Kendall's tau estimator for bivariate zero-inflated count data

This paper extends the work of Pimentel et al. (2015), presenting an estimator of Kendall's τ for bivariate zero-inflated count data. We provide achievable bounds of our proposed estimator and suggest how to estimate them, thereby making the estimator useful in practice.</p

Joint modeling with time-dependent treatment and heteroskedasticity: Bayesian analysis with application to the Framingham Heart Study

Medical studies for chronic disease are often interested in the relation between longitudinal risk factor profiles and individuals' later life disease outcomes. These profiles may typically be subject to intermediate structural changes due to treatment or environmental influences. Analysis of such studies may be handled by the joint model framework. However, current joint modeling does not consider structural changes in the residual variability of the risk profile nor consider the influence of subject-specific residual variability on the time-to-event outcome. In the present paper, we extend the joint model framework to address these two heterogeneous intra-individual variabilities. A Bayesian approach is used to estimate the unknown parameters and simulation studies are conducted to investigate the performance of the method. The proposed joint model is applied to the Framingham Heart Study to investigate the influence of anti-hypertensive medication on the systolic blood pressure variability together with its effect on the risk of developing cardiovascular disease. We show that anti-hypertensive medication is associated with elevated systolic blood pressure variability and increased variability elevates risk of developing cardiovascular disease.Comment: 34 pages, 4 figure

Model stability of COVID-19 mortality prediction with biomarkers

Coronavirus disease 2019 (COVID-19) is an unprecedented and fast evolving pandemic, which has caused a large number of critically ill patients and deaths globally. It is an acute public health crisis leading to overloaded critical care capacity. Timely prediction of the clinical outcome (death/survival) of hospital-admitted COVID-19 patients can provide early warnings to clinicians, allowing improved allocation of medical resources. In a recently published paper, an interpretable machine learning model was presented to predict the mortality of COVID-19 patients with blood biomarkers, where the model was trained and tested on relatively small data sets. However, the model or performance stability was not explored and assessed. By re-analyzing the data, we reveal that the reported mortality prediction performance was likely over-optimistic and its uncertainty was underestimated or overlooked, with a large variability in predicting deaths

Sharp Inequalities of Bienaym\'e-Chebyshev and Gau\ss Type for Possibly Asymmetric Intervals around the Mean

Gau\ss (1823) proved a sharp upper bound on the probability that a random variable falls outside a symmetric interval around zero when its distribution is unimodal with mode at zero. For the class of all distributions with mean at zero, Bienaym\'e (1853) and Chebyshev (1867) independently provided another, simpler sharp upper bound on this probability. For the same class of distributions, Cantelli (1928) obtained a strict upper bound for intervals that are a half line. We extend these results to arbitrary intervals for six classes of distributions, namely the general class of `distributions', the class of `symmetric distributions', of `concave distributions', of `unimodal distributions', of `unimodal distributions with coinciding mode and mean', and of `symmetric unimodal distributions'. For some of the known inequalities, such as the Gau\ss \, inequality, an alternative proof is given.Comment: 33 pages, 1 tabl

Does Intraoperative Cell Salvage Reduce Postoperative Infection Rates in Cardiac Surgery?

Objective: Primary outcome was the risk for infections after cell salvage in cardiac surgery. Design: Data of a randomized controlled trial on cell salvage and filter use (ISRCTN58333401). Setting: Six cardiac surgery centers in the Netherlands. Participants: All 716 patients undergoing elective coronary artery bypass grafting, valve surgery, or combined procedures over a 4-year period who completed the trial. Interventions: Postoperative infection data were assessed according to Centre of Disease Control and Prevention/National Healthcare Safety Network surveillance definitions. Measurements and Main Results: Fifty-eight (15.9%) patients with cell salvage had infections, compared with 46 (13.1%) control patients. Mediation analysis was performed to estimate the direct effect of cell salvage on infections (OR 2.291 [1.177;4.460], p = 0.015) and the indirect effects of allogeneic transfusion and processed cell salvage blood on infections. Correction for confounders, including age, seks and body mass index was performed. Allogeneic transfusion had a direct effect on infections (OR = 2.082 [1.133;3.828], p = 0.018), but processed cell salvage blood did not (OR = 0.999 [0.999; 1.001], p = 0.089). There was a positive direct effect of cell salvage on allogeneic transfusion (OR = 0.275 [0.176;0.432], p < 0.001), but a negative direct effect of processed cell salvage blood (1.001 [1.001;1.002], p < 0.001) on allogeneic transfusion. Finally, there was a positive direct effect of cell salvage on the amount of processed blood. Conclusions: Cell salvage was directly associated with higher infection rates, but this direct effect was almost completely eliminated by its indirect protective effect through reduced allogeneic blood transfusion

The Intra- and Interobserver Agreement on Diagnosis of Dupuytren Disease, Measurements of Severity of Contracture, and Disease Extent

This agreement study aimed to determine the intra- and interobserver agreement of four variables for diagnosing DD, determining severity of contracture, and disease extent. One of them is a new measurement on the area of nodules and cords, to be able to determine disease extent in early cases without flexion deformities. Intra-observer agreement was slightly higher on average than interobserver agreement. Overall, the intra- and interobserver agreement in diagnosing DD and determining the severity of flexion contracture is high. Also, the newly introduced variable area of nodules and cords has high intra- and interobserver agreement, indicating that it is suitable to measure disease extent

Disease course of primary Dupuytren’s disease:5-year results of a prospective cohort study

Background: Predicting progression of Dupuytren disease becomes relevant in an upcoming era with progression-preventing treatment. This study aimed to determine the course of Dupuytren disease and identify factors associated with progression. Methods: Two hundred fifty-eight patients with Dupuytren disease participated in this prospective cohort study, obtaining 17,645 observations in 5 years. Outcomes were disease extent (surface area) and contracture severity (total passive extension deficit). Demographics, lifestyle, health status, exposure to manual work, and genetic risk scores were gathered as potential predictors. Subject-specific, mixed-effects models were used to estimate disease course, and logistic regression with least absolute shrinkage and selection operator was used to evaluate factors associated with the presence of progression. Results: On average, Dupuytren disease was progressive in all finger rays with regard to area [yearly increase, 0.07 cm(2) (95% CI, 0.02 to 0.13 cm(2)) to 0.25 cm(2) (95% CI, 0.11 to 0.39 cm(2))]. Progression in total passive extension deficit was only present on the small finger side [yearly increase, 1.75 degrees (95% CI, 0.30 to 3.20 degrees) to 6.25 degrees (95% CI, 2.81 to 9.69 degrees)]. Stability or regression in area and total passive extension deficit was observed in 11 and 13 percent and 16 and 15 percent (dominant and nondominant hands), respectively. Smoking, cancer, genetic risk score, and hand injury were univariate associated with progression in area, but after multivariate variable selection, none of these associations remained. No predictors for progression in total passive extension deficit were found. Conclusions: Dupuytren disease is progressive, especially with respect to disease extent. Progression in contracture severity is mainly present on the small finger side of the hand. None of the traditional risk and diathesis factors were associated with progression, indicating that new hypotheses about Dupuytren disease progression might be needed.</p