Abdelmonem A Afifi

CSU Mentor, Long Beach, California, United States

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Publications (88)268.64 Total impact

  • [Show abstract] [Hide abstract]
    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 six years of follow-up and 12 VFs performed. Threshold sensitivities from the first five 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 one, two, three, and five 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 models 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 · 3.66 Impact Factor
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    ABSTRACT: 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.
    Japanese Journal of Ophthalmology 08/2014; 58(6). DOI:10.1007/s10384-014-0341-5 · 1.80 Impact Factor
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    ABSTRACT: 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.
    Jama Ophthalmology 07/2014; 132(11). DOI:10.1001/jamaophthalmol.2014.2326 · 3.83 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. Published by Elsevier Inc. on behalf of Society for Adolescent Health and Medicine.
    Journal of Adolescent Health 05/2014; 55(4). DOI:10.1016/j.jadohealth.2014.04.005 · 2.75 Impact Factor
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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 · 1.86 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%/year were defined as rapid progressors. Gender, 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 multivariate 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% 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). 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 · 3.66 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.
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    ABSTRACT: This study presents reliability and validity findings for the Assessment for Disaster Engagement with Partners Tool (ADEPT), an instrument that can be used to monitor the frequency and nature of collaborative activities between local health departments (LHDs) and community-based organizations (CBOs) and faith-based organizations (FBOs) for disaster preparedness, response, and recovery.
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    ABSTRACT: To explore a multidimensional measure of health literacy that incorporates skills necessary to manage one's health environment. We designed a questionnaire to assess variation in an expanded understanding of health literacy among publicly insured adolescents in California (N = 1208) regarding their health care experiences and insurance. Factor loading and item clustering patterns reflected in the exploratory principal components factor analysis suggest that the data are parsimoniously described by 6 domains. This multidimensional measure becomes relevant in an era of health care reform in which many will for the first time have health insurance requiring them to navigate a system that uses a managed care model.
    American journal of health behavior 05/2013; 37(3):342-50. DOI:10.5993/AJHB.37.3.7 · 1.31 Impact Factor
  • The Journal of Urology 04/2013; 189(4):e193. DOI:10.1016/j.juro.2013.02.1861 · 3.75 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 · 2.75 Impact Factor
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    ABSTRACT: As U.S. health care reform is implemented in upcoming years, many will have first-time access to a complex health care system. This study developed a multi-dimensional measure of an expanded health-literacy definition that captures competencies needed to effectively navigate the health care system. Self-selected, publicly insured adolescent members (aged 13-17) of a large California health insurance network participated in a self-reported survey on their health care knowledge, attitudes, and experiences. Data from teens receiving health care in the past 12 months (n=1,209) were examined using Factor Analysis to investigate the emergence of underlying health-literacy domains. Domain scores were then used as predictors in Ordinal Logistic regression models to evaluate associations with wellness visits, general health, and emotional health. Factor Analysis results suggest the presence of six health-literacy domains: 1) Patient-Provider Encounter; 2) Interactions with the Health Care System; 3) Rights and Responsibilities; 4) Confidence in Health Information from a Personal Source; 5) Confidence in Health Information from a Media Source; and 6) Health Information-Seeking Competency Using Internet. Results suggest that less-frequent wellness visits are associated with lower health-literacy scores in domains 1 (p<.001), 2 (p=.031), and 4 (p=.047). Poor general health is associated with lower health-literacy scores in domains 1 (p<.001), 2 (p<.001), 4 (p<.001), and 6 (p=.005). Poor emotional health is associated with lower health-literacy scores in domains 1 (p=.001), 2 (p=.003), 4 (p=.001), and 5 (p=.002). Our findings suggest that improving skills in certain health-literacy domains may increase preventive care and health among an adolescent population.
    140st APHA Annual Meeting and Exposition 2012; 10/2012
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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 · 3.66 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 · 3.66 Impact Factor
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    Investigative ophthalmology & visual science 01/2012; 53(1):118. DOI:10.1167/iovs.11-9240 · 3.66 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 · 3.75 Impact Factor
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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 · 3.05 Impact Factor
  • Sexually Transmitted Infections 07/2011; 87(Suppl 1):A56-A56. DOI:10.1136/sextrans-2011-050109.73 · 3.08 Impact Factor

Publication Stats

2k Citations
268.64 Total Impact Points

Institutions

  • 2014
    • CSU Mentor
      Long Beach, California, United States
  • 1970–2014
    • University of California, Los Angeles
      • • Department of Epidemiology
      • • Department of Biostatistics
      • • Department of Medicine
      Los Ángeles, California, United States
  • 2010
    • County of Los Angeles Public Health
      Los Angeles, California, United States
  • 2009
    • Providence St. Vincent Medical Center
      Oregon City, Oregon, United States
  • 1966
    • University of California, Berkeley
      Berkeley, California, United States