Charting Trends in Medicare Reimbursement for Lower Extremity Imaging.

Background: Medicare reimbursement is rapidly declining in many specialties. An in-depth analysis of Medicare reimbursement for routinely performed diagnostic imaging procedures in the United States is warranted. Purpose/Hypothesis: The purpose of this study was to evaluate Medicare reimbursement trends for the 20 most common lower extremity imaging procedures performed between 2005 and 2020, including radiographs, computed tomography (CT), and magnetic resonance imaging (MRI). We hypothesized that Medicare reimbursement for imaging procedures would decline substantially over the studied period. Study Design: Cohort study. Methods: The Physician Fee Schedule Look-up Tool from the Centers for Medicare and Medicaid Services was analyzed for reimbursement rates and relative value units associated with the top 20 most utilized Current Procedural Terminology (CPT) codes in lower extremity imaging from 2005 to 2020. Reimbursement rates were adjusted for inflation and listed in 2020 US dollars using the US Consumer Price Index. To compare year-to-year changes, the percentage change per year and compound annual growth rate were calculated. A 2-tailed t test was used to compare the unadjusted and adjusted percentage change over the 15-year period. Results: After adjusting for inflation, mean reimbursement for all procedures decreased by 32.41% (P = .013). The mean adjusted percentage change per year was -2.82%, and the mean compound annual growth rate was -1.03%. Compensation for the professional and technical components for all CPT codes decreased by 33.02% and 85.78%, respectively. Mean compensation for the professional component decreased by 36.46% for radiography, 37.02% for CT, and 24.73% for MRI. Mean compensation for the technical component decreased by 7.76% for radiography, 127.66% for CT, and 207.88% for MRI. Mean total relative value units decreased by 38.7%. The commonly billed imaging procedure CPT 73720 (MRI lower extremity, other than joint, with and without contrast) had the greatest adjusted decrease of 69.89%. Conclusion: Medicare reimbursement for the most billed lower extremity imaging studies decreased by 32.41% between 2005 and 2020. The greatest decreases were noted in the technical component. Of the modalities, MRI had the largest decrease, followed by CT and then radiography.

Predicting and validating a model of suppressor of IKKepsilon through biophysical characterization.

Suppressor of IKKepsilon (SIKE) is a 207 residue protein that is implicated in the TLR3-TANK-binding kinase-1-mediated response to viral infection. SIKE's function in this pathway is unknown, but SIKE forms interactions with two distinct cytoskeletal proteins, α-actinin and tubulin, and SIKE knockout reduces cell migration. As structure informs function and in the absence of solved structural homologs, our studies were directed toward creating a structural model of SIKE through biochemical and biophysical characterization to probe and interrogate SIKE function. Circular dichroism revealed a primarily (73%) helical structure of minimal stability ( =32°C) but reversibly denatured. Limited proteolysis (LP) and chemical modification identified the N-terminal 2/3 of the protein as dynamic and accessible, whereas size exclusion chromatography (SEC) confirmed three homo-oligomeric species. SEC coupled to chemical crosslinking characterized the primary species as dimeric, a secondary hexameric species, and a higher order aggregate/polymer. Fluorescence polarization using intrinsic tryptophan fluorescence contextualized the anisotropy value for the SIKE dimer (molecular weight 51.8 kDa) among proteins of known structure, bovine serum albumin (BSA; 66 kDa), and glutamate dehydrogenase (GDH; 332 kDa). Radii of gyration for BSA and GDH provided exclusionary values for SIKE tertiary and dimeric quaternary models that otherwise conformed to secondary structure, LP, and modification data. Dimeric quaternary models were further culled using acrylamide quenching data of SIKE's single tryptophan that showed a single, protected environment. The low cooperativity of folding and regions of dynamic and potentially disordered structure advance the hypothesis that SIKE forms a conformational ensemble of native states that accommodate SIKE's interactions with multiple, distinct protein-binding partners.