Abdelmonem A Afifi

CSU Mentor, Long Beach, California, United States

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Publications (94)313.05 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: AimsTo assess the effect of a multi-component primary care delivered brief intervention for reducing risky psychoactive drug use (RDU) among patients identified by screening.DesignMulticenter single-blind two-arm randomized controlled trial of patients enrolled from February 2011 to November 2012 with 3-month follow-up. Randomization and allocation to trial group were computer-generated.SettingPrimary care waiting rooms of five federally qualified health centers in Los Angeles County (LAC), USA.ParticipantsA total of 334 adult primary care patients (171 intervention; 163 control) with RDU scores (4–26) on the World Health Organization (WHO) Alcohol, Smoking and Substance Involvement Screening Test (ASSIST) self-administered on tablet computers. 261 (78%) completed follow-up. Mean age was 41.7 years; 62.9% were male; 37.7% were Caucasian.Intervention(s) and MeasurementIntervention patients received brief (typically 3–4 minutes) clinician advice to quit/reduce their drug use reinforced by a video doctor message, health education booklet and up to two 20–30–minute follow-up telephone drug use coaching sessions. Controls received usual care and cancer screening information. Primary outcome was patient self-reported use of highest scoring drug (HSD) at follow-up.FindingsIntervention and control patients reported equivalent baseline HSD use at 3-month follow-up. After adjustment for covariates, in the complete sample linear regression model, intervention patients used their HSD on 3.5 fewer days in the previous month relative to controls (P<0.001), and in the completed sample model, intervention patients used their HSD 2.2 fewer days than controls (P < 0.005). No compensatory increases in use of other measured substances were found.ConclusionsA primary-care based, clinician-delivered brief intervention with follow-up coaching calls may decrease risky psychoactive drug use.
    Addiction 11/2015; 110(11). DOI:10.1111/add.12993 · 4.74 Impact Factor
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    ABSTRACT: Purpose: To measure the magnitude and direction of visual field (VF) rates of change in glaucoma patients after intraocular pressure (IOP) reduction with trabeculectomy. Design: Retrospective, comparative, longitudinal cohort study. Participants: Patients with open-angle glaucoma. Methods: Patients who underwent trabeculectomy (Trab) with mitomycin-C (74 eyes of 64 patients) with ≥4 reliable VF measurements before and after trabeculectomy and at least 4 years of follow-up before and after surgery were included. Decay or improvement exponential models were used to calculate pointwise rates of perimetric change before and after surgery. A separate comparison (Comp) group with unoperated glaucoma (71 eyes of 65 patients) with similar baseline damage, number of VF tests, and follow-up was used to address possible regression to the mean. Proportions of VF locations decaying or improving before and after surgery in the Trab group, and during the first and second halves of follow-up in the Comp group, were calculated. A multivariate analysis was used to explore variables associated with VF improvement. Main outcome measures: The rate of pointwise VF change before and after surgery in the Trab group and Comp group. Results: Patients in the Trab group were followed for 5.1±2.1 years (mean ± standard deviation) before and 5.4±2.3 years after surgery, with 8.9±4.7 VF tests before and 9.0±4.4 VF tests after surgery. The mean rate of change for all VF locations slowed from -2.5±9.3%/year before surgery to -0.10±13.1%/year after surgery (P < 0.001). In the Trab group, 70% of locations decayed and 30% improved preoperatively; postoperatively, 56% decayed and 44% improved. The differences between the Trab and Comp groups were significant (P < 0.0001, chi-square test). The magnitude of IOP reduction correlated with the excess number of VF locations that exhibited long-term improvement postoperatively (P = 0.009). In the Trab group, 57% of eyes had ≥10 improving VF locations postoperatively. Conclusions: The results show that trabeculectomy slows the rate of perimetric decay and provides evidence of sustained, long-term improvement of visual function in glaucoma. These findings suggest the possibility of reversal of glaucomatous dysfunction of retinal ganglion cells and their central projections.
    Ophthalmology 10/2015; DOI:10.1016/j.ophtha.2015.09.027 · 6.14 Impact Factor
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    ABSTRACT: Purpose: We investigated the longitudinal relationships between the changes in neuroretinal rim area (RA) and the slow (SC) and fast (FC) components of visual field (VF) decay at various stages of glaucoma. Methods: We divided 465 eyes of 338 patients into glaucoma suspect, and preperimetric, early, and moderate/advanced glaucoma. All patients had a minimum of 3 confocal scanning laser ophthalmoscopic examinations and 4 VF tests with follow-up of 4 or more years. A pointwise exponential regression was used to perform trend analyses on thresholds at each VF test location, which was partitioned into SC and FC. A mixed effects linear model was used to explore the associations of RA change with mean deviation (MD), visual field index (VFI), SC, and FC. Results: Decreased RA was associated with lower mean threshold sensitivities of FC regardless of baseline severity of glaucoma (P ≤ 0.03). The mean threshold sensitivities in SC were not correlated with RA change at any stage. Decreased RA was correlated with worse MD in preperimetric, early, and moderate/advanced glaucoma (P < 0.05). Decreased RA was correlated with worse VFI in preperimetric and early glaucoma only (P ≤ 0.04). Conclusions: A decrease in rim area was significantly correlated with the fast VF component regardless of the baseline severity of glaucoma. Mean deviation and VFI correlated with change of rim area only in certain stages of glaucoma. The identification of the fast component seems a more robust and useful measure of glaucomatous change than MD or VFI.
    Investigative ophthalmology & visual science 09/2015; 56(10):5997-6006. DOI:10.1167/iovs.15-17006 · 3.40 Impact Factor
  • Andrew Chen · Eun Ah Kim · Dennis J Aigner · Abdelmonem Afifi · Joseph Caprioli ·
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    ABSTRACT: A metric of efficiency, a function of the ratio of quality to cost per patient, will allow the health care system to better measure the impact of specific reforms and compare the effectiveness of each. To develop and evaluate an efficiency index that estimates the performance of an ophthalmologist's practice as a function of cost, number of patients receiving care, and quality of care. Retrospective review of 36 ophthalmology subspecialty practices from October 2011 to September 2012 at a university-based eye institute. The efficiency index (E) was defined as a function of adjusted number of patients (Na), total practice adjusted costs (Ca), and a preliminary measure of quality (Q). Constant b limits E between 0 and 1. Constant y modifies the influence of Q on E. Relative value units and geographic cost indices determined by the Centers for Medicare and Medicaid for 2012 were used to calculate adjusted costs. The efficiency index is expressed as the following: E = b(Na/Ca)Qy. Independent, masked auditors reviewed 20 random patient medical records for each practice and filled out 3 questionnaires to obtain a process-based quality measure. The adjusted number of patients, adjusted costs, quality, and efficiency index were calculated for 36 ophthalmology subspecialties. The median adjusted number of patients was 5516 (interquartile range, 3450-11 863), the median adjusted cost was 1.34 (interquartile range, 0.99-1.96), the median quality was 0.89 (interquartile range, 0.79-0.91), and the median value of the efficiency index was 0.26 (interquartile range, 0.08-0.42). The described efficiency index is a metric that provides a broad overview of performance for a variety of ophthalmology specialties as estimated by resources used and a preliminary measure of quality of care provided. The results of the efficiency index could be used in future investigations to determine its sensitivity to detect the impact of interventions on a practice such as training modules or practice restructuring.
    Jama Ophthalmology 05/2015; 133(8). DOI:10.1001/jamaophthalmol.2015.1447 · 3.32 Impact Factor
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    ABSTRACT: Purpose: To evaluate and compare the ability of pointwise linear, exponential, and logistic functions, and combinations of functions, to model the longitudinal behavior of visual field (VF) series and predict future VF loss in patients with glaucoma. Methods: Visual field series from 782 eyes (572 patients) with open-angle glaucoma had greater than 6 years of follow-up and 12 VFs performed. Threshold sensitivities from the first 5 years at each location were regressed with linear, exponential, and logistic functions to estimate model parameters. A multiple-model approach applied the model with the lowest root mean square error (RMSE) at each location as the preferred model for future predictions. Predictions for each model were compared at 1, 2, 3, and 5 years after the last VF used to determine model parameters. Results: There were no clinically important differences between any of the models tested for fit; however, the logistic function had the lowest average RMSE (P < 0.001). For predictions, the exponential model consistently had the lowest average prediction RMSE for all time intervals (P < 0.001); the multiple-model approach did not perform better than the exponential model (P < 0.001). Conclusions: While the logistic model best fit glaucomatous VF behavior over a long time period, the exponential model provided the best average predictions. A multiple-model approach for VF predictions was associated with a greater prediction error than with the best-performing single-model approach. A model's goodness of fit is not indicative of its predictive ability for measurements of glaucomatous VFs.
    Investigative Ophthalmology &amp Visual Science 11/2014; 55(12). DOI:10.1167/iovs.14-15435 · 3.40 Impact Factor
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    ABSTRACT: Purpose: Our aim was to compare fit and predictive performance effectiveness of four pointwise regression models in measuring the visual field (VF) decay rate of progression in patients with open-angle glaucoma. Methods: We selected Humphrey VF data of patients with open-angle glaucoma with a minimum follow-up time of 6 years. For each eye (n = 798 from 588 patients), we regressed threshold sensitivity (y) at each VF test location for the entire VF series against follow-up time (x), with four candidate first-order regression models: (1) ordinary least-squares linear regression model (y = β 0 + β 1 x); (2) nondecay exponential regression model (y = β 0 + β 1e (x) ); (3) decay exponential regression model ([Formula: see text]); (4) Tobit-censored, maximum-likelihood linear regression model (y* = [Formula: see text], ε ~ N(0, σ(2))), where x is follow-up time and y is threshold sensitivity. Results: The average [± standard deviation (SD)] baseline VF mean deviation (MD) was -8.2 (±5.5) dB, the mean follow-up was 8.7 (±1.9) years, and the number of follow-up VFs was 14.7 (±4.4). The decay exponential model was the best-fitting (42.7 % of locations) and best-forecasting (65.5 % of locations) model. The decay exponential model was the best prediction model in all categories of severity. Conclusions: It is not clear that the ordinary least-squares linear regression model is always the favored model for fitting and forecasting VF data in patients with glaucoma. The pointwise decay exponential regression (PER) model was the best-fitting and best-predicting model across a wide range of glaucoma severity and can be readily understood by clinicians.
    Japanese Journal of Ophthalmology 08/2014; 58(6). DOI:10.1007/s10384-014-0341-5 · 1.68 Impact Factor
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    ABSTRACT: Importance A visual field parameter that is resistant to cataract formation and extraction would help monitor glaucomatous visual field progression in patients with coexisting glaucoma and cataract.Objective To evaluate the effect of cataract surgery on the slow and fast components of visual field decay in a group of patients with glaucoma.Design, Setting, and Participants Retrospective, interventional, longitudinal study. Eighty-five eyes of 68 patients with open-angle glaucoma who had cataract extraction were included. All patients had 5 or more reliable visual field measurements before and after surgery.Interventions A pointwise exponential regression was used to perform trend analysis on thresholds at visual field test locations before and after cataract surgery. The test locations were ranked according to the decay rate and were partitioned into slow and fast groups.Main Outcomes and Measures The slow and fast visual field rate components were measured before and after cataract surgery and were compared. Linear regressions of the mean deviation and the visual field parameter were performed against time and were compared before and after surgery.Results The mean (SD) mean deviation was −5.5 (5.1) dB before cataract surgery and −5.0 (4.9) dB after cataract surgery (P = .002). The mean (SD) Visual Field Index was 86.4% (13.5%) before cataract surgery and 86.6% (13.3%) after cataract surgery (P = .30). The mean (SD) slow component rate decreased from 0.48% (0.73%) per year before surgery to 0.26% (0.42%) per year after surgery (P = .04). No statistically significant difference was identified in the fast component mean (SD) rate per year before surgery (3.37% [4.05%]) vs per year after surgery (3.46% [3.56%]) (P = .29).Conclusions and Relevance Cataract progression seems to be the main determinant for the slow visual field rate component and does not change the fast visual field rate component. We conclude that the method used can help reduce the confounding effects of cataract progression and cataract extraction on measured perimetric progression in glaucoma.
    Jama Ophthalmology 07/2014; 132(11). DOI:10.1001/jamaophthalmol.2014.2326 · 3.32 Impact Factor
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    ABSTRACT: Purpose: To evaluate a health systems intervention to increase adolescents' receipt of high-quality sexual and reproductive health care services. Methods: Quasi experimental design. Twelve high schools in a large public school district were matched into pairs. Within each pair, schools were assigned to condition so that no control school shared a geographic border with an intervention school. Five yearly surveys (T1, T2, …, T5) were administered from 2005 to 2009 (N = 29,823) to students in randomly selected classes in grades 9-12. Community-based providers of high-quality sexual and reproductive health care services were listed on a referral guide for use by school nurses to connect adolescents to care. Results: Statistically significant effects were found for intervention school females on three outcomes, relative to controls. Relative to T1, receipt of birth control in the past year was greater at T4 (adjusted odds ratio [AOR] = 1.85; 95% confidence interval [CI], 1.09-3.15) and T5 (AOR = 2.22; 95% CI, 1.32-3.74). Increases in sexually transmitted disease testing and/or treatment in the past year were greater in T1-T3 (AOR = 1.78; 95% CI, 1.05-3.02), T1-T4 (AOR = 1.73; 95% CI, 1.01-2.97), T1-T5 (AOR = 1.97; 95% CI, 1.17-3.31), and T2-T5 (AOR = 1.76; 95% CI, 1.06-2.91). Increases in ever receiving an HIV test were greater in T1-T4 (AOR = 2.14; 95% CI, 1.08-4.26). Among males, no intervention effects were found. Conclusions: A school-based structural intervention can improve female adolescents' receipt of services.
    Journal of Adolescent Health 05/2014; 55(4). DOI:10.1016/j.jadohealth.2014.04.005 · 3.61 Impact Factor
  • Jess F Kraus · Paul Hsu · Kathryn Schafer · A A Afifi ·
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    ABSTRACT: Abstract Objective: To report on the occurrence of sustained outcomes including post-concussion symptoms, health services used and indicators of social disruption following a mild traumatic brain injury (MTBI). Research design: A dual cohort comparing MTBI Emergency Department (ED) patients and a comparison group of non-head injured ED patients. Methods and procedures: The outcomes measures employed were the Rivermead Post-Concussion Symptoms Questionnaire (RPQ) and indicators of health services used and social disruption all recorded at the ED and at 3 and 6 months post-ED discharge. 'Sustained' meant a positive response to these measures at 3 and 6 months. Main outcomes and results: Reasonable follow-up success was achieved at 3 and 6 months and the cohorts were alike on all demographic descriptors. RPQ average score and symptom occurrence were far more frequent among MTBI patients than for the comparison cohort from 3 to 6 months. The use of health services and indicators of social disruption were also more frequent among MTBI post-discharge patients. Conclusions: These findings argue that some with an MTBI suffer real complaints and they are sustained from 3 to at least 6 months. More effort should be given toward specificity of these symptoms from those reported by members of the comparison group.
    Brain Injury 05/2014; 28(10):1-9. DOI:10.3109/02699052.2014.916420 · 1.81 Impact Factor
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    ABSTRACT: Purpose: To describe changes in the visual field (VF) threshold sensitivity (decibels, dB) for the fast and slow rate components of VF decay in patients after trabeculectomy. Methods: This was a retrospective review of the VFs of open-angle glaucoma patients who underwent trabeculectomy. All eyes had ≥ 4 reliable pre– and post–operative VFs. The last pre– and first post–operative VFs were limited to within 1.5 years of the surgery date and the minimum VF follow–up pre– and post operatively were 2 years. With point–wise exponential regression (PER) every VF location was assigned to either fast or slow decay components. PER decay curves were fit to the sensitivities of the pre– and post−operative VF measurements separately. Delta (δ) was defined as the sensitivity difference between the first post-operative and the last pre–operative VF at each test location as estimated by the exponential curve fits. The VF mean deviation (MD) was similarly fit for the pre– and post–operative VFs with a linear regression. Results: Seventy–one eyes (65 subjects) were followed for an average of 11.9 ± 2.9 years (5.5 ± 2.4 years pre –operatively and 5.5 ± 2.4 years post–operatively) with an average of 20.2 ± 8.1 VFs (10.7 ± 5.9 VFs pre operatively and 9.5 ± 4.7 VFs post–operatively). Post–operatively the average sensitivity of the fast component test locations significantly increased from 20.4 ± 6.1 dB to 22.1 ± 5.4 dB (p < 0.0001), and significantly decreased for the slow component from 24.7 ± 3.7 dB to 23.9 ± 4.1 dB (p = 0.004). For the fast component locations, the sensitivity (δ) improved (1.74 ± 2.2 dB) but deteriorated (-0.79 ± 2.2 dB) for slow locations (p < 0.0001). The average MD pre–operatively (-8.4 ± 5.3) was not significantly different post–operatively (-9 ± 6.6) (p = 0.12). Conclusions: After trabeculectomy significant differential effects on the fast and slow components of VF decay were observed. The sensitivity of the slow component of VF decay decreased slightly, consistent with progressive cataract. However, the sensitivity of the fast VF component increased significantly, suggesting that reversibility of retinal ganglion cell dysfunction after robust intraocular pressure reduction is more common than previously thought. Overall measures of VF sensitivity, such as MD, do not detect these differential changes.
    ARVO 2014, Orlando, FL; 05/2014
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    ABSTRACT: Purpose: To investigate baseline prognostic factors predicting rapid deterioration of the visual field in primary open-angle glaucoma patients. Methods: Seven hundred sixty-seven eyes of 566 glaucoma patients from the Advanced Glaucoma Intervention Study (AGIS) and the clinical database from Jules Stein Eye Institute's Glaucoma Division were included. The rates of decay at each visual field test location were calculated with pointwise exponential regression analysis (PER), and the rates were separated into faster and slower components for each series. Subjects with a faster component decay rate (≥ 36%/y) were defined as rapid progressors. Sex, race, age, visual acuity, intraocular pressure, mean deviation (MD), number of medications, use of diabetic or hypertension medications, and vertical cup-to-disc ratio at baseline were entered in a multivariable prognostic logistic regression model. Results: The average (± SD) MD was -8.02 (± 6.13), and the average age was 68.64 (± 11.71) years for the study group. Two hundred twenty-two eyes (28.9%) were identified as rapid progressors. The following baseline factors were predictors of faster deterioration: worse MD (P < 0.001, odds ratio [OR]: 1.11; 95% confidence interval [CI]: 1.07-1.15), larger vertical cup-to-disc ratio (P = 0.001, OR: 1.23; 95% CI: 1.09-1.39), and older age (P = 0.02, OR: 1.24; 95% CI: 1.04-1.48). After excluding the variables related to glaucoma severity at baseline (baseline MD and baseline vertical cup-to-disc ratio), the likelihood of being a rapid progressor was 54% greater in African Americans than in Caucasians (P = 0.03, OR: 1.55; 95% CI: 1.06-2.27). Conclusions: Patients with more severe glaucomatous damage, as measured by both visual field or optic disc cupping and older age, are at highest risk for rapid worsening of the disease, as are African Americans compared to Caucasians. More aggressive treatment of such patients should be considered to prevent visual disability.
    Investigative ophthalmology & visual science 01/2014; 55(4). DOI:10.1167/iovs.13-12261 · 3.40 Impact Factor
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    ABSTRACT: Purpose To evaluate a health systems intervention to increase adolescents' receipt of high-quality sexual and reproductive health care services. Methods Quasi experimental design. Twelve high schools in a large public school district were matched into pairs. Within each pair, schools were assigned to condition so that no control school shared a geographic border with an intervention school. Five yearly surveys (T1, T2, …, T5) were administered from 2005 to 2009 (N = 29,823) to students in randomly selected classes in grades 9–12. Community-based providers of high-quality sexual and reproductive health care services were listed on a referral guide for use by school nurses to connect adolescents to care. Results Statistically significant effects were found for intervention school females on three outcomes, relative to controls. Relative to T1, receipt of birth control in the past year was greater at T4 (adjusted odds ratio [AOR] = 1.85; 95% confidence interval [CI], 1.09–3.15) and T5 (AOR = 2.22; 95% CI, 1.32–3.74). Increases in sexually transmitted disease testing and/or treatment in the past year were greater in T1–T3 (AOR = 1.78; 95% CI, 1.05–3.02), T1–T4 (AOR = 1.73; 95% CI, 1.01–2.97), T1–T5 (AOR = 1.97; 95% CI, 1.17–3.31), and T2–T5 (AOR = 1.76; 95% CI, 1.06–2.91). Increases in ever receiving an HIV test were greater in T1–T4 (AOR = 2.14; 95% CI, 1.08–4.26). Among males, no intervention effects were found. Conclusions A school-based structural intervention can improve female adolescents' receipt of services.

  • The Journal of Urology 04/2013; 189(4):e193. DOI:10.1016/j.juro.2013.02.1861 · 4.47 Impact Factor
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    ABSTRACT: We conducted an intervention to improve the implementation of a high school condom availability program, and evaluated its effect on students' awareness of the program and acquisition of condoms. Twelve public high schools in the Los Angeles, CA area participated, half each in the intervention and control conditions. Project staff facilitated intervention schools' self-assessment of compliance with the school district's condom availability policy, creating an action plan by determining which mandatory program elements were lacking and identifying steps to improve compliance. Staff provided technical assistance and follow-up to assist schools in improving program implementation. From 2005 to 2009 (T1-T5), 29,823 students were randomly selected by classroom and they completed surveys. We tested for changes in students' awareness and acquisition of condoms over time between conditions using mixed model logistic regression analyses. Records of condom orders by schools also were reviewed. Awareness increased significantly among intervention versus control participants from T1 to T3 (adjusted odds ratio [AOR]: 1.28; 95% confidence interval [CI]: 1.01, 1.62), T4 (AOR: 2.17; 95% CI: 1.70, 2.76), and T5 (AOR: 2.78; 95% CI: 2.18, 3.56). Acquisition of condoms increased significantly among intervention versus control participants from T1 to T4 (AOR: 1.69; 95% CI: 1.23, 2.32) and T5 (AOR: 1.81; 95% CI: 1.32, 2.49). Results were similar across gender and different levels of sexual experience. Orders of condoms increased markedly in intervention schools by T5. Feasible minor enhancements to condom availability program implementation improved program delivery, resulting in increased student awareness of the program and acquisition of condoms.
    Journal of Adolescent Health 12/2012; 51(6):572-9. DOI:10.1016/j.jadohealth.2012.03.010 · 3.61 Impact Factor
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    ABSTRACT: This study was conducted to validate a recently described technique for measuring the rates of visual field (VF) decay in glaucoma. A pointwise exponential regression (PER) model was used to calculate average rates of faster and slower deteriorating VF components, and that of the entire VF. Rapid progressors had a faster component rate of >25%/year. Mean deviation (MD) and visual field index (VFI) forecasts were calculated by (1) extrapolation of linear regression of MD and VFI, and (2) calculation de novo from the PER-predicted final thresholds. The mean (± SD) years of follow-up and number of VFs were 9.2 (± 2.7) and 13.7 (± 5.8), respectively. The median rates of the decay were -0.1 and 3.6 (%/year) for the slower and the faster components, respectively. The "rapid progressors" (32% of eyes) had a mean decay rate of 52.2%/year. In comparison with actual values, the average absolute difference and the mean squared error for MD forecasts with linear extrapolation of indices were 3.58 dB and 31.91 dB(2), and with the de novo recalculation from PER predictions were 2.95 dB and 17.49 dB(2), respectively. Similar results were obtained for VFI forecasts. Comparisons of the prediction errors for both the MD and VFI favored the PER forecasts (P < 0.001). PER for measuring rates of VF decay is a robust indicator of rates across a wide range of disease severity and can predict future global indices accurately. The identification of "rapid progressors" identifies high-risk patients for appropriate treatment.
    Investigative ophthalmology & visual science 06/2012; 53(9):5403-9. DOI:10.1167/iovs.12-9930 · 3.40 Impact Factor
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    ABSTRACT: The aim of this study was to examine the association between the local food environment and obesity proportions among 3- to 4-year-old children who were participants in the WIC program in Los Angeles County using spatial analyses techniques. ArcGIS, spatial analysis software, was used to compute the retail food environment index (RFEI) per ZIP code. GeoDa, spatial statistics software was employed to check for spatial autocorrelation and to control for permeability of the boundaries. Linear regression and ANOVA were used to examine the impact of the food environment on childhood obesity. Fast-food restaurants represented 30% and convenience stores represented 40% of the sum of food outlets in areas where WIC participants reside. Although there was no statistically significant association between RFEI and 3- to 4-year-old obesity proportions among WIC children, analysis of variance (ANOVA) tests demonstrated statistically significant positive associations between obesity and the number of convenience stores and the number of supermarkets. Our findings suggest that RFEI, as currently constructed, may not be the optimal way to capture the food environment. This study suggests that convenience stores and supermarkets are a likely source of excess calories for children in low-income households. Given the ubiquity of convenience stores in low-income neighborhoods, interventions to improve availability of healthy food in these stores should be part of the many approaches to addressing childhood obesity. This study adds to the literature by examining the validity of the RFEI and by demonstrating the need and illustrating the use of spatial analyses, using GeoDA, in the environment/obesity studies.
    05/2012; 4(1). DOI:10.5210/ojphi.v4i1.3936
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    ABSTRACT: To explore whether pointwise rates of visual field progression group together in patterns consistent with retinal nerve fiber layer (RNFL) bundles. Three hundred eighty-nine eyes of 309 patients from the Advanced Glaucoma Intervention Study with ≥6 years of follow-up and ≥12 reliable visual field exams were selected. Linear and exponential regression models were used to estimate pointwise rates of change over time. Clustering of pointwise rates of progression was investigated with hierarchical cluster analysis using Pearson's correlation coefficients as distance measure and an average linkage scheme for building the hierarchy with cutoff value of r > 0.7. The average mean deviation (±SD) was -10.9 (±5.4). The average (±SD) follow-up time and number of visual field exams were 8.1 (±1.1) years and 15.7 (±3.0), respectively. Pointwise rates of progression across the visual field grouped into clusters consistent with anatomic patterns of RNFL bundles with both linear (10 clusters) and exponential (six clusters) regression models. One hundred forty-four (37%) eyes progressed according to the two-omitting pointwise linear regression model. ointwise rates of change in glaucoma patients cluster into regions consistent with RNFL bundle patterns. This finding validates the clinical significance of such pointwise rates. The correlations among pointwise rates of change can be used for spatial filtering purposes, facilitating detection or prediction of glaucoma progression.
    Investigative ophthalmology & visual science 03/2012; 53(4):2390-4. DOI:10.1167/iovs.11-9021 · 3.40 Impact Factor
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    Investigative ophthalmology & visual science 01/2012; 53(1):118. DOI:10.1167/iovs.11-9240 · 3.40 Impact Factor
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    ABSTRACT: The prognostic usefulness of the Fuhrman nuclear grading system has been questioned for chromophobe renal cell carcinoma due to its frequent nuclear and nucleolar pleomorphism. Chromophobe tumor grade, a novel 3-tier tumor grading system based on geographic nuclear crowding and anaplasia, was recently reported to be superior to the Fuhrman system. We compared the 2 scoring systems in a large sporadic chromophobe renal cell carcinoma cohort to determine which grading scheme provides the most predictive assessment of clinical risk. We identified a total of 84 cases of sporadic chromophobe renal cell carcinoma in 82 patients from a total of 2,634 cases (3.2%) spanning 1989 to 2010. A subset of 11 tumors had secondary areas of sarcomatoid transformation. All cases were reviewed for Fuhrman nuclear grade and chromophobe tumor grade according to published parameters by an expert genitourinary pathologist blinded to clinicopathological information. The distribution of Fuhrman nuclear grades 1 to 4 was 0%, 52.4%, 32.9% and 14.7% of cases, and the distribution of chromophobe tumor grades 1 to 3 was 48.8%, 36.5% and 14.7%, respectively. Metastasis developed in 20 patients (24.4%). Survival analysis revealed statistically significant differences in recurrence-free survival when adjusted for chromophobe tumor grade and Fuhrman nuclear grade. Chromophobe tumor grade showed a slightly higher AUC for recurrence-free survival and overall survival than the Fuhrman nuclear grading system. Neither chromophobe tumor grade nor Fuhrman nuclear grade was retained as an independent predictor of outcome in multivariate modeling when patients with sarcomatoid lesions were excluded. Chromophobe tumor grade effectively stratifies patients with chromophobe renal cell carcinoma across all grading levels. Since it does not rely on nuclear features, it avoids the hazard of overestimating the malignant potential of chromophobe renal cell carcinoma. Overall chromophobe tumor grade has higher predictive accuracy than the Fuhrman nuclear grading system.
    The Journal of urology 12/2011; 186(6):2168-74. DOI:10.1016/j.juro.2011.07.068 · 4.47 Impact Factor
  • Leeka Kheifets · Abdelmonem Afifi · Jason Monroe · John Swanson ·
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    ABSTRACT: For 30 years, there have been suggestions that extremely low frequency magnetic fields such as those are produced by electric power systems may be associated with elevated risks of childhood leukemia. These suggestions are driven by epidemiological evidence, and it has been common to characterize that evidence as showing a threshold effect, with no increase in risk below a threshold, often 0.3 or 0.4 μT, and a constant risk above it. Such a threshold would, however, be biologically unlikely. We tested alternative dose-response relationships quantitatively. We obtained five exposure data sets, applied several candidate dose-response relationships to each one, and performed a regression analysis to see how well they fit each of the three epidemiological data sets. Threshold dose-response relationships performed only moderately. Linear relationships were generally even poorer. The fit was improved by adding quadratic terms or performing non-linear regression. There are limitations in our analysis, stemming from the available data, but addressing this issue in a data-based, quantitative manner should improve understanding, allow better calculations to be made of attributable numbers, and hence ultimately inform public policy making.
    Journal of Exposure Science and Environmental Epidemiology 11/2011; 21(6):625-33. DOI:10.1038/jes.2010.38 · 3.19 Impact Factor

Publication Stats

2k Citations
313.05 Total Impact Points


  • 2005-2015
    • CSU Mentor
      Long Beach, California, United States
    • Duke University
      Durham, North Carolina, United States
  • 2014
    • University of California, Davis
      Davis, California, United States
  • 1970-2014
    • University of California, Los Angeles
      • • School of Public Health
      • • Department of Biostatistics
      Los Ángeles, California, United States
  • 1996
    • Electric Power Research Institute
      Palo Alto, California, United States
  • 1966
    • University of California, Berkeley
      Berkeley, California, United States