishing an RBRVS for evaluation/management services and for invasive procedures. Overall results are presented in a companion article.

Costs and Cost Analysis↗
PubMed1988

Measurement and analysis of intraservice work.

The work that physicians perform represents a major resource input to medical services and procedures. In this article we describe the concepts of work and its dimensions, as well as the methods developed to measure them. We also describe the design and results of a national probability survey of physicians in 18 specialties. We present the results--estimated values of work and its dimensions--for selected services. Our findings indicate that physicians can give reliable and valid ratings of work and that we can model this work as a function of four dimensions: time, mental effort and judgment, technical skill and physical effort, and stress. Analyzing the complex functional relationship between work and these four dimensions shows that all four dimensions are important and statistically significant in predicting work. Time is a more important dimension in predicting work for medical specialties than for surgical specialties, with the estimated regression coefficients between .3 and .5 and .2 and .3, respectively. In contrast, technical skill is a more important dimension in predicting work in surgical specialties than for medical specialties, with the estimated regression coefficients between .3 and .5 and .2 and .3, respectively. Finally, we found that an exponential equation of the four dimensions precisely describes total work.

Clinical Competence↗
PubMed1988

A method for estimating the preservice and postservice work of physicians' services.

The goal of the Resource-Based Relative Value Scale is to measure the resource costs of physicians' services, or, more centrally, the physicians' total work. This article describes the estimation of relative values for physicians' work before and after the performance of a service (preservice and postservice work). For methodological and practical reasons, we could not obtain direct ratings of preservice and postservice work except for a few services. We therefore developed a systematic process to estimate preservice and postservice time and rate of work per unit of time. Then time and work per unit of time were multiplied to estimate work. The major finding of our investigation is that preservice and postservice work make up a substantial portion of total work. The typical percentages of total work accounted for by preservice and postservice work range from 26% and 33% for imaging services and evaluation and management services, respectively, to 46% for invasive services performed in a hospital inpatient setting.

Ambulatory Surgical Procedures↗
PubMed1988

Cross-specialty linkage of resource-based relative value scales. Linking specialties by services and procedures of equal work.

This article describes methods used to combine into a common scale resource-based relative values from separate specialties. The key to producing a common scale is identifying pairs ("links") of services from different specialties that require approximately equal amounts of intraservice work. We distinguished two kinds of pairs of link services, those judged to be the same and those judged to be equivalent, usually within a narrow category of medical activity. Working with a cross-specialty panel of physicians and with data on time factors from a national survey, we selected sufficient links to connect each specialty to others by at least four links. We then used the weighted least-squares method to locate all the links optimally on a single, common scale. Analyses of the accuracy of this scale showed that the typical disagreement between specialties about where to locate the intraservice work of a given service was only 7%. Other analyses showed that the accuracy of the common scale was not sensitive to different classes of links.

Data Collection↗
PubMed1988

Relative cost differences among physicians' specialty practices.

Practice costs, defined as those costs of medical practice that exclude the physician's own time and effort, represent a substantial portion of the resources necessary to perform a service. In this article we describe the development of the practice cost index used in constructing the Resource-Based Relative Value Scale (RBRVS). We derived the practice cost index value for each specialty, using specialty-specific practice costs and gross revenue data. The index values for all other specialties are standardized to the value for general surgery, and these are used to adjust the resource-based relative values for services performed by each specialty; in this way, the RBRVS incorporates practice cost variations. The data used in the construction of the practice cost index are the 1983 Physician Practice Cost and Income Survey data, adjusted to reflect the relative levels of 1986 professional liability insurance. Our findings show that among most specialties, the range of relative difference in practice costs as a percentage of gross revenue is approximately 15%. Four specialties fall outside this range: pathology, psychiatry, rheumatology, and orthopedic surgery. We discuss problems with the available data on practice costs as these relate to their use in the RBRVS and conceptual issues in applying practice costs to the construction of the RBRVS.

Costs and Cost Analysis↗
PubMed1988

Results and policy implications of the resource-based relative-value study.

The resource-based relative-value scale (RBRVS) is a measure of relative levels of resource input expended when physicians produce services and procedures. It is a function of the physician's work input, the opportunity cost of specialty training, and the relative practice costs for each specialty. This paper presents resource-based relative values (RBRVs) for selected procedures of four major specialties--family practice, internal medicine, general surgery, and thoracic and cardiovascular surgery. We compare RBRVs with current charges and find several general patterns. Invasive procedures are typically compensated at more than double the rate of evaluation-and-management services, when both consume the same resource inputs. Imaging and laboratory procedures fall between invasive and evaluation-and-management services. We analyze the financial implications of the RBRVS by developing a simple model and simulating the effects of an RBRVS-based fee schedule on physicians' revenues in various specialties. We use Medicare data to perform the simulation under the "budget-neutral" assumption. Results show that an RBRVS-based fee schedule affects specialties differently. The average family practitioner could receive 60 percent more revenue from Medicare, whereas the average ophthalmologist could lose 40 percent of current revenues. The effects on other specialties fall between these two.

Economics, Medical↗
PubMed1988

Additives to biological substances. IV--Lyophilization conditions in the preparation of international standards: an analysis by high-performance liquid chromatography of the effects of secondary desiccation.

Many International Standards, Reference Preparations and Reference Reagents are routinely prepared by lyophilization in the presence of 'inert' carriers followed by an extensive period of secondary desiccation. In this study we have used high-performance liquid chromatography (HPLC) to analyse the effects of lyophilization and secondary desiccation on initial degradation and subsequent stability of a model protein, insulin. Secondary desiccation was found to promote a reaction of the insulin with a carrier consisting of non-volatile buffer salts and a sugar. Secondary desiccation did not improve the stability of the insulin as determined by accelerated thermal degradation and analysis using the Arrhenius equation. We conclude that careful consideration needs to be given, on a case-by-case basis, to the selection of the procedures for the preparation of International Standards, particularly those ampouled in the absence of carrier proteins and intended for physicochemical analysis such as HPLC.

Chromatography, High Pressure Liquid↗
PubMed1988

The interaction of alpha thalassaemia and sickle cell-beta zero thalassaemia.

The effects of alpha thalassaemia on sickle cell-beta zero thalassaemia have been studied by comparing haematological and clinical features in four subjects homozygous for alpha thalassaemia 2 (2-gene group), 27 heterozygotes (3-gene group), and 55 with a normal alpha globin gene complement (4-gene group). Alpha thalassaemia was associated with significantly higher haemoglobin levels and lower reticulocyte counts independent of the presence of splenomegaly. Contrary to expectation, alpha thalassaemia was associated with small but significant increases in mean cell volume and mean corpuscular haemoglobin concentration. Splenomegaly at age 5 years and episodes of acute splenic sequestration were significantly more frequent in the 4-gene group. There were no significant differences in painful crises, acute chest syndrome, or other clinical features.

Adolescent↗
PubMed1988

Zulu XX/XX dispermic chimaera from Natal with two populations of red blood cells and patchy skin pigmentation.

The chimaera is female and has two children. Her blood contains 99% group O, type AcP:BA, Pep-A:8-2 and 1% group A2B, type AcP:RA, Pep-A:1 red cells. H-, A- and B-transferase activities were demonstrated in her serum. The level of the H enzyme activity is low but is at the lower end of the normal range for group O persons. The levels of the A and B enzymes are also low but are higher than expected in a person with 1% A2B red cells in the blood. The levels of the A and B enzymes indicate that tissues other than the chimaera's haemopoietic tissue carry her genetically A2B cell line and are contributing the corresponding transferases to her plasma. Gross patchy skin pigmentation is present on the upper part of her body. The chimaera has evidently inherited two dissimilar germ nuclei from each parent.

Blood Group Antigens↗
PubMed1988

Varicella optic neuritis.

A 14-year-old girl developed severe bilateral optic neuritis 1 week after the onset of chickenpox. Though previous case reports state that complete recovery is the rule, this child had a persistent decrease in visual acuity in the right eye and loss of color vision and defects in visual fields in both eyes.

Adolescent↗
PubMed1988

A comparison of two cyclosporine protocols at the University of Minnesota.

1. There have been 1,426 renal transplants performed at the University of Minnesota from January 1, 1980 through August 31, 1988. CsA+P was used by 260 adult recipients, CsA+P+AZA(+ALG) by 536. 2. In general, there are no significant differences in actuarial graft or patient survival rates between the 2 CsA protocols. This is true for all adults, for all adult CAD recipients, and for a matched control group of adult CAD recipients. 3. Cox's proportional hazards regression model also indicates that there is no significant difference between the 2 CsA regimens. Donor type, number of transplants, and age at transplant influence graft survival in all adult recipients. The use of LRD is still indicated in the CsA era. Diabetic status, age at transplant, and number of transplants affect patient survival. The model fits the observed data quite well. 4. Actuarial analysis and Cox regression failed to document a beneficial effect of HLA-A, B, and DR matching in patients receiving either CsA protocol. Our data do not support the HLA matching point system currently used by UNOS or the Terasaki proposal to give points based on mismatching. 5. A matched control analysis of adult CAD recipients indicates that CsA+P+AZA+ALG has alleviated the problems of our CsA+P protocol without lowering the graft and patient survival rates. Thus, the sequential therapy group has equivalent graft and patient survival rates but shorter duration of ATN, lower serum creatinine levels at 1 year, and fewer patients who require modifications of protocol. Sequential therapy is our treatment of choice.

Adult↗
PubMed1988

Quantitative analysis of the tomographic thallium-201 myocardial bullseye display: critical role of correcting for patient motion.

Single photon emission computed tomography (SPECT) myocardial 201TI imaging appears to offer major improvements over planar imaging. Quantitative analysis of the 201TI images appears to offer major advantages over subjective analysis in planar imaging, but the three-dimensional data available in SPECT images requires special approaches to analysis and display. Thus the myocardial "bullseye" display was developed to summarize and analyze the three-dimensional images of the left ventricle in two dimensions. The relative 201TI distribution to each region of the left ventricle of an individual patient can be displayed as the number of s.d.s away from normal that the region falls. We found that patient motion during the 22 min required for SPECT imaging appeared to produce artifactual defects. Thus, computer programs were developed to quantitate motion between consecutive frames of a [201TI] SPECT myocardial imaging study, simulate nonreturning vertical motion in normal patients, and correct the acquired data for motion. Motion as small as 0.5-1.0 pixel (3-6 mm) in the vertical (axial) direction caused artifactual defects in the quantitative bullseye display that resulted in a false-positive rate of up to 40% for a +1.0 pixel shift. Patient motion of magnitude greater than the threshold value for artifact-production (0.5 pixel) occurred at a rate of 10%, and should be corrected before tomographic reconstruction.

Heart↗
PubMed1987

Renal transplantation at the University of Minnesota during the 1980s.

1. There have been 1,225 renal allografts performed at the University of Minnesota between January 1, 1980 and May 31, 1987. Significant risk factors for graft survival include donor type, retransplantation, and age at time of transplant. In addition, diabetes is a significant risk factor in patient survival. 2. Three immunosuppressive regimens have been used during this time period: AZA + P + ALG, CsA + P, and CsA + AZA + P (+ ALG for CAD grafts). The 3 protocols have been received by 411, 205, and 356 primary renal allograft recipients, respectively. No overall differences between the therapies exist with respect to graft or patient survival. However, females, recipients of CAD organs (especially the recipient with diabetes), and patients 18-50 years of age at transplant have improved graft survival results using CsA + AZA + P (+ ALG). Females and the 18-50-year-old recipients also have improved results with respect to patient survival. 3. The 3 protocols [AZA + P + ALG; CsA + P; and CsA + AZA + P + ALG] have been used for 125, 112, and 174 primary recipients of CAD organs, respectively. Recipients of CsA + AZA + P + ALG have significantly better graft survival overall in the diabetic and poorly matched subgroups. Other high-risk (but small sample size) subgroups show statistically nonsignificant, but clinically important, improvements. These groups include patients over 50 years of age, patients with preformed antibodies, as well as those with compatible ABO blood types. Similar trends exist with respect to patient survival. 4. Risk factor analysis of all patients receiving CsA + AZA + P (+ ALG) indicates that donor type, retransplantation, and age at the time of transplant are still serious risk factors for graft survival. Only age at transplant influences patient survival significantly. 5. The failure to find any significant risk factors in primary recipients of CAD organs in the CsA + AZA + P(+ ALG) era, combined with the generally consistent good graft and patient survival rates, suggest that the traditionally high-risk patient can be successfully transplanted with excellent results. 6. Pediatric patients can be successfully transplanted with results equivalent to 18-50-year-old patients and better than those recipients over 50 years of age at the time of transplant. Random transfusions and combination therapy are at least as good as DST and AZA + P + ALG.

Adolescent↗
PubMed1987

Use of cross-correlation function to detect patient motion during SPECT imaging.

We have developed a procedure to detect patient motion during a tomographic acquisition. The method uses frame-to-frame cross-correlation functions of the summed profiles in the vertical and horizontal directions of the planar images. The quantitative output derived from examination of the variation of the change in the pixel value, corresponding to the maximum of the cross-correlation function at each view, provides an effective and nonsubjective means of performing quality control on the presence and amount of movement during a single photon emission computed tomographic scan. In contrast to cine mode and sinogram display, easy to interpret hard copy can be generated through this procedure.

Algorithms↗
PubMed1986

Hepatic oxidative drug metabolism and the microsomal milieu in a rat model of congenital hyperbilirubinemia.

The aims of this study were to evaluate the hypothesis that impaired glucuronidation of bilirubin and possibly of drug oxidation in the liver of homozygous (jj) Gunn rats may be due to an altered microsomal milieu. Accordingly, we investigated and compared in vivo and in vitro demethylation of aminopyrine, hepatic cytochrome P-450 levels, microsomal lipid composition, and microsomal membrane fluidity in icteric, homozygous (jj) Gunn rats and in their anicteric heterozygous (jJ) littermates. In both males and females, [14C]aminopyrine demethylation in vivo, using the 14CO2 breath test, was unimpaired in the icteric animals. Likewise, cytochrome P-450 levels in the icteric and nonicteric groups were similar, and aminopyrine kinetics in vitro in the females were comparable in icteric and nonicteric littermates. The main lipid classes were also similar in the homozygous and heterozygous female Gunn rats, whereas only minor changes were seen in the phospholipid fatty acyl composition with a small, but significant, increase in the unsaturated index in the icteric group. Despite this, there was no apparent effect on hepatic microsomal membrane fluidity as measured by the order parameter of I[12,3] and the rotational correlation time of I[1,14] in either female or male sets of homozygous and heterozygous Gunn rats. Our data, therefore, do not support an alteration of composition or fluidity of the microsomal milieu as a mechanism of impaired bilirubin glucuronidation and possibly of oxidation in these animals. They also absolve long-term unconjugated hyperbilirubinemia as a mechanism of hepatic microsomal dysfunction. Our study, therefore, indirectly suggests that abnormal glucuronidation of bilirubin and some other aglycones in homozygous Gunn rats is due to genetic abnormalities involving the enzyme(s) itself.

Aminopyrine↗