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Biomedical subjects

David Huang

Publications and source records attributed to David Huang.

At least 19 recordsLinked to original sources
PubMed2006

Lay patient navigator program implementation for equal access to cancer care and clinical trials: essential steps and initial challenges.

BACKGROUND: Disparities in cancer detection, treatment, and outcomes among racial/ethnic minorities and low-income patients are well documented. One way to reduce these disparities is to use patient navigators to address barriers to care. However, little information about optimal characteristics of navigator programs or considerations for those interested in setting up such programs is available. METHODS: The design and implementation of a patient navigator program for underserved cancer patients in an urban, nonacademic community hospital setting is described. The program, which used lay navigators, was conceived as a component of the Urban Latino African American Cancer (ULAAC) Disparities Project in South Los Angeles, a National Cancer Institute (NCI)-sponsored project to improve cancer care and clinical trial access for minority and low-income patients. RESULTS: Careful initial planning, including input from a community advisory committee, was essential to smooth program implementation. Thirty-one volunteers completed navigator training in the program's first year of operation. Of 135 patients offered navigation services, 75 (56%) accepted, and preliminary feedback from patients, navigators, and providers suggests high levels of satisfaction with navigation. Standardized templates used by navigators and staff to record key information are proving helpful for monitoring quality and outcomes (such as effectiveness in addressing specific barriers to care) and continually improving the program. CONCLUSIONS: The ULAAC program represents a viable model for developing lay navigator programs in community hospitals. Preliminary assessments suggest that the program has a positive effect on minority and low-income cancer patients' experience with care and reduces barriers to care. Additional time and research are needed, however, to fully assess the impact on care and outcomes.

Clinical Trials as Topic↗
PubMed2006

Impact of California's Proposition 36 on the drug treatment system: treatment capacity and displacement.

OBJECTIVES: California's Proposition 36 offers nonviolent drug offenders community-based treatment as an alternative to incarceration or probation without treatment. We examined how treatment capacity changed to accommodate Proposition 36 clients and whether displacement of other clients was an unintended consequence. METHODS: Treatment admissions were compared for the year before and 2 years after the law was enacted. Surveys of county administrators and treatment providers were conducted in Kern, Riverside, Sacramento, San Diego, and San Francisco counties. RESULTS: The number of Proposition 36 offenders admitted to treatment continued to increase in the state (approximately 32000 in Year 1 and 48000 in Year 2) and in the 5 counties; total treatment admissions stabilized in Year 2 after increasing in Year 1. Voluntary clients decreased by 8000 each year statewide, but the change varied across counties. One third of treatment providers reported decreased treatment availability for non-Proposition 36 clients in Year 2. CONCLUSION: Despite expanded treatment capacity (mostly in outpatient treatment), indirect evidence suggests that displacement of voluntary clients may have occurred in part because of the demand for treatment by Proposition 36 clients.

Adolescent↗
PubMed2006

Optical coherence tomography of the anterior segment in secondary glaucoma with corneal opacity after penetrating keratoplasty.

AIM: To evaluate secondary glaucoma after penetrating keratoplasty with anterior-segment optical coherence tomography (OCT). DESIGN: Case series. METHODS: Four eyes of four patients with corneal opacity and increased intraocular pressure (IOP) were evaluated using high-speed (2000 axial scans/s) OCT at 1.3 microm wavelength. Cross-sectional images of the anterior segment were analysed to assess the cause of increase in pressure. RESULTS: Slit-lamp evaluation of the anterior chamber in all cases was limited by corneal opacity. The OCT imaging allowed visualisation of anterior-segment structures behind the opaque corneas. Using OCT, iris-intraocular lens adhesion and pupillary block were identified as the probable reasons for the increased IOP in one case. Peripheral anterior synechiae and angle closure were identified in the three remaining cases. In two cases, we found that the tip of the aqueous drainage tube was blocked by peripheral anterior synechiae. CONCLUSIONS: OCT is similar to ultrasound in that it allows visualisation through opaque corneas. However, OCT has an advantage in that it requires neither contact nor immersion. It is a valuable tool for evaluating the depth of the anterior chamber angle and the causes of secondary angle closure.

Aged, 80 and over↗
PubMed2006

Retinal assessment using optical coherence tomography.

Over the 15 years since the original description, optical coherence tomography (OCT) has become one of the key diagnostic technologies in the ophthalmic subspecialty areas of retinal diseases and glaucoma. The reason for the widespread adoption of this technology originates from at least two properties of the OCT results: on the one hand, the results are accessible to the non-specialist where microscopic retinal abnormalities are grossly and easily noticeable; on the other hand, results are reproducible and exceedingly quantitative in the hands of the specialist. However, as in any other imaging technique in ophthalmology, some artifacts are expected to occur. Understanding of the basic principles of image acquisition and data processing as well as recognition of OCT limitations are crucial issues to using this equipment with cleverness. Herein, we took a brief look in the past of OCT and have explained the key basic physical principles of this imaging technology. In addition, each of the several steps encompassing a third generation OCT evaluation of retinal tissues has been addressed in details. A comprehensive explanation about next generation OCT systems has also been provided and, to conclude, we have commented on the future directions of this exceptional technique.

Anatomy, Cross-Sectional↗
PubMed2006

Automated detection of clinically significant macular edema by grid scanning optical coherence tomography.

OBJECTIVE: To compare the detection of clinically significant diabetic macular edema (DME) by an optical coherence tomography (OCT) grid scanning protocol and biomicroscopic examination. DESIGN: Retrospective case series. PARTICIPANTS: Outpatients at the Doheny Eye Institute. METHODS: The clinical and imaging records of a consecutive series of 71 eyes of 40 patients referred for DME who underwent OCT using the both the Macular Grid 5 (MG5) scanning protocol (to allow a more evenly distributed sampling of points in the macula) and the standard Fast Macular Thickness Map (FMTM) pattern were reviewed. An automated algorithm was developed to generate a retinal thickness map using the MG5 data, which was then compared with a normative database to identify presumed areas of retinal edema. Clinically significant macular edema (CSME) was also identified by clinical examination and stereoscopic fundus photographs for comparison with the results of the OCT protocols. MAIN OUTCOME MEASURES: Sensitivity and specificity of scanning protocols. RESULTS: Optical coherence tomograms were inspected visually, and automatically detected retinal boundaries were found to be correct in 69 of 71 MG5 scans and in 65 of 71 FMTM scans. Macular Grid 5 scanning was performed twice in each eye, and the repeatability (pooled standard deviation) of the total area of edema was 0.48 mm2 (coefficient of variation, 6.8%). Sensitivity and specificity of the MG5 for detection of CSME relative to the clinical examination were 89% and 86%, respectively, with kappa being 0.74. Macular Grid 5 and FMTM assessment of foveal CSME also showed good agreement, with kappa being 0.68. CONCLUSIONS: The analysis algorithm for the OCT MG5 grid scan seems to be accurate and repeatable. Automated detection of CSME by the MG5 analysis correlated well with the clinical grading and standard OCT analysis (FMTM). Macular Grid 5 provides more information regarding the perifoveal macula than FMTM and may be of value to clinicians in planning treatment and in future studies of macular edema.

Algorithms↗
PubMed2006

A feasibility study of optical coherence tomography for guiding deep brain probes.

Deep brain simulation (DBS) is effective for the treatment of various diseases including Parkinson's disease and essential tremor. However, anatomical targeting combined with microelectrode mapping of the region requires significant surgical time. Also, the fine-tipped microelectrode imposes a risk of hemorrhage in the event that the trajectory intersects subcortical vessels. To reduce the operation time and the risk of hemorrhage, we propose to use optical coherence tomography (OCT) to guide the insertion of the DBS probe. We conducted in vitro experiments in the rat brain to study the feasibility of this application. The result shows that OCT is able to differentiate structures in the rat brain. White matter tends to have higher peak reflectivity and steeper attenuation rate compared to gray matter. This structural information may help guide DBS probe advance and electrical measurements.

Animals↗
PubMed2006

Long-term morbidity and mortality among a sample of cocaine-dependent black and white veterans.

Racial minorities generally exhibit worse health status than do whites. To assess the presence of similar phenomena among long-term cocaine-using veterans, this study examined racial variations in mortality and health status among cocaine-dependent men who were originally recruited at their admissions to cocaine treatment in 1988-1989 and were interviewed approximately 12 years later in 2002-2003. Mortality was higher among whites (15%) than blacks (6%), particularly due to drug overdose. Controlling for socioeconomic factors, cocaine severity, and depression, the racial difference was still significant in the survival analysis. Racial differences were examined in the health status of those interviewed in the 12-year follow-up study (178 blacks and 65 whites), after confirmation of their comparable socioeconomic backgrounds and levels of healthcare access and utilization. Contrary to expectations, few racial differences were found on most health indicators, although the level of cocaine use was higher among blacks. Furthermore, fewer blacks reported having hepatitis or sexually transmitted diseases than did whites. The study results suggest that black cocaine-dependent veterans do not have worse health status when compared with white veterans on most health indicators.

Adult↗
PubMed2006

Measuring total corneal power before and after laser in situ keratomileusis with high-speed optical coherence tomography.

PURPOSE: To measure total corneal power using optical coherence tomography (OCT). SETTING: Refractive surgery practices at 2 academic eye centers in Cleveland, Ohio, and Los Angeles, California, USA. METHODS: Thirty-two eyes of 17 patients having myopic laser in situ keratomileusis (LASIK) were enrolled in a prospective observational study. Manifest refraction, OCT, and Placido ring corneal topography with the Atlas 995 (Carl Zeiss Meditec, Inc.) were performed preoperatively and 3 months after laser in situ keratomileusis (LASIK). A high-speed (2000 axial scans/second) corneal and anterior segment OCT prototype was used. The total corneal power was calculated by summation of the anterior and posterior surface powers, and the value was compared with that determined by simulated keratometry. Two methods of measuring total corneal power were tested: the direct method, which used OCT to measure both corneal surfaces directly, and the hybrid method, which combined OCT with anterior corneal topography. RESULTS: The repeatability (pooled standard deviation) of measuring total corneal power using the hybrid method was 3 times better than that using the direct method. It was 0.23 diopter (D) before LASIK and 0.26 D after LASIK. Preoperative total power was 1.13 D (2.6%) lower than the simulated keratometry. Compared to the LASIK-induced change in spherical equivalent refraction, the change in total corneal power was equivalent, while the change in simulated keratometry power was significantly smaller (-18.8%) (P<.001). CONCLUSIONS: Keratometry using the traditional index of 1.3375 overestimated the total power in preoperative corneas and underestimated LASIK-induced refractive change. Measuring both corneal surfaces using a combination of OCT and Placido ring topography provided a better measure of total corneal power that closely tracked the refractive change in post-LASIK eyes.

Anterior Eye Segment↗
PubMed2006

Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes.

PURPOSE: To investigate intrastromal corneal ring segment depth with a high-speed corneal optical coherence tomography (OCT) system. SETTING: Doheny Eye Institute, University of Southern California, Los Angeles, California, USA. METHODS: A prospective observational case series comprised 4 eyes of 4 patients receiving Intacs intrastromal corneal ring segments (Addition Technology, Inc.) for keratoconus. Optical coherence tomography (OCT) was performed between 7 days and 43 days after implantation. RESULTS: The slitlamp impression of intrastromal corneal ring segment implantation depth did not correlate well with OCT measurements (r(2) = 0.68). The fractional implantation depth was correlated with several surgical variables using a stepwise multivariate regression model, and 2 statistically significant correlations were found. The position of the distal portions of the ring segments was shallower than that of the portion closer to the insertion site (P = .003). Segments placed in the inferior cornea (P = .008) experienced more distal shallowing. Shallower depth was associated with greater fractional anterior stromal compression (P = .04). CONCLUSIONS: Shallower placement of intrastromal corneal ring segments may result in more complications, such as epithelial-stromal breakdown and extrusion, because of the greater anterior stromal tensile strain. The distal and inferior portions of intrastromal corneal ring segments tended to be placed at a shallower depth. Optical coherence tomography provided precise measurement of ring segment depth and may help identify implants that pose a greater risk for depth-related complications.

Adult↗
PubMed2006

In vivo architectural analysis of 3.2 mm clear corneal incisions for phacoemulsification using optical coherence tomography.

PURPOSE: To analyze in vivo the architecture of clear corneal incisions (CCIs) for phacoemulsification using optical coherence tomography (OCT). SETTING: Anterior Segment Department, Asociacion Para Evitar la Ceguera en Mexico, Hospital Dr Luis Sanchez Bulnes, Mexico. METHODS: A prospective masked study analyzed 20 unsutured CCIs placed superiorly and created in a uniplanar fashion with a 3.2 mm slit-angled metal keratome. All wounds were evaluated with a retinal OCT model 1, 3, and 30 days postoperatively. Intraocular pressure (IOP) and incision leakage were checked. The architecture was described according to the angle of incidence, apposition of the epithelial and endothelial margins, and wound sealing. RESULTS: No leakage was detected. The angle varied from 33 to 85 degrees; angles greater than 75 degrees were done by a surgeon in training. Wound apposition at the epithelial margin was achieved in all cases. In contrast, imperfect apposition of the endothelial margin was seen in 45% of incisions on day 1 and in 15% on day 30. Incomplete sealing of the wound was seen by OCT in 25% of cases at 24 hours and persisted in 10% of all cases at 1 month. This gaping occurred on the endothelial side and never translated to the epithelial margin. No statistical correlation was found between gaping and the angle of the incision, IOP variations, or surgeon experience. CONCLUSIONS: Although in vivo CCIs caused minor anatomic imperfections, they were clinically stable independent of incision angle, IOP variation, and surgeon experience. Incision stability may be related to careful wound construction, epithelial viability, stromal edema, and efficient endothelial pumping.

Cornea↗
PubMed2006

High-speed optical coherence tomography for management after laser in situ keratomileusis.

PURPOSE: To report applications of optical coherence tomography (OCT) in the management of laser in situ keratomileusis (LASIK) related problems. SETTING: Doheny Eye Institute and Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA. METHODS: Five patients referred for LASIK-related problems were enrolled in a prospective observational study. Clinical examination, ultrasound (US) pachymetry, Placido ring slit-scanning corneal topography (Orbscan II, Bausch & Lomb), and high-speed corneal OCT were performed. RESULTS: In cases of regression and keratectasia, OCT provided thickness measurements of the cornea, flap, and posterior stromal bed. Locations of tissue loss and flap interface planes were identified in a case with a recut enhancement complication. The information was used to determine whether further laser ablation was safe, confirm keratectasia, and manage complications. Optical coherence tomography measurements of central corneal thickness agreed well with US pachymetry measurements (difference 6.4 microm +/- 11.7 [SD]) (P = .026), while Orbscan significantly underestimated corneal thickness (-67.5 +/- 72.5 microm) (P = .17). CONCLUSIONS: High-speed OCT provided noncontact imaging and measurement of LASIK anatomy. It was useful in monitoring LASIK results and evaluating complications.

Adult↗
PubMed2006

A 12-year follow-up of a treated cocaine-dependent sample.

The study examined long-term outcomes (mortality, substance use, mental health, employment, criminal involvement) among a cocaine-dependent sample. This 12-year follow-up study, conducted in 2002-2003, updates information obtained at intake and two face-to-face interviews conducted in 1990-1991 and 1991-1992 among 321 male cocaine-dependent veterans admitted to drug treatment in 1988-1989. At the 2002-2003 follow-up, 28 had died and 266 were interviewed. A mixed model examining the longitudinal relationships demonstrated that treatment was associated with lower levels of cocaine use over the 12-year follow-up period after entry into the index treatment and more stable recovery (i.e., continuously abstinent from cocaine for at least 5 years). Few measures at intake predicted stable recovery at follow-up: only being White (vs. being African American) and having greater confidence in ability to avoid cocaine use in high-risk situations. Individuals achieving stable recovery reported less psychiatric symptoms, criminal involvement, and unemployment during the year prior to the interview. Adverse outcomes were apparent for a significant number of cocaine-dependent users who continued to use cocaine for a long period.

Adult↗
PubMed2006

Corneal pachymetry mapping with high-speed optical coherence tomography.

OBJECTIVE: To map corneal thickness before and after LASIK with optical coherence tomography (OCT). DESIGN: Cross-sectional observational study. PARTICIPANTS: Forty-two eyes of 21 normal subjects undergoing LASIK. METHODS: A high-speed (2000 axial scans/second) 1.3-microm-wavelength corneal and anterior segment OCT prototype was used for corneal scanning. The scan pattern consisted of 10-mm radial lines on 8 meridians centered on the vertex reflection. The entire scan pattern of 1024 a-scans was acquired in 0.5 seconds. We developed automated computer processing for 3-dimensional corneal reconstruction and measurement. Corneal thickness was measured normal to the anterior surface and presented as color pachymetry maps and zonal statistics. The maps were divided into a central zone (<2 mm) and 3 annular areas (pericentral, 2-5 mm; transitional, 5-7 mm; peripheral, 7-10 mm), which were further divided into quadrantal zones. The average, minimum, and maximum corneal thicknesses were computed for zones within the 7-mm diameter. Optical coherence tomography and ultrasound pachymetry were measured 3 times at the preoperative and 3-month postoperative visits. Reproducibility was assessed by the pooled standard deviations (SDs) of the repeated measurements. MAIN OUTCOME MEASURES: Optical coherence tomography pachymetric map and zonal statistic, and ultrasound pachymetry. RESULTS: Before LASIK, central corneal thicknesses (CCTs) were 546.9+/-29.4 microm (mean +/- SD) for OCT and 553.3+/-33.0 microm for ultrasound. After LASIK, CCTs were 513.7+/-44.5 microm for OCT and 498+/-46.6 microm for ultrasound. Optical coherence tomography and ultrasound CCT were highly correlated (Pearson correlation r = 0.97 before LASIK and 0.98 afterwards). Optical coherence tomography CCT was slightly less than ultrasound CCT before surgery (mean difference, -6.4 microm; 95% limits of agreement, -23.2 to 10.4 microm) but slightly greater after LASIK (15.7 microm; -1.6 to 33 microm). These differences were statistically significant, but no more than the CCT measurement differences between ultrasound pachymeters. The reproducibility of the OCT zonal pachymetry averages was roughly 2 microm. CONCLUSIONS: High-speed OCT provided noncontact, rapid, reproducible pachymetric mapping over a wide area of the cornea. It is equivalent to ultrasound for CCT measurement before and after LASIK. This technology could be valuable for planning keratorefractive procedures and diagnosis of corneal diseases.

Adult↗
PubMed2006

Benefit-cost in the California treatment outcome project: does substance abuse treatment "pay for itself"?

OBJECTIVE: To examine costs and monetary benefits associated with substance abuse treatment. DATA SOURCES: Primary and administrative data on client outcomes and agency costs from 43 substance abuse treatment providers in 13 counties in California during 2000-2001. STUDY DESIGN: Using a social planner perspective, the estimated direct cost of treatment was compared with the associated monetary benefits, including the client's costs of medical care, mental health services, criminal activity, earnings, and (from the government's perspective) transfer program payments. The cost of the client's substance abuse treatment episode was estimated by multiplying the number of days that the client spent in each treatment modality by the estimated average per diem cost of that modality. Monetary benefits associated with treatment were estimated using a pre-posttreatment admission study design, i.e., each client served as his or her own control. DATA COLLECTION: Treatment cost data were collected from providers using the Drug Abuse Treatment Cost Analysis Program instrument. For the main sample of 2,567 clients, information on medical hospitalizations, emergency room visits, earnings, and transfer payments was obtained from baseline and 9-month follow-up interviews, and linked to information on inpatient and outpatient mental health services use and criminal activity from administrative databases. Sensitivity analyses examined administrative data outcomes for a larger cohort (N=6,545) and longer time period (1 year). PRINCIPAL FINDINGS: On average, substance abuse treatment costs $1,583 and is associated with a monetary benefit to society of $11,487, representing a greater than 7:1 ratio of benefits to costs. These benefits were primarily because of reduced costs of crime and increased employment earnings. CONCLUSIONS: Even without considering the direct value to clients of improved health and quality of life, allocating taxpayer dollars to substance abuse treatment may be a wise investment.

California↗
PubMed2005

Regulation of the cytoplasmic quality control protein degradation pathway by BAG2.

The cytoplasm is protected against the perils of protein misfolding by two mechanisms: molecular chaperones (which facilitate proper folding) and the ubiquitin-proteasome system, which regulates degradation of misfolded proteins. CHIP (carboxyl terminus of Hsp70-interacting protein) is an Hsp70-associated ubiquitin ligase that participates in this process by ubiquitylating misfolded proteins associated with cytoplasmic chaperones. Mechanisms that regulate the activity of CHIP are, at present, poorly understood. Using a proteomics approach, we have identified BAG2, a previously uncharacterized BAG domain-containing protein, as a common component of CHIP holocomplexes in vivo. Binding assays indicate that BAG2 associates with CHIP as part of a ternary complex with Hsc70, and BAG2 colocalizes with CHIP under both quiescent conditions and after heat shock. In vitro and in vivo ubiquitylation assays indicate that BAG2 is an efficient and specific inhibitor of CHIP-dependent ubiquitin ligase activity. This activity is due, in part, to inhibition of interactions between CHIP and its cognate ubiquitin-conjugating enzyme, UbcH5a, which may in turn be facilitated by ATP-dependent remodeling of the BAG2-Hsc70-CHIP heterocomplex. The association of BAG2 with CHIP provides a cochaperone-dependent regulatory mechanism for preventing unregulated ubiquitylation of misfolded proteins by CHIP.

Adenosine Triphosphate↗
PubMed2005

A Re(V)-catalyzed C-N bond-forming route to human lipoxygenase inhibitors.

[reaction: see text] A regioselective synthesis of propargylamines by the coupling of propargyl alcohols with tosylamines and carbamates catalyzed by an air- and moisture-tolerant rhenium-oxo complex is described. The ability to couple functionalized components allows for convergent approaches to nitrogen-containing heterocyclic compounds such as the marine antibiotic pentabromopseudilin. These compounds were assayed against human lipoxygenase and found to be both potent and selective.

Catalysis↗
PubMed2005

Use of lung transplantation survival models to refine patient selection in cystic fibrosis.

Lung transplantation in cystic fibrosis may improve survival for patients with low 5-year predicted survival. Identifying characteristics that affect post-transplantation survival may improve patient selection and survival benefit. Using Cystic Fibrosis Foundation Patient Registry and United Network for Organ Sharing data, we identified 845 lung transplant recipients from 1991-2001, and 12,826 control patients from 1997. We used Cox proportional hazards models to identify variables that influence post-transplantation survival. To estimate the survival benefit of transplantation for patients affected by identified variables, we compared Kaplan-Meier survival curves of transplanted and control patients stratified by 5-year predicted survival. Post-transplantation survival improved annually. Youth, Burkholderia cepacia, and cystic fibrosis-related arthropathy increased the post-transplantation hazard of death. Compared with control subjects, transplanted adults with a 5-year predicted survival of less than 50% without B. cepacia or arthropathy have improved survival. Transplanted adults with B. cepacia, arthropathy, or a 5-year predicted survival of greater than 50% have decreased survival. Transplantation never improves survivorship for pediatric patients. Patients with arthropathy, B. cepacia infection, or younger age derive no aggregate survival benefit and must appraise carefully the high risk of decreased post-transplantation survival. Adult patients with low 5-year predicted survival without B. cepacia infection should receive priority for lung transplantation.

Adult↗