Personalized medicine is a rapidly expanding area of health research wherein patient level information is used to inform their treatment. Dynamic treatment regimens (DTRs) are a means of formalizing the sequence of treatment decisions that characterize personalized management plans. Identifying the DTR which optimizes expected patient outcome is of obvious interest and numerous methods have been proposed for this purpose. We present a new approach which builds on two established methods: Q-learning and G-estimation, offering the doubly robust property of the latter but with ease of implementation much more akin to the former. We outline the underlying theory, provide simulation studies that demonstrate the double-robustness and efficiency properties of our approach, and illustrate its use on data from the Promotion of Breastfeeding Intervention Trial.

We observed Andean Condors (Vultur gryphus), King Vultures (Sarcoramphus papa), Black Vultures (Coragyps atratus), Turkey Vultures (Cathartes aura), and Crested Caracaras (Polyborus plancus) interacting at 217 animal carcasses at two sites in northern Peru. At 53 carcasses for which we knew order of arrival, Turkey Vultures usually arrived first, Black Vultures second, and condors third. On the basis of our observations of 8,066 aggressive encounters between birds, we constructed dominance hierarchies by calculating the proportion of encounters won by an individual of one species, sex, or age during encounters with an individual of another species, sex, or age. Within each species there was a positive relationship between a bird's dominance and its age. In condors, males dominated females of the same age. Interspecific dominance was correlated positively with body mass. There are convergent similarities between the organizations of guilds of Old and New World vultures.

Measurement error and misclassification of variables frequently occur in epidemiology and involve variables important to public health. Their presence can impact strongly on results of statistical analyses involving such variables. However, investigators commonly fail to pay attention to biases resulting from such mismeasurement. We provide, in two parts, an overview of the types of error that occur, their impacts on analytic results, and statistical methods to mitigate the biases that they cause. In this first part, we review different types of measurement error and misclassification, emphasizing the classical, linear, and Berkson models, and on the concepts of nondifferential and differential error.We describe the impacts of these types of error in covariates and in outcome variables on various analyses, including estimation and testing in regression models and estimating distributions. We outline types of ancillary studies required to provide information about such errors and discuss the implications of covariate measurement error for study design. Methods for ascertaining sample size requirements are outlined, both for ancillary studies designed to provide information about measurement error and for main studies where the exposure of interest is measured with error. We describe two of the simpler methods, regression calibration and simulation extrapolation (SIMEX), that adjust for bias in regression coefficients caused by measurement error in continuous covariates, and illustrate their use through examples drawn from the Observing Protein and Energy (OPEN) dietary validation study. Finally, we review software available for implementing these methods. The second part of the article deals with more advanced topics.

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This study shows that compliance with patching treatment averages less than 50% and is influenced by several factors. A greater understanding of these influences should improve treatment outcome. (ClinicalTrials.gov number, NCT00274664).

In experimental aneurysms in swine, BPM/GDCs accelerated aneurysm fibrosis and intensified neck neointima formation without causing parent artery stenosis or thrombosis. The use of BPM/GDCs may improve long-term anatomical outcomes by decreasing aneurysm recanalization due to stronger in situ anchoring of coils by organized fibrous tissue. The retraction of this scar tissue may also decrease the size of aneurysms and clinical manifestations of mass effect observed in large or giant aneurysms.

The purpose of this study was to measure the in vivo tensile behavior of a double-looped semitendinosus and gracilis graft used to reconstruct a torn anterior cruciate ligament in the human knee. In 14 subjects, intraoperative tension was measured for each of the four graft bundles during passive motion from 0 to 90 degrees of flexion. Two hypotheses were tested: (a) the peak tension carried by each of the four bundles was equal during passive motion, and (b) the mechanics of the bundles mimicked the functional bands of the native anterior cruciate ligament. The total tension was also calculated and used to determine strength requirements for fixation devices. The peak tensions of the four bundles during passive motion were not equal; however, enough tension was present in each bundle that load-sharing occurred between bundles. The pattern of tension between the anterior and posterior bundles mimicked the reciprocating load-sharing behavior of the functional bands of the native anterior cruciate ligament. Reciprocal tensile behavior was consistently achieved with the use of a single femoral tunnel centered on the most isometric line without the need for two separate femoral sockets. The maximum total tension was 296 N; this was nearly equal to the strength of one commonly used fixation device.

The tension in an anterior cruciate ligament graft may not be normal when the femoral tunnel is placed using the single-incision arthroscopic technique because the femoral tunnel is drilled through the tibial tunnel. We hypothesized that the in vivo tensile behavior of the double-looped semitendinosus and gracilis tendon graft can be normal or abnormal compared with the native anterior cruciate ligament, that the placement and angle of the tibial tunnel can predict the tensile behavior of the graft, that the graft with abnormal tensile behavior is associated with a nonanatomically placed tibial tunnel, and that the tensile behavior of the graft determines the stability of the reconstructed knee at 1 year. Total tension in the graft and knee flexion angle were measured in 14 subjects as the knee was flexed from 0 degree to 90 degrees. A graft force greater than 40 N at 80 degrees of flexion was considered abnormal. One year after surgery, the angle and position of the tibial tunnel were determined from roentgenograms, and knee stability was measured with a KT-1000 arthrometer. The criteria for anatomic tibial tunnel placement in the sagittal and coronal planes were derived from magnetic resonance images of uninjured knees. The tensile graft behavior was either normal (4 of 14) or abnormal (10 of 14) with the single-incision arthroscopic technique. The angle of the tibial tunnel in the coronal plane was predictive of abnormal tensile behavior. Abnormal tensile behavior occurred in anatomically placed tibial tunnels and was compatible with a stable and functional reconstructed knee at 1 year.