No Apparent Workup for most new Indeterminate Pulmonary Nodules in US Commercially-Insured Patients.

BACKGROUND: A recent study estimated that more than 1.5 million Americans have an indeterminate pulmonary nodule (IPN) identified on a chest computed tomography (CT) scan each year outside of lung cancer screening programs. However, the cost and pattern of subsequent IPN workup have not been described for real-world settings. OBJECTIVES: To examine the pattern and cost of IPN workup in real-world practice using insurer administrative claims data for commercially-insured individuals. METHODS: The primary source for this retrospective observational study was the MarketScan® 2013-2016 databases, which include information on 28 to 47 million insured lives. The newly diagnosed IPN study population consisted of members with an IPN diagnosis code on a claim in 2014 who did not have prior diagnosis of an IPN or lung cancer in 2013 and who had coverage from 2014 to 2016. Subsequent claims were examined for workups included in the American College of Chest Physicians (ACCP) guideline recommendations and the costs of workup were tabulated. RESULTS: Of the 15 064 patients in the study population, only 5471 (36%) received any subsequent workup. The average and median costs of workup for these patients were $3270 and $2068, respectively. Spread across the commercially-insured population, the workup is estimated to cost between $1 and $2 per member per year. CONCLUSIONS: The majority of commercially-insured members with newly identified IPNs do not appear to have any guideline-recommended workup, despite a low incremental cost of such workup services on a population basis.

A mechanical analog of the two-bounce resonance of solitary waves: Modeling and experiment.

We describe a simple mechanical system, a ball rolling along a specially-designed landscape, which mimics the well-known two-bounce resonance in solitary wave collisions, a phenomenon that has been seen in countless numerical simulations but never in the laboratory. We provide a brief history of the solitary wave problem, stressing the fundamental role collective-coordinate models played in understanding this phenomenon. We derive the equations governing the motion of a point particle confined to such a surface and then design a surface on which to roll the ball, such that its motion will evolve under the same equations that approximately govern solitary wave collisions. We report on physical experiments, carried out in an undergraduate applied mathematics course, that seem to exhibit the two-bounce resonance.