RESUMO
Mendelian randomization (MR) uses genetic variation as a natural experiment to investigate the causal effects of modifiable risk factors (exposures) on outcomes. Two-sample Mendelian randomization (2SMR) is widely used to measure causal effects between exposures and outcomes via genome-wide association studies. 2SMR can increase statistical power by utilizing summary statistics from large consortia such as the UK Biobank. However, the first-order term approximation of standard error is commonly used when applying 2SMR. This approximation can underestimate the variance of causal effects in MR, which can lead to an increased false-positive rate. An alternative is to use the second-order approximation of the standard error, which can considerably correct for the deviation of the first-order approximation. In this study, we simulated MR to show the degree to which the first-order approximation underestimates the variance. We show that depending on the specific situation, the first-order approximation can underestimate the variance almost by half when compared to the true variance, whereas the second-order approximation is robust and accurate.
Assuntos
Carcinoma de Células Acinares/secundário , Neoplasias Orbitárias/secundário , Neoplasias Parotídeas/patologia , Carcinoma de Células Acinares/cirurgia , Feminino , Humanos , Metástase Linfática , Imageamento por Ressonância Magnética , Pessoa de Meia-Idade , Neoplasias Orbitárias/cirurgia , Neoplasias Parotídeas/cirurgia , Neoplasias da Glândula Submandibular/secundário , Neoplasias da Glândula Submandibular/cirurgiaRESUMO
The differential diagnosis of a medial canthal cystic mass in the new-born child includes dacryocoele, dermoid and, much more rarely, encephalocoele. We present a child with coexistent bilateral dacryocoeles and bifrontal anterior orbital hydrencephalocoeles.