Selection of two cut-off points via generalized Youden index and receiving operating characteristic surface to predict preeclampsia using the hemoglobin levels in the first trimester of pregnancy

Introduction: Researchers are extensively using biomarkers to detect diseases. Commonly, a cut-off point is selected for separating sick and healthy people. Sometimes it is necessary to obtain more than one cut-off points, by classifying subjects into more than two groups. As such, in the present paper, generalized Youden index has been used to classify subjects into three groups. The main intention of this study was to determine the optimal cut-off points for the hemoglobin levels in the first trimester of pregnancy in order to predict preeclampsia.Materials and Methods: We used data of the hemoglobin levels in the first trimester of pregnancy and preeclampsia from 620 pregnant women who were referred to Tehran's Milad Hospital in 2009-2010. The optimal cut-off points for prediction of preeclampsia in the first trimester were obtained by using generalized Youden index and volume under the receiving operating characteristics (ROC) surface (VUS). Statistical analysis was performed using by R software version 2-15-1 and DiagTest3Grp package. Results: The estimated cut-off points, using by Youden index, were 13.18 and 14.5 with correct classification proportions of 70%, 35% and 15%, respectively. The estimated cut-off points, using by ROC surface were 12.4 and 13.1 and correct classification proportions were 42%, 35% and 55%, in order. The volume under the ROC surface was 0.25.Conclusion: The generalized Youden index, as a complementary index for VUS, can be adopted to achieve greeter diagnostic accuracy; it can also be used to achieve a three group classification of subject

Is a safety guide wire necessary for transurethral lithotripsy using semi-rigid ureteroscope? Results from a prospective randomized controlled trial

Purpose: Experts recommend us to keep a safety guidewire during the process of upper urinary tract endoscopy, though there is a lack of high-level evidence to support the efficacy and safety of this opinion. This study was conducted to compare the outcome of ureteral stone breakage in the presence or absence of a safety guidewire. Materials and methods: Patients candidate for endoscopic breakage of ureteral stone using a semi-rigid ureteroscope, were randomly assigned in two groups based on keeping a safety guidewire (group1) or removing the guidewire (group2) before the process of breaking ureteral stone by lithoclast. Demographic factors, history of previous stone treatment, kidney function, stone location, symptoms duration and severity were recorded for each patient. Primary outcomes included success rate of stone treatment and secondary outcomes included number of attempts to enter to ureter, success rate of ureteral entry, success rate of stone achievement, stone migration rate and the success rate of ureteral stent insertion. The recorded data were entered to the SPSS software and descriptive statistical analysis including power calculation and non-inferiority design for the primary and secondary outcomes, was performed. P-value less than 0.05 was considered significant. Results: From January 2016 till May 2018, 320 patients were randomized with 160 patients in each arm. Considering the cases who were missed due to follow-up loss, there were 153 patients in group 1 and 147 patients in group 2 at the end of the study. Baseline data were equally distributed in both groups. Based on the initial analysis, the studied variables had no significant difference between two groups; though, according to the subgroup analysis of patients with proximal ureter stones, patients in Group 1 had higher rates of ureteral injury comparing to the patients in Group 2 (p = 0.03). Conclusion: According to our findings, keeping the safety guidewire through the process of endoscopic stone breakage (stone size: less than 1.5Cm) seems to add no significant benefit to the procedure outcome, while it increases the ureteral injuries in the proximal ureter stones, but not in mid or distal ureter stones