In the evaluation of diagnostic accuracy of tests, a gold standard on the disease status is required. However, in many complex diseases, it is impossible or unethical to obtain such a gold standard. If an imperfect standard is used, the estimated accuracy of the tests would be biased. This type of bias is called imperfect gold standard bias. In this article we develop a nonparametric maximum li...

OBJECTIVE To determine the utility of biochemical parameters such as lactic acid (LA), C-reactive protein (CRP), microalbuminuria (MAU), and base deficit (BD) as early markers of complications in the immediate postoperative evolution of elective open gastrointestinal surgeries. DESIGN AND METHODS Sixty-two patients subject to elective open gastrointestinal surgery were evaluated during a peri...

UNLABELLED Background : Anti-CCP is a test commonly used for the diagnosis of rheumatoid arthritis. The aim of this study was to determine the diagnostic values of ACCP compared to anti-MCV in rheumatoid arthritis patients in north of Iran. METHODS The serum samples of 150 RA patients and 75 controls, with the mean age of 49.6+11.8 and 48.8+12 years respectively, were tested using the commerc...

BACKGROUND Diagnostic and prognostic or predictive models serve different purposes. Whereas diagnostic models are usually used for classification, prognostic models incorporate the dimension of time, adding a stochastic element. CONTENT The ROC curve is typically used to evaluate clinical utility for both diagnostic and prognostic models. This curve assesses how well a test or model discrimin...

Deriving predictive models in medicine typically relies on a population approach where a single model is developed from a dataset of individuals. In this paper we describe and evaluate a personalized approach in which we construct a new type of decision tree model called decision-path model that takes advantage of the particular features of a given person of interest. We introduce three persona...

Receiver operating characteristic (ROC) curve is widely applied in measuring discriminatory ability of diagnostic or prognostic tests. This makes the ROC analysis one of the most active research areas in medical statistics. Many parametric and semiparametric estimation methods have been proposed for estimating the ROC curve and its functionals. In this paper, we propose the Bayesian bootstrap (...

To verify the efficiency and to determine the cutoff values that discriminate children/adolescents with and without vocal complaints, as well as the measures of sensibility, specificity and efficiency of the Brazilian Pediatric Voice-Related Quality-of-Life Survey (P-VRQOL). The participants included 230 parents of children/adolescents of both genders, aged between 2 years and 18 years, with an...

OBJECTIVES To investigate the learning curve of percutaneous nephrolithotomy under total ultrasound guidance. METHODS One hundred and twenty consecutive PCNL operations under total ultrasound guidance performed by a novice surgeon in a tertiary referral center were studied. Operations were analyzed in cohorts of 15 to determine when a plateau was reached for the variables such as operation du...

Receiver operating characteristic (ROC) curve has been widely used in medical science for its ability to measure the accuracy of diagnostic tests under the gold standard. However, in a complicated medical practice, a gold standard test can be invasive, expensive, and its result may not always be available for all the subjects under study. Thus, a gold standard test is implemented only when it i...

Test sensitivity and specificity for the FAMACHA(©) clinical test for anaemia due to haemonchosis have previously been shown to be adequate in differentiating between heavily/less heavily infected sheep, but these properties give no objective guidance for setting the optimum threshold at which anthelmintic treatment should occur. The aim of this work was to use Receiver Operating Characteristic...