Our primary objective is to provide the clinical informatics community with an introductory tutorial on calibration measurements and calibration models for predictive models using existing R packages and custom implemented code in R on real and simulated data. Clinical predictive model performance is commonly published based on discrimination measures, but use of models for individualized predictions requires adequate model calibration. This tutorial is intended for clinical researchers who want to evaluate predictive models in terms of their applicability to a particular population. It is also for informaticians and for software engineers who want to understand the role that calibration plays in the evaluation of a clinical predictive model, and to provide them with a solid starting point to consider incorporating calibration evaluation and calibration models in their work. Covered topics include (1) an introduction to the importance of calibration in the clinical setting, (2) an illustration of the distinct roles that discrimination and calibration play in the assessment of clinical predictive models, (3) a tutorial and demonstration of selected calibration measurements, (4) a tutorial and demonstration of selected calibration models, and (5) a brief discussion of limitations of these methods and practical suggestions on how to use them in practice.

Introduction:The objective of the present feasibility study was to investigate the use of a new treatment modality-percutaneous peripheral nerve stimulation (PNS)-in controlling the often severe and long-lasting pain following total knee arthroplasty (TKA).Methods: For patients undergoing a primary, unilateral TKA, both femoral and sciatic open-coil percutaneous leads (SPR Therapeutics, Cleveland, OH) were placed up to seven days prior to surgery using ultrasound guidance. The leads were connected to external stimulators and used both at home and in the hospital for up to six weeks total.Results: In six of seven subjects (86%), the average of daily pain scores across the first two weeks was <4 on the 0-10 Numeric Rating Scale for pain. A majority of subjects (four out of seven; 57%) had ceased opioid use within the first week (median time to opioid cessation for all subjects was six days). Gross sensory/motor function was maintained during stimulation, enabling stimulation during physical therapy and activities of daily living. At 12 weeks following surgery, six of seven subjects had improved by >10% on the Six-Minute Walk Test compared to preoperative levels, and WOMAC scores improved by an average of 85% compared to before surgery. No falls, motor block, or lead infections were reported.Conclusions: This feasibility study suggests that for TKA, ultrasound-guided percutaneous PNS is feasible in the immediate perioperative period and may provide analgesia without the undesirable systemic effects of opioids or quadriceps weakness induced by local anesthetics-based peripheral nerve blocks.

Background and Purpose-To evaluate whether increased neuroimaging use is associated with increased brain arteriovenous malformation (BAVM) detection, we examined detection rates in the Kaiser Permanente Medical Care Program of northern California between 1995 and 2004. Methods-We reviewed medical records, radiology reports, and administrative databases to identify BAVMs, intracranial aneurysms (IAs: subarachnoid hemorrhage [SAH] and unruptured aneurysms), and other vascular malformations (OVMs: dural fistulas, cavernous malformations, Vein of Galen malformations, and venous malformations). Poisson regression (with robust standard errors) was used to test for trend. Random-effects meta-analysis generated a pooled measure of BAVM detection rate from 6 studies. Results-We identified 401 BAVMs (197 ruptured, 204 unruptured), 570 OVMs, and 2892 IAs (2079 SAHs and 813 unruptured IAs). Detection rates per 100 000 person-years were 1.4 (95% CI, 1.3 to 1.6) for BAVMs, 2.0 (95% CI, 1.8 to 2.3) for OVMs, and 10.3 (95% CI, 9.9 to 10.7) for IAs. Neuroimaging utilization increased 12% per year during the time period (PϽ0.001). Overall, rates increased for IAs (PϽ0.001), remained stable for OVMs (Pϭ0.858), and decreased for BAVMs (Pϭ0.001). Detection rates increased 15% per year for unruptured IAs (PϽ0.001), with no change in SAHs (Pϭ0.903). However, rates decreased 7% per year for unruptured BAVMs (Pϭ0.016) and 3% per year for ruptured BAVMs (Pϭ0.005). Meta-analysis yielded a pooled BAVM detection rate of 1.3 (95% CI, 1.2 to 1.4) per 100 000 person-years, without heterogeneity between studies (Pϭ0.25). Key Words: brain AVM Ⅲ cerebral aneurysm Ⅲ vascular malformation Ⅲ incidence Ⅲ MRI B rain arteriovenous malformations (BAVMs) are lesions of the cerebral vasculature in which arterial blood flow is shunted directly into the venous system without passing through a capillary system, resulting in high-flow lesions prone to rupture. The estimated detection rate of BAVMs has been reported to be Ϸ1 per 100 000 person-years, accounting for 1% to 2% of all strokes. 1 In order of decreasing frequency, the clinical presentations of BAVMs include hemorrhage, seizures, headaches, and neurologic deficits. 2 The primary management aspect of BAVMs is prevention of rupture and the resulting intracranial hemorrhagic event. 3 The annual risk of intracranial hemorrhage after diagnosis of BAVMs is Ϸ2% to 4% per year; the rate is higher for those with initially ruptured and lower for those with unruptured presentations. 1,4,5 BAVMs that do not bleed can cause seizures, headaches, or neurologic deficits due to a mass effect and involvement of neighboring eloquent brain regions. 3,6 Initial discovery of BAVMs in patients usually follows clinical presentation, most commonly hemorrhage from a ruptured lesion. Advances in neuroimaging techniques, including magnetic resonance imaging (MRI), computed tomography (CT), and cerebral angiography, have provided improved resolution for detecting and evaluating BAVMs. [7][8][9] With the ability to detect ...