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PubMed2003

Racial and ethnic disparities in the clinical practice of emergency medicine.

There is convincing evidence that racial and ethnic disparities exist in the provision of health care, including the provision of emergency care; and that stereotyping, biases, and uncertainty on the part of health care providers all contribute to unequal treatment. Situations, such as the emergency department (ED), that are characterized by time pressure, incomplete information, and high demands on attention and cognitive resources increase the likelihood that stereotypes and bias will affect diagnostic and treatment decisions. It is likely that there are many as-yet-undocumented disparities in clinical emergency practice. Racial and ethnic disparities may arise in decisions made by out-of-hospital personnel regarding ambulance destination, triage assessments made by nursing personnel, diagnostic testing ordered by physicians or physician-extenders, and in disposition decisions. The potential for disparate treatment includes the timing and intensity of ED therapy as well as patterns of referral, prescription choices, and priority for hospital admission and bed assignment. At a national roundtable discussion, strategies suggested to address these disparities included: increased use of evidence-based clinical guidelines; use of continuous quality improvement methods to document individual and institutional disparities in performance; zero tolerance for stereotypical remarks in the workplace; cultural competence training for emergency providers; increased workforce diversity; and increased epidemiologic, clinical, and services research. Careful scrutiny of the clinical practice of emergency medicine and diligent implementation of strategies to prevent disparities will be required to eliminate the individual behaviors and systemic processes that result in the delivery of disparate care in EDs.

Adult↗

PubMed2004

HLA disparity determines disease activity through pregnancy in women with inflammatory bowel disease.

OBJECTIVES: Inflammatory bowel disease (IBD) activity during pregnancy is variable and factors influencing the course unknown. We studied the relationship between maternal-fetal HLA disparity and IBD course. METHODS: Women with IBD and childbirth were recruited and medical records were reviewed for five time periods. Twenty milliliters of blood was obtained from mother and child for genotyping. Each mother/child pair was assigned an HLA disparity status (+/-) for HLA A, B, C, DRB1, and DQ loci. Odds ratios were calculated comparing HLA disparity in women whose IBD improved versus those whose disease worsened or remained active. RESULTS: Fifty pregnancies in 38 women were studied. Forty-two of 50 pregnancies (84%) were disparate at the DRB1 locus; 34 (68%) were mismatched at the DQ locus. There was no difference in average disease score or overall activity score based on DRB1 or DQ disparity (p > 0.05 for all comparisons). There were 31 pregnancies disparate at both DRB1 and DQ loci; a significant difference was found in average disease scores and overall activity scores between women mismatched at both loci versus only one or neither locus (OR 8.4 [1.5-14, p = 0.01). Logistic regression identified prepartum disease activity and disparity at both DRB1 and DQ as significant predictors of overall disease activity during pregnancy. CONCLUSION: Improvement of IBD symptoms during pregnancy is associated with disparity in HLA class II antigens between mother and fetus. This suggests that the maternal immune response to paternal HLA antigens plays a role in pregnancy-induced remission. What is accepted and what this research adds are as follows: . The course of IBD during pregnancy is variable. . The factors involved with disease course are unknown. . The data presented here provides a scientific mechanism for disease course during pregnancy. . This is a novel work and it corroborates what has been seen in other autoimmune conditions.

Colitis, Ulcerative↗

PubMed2001

Processing of shape defined by disparity in monkey inferior temporal cortex.

Neurons in the monkey inferior temporal cortex (IT) have been shown to respond to shapes defined by luminance, texture, or motion. In the present study, we determined whether IT neurons respond to shapes defined solely by binocular disparity, and if so, whether signals of disparity and other visual cues to define shape converge on single IT neurons. We recorded extracellular activity from IT neurons while monkeys performed a fixation task. Among the neurons that responded to at least one of eight random-dot stereograms (RDSs) containing different disparity-defined shapes, 21% varied their responses to different RDSs. Responses of most of the neurons were positively correlated between two sets of RDSs, which consisted of different dot patterns but defined the same set of eight shapes, whereas responses to RDSs and their monocular images were not correlated. This indicates that the response modulation for the eight RDSs reflects selectivity for shapes (or their component contours) defined by disparity, although responses were also affected by dot patterns per se. Among the neurons that showed selectivity for shapes defined by luminance or disparity, 44% were activated by both cues. Responses of these neurons to luminance-defined shapes and those to disparity-defined shapes were often positively correlated to each other. Furthermore the stimulus rank, which was determined by the magnitude of responses to shapes, generally matched between these cues. The same held true between disparity and texture cues. The results suggest that the signals of disparity, luminance, and texture cues to define the shapes converge on a population of single IT neurons to produce the selectivity for shapes.

Animals↗

PubMed2006

Disparities in access to essential new prescription drugs between non-Hispanic whites, non-Hispanic blacks, and Hispanic whites.

Prior studies do not address racial and ethnic disparities in essential new drug use and whether disparities decrease through time. Using the Medical Expenditure Panel Survey (1996-2001), racial and ethnic disparities were examined separately by comparing non-Hispanic whites to non-Hispanic blacks and Hispanic whites, respectively. New drugs were defined as approved within the past 5 years, and an expert panel identified essential drugs. Negative binomial models adjusted for socioeconomic and health characteristics. The mean annual number of times essential new drugs were obtained among non-Hispanic whites, non-Hispanic blacks, and Hispanic whites were 1.02, 0.94, and 0.70, respectively. After adjusting for confounders, ethnic disparities generally were not significant, but racial disparities became significant. This study did not identify declining disparities during early years of drugs' life cycles. Disparities exist in new, essential drug acquisition between non-Hispanic whites and non-Hispanic blacks. Socioeconomic and health characteristics explain many of the observed disparities.

Adolescent↗

PubMed2006

Racial and ethnic disparities in breast cancer mortality: are we doing enough to address the root causes?

Breast cancer is the most common noncutaneous malignancy and the second most lethal form of cancer among women in the United States. Mortality from breast cancer has declined since the late 1980s, but this decline has been steeper among white women compared with black women. As a result, the black:white mortality rate ratio has increased over the last two decades. Other ethnic minorities also suffer from disproportionately high breast cancer mortality rates. This review discusses the causes of racial and ethnic disparities in breast cancer mortality and describes the most common approaches to reducing these disparities. The literature suggests that outcome disparities are related to patient-, provider-, and health system-level factors. Lack of insurance, fear of testing, delay in seeking care, and unfavorable tumor characteristics all contribute to disparities at the patient level. At the provider level, insufficient screening, poor follow-up of abnormal screening tests, and nonadherence to guideline-based treatments add to outcome disparities. High copayment requirements, lack of a usual source of care, fragmentation of care, and uneven distribution of screening and treatment resources exacerbate disparities at the health system level. Although pilot programs have increased breast cancer screening among select populations, persistent disparities in mortality suggest that changes are needed at the policy level to address the root causes of these disparities.

Breast Neoplasms↗

PubMed1996

Differentiation of Entamoeba histolytica and Entamoeba dispar in cyst-passers by immunoblot.

Differentiation of invasive strains of Entamoeba histolytica according to their pathogenicity has been a topic of long debate, but now the pathogenic species only is regarded as E. histolytica while the non pathogenic species is E. dispar. The present study applied immunoblot to differentiate infections of the two species among microscopically-detected cyst-passers in Korea. The crude extract of E. histolytica separated in 5.20% gradient gels, revealed many fractions of 94, 81, 71, 50, 44, 38.5, 37.5, 29, 19, and 18 kDa when the cysteine proteinase inhibitor, E64, was supplemented. The scrum IgG antibody of 3 proven E, histolytica cases reacted with the antigenic fractions of 117, 110, 99, 68, 66, 60, 54, 52, 46, and 45 kDa. Sera of PCR confirmed 3 cases of E. dispar reacted only to the 117 kDa fraction of the E. histolytica crude extract which was regarded as non-specific. To the antigen of monoxenic E. dispar, sera of E. dispar and E. histolytica cases showed the same immunoblot reactions. The serum IgA antibody reacted with several antigenic fractions of both E. histolytica and E. dispar, but IgM and IgE antibodies showed no reaction to either antigen. Sera of 24 symptomless amebic cyst passers were screened with the E. histolytica antigen; two were found to be infected by E. histolytica and 22 were by E. dispar. The present findings suggest that in Korea most of asymptomatic cyst passers of E. histolytica are carriers of E. dispar. Immunoblot using E. histolytica antigen is a good technique for the differentiation of E. histolytica and E. dispar infections.

Animals↗

PubMed2003

Disparities in health and health care: focusing efforts to eliminate unequal burdens.

Disparities in health and health care have been around for more than two centuries. Evidence suggests that health disparities in ethnic and racial minorities continue to be problematic, with little progress made to eliminate them over time. Ethnic and racial disparities exist for multiple and complex reasons. However, new solutions are needed to resolve some of these old problems. Framing the debate and discussion around the distinctiveness related to disparities in health and health care is a necessary beginning in eliminating unequal burdens in health status. Focusing efforts to eliminate unequal burdens can strengthen existing solutions and policy formation related to this issue. This article defines disparities in health and health care, describes current health disparities impacting ethnic/racial groups, reviews historical factors associated with existing disparities in ethnic/racial groups, and concludes with challenges and solutions to alleviate these disparities.

Cultural Diversity↗

PubMed1985

Participation of class II alloantigens in in vivo regulation of K/D region disparate thyroid graft rejection in mice.

Class I and II molecules preferentially activate cytotoxic T cells and helper T cells, respectively, in primary in vitro alloactivation of T lymphocytes. Collaboration between these subpopulations leads to an efficient anti-class I specific cytotoxic response. We tested whether the presence of class II, in addition to class I, alloantigens on thyroid allografts in vivo induces augmentation of anti-class I antigen immune response and leads to rejection of K/D region disparate grafts which otherwise would have been accepted. Different pairs of K or D region disparate mouse strains were selected in which transplantation across a class I antigen disparity alone resulted in long-term graft acceptance. In some pairs of mouse strains, co-transplantation of recipient mice with a second thyroid graft sharing the K/D region of the first, but additionally expressing an allo class II molecule, led to accelerated K/D region disparate thyroid graft rejection. Transplantation of thyroid allografts expressing both class II and I alloantigens did not induce increased host anti-class I antigen cytotoxic response, or affect the frequency of specific precursor cytotoxic T cells. In one pair of congenic mouse strains, acute rejection of K/D region disparate thyroid grafts occurred in the absence of class II alloantigen stimulation; in other strains, co-transplantation of class I and II alloantigen disparate thyroid allografts was not sufficient to induce K/D region disparate graft rejection. The results thus demonstrate that a class II alloantigen on a thyroid graft may augment the rejection response directed against the graft class I alloantigens. The class II alloantigen stimulation was not always essential or sufficient for induction of class I antigen disparate thyroid graft rejection, and was dependent on the specific I region and/or K/D region gene allele.

Animals↗

PubMed1988

Disparity range for binocular summation.

Binocular summation of contrast and stereopsis have been linked because they both disappear under certain pathological conditions. The dependence of stereopsis on spatial frequency prompted us to examine how binocular summation varies with both spatial frequency and binocular disparity. We therefore measured binocular summation at different disparities using spatially localized stimuli which were also restricted in their Fourier composition. Contrast thresholds were measured using three interleaved forced-choice staircases for left and right eye monocular stimuli and a binocular stimulus composed of the two monocular stimuli presented simultaneously. At zero disparity binocular thresholds were 1.4 to 1.6 times lower than monocular. As disparity was increased the ratio between the thresholds became smaller, such that at large disparities it was near 1.2, the value expected from probability summation. The range of disparities over which probability summation was exceeded varied with the spatial frequency of the stimulus. At 6.0 cpd the range was 2-3 deg, but at 2.0 cpd or 0.75 cpd the range increased to 4-6 deg. These values closely parallel the range of disparities over which stereoscopic depth sensations occur, but they exceed the limits within which disparate images of an object can be fused into a single percept. The results support the contentions that "neural" summation occurs in the mechanism for stereopsis, that this mechanism uses spatial frequency selective channels, and that this mechanism is separate from the mechanism which mediates fusion.

Adult↗

PubMed1987

Fixation disparity in binocular stress.

Fixation disparity has been taken as a sign of stress on binocular vision because it is established that prism stress creates fixation disparity. This paper looks at the effect on fixation disparity of the stress caused by requiring subjects to read in inadequate illumination. It is found that the reduction in illumination does not in itself immediately change the magnitude of the fixation disparity. There is, however, an increase in the mean slope of the central part of the fixation disparity curve which suggests that when the effect of reduced illumination is added to prism stress, fixation disparity is increased. The stress created by asking subjects to read in reduced illumination for half an hour resulted in the mean associated heterophoria being increased, and over half the subjects reported symptoms of stress. It is concluded that fixation disparity is changed by this type of visual stress in some subjects, and in near vision is increased to a more marked degree of exo-disparity. Most of this increase occurs in the first ten minutes.

Adolescent↗

PubMed1999

DNA typing for HLA-A and HLA-B identifies disparities between patients and unrelated donors matched by HLA-A and HLA-B serology and HLA-DRB1.

High incidences of graft failure and graft-versus-host disease in the recipients of bone marrow transplantations (BMT) from unrelated donors (URD) may reflect the existence of allelic disparities between the patient and the URD despite apparent HLA identity at HLA-A, HLA-B, and HLA-DRB1 loci. To identify the extent and pattern of allelic disparities at HLA-A and HLA-B loci, 128 patients and 484 potential URD were evaluated by DNA typing. DNA typing for HLA-A, HLA-B, and HLA-DRB1 was performed at Memorial Sloan Kettering Cancer Center. HLA-A and HLA-B serotyping on URD was provided by the registries. By original typing (serology for HLA-A and HLA-B; DNA typing for DRB1) 187, 164, and 133 URD were 6/6, 5/6, and 4/6 matches, respectively. Following DNA typing, however, only 52.9% of the originally 6/6 matched URD remained 6/6, while 38.5%, 7.5%, and 1.1% were found to be 5/6, 4/6, and 3/6 matches. The level of disparity was higher in the originally 5/6 (P <.01) and 4/6 (P <.01) matched URD. A higher level of disparity was seen for HLA-B as compared to HLA-A. In addition, a serotype related variation was also noticed. For example, 24.1% of HLA-A2 and 60.1% of HLA-B35 seromatched URD were genotypically disparate, but no disparities were seen for HLA-A1 and HLA-B8. A higher percentage of HLA-A (67. 4%) compared with HLA-B (35.4%) serologic homozygous URD remained genotypically homozygous (P =.01). The level of allelic disparity was lower (P <.01 for 6/6; P =.02 for 5/6) if the patient had one of the 15 most common haplotypes (A1B8DR3, A2B7DR15, A3B7DR15, etc) in comparison to the rest of the group. Outcome studies will answer the question whether these disparities are associated with a higher rate of immunological complications seen with URD-BMT.

Bone Marrow Transplantation↗

PubMed1994

Size constancy, depth constancy and vertical disparities: a further quantitative interpretation.

The size and depth constancies considered here operate only at near distances (< about 2 m) in a static stimulus situation with vergence as the only cue to distance. The innervation of the extraocular muscles, as evidenced by the corollary discharge, provides information about the vergence of the eyes and hence about the egocentric distance both for symmetrical and asymmetrical vergences. Size and depth constancies are regarded as the first and second stages of a linked two-stage process. In the lateral geniculate nuclei compensatory adjustments are separately applied to each retinal image as they are received from the two eyes. The modified ocular images, with their associated vertical and horizontal disparities, now provide synaptic inputs to binocularly activated cells in the visual cortex. Then, by a process akin to the induced effect, cortical cells with geniculate afferents with vertical disparities will have their outputs expressed in terms of horizontal disparities. The horizontal disparity outputs of these cortical cells are then further multiplied by the outputs from cortical cells with geniculate afferents with horizontal disparities. It is this second multiplicative process that brings about the quadratic relationship between horizontal retinal disparity and egocentric distance. The proposed mechanisms involve the known ability of the visual system to detect and respond to vertical as well as horizontal disparities and provide a definite role for the induced effect in the perceptual process. The above neural model is based on fairly simple equations that give a remarkably adequate description of the operation of the two constancies.

Cybernetics↗

PubMed1994

Relative shear disparities and the perception of surface inclination.

A dichoptic display in which the images are cyclorotated in opposite directions does not appear inclined. This suggests that perceived inclination depends on the difference between horizontal-shear and vertical-shear disparity. Large random-dot stereoscopic displays were presented with various types of shear disparity. Perceived inclination was the same magnitude for horizontal and vertical shear disparities. Opposed horizontal and vertical shear produced greater inclination than a single-axis shear. Same-sign vertical and horizontal shear (rotation) produced no inclination. These results support the relative-shear hypothesis. Cyclovergence was measured and was insufficient to account for these effects. We conclude that perceived inclination depends on the difference between horizontal- and vertical-shear disparities. Perceived inclination was not based on vertical disparity within small displays or within large displays with a zero-disparity surround. Relative-shear disparities are therefore extracted globally rather than locally.

Adult↗

PubMed2006

Vertical-size disparities are temporally integrated for slant perception.

We investigated temporal properties of vertical-size and horizontal-size disparity processing for slant perception. Subjects indicated perceived slants for a stereoscopic stimulus in which the two magnitudes of vertical-size or horizontal-size disparities were oscillated stepwise with various frequencies (from 0.2 to 10 Hz). For the stimulus with vertical-size disparity oscillation, two slants corresponding to the two magnitudes of disparity were perceived for low-frequency conditions, whereas only a static mean slant of the two slants was perceived for high frequencies (5 and 10 Hz). For the stimulus with horizontal-size disparity oscillation, two slants were perceived for all the temporal frequency conditions. These results indicate that temporal properties of vertical- and horizontal-size disparity processing are clearly different and vertical-size disparities are temporally integrated over a period of around 500 ms for slant perception.

Depth Perception↗

PubMed2006

Disparity with respect to a local reference plane as a dominant cue for stereoscopic depth relief.

Earlier studies showed that the disparity with respect to other visible points could not explain stereoacuity performance, nor could various spatial derivatives of disparity [Glennerster, A., McKee, S. P., & Birch, M. D. (2002). Evidence of surface-based processing of binocular disparity. Current Biology, 12:825-828; Petrov, Y., & Glennerster, A. (2004). The role of the local reference in stereoscopic detection of depth relief. Vision Research, 44:367-376.] Two possible cues remain: (i) local changes in disparity gradient or (ii) disparity with respect to an interpolated line drawn through the reference points. Here, we aimed to distinguish between these two cues. Subjects judged, in a two AFC paradigm, whether a target dot was in front of a plane defined by three reference dots or, in other experiments, in front of a line defined by two reference dots. We tested different slants of the reference line or plane and different locations of the target relative to the reference points. For slanted reference lines or plane, stereoacuity changed little as the target position was varied. For judgments relative to a frontoparallel reference line, stereoacuity did vary with target position, but less than would be predicted by disparity gradient change. This provides evidence that disparity with respect to the reference plane is an important cue. We discuss the potential advantages of this measure in generating a representation of surface relief that is invariant to viewpoint transformations.

Cues↗

PubMed2000

A physiologically-based explanation of disparity attraction and repulsion.

Westheimer and Levi [(1987) Vision Research, 27, 1361-1368] found that when a few isolated features are viewed foveally, the perceived depth of a feature depends not only on its own disparity but also on those of its neighbors. The nature of this interaction is a function of the lateral separation between the features: When the distance is small the features appear to attract each other in depth but the interaction becomes repulsive at larger distances. Here we introduce a two-dimensional extension of our recent stereo model based on the physiological studies of Ohzawa, DeAngelis and Freeman [(1990) Science, 249, 1037-1041] and demonstrate through analyses and simulations that these observations can be naturally explained without introducing ad hoc assumptions about the connectivity between disparity-tuned units. In particular, our model can explain the distance-dependent attraction/repulsion phenomena in both the vertical-line configuration used by Westheimer [(1986) Journal for Neurophysiology, 370, 619-629], and the horizontal-line-and-point configuration used by Westheimer and Levi. Thus, the psychophysically observed disparity interaction may be viewed as a direct consequence of the known physiological organization of the binocular receptive fields. We also find that the transition distance at which the disparity interaction between features changes from attraction to repulsion is largely determined by the preferred spatial frequency and orientation distributions of the cells used in the disparity computation. This result may explain the observed variations of the transition distance among different subjects in the psychophysical experiments. Finally, our model can also reproduce the observed effect on the perceived disparity when the disparity magnitude of the neighboring features is changed.

Computer Simulation↗

PubMed2001

Effects of horizontal and vertical additive disparity noise on stereoscopic corrugation detection.

Stereoscopic corrugation detection in the presence of horizontal- and vertical- additive disparity noise was examined using a signal detection paradigm. Random-dot stereograms either represented a 3-D square-wave surface with various amounts of Gaussian-distributed additive disparity noise or had the same disparity values randomly redistributed. Stereoscopic detection of 2 arcmin peak amplitude corrugations was found to tolerate significantly greater amplitudes of vertical-disparity noise than horizontal-disparity noise--irrespective of whether the corrugations were horizontally or vertically oriented. However, this directional difference in tolerance to disparity noise was found to reverse when the corrugation and noise amplitudes were increased (so as to produce equivalent signal-to-noise ratios). These results suggest that horizontal- and vertical-disparity noise pose different problems for dot-matching and post-matching surface reconstruction as corrugation and noise amplitudes increase.

Adult↗

PubMed1997

Physiological computation of binocular disparity.

We previously proposed a physiologically realistic model for stereo vision based on the quantitative binocular receptive field profiles mapped by Freeman and coworkers. Here we present several new results about the model that shed light on the physiological processes involved in disparity computation. First, we show that our model can be extended to a much more general class of receptive field profiles than the commonly used Gabor functions. Second, we demonstrate that there is, however, an advantage of using the Gabor filters: similar to our perception, the stereo algorithm with the Gabor filters has a small bias towards zero disparity. Third, we prove that the complex cells as described by Freeman et al. compute disparity by effectively summing up two related cross products between the band-pass filtered left and right retinal image patches. This operation is related to cross-correlation but it overcomes some major problems with the standard correlator. Fourth, we demonstrate that as few as two complex cells at each spatial location are sufficient for a reasonable estimation of binocular disparity. Fifth, we find that our model can be significantly improved by considering the fact that complex cell receptive field are, on average, larger than those of simple cells. This fact is incorporated into the model by averaging over several quadrature pairs of simple cells with nearby and overlapping receptive fields to construct a model complex cell. The disparity tuning curve of the resulting complex cell is much more reliable than the constructed from a single quadrature pair of simple cells used previously, and the computed disparity maps for random dot stereograms with the new algorithm are very similar to human perception, with sharp transitions at disparity boundaries. Finally, we show that under most circumstances our algorithm works equally well with either of the two well-known receptive field models in the literature.

Algorithms↗