Search

Although randomized studies have high internal validity, generalizability of the estimated causal effect from randomized clinical trials to real-world clinical or educational practice may be limited. We consider the implication of randomized assignment to treatment, as compared with choice of preferred treatment as it occurs in real-world conditions. Compliance, engagement, or motivation may be better with a preferred treatment, and this can complicate the generalizability of results from randomized trials. The doubly randomized preference trial (DRPT) is a hybrid randomized and nonrandomized design that allows for estimation of the causal effect of randomization versus treatment preference. In the DRPT, individuals are first randomized to either randomized assignment or choice assignment. Those in the randomized assignment group are then randomized to treatment or control, and those in the choice group receive their preference of treatment versus control. Using the potential outcomes framework, we apply the algebra of conditional independence to show how the DRPT can be used to derive an unbiased estimate of the causal effect of randomization versus preference for each of the treatment and comparison conditions. Also, we show how these results can be implemented using full matching on the propensity score. The methodology is illustrated with a DRPT of introductory psychology students who were randomized to randomized assignment or preference of mathematics versus vocabulary training. We found a small to moderate benefit of preference versus randomization with respect to the mathematics outcome for those who received mathematics training. (Contains 2 figures and 1 table.)

Using data from a nationally representative sample, this study examined Head Start children's school outcome differences by the end of Kindergarten between children who attended Head Start program for two years and the ones who attended for one year. Propensity scores were used to match children who experienced different durations of the program on a series of demographic characteristics in order to achieve a precise estimation of the effects of program duration. The results showed that in comparison to a demographically comparable group of children who attended the Head Start program for one year, the children who experienced two years of intervention services had statistically significantly higher performance on all six academic and social outcome measures by the end of Kindergarten, which included PPVT, Woodcock-Johnson Reading Skills, Woodcock-Johnson Math Reasoning Skills, teacher-reported composite academic skills, preschool learning behaviors, and social skills. Policy and practice implications are discussed. (Contains 3 tables.)

Mortality in HIV-positive persons is increasingly due to non-HIV-related medical comorbidities. There are limited data on the prevalence and patient awareness of these comorbid conditions. Two hundred subjects at an urban HIV clinic were interviewed in 2005 to assess their awareness of 15 non-HIV-related medical comorbidities, defined as medical problems that are neither AIDS-defining by standard definitions, nor a direct effect of immune deficiency. Medical charts were subsequently reviewed to establish prevalence and concordance between self-report and chart documentation. Eighty-four percent of subjects self-reported at least i of 15 medical comorbidities and 92% had at least 1 condition chart-documented. The top 5 chart-documented conditions were hepatitis C (51.5%), pulmonary disease (28.5%), high blood pressure (27%), high cholesterol (24.5%), and obesity (22.5%). In multivariate analysis, higher number of non-HIV--related medical comorbidities was associated with older age, female gender, and intravenous drug use as route of HIV transmission. Across self-reported non-HIV--related medical comorbidities, the absolute concordance rate ranged from 67% to 96%, the sensitivity ranged from 0% to 79%; the positive predictive value ranged from 0% to 100%. While the vast majority of largely urban minority HIV-positive subjects were diagnosed with non-HIV--related medical comorbidities, there is significant room for improvement in patient awareness. In order to help patients optimally access and adhere to medication and medical care for these non-HIV--related medical comorbidities, interventions and educational campaigns to improve patient awareness that take cultural background, literacy, and educational level into account should be developed, implemented, and evaluated. DOI: 10.1089/apc.2009.0152