Abdelmonem A Afifi

Jules Stein Eye Institute, Maryland, United States

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Publications (65)133.53 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 & visual science. 11/2014;
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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;
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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; · 3.83 Impact Factor
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    ABSTRACT: To evaluate a health systems intervention to increase adolescents' receipt of high-quality sexual and reproductive health care services.
    Journal of Adolescent Health 05/2014; · 2.97 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; · 1.51 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; · 3.43 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. 01/2014;
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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. · 2.97 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. · 3.43 Impact Factor
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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. · 3.43 Impact Factor
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    Investigative ophthalmology & visual science 01/2012; 53(1):118. · 3.43 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.
    Online journal of public health informatics. 01/2012; 4(1).
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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. · 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. · 3.19 Impact Factor
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    ABSTRACT: This study was conducted to measure the rate of visual field (VF) decay in glaucoma, to separate faster and slower components of decay, and to predict the rate of VF decay. Patients who had primary glaucoma and 6 or more years of follow-up were included. Thresholds at each VF location were regressed with linear, quadratic, and exponential models. The best model was used to parse the VF into slower and faster rate components. Two independent cohorts (glaucoma [n = 87] and cataract [n = 38]) were used to determine the technique's ability to distinguish areas of glaucomatous VF changes from those caused by cataract. VF forecasts, derived from the first half of follow-up, were compared with actual VF thresholds at the end of follow-up. The mean (±SD) years of follow-up and number of VFs for the main cohort (389 eyes of 309 patients) were 8.2 (±1.1) years and 15.7 (±3.0), respectively. The proportions of best fits were linear 2%, quadratic 1%, and exponential 97%. Proportions of eyes with exponential rates of decay ≥10% for the entire visual field (VF), faster components, and slower components were 20%, 56%, and 4%, respectively. The difference in decay rates between the faster and slower components was greater in the independent glaucoma cohort (19% ± 10%) than in the cataract cohort (5% ± 5%; P < 0.001). Test location forecasts significantly correlated with measured values (r(2) = 0.67; P < 0.001). This method isolates faster and slower components of VF decay in glaucoma, can identify patients who are fast progressors, and can predict patterns of future VF loss with appropriate confidence intervals. (ClinicalTrials.gov number, NCT00000148.).
    Investigative ophthalmology & visual science 04/2011; 52(7):4765-73. · 3.43 Impact Factor
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    ABSTRACT: The prevalence of obesity among children in the United States has increased rapidly during the past few decades. Research into social and behavioral determinants of obesity could lead to innovative strategies for prevention. The objective of the present study was to examine the association between childhood obesity and preschool enrollment and number of hours in child care among low-income preschool-aged children who were participants in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC). We conducted a case-control study including 556 3- to 4-year-old children who were either obese (BMI > 95th percentile of reference standard) or normal-weight (BMI 25-75th percentile). The population was largely (96%) Hispanic, an ethnic group that has one of the highest rates of overweight and obesity in adults and children in the US. In multiple logistic regression analysis, controlling for a variety of psychosocial and cognitive home environment variables, key demographics and maternal variables, the odds ratio of being obese was 0.61 for children who attended preschool more than 4 days a week (95% CI: 0.41-0.90). Watching television or videos for an hour or more on a typical day (odds ratio 1.71 (95% CI 1.07-2.75)), and higher maternal BMI (odds ratio 1.08 (95% CI 1.05-1.11)) were independently related to odds of obesity. The impact of preschool attendance and TV viewing are potentially instructive in terms of preventive interventions for children at this age.
    Maternal and Child Health Journal 03/2011; 16(3):706-12. · 2.24 Impact Factor
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    ABSTRACT: Extramural clinical rotations are implemented by dental schools for a combination of clinical and didactic or behavioral goals. In the United States, the Pipeline, Profession, and Practice: Community-Based Dental Education program was launched to increase the number of underrepresented minority students who are recruited and retained in dental education, to expand the dental curriculum in cultural competence, and to incorporate community-based extramural rotations into the dental schools' clinical curriculum. The objective of this study was to conduct an impact analysis regarding the change in number of extramural clinical rotation weeks for Pipeline and non-Pipeline program students over the time period of 2003 to 2007. National data from the American Dental Education Association's senior survey and other secondary sources were used to determine what student, school, and community characteristics are associated with a difference in the student report of the number of required weeks they expect to spend during their last year in dental school providing care at extramural clinic settings. Students reported a mean of 7.2 weeks for Pipeline students and 6.4 weeks for non-Pipeline students in 2003, increasing to 8.2 weeks for Pipeline students and 6.6 weeks for non-Pipeline students (p<0.05) in 2007. The multivariable model showed the Pipeline program increased significantly the number of rotational weeks reported by students. Three other variables significantly increased rotation weeks: 1) a lower baseline number of reported weeks in community rotations; 2) a lower level of debt student reported upon graduation; and 3) student reports of a higher orientation toward service to others as a reason to enter dentistry.
    Journal of dental education 01/2011; 75(1):52-61. · 0.99 Impact Factor
  • Journal of Adolescent Health - J ADOLESCENT HEALTH. 01/2011; 48(2).
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    ABSTRACT: Early sexual initiation is associated with elevated teenage pregnancy and STD risk, yet little is known about the prevalence and correlates of sexual behavior among young adolescents. Better information is needed to guide interventions to prevent early sexual debut. Data from a 2005 survey of 4,557 sixth-, seventh- and eighth-grade students at 14 urban public schools in Southern California were analyzed using chi-square tests and logistic regression, to identify correlates of oral sex, intercourse and both. Overall, 9% of youth had ever had sexual intercourse, and 8% had had oral sex. Three percent reported having had oral sex only, 4% intercourse only and 5% both. Among those who reported intercourse, 69% had used a condom at last intercourse, and 43% had had multiple partners. Being male, being black and having at least one friend who had ever been involved in a pregnancy were positively associated with having had intercourse only and both intercourse and oral sex (odds ratios, 1.7-4.2). Being in eighth grade, expecting to have intercourse in the next six months and currently having a boyfriend or girlfriend were positively associated with all three outcomes (2.1-7.2). Intercourse and oral sex were highly correlated. Interventions addressing oral sex, intercourse and multiple partners should begin before sixth grade and continue throughout the middle school years. Health professionals should target adolescent risk reduction counseling toward males, blacks, youth with a boyfriend or girlfriend, and those with a friend who has been involved in a pregnancy.
    Perspectives on Sexual and Reproductive Health 09/2010; 42(3):197-205. · 1.41 Impact Factor

Publication Stats

919 Citations
133.53 Total Impact Points


  • 2012
    • Jules Stein Eye Institute
      Maryland, United States
  • 1988–2012
    • County of Los Angeles Public Health
      Los Angeles, California, United States
  • 1986–2012
    • University of California, Los Angeles
      • • Jules Stein Eye Institute
      • • Department of Biostatistics
      • • Department of Epidemiology
      Los Angeles, CA, United States
  • 2009
    • Providence St. Vincent Medical Center
      Oregon City, Oregon, United States