Robust Estimation for Linear Panel Data Models

In different fields of applications including, but not limited to, behavioral, environmental, medical sciences and econometrics, the use of panel data regression models has become increasingly popular as a general framework for making meaningful statistical inferences. However, when the ordinary least squares (OLS) method is used to estimate the model parameters, presence of outliers may significantly alter the adequacy of such models by producing biased and inefficient estimates. In this work we propose a new, weighted likelihood based robust estimation procedure for linear panel data models with fixed and random effects. The finite sample performances of the proposed estimators have been illustrated through an extensive simulation study as well as with an application to blood pressure data set. Our thorough study demonstrates that the proposed estimators show significantly better performances over the traditional methods in the presence of outliers and produce competitive results to the OLS based estimates when no outliers are present in the data set

Evidence for similar structural brain anomalies in youth and adult attention-deficit/hyperactivity disorder: a machine learning analysis

Attention-deficit/hyperactivity disorder (ADHD) affects 5% of children world-wide. Of these, two-thirds continue to have impairing symptoms of ADHD into adulthood. Although a large literature implicates structural brain differences of the disorder, it is not clear if adults with ADHD have similar neuroanatomical differences as those seen in children with recent reports from the large ENIGMA-ADHD consortium finding structural differences for children but not for adults. This paper uses deep learning neural network classification models to determine if there are neuroanatomical changes in the brains of children with ADHD that are also observed for adult ADHD, and vice versa. We found that structural MRI data can significantly separate ADHD from control participants for both children and adults. Consistent with the prior reports from ENIGMA-ADHD, prediction performance and effect sizes were better for the child than the adult samples. The model trained on adult samples significantly predicted ADHD in the child sample, suggesting that our model learned anatomical features that are common to ADHD in childhood and adulthood. These results support the continuity of ADHD’s brain differences from childhood to adulthood. In addition, our work demonstrates a novel use of neural network classification models to test hypotheses about developmental continuity

Dihydropyrimidine dehydrogenase pharmacogenetics for predicting fluoropyrimidine-related toxicity in the randomised, phase III adjuvant TOSCA trial in high-risk colon cancer patients

Background: Dihydropyrimidine dehydrogenase (DPD) catabolizes approximately 85% of the administered dose of fluoropyrimidines. Functional DPYD gene variants cause reduced/abrogated DPD activity. DPYD variants analysis may help for defining individual patients' risk of fluoropyrimidine-related severe toxicity. Methods: The TOSCA Italian randomized trial enrolled colon cancer patients for 3 or 6 months of either FOLFOX-4 or XELOX adjuvant chemotherapy. In an ancillary pharmacogenetic study, ten 49 DPYD variants (*2A rs3918290 G>A, *13 rs55886062 T>G, rs67376798 A>T, *4 rs1801158 G>A, *5 rs1801159 A>G, *6 rs1801160 G>A, *9A rs1801265 T>C, rs2297595 A>G, rs17376848 T>C, rs75017182 C>G), were retrospectively tested for associations with > grade 3 fluoropyrimidine-related adverse events (FAEs). An association analysis and a time-to-toxicity (TTT) analysis were planned. To adjust for multiple testing, the Benjamini and Hochberg's False Discovery Rate (FDR) procedure was used. 55 Results: FAEs occurred in 194/508 assessable patients (38.2%). In the association analysis, FAEs 56 occurred more frequently in *6 rs1801160 A allele carriers (FDR=0.0083). At multivariate TTT 57 analysis, significant associations were found for *6 rs1801160 A allele carriers (FDR<0.0001), 58 *2A rs3918290 A allele carriers (FDR <0.0001), rs2297595 GG genotype carriers (FDR=0.0014). 59 Neutropenia was the commonest FAEs (28.5%). *6 rs1801160 (FDR <.0001), and *2A 60 rs3918290 (FDR =0.0004) variant alleles were significantly associated with time to neutropenia. 61 Conclusions: This study adds evidence on the role of DPYD pharmacogenetics for safety of 62 patients undergoing fluoropyrimidine-based chemotherapy

Clinical corse of classic Kaposi’s sarcoma in HIV-negative patients treated with the HIV protease inhibitor indinavir.

HIV protease inhibitors (HIV-PI) have been shown to exert anti-angiogenic and anti-tumor actions independently from their antiretroviral effect. Based on these studies, HIV-seronegative patients with classic Kaposi’s sarcoma were treated with Indinavir and followed for clinical evolution, drug pharmacokinetics and KS biomarkers. A favorable clinical course was associated with high drug plasma levels, reduced production of basic fibroblast growth factor, lower numbers of circulating endothelial cell numbers, and a decrease of antibody titers against HHV8