Biomedical subjects

Abdelmonem A Afifi

Publications and source records attributed to Abdelmonem A Afifi.

4 recordsLinked to original sources

PubMed2007

Methods for improving regression analysis for skewed continuous or counted responses.

Standard inference procedures for regression analysis make assumptions that are rarely satisfied in practice. Adjustments must be made to insure the validity of statistical inference. These adjustments, known for many years, are used routinely by some health researchers but not by others. We review some of these methods and give an example of their use in a health services study for a continuous and a count outcome. For the continuous outcome, we describe re-transformation using the smear factor, accounting for missing cases via multiple imputation and attrition weights and improving results with bootstrap methods. For the count outcome, we describe zero inflated Poisson and negative binomial models and the two-part model to account for overabundance of zero values. Recent advances in computing and software development have produced user-friendly computer programs that enable the data analyst to improve prediction and inference based on regression analysis.

Data Interpretation, Statistical↗

PubMed2006

Public health impact of extremely low-frequency electromagnetic fields.

INTRODUCTION: The association between exposure to extremely low-frequency electric and magnetic fields (ELF) and childhood leukemia has led to the classification of magnetic fields by the International Agency for Research on Cancer as a "possible human carcinogen." This association is regarded as the critical effect in risk assessment. Creating effective policy in light of widespread exposure and the undisputed value of safe, reliable, and economic electricity to society is difficult and requires estimates of the potential public health impact and associated uncertainties. OBJECTIVES: Although a causal relationship between magnetic fields and childhood leukemia has not been established, we present estimates of the possible pubic health impact using attributable fractions to provide a potentially useful input into policy analysis under different scenarios. METHODS: Using ELF exposure distributions from various countries and dose-response functions from two pooled analyses, we calculate country-specific and worldwide estimates of attributable fractions (AFs) and attributable cases. RESULTS: Even given a wide range of assumptions, we find that the AF remains < 10%, with point estimates ranging from < 1% to about 4%. For small countries with low exposure, the number of attributable cases is less than one extra case per year. Worldwide the range is from 100 to 2,400 cases possibly attributable to ELF exposure. CONCLUSION: The fraction of childhood leukemia cases possibly attributable to ELF exposure across the globe appears to be small. There remain, however, a number of uncertainties in these AF estimates, particularly in the exposure distributions.

Bayes Theorem↗

PubMed2006

Workforce reentry for people with HIV/AIDS: intervention effects and predictors of success.

Treatment that prolongs the lives of people with HIV/AIDS and improves their quality of life is relatively recent and little is known about factors that may predict their successful re-entry to the workforce. No data exist concerning the effectiveness of programs to assist people with HIV/AIDS in their efforts to return to work. We used logistic regression and Kaplan-Meier survival curves to predict return to work using data from 126 individuals who participated in an HIV/AIDS return to work program. Results from the 24 month follow-up revealed that program participation, general health, benefits status, and gender, predicted successful re-entry to the workforce. We discuss these findings in the context of the need for more explicitly-defined interventions, as well as the need for additional information on factors that may hinder or facilitate workforce re-entry among people with HIV/AIDS.

Adult↗

PubMed2005

Geographic and socioeconomic variation in the treatment of prostate cancer.

PURPOSE: Within a framework of quality assessment, primary treatment choice constitutes an indicator of quality of care. This study examines geographic and socioeconomic variation in the primary treatment of men with prostate cancer during the era of prostate-specific antigen testing. METHODS: Using the National Cancer Institute's Surveillance, Epidemiology, and End Results public use data files, we identified men with localized/regional prostate cancer who underwent surgery, radiation therapy, or watchful waiting. We used the year 2000 US Census information to ascribe education and income levels to these men based on their county of residence and ethnicity. RESULTS: Among the 96,769 men with localized/regional prostate cancer (during 1995 to 1999) who had sufficient information for analysis, we observed significant geographic variation nationwide in surgical, radiation, and watchful waiting treatment rates (P <.0015). Patterns noted 10 years ago, such as higher surgical rates in western regions, persisted. Ethnicity, income, and grade were all independently associated with primary treatment, or lack thereof. Blacks and low-income patients had the lowest rates of surgery and radiation. Grade was the best predictor of aggressive treatment. CONCLUSION: Nonclinical factors, such as ethnicity and income, were associated with the use of watchful waiting rather than surgery or radiation in men with early-stage prostate cancer. These findings have implications for quality of care.

Aged↗