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Successful treatment of endogenous Cushing disease (CD) is often followed by a period of adrenal insufficiency (AI). We performed an exploratory study on genetic factors potentially involved in the hypothalamic-pituitary-adrenal (HPA) axis recovery in patients with CD after remission. We identified 90 patients who achieved remission after surgery and had a minimum of 3 months follow-up. Variants in a selected panel of genes that were rare in the general population and predicted as damaging in silico were retrieved from whole exome sequencing analysis. We did not identify any variant with significant correlation with recovery time after adjusting for multiple comparisons. On gene-specific analysis the BAG1 gene showed a correlation with shorter duration of postsurgical AI, but both patients with BAG1 variants later experienced a recurrence. After excluding patients with recurrence, no statistical association was recorded. To conclude, we did not identify a strong genetic modifier of HPA recovery in this exploratory study.

Missense and truncating variants in the X-chromosome-linked CLCN4 gene, resulting in reduced or complete loss-of-function (LOF) of the encoded chloride/proton exchanger ClC-4, were recently demonstrated to cause a neurocognitive phenotype in both males and females. Through international clinical matchmaking and interrogation of public variant databases we assembled a database of 90 rare CLCN4 missense variants in 90 families: 41 unique and 18 recurrent variants in 49 families. For 43 families, including 22 males and 33 females, we collated detailed clinical and segregation data. To confirm causality of variants and to obtain insight into disease mechanisms, we investigated the effect on electrophysiological properties of 59 of the variants in Xenopus oocytes using extended voltage and pH ranges. Detailed analyses revealed new pathophysiological mechanisms: 25% (15/59) of variants demonstrated LOF, characterized by a “shift” of the voltage-dependent activation to more positive voltages, and nine variants resulted in a toxic gain-of-function, associated with a disrupted gate allowing inward transport at negative voltages. Functional results were not always in line with in silico pathogenicity scores, highlighting the complexity of pathogenicity assessment for accurate genetic counselling. The complex neurocognitive and psychiatric manifestations of this condition, and hitherto under-recognized impacts on growth, gastrointestinal function, and motor control are discussed. Including published cases, we summarize features in 122 individuals from 67 families with CLCN4-related neurodevelopmental condition and suggest future research directions with the aim of improving the integrated care for individuals with this diagnosis.

Skeletal muscle tissue engineering technologies have the potential to treat volumetric muscle loss (VML) by growing exogenous muscle tissue. However, there has been limited success in engineering human cell-sourced skeletal muscle with structure and function comparable to native adult human muscle. The use of growth factors at optimal concentrations and delivery times is critical in enhancing the in vitro myogenesis of satellite cells used in engineered skeletal muscle. The mitogenic protein human epidermal growth factor (hEGF) is of particular interest because it enhances satellite cell proliferation and sarcomeric structure formation in myogenic cell cultures. In this study, we used our scaffold-free tissue-engineered skeletal muscle units (SMUs) to examine the effects of hEGF on the structure and function of human cell-sourced engineered skeletal muscle. During our established SMU fabrication process, human muscle cell isolates were exposed to media treated with 7.5 nM hEGF at three different time spans during the 21-day cell culture period: 0 to 6 days postseeding (hEGF-treated Muscle Growth Media [MGM] Only), 7 to 21 days postseeding (hEGF-treated Muscle Differentiation Media (MDM) Only), and 0 to 21 days postseeding (hEGF-treated MGM+MDM). Control cell cultures were fed standard MGM and MDM (no hEGF treatment). During the fabrication process, light microscopy was used to examine proliferation and differentiation of myogenic cells in the monolayer. After SMU formation, the three-dimensional constructs underwent tetanic force production measurements to evaluate contractile function and immunohistochemical staining to examine SMU structure. Results indicated that hEGF administration impacted myogenesis, by increasing myotube diameter in hEGF-treated MGM only and hEGF-treated MDM-only cell cultures, and by increasing myotube density in hEGF-treated MGM+MDM cultures. The exposure of myogenic cells to hEGF during any time period of the fabrication process led to a significant increase in SMU myosin heavy-chain content. SMUs exposed to hEGF-treated MDM and hEGF-treated MGM+MDM exhibited greater cross-sectional areas and more organized sarcomeric structure. Furthermore, hEGF-treated MGM+MDM SMUs displayed significantly enhanced contractile function compared with controls, indicating advanced functional maturation. In conclusion, hEGF supplementation in human primary myogenic cell cultures advances tissue-engineered skeletal muscle structural and functional characteristics. IMPACT STATEMENT: Our research suggests that human epidermal growth factor (hEGF) serves as a critical growth factor in enhancing in vitro skeletal muscle cell proliferation and differentiation during myogenesis and advances human skeletal muscle engineered tissues toward a more native adult skeletal muscle phenotype. Understanding the impact of hEGF on engineered skeletal muscle function and structure is valuable in determining the optimal culture conditions for the development of tissue engineering-based therapies for volumetric muscle loss.

Tissue engineering methodologies have the potential to treat volumetric muscle loss via the growth of exogenous skeletal muscle grafts from small autogenous muscle biopsies. A significant obstacle preventing the widespread use of engineered skeletal muscle grafts in a clinical setting is the high number of skeletal muscle stem cells, known as satellite cells, required for fabrication of human-sized skeletal muscle tissue. Additionally, there is a lack of work adapting engineered constructs created for animal models into skeletal muscle engineered from a primary human skeletal muscle cell source. For this study, we used scaffold-free tissue-engineered skeletal muscle units (SMUs) to determine the impact of cell seeding density on the ability to fabricate functional human engineered skeletal muscle. Following established protocols, human skeletal muscle isolates were cultured into SMUs at five different cell seeding densities: 1000, 2500, 5000, 10,000, and 25,000 cells/cm(2). Following previous human SMU work, SMUs prepared at a cell seeding density of 10,000 cells/cm(2) served as controls. Additionally, the impact of cell monolayer confluency on the outcome of human cell-sourced SMU fabrication was investigated at both the 1000 and 10,000 cells/cm(2) seeding densities. Light microscopy was used to examine myotube formation and hypertrophy in cell monolayers. After the formation of three-dimensional constructs, SMUs underwent maximum tetanic isometric force production measurements and immunohistochemical staining to examine SMU contractile function and muscle-like structure, respectively. Results indicate that the 25,000 cells/cm(2) cell seeding density was detrimental to the contractile function of human cell-sourced SMUs, which had significantly lower maximum tetanic forces compared with SMUs seeded at lower densities. Compared with control, low cell seeding densities (1000–5000 cells/cm(2)) have no detrimental impact on SMU skeletal muscle growth, maturation, or contractility. Cell cultures seeded at 1000 cells/cm(2) and allowed to proliferate to 90–100% confluency before treatment in muscle differentiation media (MDM) resulted in SMUs with greater contractile forces and total muscle structure compared with cell cultures switched to MDM when underconfluent or overconfluent. In conclusion, initial cell seeding density for SMU fabrication can be decreased to as low as 1000 cells/cm(2) without negatively impacting SMU muscle-like structure and function. IMPACT STATEMENT: Our research suggests that during the translation of skeletal muscle tissue engineering technologies from animal to human cell sources, initial starting cell seeding density can be significantly lowered without negatively impacting engineered skeletal muscle growth, maturation, or contractile function. Decreasing the initial cell density, and, thus, the muscle biopsy size required to fabricate an engineered human skeletal muscle, increases the potential for the clinical adoption of tissue-engineered based therapies for volumetric muscle loss.

Formalin fixation of paraffin-embedded tissue samples is a well-established method for preserving tissue and is routinely used in clinical settings. Although formalin-fixed, paraffin-embedded (FFPE) tissues are deemed crucial for research and clinical applications, the fixation process results in molecular damage to nucleic acids, thus confounding their use in genome sequence analysis. Methods to improve genomic data quality from FFPE tissues have emerged, but there remains significant room for improvement. Here, we use whole-genome sequencing (WGS) data from matched Fresh Frozen (FF) and FFPE tissue samples to optimize a sensitive and precise FFPE single nucleotide variant (SNV) calling approach. We present methods to reduce the prevalence of false-positive SNVs by applying combinatorial techniques to five publicly available variant callers. We also introduce FFPolish, a novel variant classification method that efficiently classifies FFPE-specific false-positive variants. Our combinatorial and statistical techniques improve precision and F1 scores compared to the results of publicly available tools when tested individually.

Volumetric muscle loss (VML) contributes to the number of soft tissue injuries that necessitate reconstructive surgery, but treatment options are often limited by tissue availability and donor site morbidity. To combat these issues, our laboratory has developed scaffold-free tissue-engineered skeletal muscle units (SMUs) as a novel treatment for VML injuries. Recently, we have begun experiments addressing VML in facial muscle, and the optimal starting cell population for engineered skeletal muscle tissue for this application may not be cells derived from hindlimb muscles due to reported heterogeneity of cell populations. Thus, the purpose of this study was to compare SMUs fabricated from both craniofacial and hindlimb sources to determine which cell source is best suited for the engineering of skeletal muscle. Herein, we assessed the development, structure, and function of SMUs derived from four muscle sources, including two hindlimb muscles (i.e., soleus and semimembranosus [SM]) and two craniofacial muscles (i.e., zygomaticus major and masseter). Overall, the zygomaticus major exhibited the least efficient digestion, and SMUs fabricated from this muscle exhibited the least aligned myosin heavy chain staining and consequently, the lowest average force production. Conversely, the SM muscle exhibited the most efficient digestion and the highest number of myotubes/mm(2); however, the SM, masseter, and soleus groups were roughly equivalent in terms of force production and histological structure. IMPACT STATEMENT: An empirical comparison of the development, structure, and function of engineered skeletal muscle tissue fabricated from different muscles, including both craniofacial and hindlimb sources, will not only provide insight into innate regenerative mechanisms of skeletal muscle but also will give our team and other researchers the information necessary to determine which cell sources are best suited for the skeletal muscle tissue engineering.

Coping with discomfort and the uncertainties of daily adjustments are prominent challenges confronting individuals with type 2 diabetes mellitus (T2DM) who require multiple daily injections (MDI) of insulin. For this growing population, wearable, disposable devices capable of delivering consistent and sustained doses of basal-bolus therapy may help to alleviate concerns and improve outcomes. However, studies on the comparative effectiveness of new, innovative delivery systems versus MDI on insulin requirements, glycemic control, and health care costs are sparse.To examine glycemic control, insulin use, and diabetes medication costs for users of the V-Go Wearable Insulin Delivery device compared with MDI insulin therapy among individuals with T2DM in a commercially insured population in the United States.This retrospective cohort study queried administrative claims data from the HealthCore Integrated Research Database from July 1, 2011, through July 31, 2017. Cohorts included individuals with T2DM aged 21-80 years either newly initiating V-Go or using MDI for basal/bolus insulin. The date of earliest claim for V-Go prescription fill or for bolus insulin was defined as the index date, depending on the cohort. Previous insulin therapy was required in both cohorts. Baseline hemoglobin A1c (A1c) values were identified during the 6 months before and 15 days after the index date; results closest to 12 months after the index date were selected as follow-up. Insulin use and diabetes medication cost data were examined during the 6 months baseline and the second half of the 1-year follow-up. V-Go and MDI users were 1:1 matched on baseline insulin exposure, A1c level, and other characteristics of interest. Univariate and multivariate tests were used to compare follow-up outcomes.Matched cohorts included 118 well-balanced pairs (mean age: 56 years; mean baseline A1c: 9.2%). During follow-up, both cohorts experienced improvements in glycemic control relative to baseline (% with A1c ≤ 9%, baseline/follow-up: V-Go 49/69,This study was the first to evaluate clinical and economic outcomes associated with the use of V-Go for up to a 1-year follow-up period. Relative to MDI users, V-Go users had similar glycemic control but lower insulin use and lower diabetes medication costs during follow-up. V-Go therapy may provide an opportunity to improve quality measures more cost-effectively in people with T2DM who require basal-bolus therapy.This study was funded by Valeritas. Nguyen is an employee of Valeritas. Zhou, Grabner, Barron, and Quimbo are employees of HealthCore, which received funding for this study from Valeritas. Raval was an employee of HealthCore at the time the study was conducted. Partial findings from this study were presented at the International Society of Pharmacoeconomics and Outcomes Research 23rd Annual International Meeting; May 19-23, 2018; Baltimore, MD; and the 54th European Association for the Study of Diabetes Annual Meeting; October 1-5, 2018; Berlin, Germany.

Volumetric muscle loss (VML) is the loss of skeletal muscle that results in significant and persistent impairment of function. The unique characteristics of craniofacial muscle compared trunk and limb skeletal muscle, including differences in gene expression, satellite cell phenotype, and regenerative capacity, suggest that VML injuries may affect craniofacial muscle more severely. However, despite these notable differences, there are currently no animal models of craniofacial VML. In a previous sheep hindlimb VML study, we showed that our lab's tissue engineered skeletal muscle units (SMUs) were able to restore muscle force production to a level that was statistically indistinguishable from the uninjured contralateral muscle. Thus, the goals of this study were to: 1) develop a model of craniofacial VML in a large animal model and 2) to evaluate the efficacy of our SMUs in repairing a 30% VML in the ovine zygomaticus major muscle. Overall, there was no significant difference in functional recovery between the SMU-treated group and the unrepaired control. Despite the use of the same injury and repair model used in our previous study, results showed differences in pathophysiology between craniofacial and hindlimb VML. Specifically, the craniofacial model was affected by concomitant denervation and ischemia injuries that were not exhibited in the hindlimb model. While clinically realistic, the additional ischemia and denervation likely created an injury that was too severe for our SMUs to repair. This study highlights the importance of balancing the use of a clinically realistic model while also maintaining control over variables related to the severity of the injury. These variables include the volume of muscle removed, the location of the VML injury, and the geometry of the injury, as these affect both the muscle's ability to self-regenerate as well as the probability of success of the treatment.

Background: Fibromyalgia (FM) and systemic lupus erythematosus (SLE) are both characterised by non-specific symptoms such as pain and fatigue. To make diagnosis even more challenging, fibromyalgia is overrepresented in the SLE population. Objectives: To identify which symptoms can discriminate between patients with comorbid FM and patients without comorbid FM in the SLE population, using a routinely distributed questionnaire. Methods: Patients with SLE (n=88) completed a Multi-Dimensional Health Assessment Questionnaire (MDHAQ) [1] and the 2011 FM Criteria questionnaire [2]. FM status was determined using the 2016 modification of the 2010/2011 FM criteria [3]. The MDHAQ contains a 60-item symptom checklist section, giving a score of 0-60. Patients with complete data were analysed for specific symptoms that were discriminating for FM using student’s t test with Bonferroni correction. Results: SLE patients with FM reported a higher prevalence of positive responses for every symptom except for ‘dark or bloody stools’ and ‘burning in sexual organs’. Nineteen symptoms demonstrated a significant difference between those with and without FM. The most discriminating symptoms were muscle pain, swelling (of hands, ankles and in other joints), back pain, neck pain, problems with thinking and dry mouth (all p Conclusion: The symptom checklist section of the MDHAQ can provide clues that help discriminate between SLE patients with and without FM. Clinicians can find valuable information in the specific symptoms experienced by the patient, as well as the overall number of symptoms. Grouping the discriminatory symptoms together in the questionnaire may assist clinicians to consider the diagnosis of FM more easily in patients with SLE. References [1] Pincus, T., Y. Yazici, and M. Bergman, Development of a multi-dimensional health assessment questionnaire (MDHAQ) for the infrastructure of standard clinical care. Clinical & Experimental Rheumatology,2005. 23(5Suppl 39): p.S19-28. [2] Wolfe, F., et al., Fibromyalgia criteria and severity scales for clinical and epidemiological studies: a modification of the ACR Preliminary Diagnostic Criteria for Fibromyalgia. J Rheumatol, 2011. 38(6): p.1113-22. [3] Wolfe, F., et al. 2016Revisions to the 2010/2011 fibromyalgia diagnostic criteria. in Seminars in arthritis and rheumatism. 2016. Elsevier. Disclosure of Interests: Frank Huang: None declared, Sean O’Neill: None declared, Ray Fang: None declared, Matthew Nguyen: None declared, Kathryn Gibson Grant/research support from: UCB, Abbvie, Speakers bureau: UCB, Janssen

Background: Fibromyalgia (FM) is disproportionately common in patients with systemic lupus erythematosus (SLE) and difficult to diagnose on a background of classical SLE symptoms [1]. The Multi-Dimensional Health Assessment Questionnaire (MDHAQ) has been shown to be useful to recognise improvement over 2 months in a variety of rheumatic conditions including SLE [2] but has not previously been shown to be useful to alert the clinician to comorbid FM in the latter condition. Conversely, the 2011 FM self-report questionnaire is disease-specific and available for use in clinical and epidemiological studies. Administration of multiple forms may be difficult in a busy clinical setting. Objectives: To identify comorbid FM in patients with SLE using patient-reported outcomes (PROs) from the routinely distributed MDHAQ, in comparison to the 2016 revision of the 2010/2011 FM criteria. Methods: Patients with SLE completed an MDHAQ and the 2011 FM Criteria questionnaire. FM status was assigned using the 2016 revision of the 2010/2011 FM criteria as the gold standard. The MDHAQ features six main PROs: body pain, patient global and fatigue score on a 0-10 visual analogue scale, as well as a functional impact score, self-report joint count and symptom checklist which have a range of 0-10, 0-48 and 0-60 respectively. Composite indices consisting of either two or three of patient pain score 6, self-report joint count 16 and symptom checklist 16 or three of four of the same measures plus a fatigue score 6 have been described previously to provide clues to comorbid FM in other rheumatic diseases [3,4]. Individual PROs and these composite indices were compared between patients with and without FM by student’s unpaired t-test and Area Under the Curve (AUC) analysis. The physician’s diagnosis of FM was analysed against the FM criteria using Cohen’s kappa. Physicians were blinded to the results of the 2016 FM criteria. Results: 88 patients with SLE were studied, of whom 23 (26%) satisfied FM criteria. Those with FM reported higher scores in all PROs. A patient global of 6 could correctly classify 90% of patients and provided the highest AUC of 0.95, followed by the symptom checklist and body pain. An index of three measures (pain score, self-report joint count and symptom checklist) gave an AUC of 0.90. An index of four measures (additional fatigue criterion) gave an AUC of 0.93. Both indices correctly classified 89% of patients with a cut-off of 2 and 3 respectively. The physician’s diagnoses had moderate agreement with the FM criteria (kappa = 0.43). Conclusion: Comorbid FM is prevalent in SLE yet often missed by physicians. In busy clinical settings, composite indices provide useful clues to coexisting FM in SLE, although a simple MDHAQ patient global is quick and potentially just as valuable in this patient group. These findings require further validation in a larger cohort. References: [1] Wolfe F, Petri M, Alarcon GS, Goldman J, Chakravarty EF, Katz RS, et al. Fibromyalgia, systemic lupus erythematosus (SLE), and evaluation of SLE activity. J Rheumatol. 2009;36(1):82-8. [2] Castrejon, I., M.J. Bergman, and T. Pincus, MDHAQ/RAPID3 to recognise improvement over 2 months in usual care of patients with osteoarthritis, systemic lupus erythematosus, spondyloarthropathy, and gout, as well as rheumatoid arthritis. J Clin Rheumatol, 2013. 19(4):p.169-74 [3] Gibson K et al. 2016 MDHAQ as a useful screening tool for fibromyalgia in busy clinical settings Ann Rheum Dis, volume 75, supplement 2, page 88 [4] Schmuckler J, et al. 2018 A simple index based on scores on a multidimensional health assessment questionnaire (MDHAQ) provides information quite similar to ACR criteria for fibromyalgia in routine care Ann Rheum Dis, volume 77, Suppl, page A465 Disclosure of Interests: Frank Huang: None declared, Sean O’Neill: None declared, Ray Fang: None declared, Matthew Nguyen: None declared, Kathryn Gibson Grant/research support from: UCB, Abbvie, Speakers bureau: UCB, Janssen

Patient-reported outcome (PRO) instruments are widely used to assess quality of life in Systemic Lupus Erythematosus (SLE) research, and there is growing evidence for their use in clinical care. In this review, we evaluate the current evidence for their use in assessing quality of life in SLE in both research and clinical settings and examine the different characteristics of the commonly used PRO tools. There are now several well-validated generic and SLE-specific tools that have demonstrated utility in clinical trials and several tools that complement activity and damage measures in the clinical setting. PRO tools may help overcome physician–patient discordance in SLE and are valuable in the assessment of fibromyalgia and type 2 symptoms such as widespread pain and fatigue. Future work will identify optimal PRO tools for different settings but, despite current limitations, they are ready to be incorporated into patient care.

Fatigue remains a debilitating feature of systemic lupus erythematosus (SLE). Although in some cases this may be the result of intercurrent fibromyalgia, mood disorder or untreated metabolic syndrome, in many cases the cause is unclear. The aim of this study was to investigate the relationship between fatigue and red cell distribution width (RDW), a measure of variability in erythrocyte size and volume.A total of 225 patients were recruited from three clinics in England and Australia. Patients completed the Functional Assessment of Chronic Illness Therapy (FACIT) Fatigue Score or 12-item Short Form survey (SF-12) to measure fatigue, which was compared with RDW and haemoglobin. In a subgroup of 72 patients, markers of disease activity were also assessed for correlation with fatigue using univariate and multivariate analysis with fatigue as the dependent variable.In all three groups, significant correlations between fatigue and RDW were observed (p0.001; p=0.02; p0.001 respectively) and this was preserved in multivariate analysis. There was no correlation between fatigue and haemoglobin in two groups (with the correlation between RDW and fatigue remaining significant in non-anaemic patients in the third group). In subgroup analysis, fatigue was not associated with any measures of disease activity.We report a reproducible, statistically significant association between RDW and fatigue levels in a diverse population of patients with SLE. The findings of this study raise the possibility of a potential novel biological basis for fatigue in those in whom there is a lack of an alternate explanation.

Background 80%–90% of patients with SLE report fatigue to be the single most debilitating symptom of their disease. Functional Iron Deficiency (FID), a state of inefficient iron utilisation, has recently been linked with fatigue in a number of conditions. Red Blood Cell Distribution Width (RDW) is a convenient marker of FID. Purpose To study the relationship between FID (as measured by RDW) and fatigue in patients with SLE. Methods Three cohorts were recruited and all patients were required to fulfil ACR criteria of lupus. Juvenile–onset SLE Cohort at University College London Hospital (UCLH), London (UK) Adult Cohort at UCLH, London (UK) Adult Cohort at Liverpool Hospital, Sydney (Australia) In cohorts 1 and 3, patients completed the FACIT Fatigue Score. This generates a numerical score (between 0–52), where a lower score represents more fatigue. In cohort 2, fatigue was measured using the SLE-specific quality of life index, LUPUS QoL. This includes a score of vitality level (a lower score is suggestive of more fatigue). RDW was recorded, in addition to standard markers of lupus disease activity including Erythrocyte Sedimentation Rate (ESR), Complement C3, anti-double-stranded DNA binding (anti-dsDNA), C-reactive protein (CRP) and SLEDAI/BILAG. Spearman’s rank was used to analyse variables with a p-value of Results In cohort 1, 72 patients aged 14–42 (median 21) were recruited. FACIT score did not correlate with anti-dsDNA (p=0.4), C3 (p=0.06), ESR (p=0.06), CRP (p=0.1) or SLEDAI (p=0.6). There was a strongly significant correlation between FACIT and RDW (p≤0.001; r=−0.44); figure 1. In cohort 2, 106 patients were recruited aged 18–75 (median 44.5). RDW correlated with ESR (p=0.03; r=−0.20), BILAG (p=0.002; r=−0.30) and vitality scores (p=0.02; r=0.23); figure 2. In cohort 3, 47 patients aged 19–75 (median 46) were recruited. FACIT correlated with RDW (p=0.03; r=−0.32); figure 3. Conclusions An elevated RDW correlates with higher levels of fatigue. For the first time a serologically marker has shown strong association with fatigue in patients with lupus. This is demonstrated in three groups of varying age, ethnicity and geography and using two different fatigue scores.

Michael Grabner,1 Yong Chen,2 Matthew Nguyen,3 Scott D Abbott,3 Ralph Quimbo1 1HealthCore, Inc., Wilmington, DE, USA; 2Merck and Co., Inc., Whitehouse Station, NJ, USA; 3Valeritas, Inc., Bridgewater, NJ, USA Objective: To inform the design and assess the feasibility of a prospective effectiveness study evaluating an insulin delivery device for patients with diabetes mellitus to be conducted within the membership of a large US commercial insurer. Methods: Providers who issued ≥1 insulin prescription between January 1, 2011 and September 30, 2011 were selected from administrative claims contained in the HealthCore Integrated Research DatabaseSM. Adult diabetes patients with visits to these providers were identified. Providers were dichotomized into high- [HVPs] and low-volume providers [LVPs] based on median number of diabetes patients per provider. Results: We identified 15,349 HVPs and 15,313 LVPs (median number of patients = 14). Most HVPs were located in the Midwest (6,291 [41.0%]) and South (5,092 [33.2%]), while LVPs were evenly distributed across regions. Over 80% (12,769) of HVPs practiced family or internal medicine; 6.4% (989) were endocrinologists. HVPs prescribed insulin to an average of 25% of patients. Patients of HVPs (522,527) had similar characteristics as patients of LVPs (80,669), except for geographical dispersion, which followed that of providers. Approximately 65% of patients were aged 21-64 years and 97% had type 2 diabetes. Among patients with ≥1 available HbA1C result during 2011 (103,992), 48.3% (50,193) had an average HbA1C ≥7.0%. Among patients initiating insulin, 79.6% (22,205) had an average HbA1C ≥7.0%. Conclusion: The observed provider and patient populations support the feasibility of the prospective study. Sampling of patients from HVPs is efficient while minimizing bias as patient characteristics are similar to those from LVPs. The study also highlights unmet needs for improved glycemic control since approximately half of patients with diabetes are not on goal. Keywords: diabetes mellitus, claims analysis, prospective study design, insulin delivery