Limin Peng

Emory University, Atlanta, Georgia, United States

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Publications (49)170.33 Total impact

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    ABSTRACT: Clinical guidelines recommend point-of-care glucose testing and the use of supplemental doses of rapid-acting insulin before meals and at bedtime for correction of hyperglycemia. The efficacy and safety of this recommendation, however, have not been tested in the hospital setting. In this open-label, randomized controlled trial, 206 general medicine and surgery patients with type 2 diabetes treated with a basal-bolus regimen were randomized to receive either supplemental insulin (n = 106) at bedtime for blood glucose (BG) >7.8 mmol/L or no supplemental insulin (n = 100) except for BG >19.4 mmol/L. Point-of-care testing was performed before meals, at bedtime, and at 3:00 a.m. The primary outcome was the difference in fasting BG. In addition to the intention-to-treat analysis, an as-treated analysis was performed where the primary outcome was analyzed for only the bedtime BG levels between 7.8 and 19.4 mmol/L. There were no differences in mean fasting BG for the intention-to-treat (8.8 ± 2.4 vs. 8.6 ± 2.2 mmol/L, P = 0.76) and as-treated (8.9 ± 2.4 vs. 8.8 ± 2.4 mmol/L, P = 0.92) analyses. Only 66% of patients in the supplement and 8% in the no supplement groups received bedtime supplemental insulin. Hypoglycemia (BG <3.9 mmol/L) did not differ between groups for either the intention-to-treat (30% vs. 26%, P = 0.50) or the as-treated (4% vs. 8%, P = 0.37) analysis. The use of insulin supplements for correction of bedtime hyperglycemia was not associated with an improvement in glycemic control. We conclude that routine use of bedtime insulin supplementation is not indicated for management of inpatients with type 2 diabetes. © 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.
    Diabetes Care 02/2015; DOI:10.2337/dc14-1796 · 8.57 Impact Factor
  • Ruosha Li, Limin Peng
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    ABSTRACT: Semi-competing risks data frequently arise in biomedical studies when time to a disease landmark event is subject to dependent censoring by death, the observation of which however is not precluded by the occurrence of the landmark event. In observational studies, the analysis of such data can be further complicated by left truncation. In this work, we study a varying coefficient subdistribution regression model for left-truncated semi-competing risks data. Our method appropriately accounts for the specifical truncation and censoring features of the data, and moreover has the flexibility to accommodate potentially varying covariate effects. The proposed method can be easily implemented and the resulting estimators are shown to have nice asymptotic properties. We also present inference, such as Kolmogorov–Smirnov type and Cramér–Von-Mises type hypothesis testing procedures for the covariate effects. Simulation studies and an application to the Denmark diabetes registry demonstrate good finite-sample performance and practical utility of the proposed method.
    Journal of Multivariate Analysis 10/2014; 131:65–78. DOI:10.1016/j.jmva.2014.06.005 · 0.94 Impact Factor
  • Limin Peng, Jinfeng Xu, Nancy Kutner
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    ABSTRACT: Varying covariate effects often manifest meaningful heterogeneity in covariate-response associations. In this paper, we adopt a quantile regression model that assumes linearity at a continuous range of quantile levels as a tool to explore such data dynamics. The consideration of potential non-constancy of covariate effects necessitates a new perspective for variable selection, which, under the assumed quantile regression model, is to retain variables that have effects on all quantiles of interest as well as those that influence only part of quantiles considered. Current work on l 1-penalized quantile regression either does not concern varying covariate effects or may not produce consistent variable selection in the presence of covariates with partial effects, a practical scenario of interest. In this work, we propose a shrinkage approach by adopting a novel uniform adaptive LASSO penalty. The new approach enjoys easy implementation without requiring smoothing. Moreover, it can consistently identify the true model (uniformly across quantiles) and achieve the oracle estimation efficiency. We further extend the proposed shrinkage method to the case where responses are subject to random right censoring. Numerical studies confirm the theoretical results and support the utility of our proposals.
    Statistics and Computing 09/2014; 24(5). DOI:10.1007/s11222-013-9406-4 · 1.75 Impact Factor
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    ABSTRACT: OBJECTIVE Effective treatment algorithms are needed to guide diabetes care at hospital discharge in general medicine and surgery patients with type 2 diabetes. RESEARCH DESIGN AND METHODS This was a prospective, multicenter open-label study aimed to determine the safety and efficacy of a hospital discharge algorithm based on admission HbA(1c). Patients with HbA(1c) < 7% (53.0mmol/mol) were discharged on their preadmission diabetes therapy, HbA(1c) between 7 and 9% (53.0-74.9 mmol/mol) were discharged on a preadmission regimen plus glargine at 50% of hospital daily dose, and HbA(1c) > 9% were discharged on oral antidiabetes agents (OADs) plus glargine or basal bolus regimen at 80% of inpatient dose. The primary outcome was HbA(1c) concentration at 12 weeks after hospital discharge. RESULTS A total of 224 patients were discharged on OAD (36%), combination of OAD and glargine (27%), basal bolus (24%), glargine alone (9%), and diet (4%). The admission HbA(1c) was 8.7 +/- 2.5% (71.6 mmol/mol) and decreased to 7.3 +/- 1.5% (56 mmol/mol) at 12 weeks of follow-up (P < 0.001). The change of HbA(1c) from baseline at 12 weeks after discharge was -0.1 +/- 0.6, -0.8 +/- 1.0, and -3.2 +/- 2.4 in patients with HbA(1c) < 7%, 7-9%, and > 9%, respectively (P < 0.001). Hypoglycemia (< 70 mg/dL) was reported in 22% of patients discharged on OAD only, 30% on OAD plus glargine, 44% on basal bolus, and 25% on glargine alone and was similar in patients with admission HbA(1c) <= 7% (26%) compared with those with HbA(1c) > 7% (31%, P = 0.54). CONCLUSIONS Measurement of HbA(1c) on admission is beneficial in tailoring treatment regimens at discharge in general medicine and surgery patients with type 2 diabetes.
    Diabetes Care 08/2014; 37(11). DOI:10.2337/dc14-0479 · 8.57 Impact Factor
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    ABSTRACT: Dependent censoring occurs in many biomedical studies and poses considerable methodological challenges for survival analysis. In this work, we develop a new approach for analyzing dependently censored data by adopting quantile regression models. We formulate covariate effects on the quantiles of the marginal distribution of the event time of interest. Such a modeling strategy can accommodate a more dynamic relationship between covariates and survival time compared to traditional regression models in survival analysis, which usually assume constant covariate effects. We propose estimation and inference procedures, along with an efficient and stable algorithm. We establish the uniform consistency and weak convergence of the resulting estimators. Extensive simulation studies demonstrate good finite-sample performance of the proposed inferential procedures. We illustrate the practical utility of our method via an application to a multicenter clinical trial that compared warfarin and aspirin in treating symptomatic intracranial arterial stenosis.
    Statistica Sinica 07/2014; 24(3):1411-1432. DOI:10.5705/ss.2012.303 · 1.23 Impact Factor
  • Ruosha Li, Limin Peng
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    ABSTRACT: We study quantile regression when the response is an event time subject to potentially dependent censoring. We consider the semicompeting risks setting, where the time to censoring remains observable after the occurrence of the event of interest. Although such a scenario frequently arises in biomedical studies, most of current quantile regression methods for censored data are not applicable because they generally require the censoring time and the event time to be independent. By imposing quite mild assumptions on the association structure between the time-to-event response and the censoring time variable, we propose quantile regression procedures, which allow us to garner a comprehensive view of the covariate effects on the event time outcome as well as to examine the informativeness of censoring. An efficient and stable algorithm is provided for implementing the new method. We establish the asymptotic properties of the resulting estimators including uniform consistency and weak convergence. The theoretical development may serve as a useful template for addressing estimating settings that involve stochastic integrals. Extensive simulation studies suggest that the method proposed performs well with moderate sample sizes. We illustrate the practical utility of our proposals through an application to a bone marrow transplant trial.
    Journal Of The Royal Statistical Society 03/2014; DOI:10.1111/rssb.12063
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    ABSTRACT: Few studies have reported on the quality of diabetes care and glycemic control adjusted for medication use in long term care (LTC) facilities. This observational study analyzed diabetes prevalence and management and the impact of glycemic control on clinical outcome in elderly subjects admitted to 3 community LTC facilities. Among 1409 LTC residents (age 79.7 ± 12 years), the prevalence of diabetes was 34.2%. Subjects with diabetes were either on no pharmacological agents (10%) or were treated with sliding scale regular insulin (SSI, 25%), oral antidiabetic drugs (OAD, 5%), insulin (34%), or with combination of OAD and insulin (26%). Patients with diabetes had a mean daily BG of 156 ± 39 mg/dL and a mean admission HbA1c of 6.7% ± 1.1%. Compared with nondiabetes, residents with diabetes had higher number of complications (54% vs 45%, P < .001), infections (26% vs 21%, P = .036), emergency room (ER) and hospital transfers (37% vs 30%, P = .003), but similar mortality (15% vs 14%, P = .56). A total of 43% of residents with diabetes had a BG less than 70 mg/dL, and those with hypoglycemia had longer median length of stay (LOS, 52 vs 29 days, P < .001), more ER or hospital transfers (56% vs 69%, P = .005), and mortality (20% vs 10%, P = .002) compared with residents without hypoglycemia. Diabetes is common in LTC residents and is associated with higher resource utilization and complications. Hypoglycemia is common and is associated with increased need of emergency room visits and hospitalization and higher mortality. Our findings emphasize the need for randomized trials evaluating the impact of different approaches to glycemic management on clinical outcome in LTC residents with diabetes.
    Journal of the American Medical Directors Association 09/2013; 14(11). DOI:10.1016/j.jamda.2013.08.001 · 4.78 Impact Factor
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    ABSTRACT: Objective: Hyperglycemia is associated with increased mortality in critically ill patients treated with total parenteral nutrition (TPN). The role of glucose variability (GV) in predicting outcomes in these patients is not known.Methods: This retrospective study included medical and surgical patients receiving TPN in a community teaching hospital. GV was calculated by standard deviation (SD) of blood glucose (BG) values and by mean BG daily delta change (daily max - daily minimum).Results: 276 medical and surgical patients (mean age: 51±18 yr), 19% with history of diabetes (DM), and 74% with ICU admission were treated with TPN. During TPN mean daily BG was 142.9±33 mg/dl, frequency of hypoglycemia <70 mg/dl and <40 mg/dl was 41% and 3%, respectively, and hospital mortality was 27.2%. The mean GV by SD: 38±21 mg/dl and by mean delta change: 58±34 mg/dl. GV was significantly higher in deceased patients (SD: 48±25 vs. 34±18 mg/dL and Δ change: 75±39 vs. 51±29 mg/dl, both p<0.01) than non-deceased patients. Multivariate analysis adjusted for age, DM status, gender, APACHE score, mean daily glucose and hypoglycemia revealed that GV was an independent predictor of hospital mortality (p<0.05). The association between GV and mortality was limited to patients without a history of DM and was not present in patients with DM.Conclusion: High GV is associated with increased hospital mortality independent of the presence and severity of hyperglycemia or hypoglycemia during TPN therapy. Prospective randomized trials are needed to determine if reduction in GV with intensive glycemic control improves clinical outcomes in patients treated with TPN.
    Endocrine Practice 09/2013; 20(1):1-17. DOI:10.4158/EP13131.OR · 2.59 Impact Factor
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    ABSTRACT: To determine differences in inpatient glycemic control and response to two different glargine-based insulin regimens in general medicine and surgery patients with type 2 diabetes (T2D). This is a post-hoc analysis of a prospective, multicenter, randomized trial of 298 non-ICU medicine and surgery patients with T2D treated with Basal Bolus regimen with glargine once daily and glulisine before meals and with Basal Plus regimen with glargine once daily and supplemental doses of glulisine before meals for blood glucose (BG)>140mg/dl. Major study outcomes included differences in mean daily BG, frequency of treatment failures (defined as >2 consecutive BG>240mg/dl or a mean daily BG>240mg/dl), and hypoglycemia between the medicine and surgery cohorts. Patients treated with Basal Bolus or with Basal Plus experienced similar improvement in mean daily BG after 1st day of therapy (p=0.16), number of treatment failures (p=0.11) and hypoglycemic events (p=0.50). Compared to surgery patients (n=130), medicine patients (n=168) had higher admission BG (p=0.01) and HbA1c levels (p<0.01); however, they had similar response to either treatment regimen without differences in mean daily BG after 1st day of therapy (p=0.18), number of treatment failures (p=0.58), daily insulin requirements (p=0.36), or in the frequency of hypoglycemia (p=0.79). The Basal Plus regimen with glargine once daily and correction doses with glulisine before meals resulted in similar glycemic control to basal bolus regimen. We observed no differences in response to either basal insulin regimen between medicine and surgery patients with type 2 diabetes.
    Journal of diabetes and its complications 08/2013; DOI:10.1016/j.jdiacomp.2013.05.007 · 1.93 Impact Factor
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    ABSTRACT: OBJECTIVE This study investigated the safety and efficacy of sitagliptin (Januvia) for the inpatient management of type 2 diabetes (T2D) in general medicine and surgery patients.RESEARCH DESIGN AND METHODS In this pilot, multicenter, open-label, randomized study, patients (n = 90) with a known history of T2D treated with diet, oral antidiabetic agents, or low total daily dose of insulin (≤0.4 units/kg/day) were randomized to receive sitagliptin alone or in combination with glargine insulin (glargine) or to a basal bolus insulin regimen (glargine and lispro) plus supplemental (correction) doses of lispro. Major study outcomes included differences in daily blood glucose (BG), frequency of treatment failures (defined as three or more consecutive BG >240 mg/dL or a mean daily BG >240 mg/dL), and hypoglycemia between groups.RESULTSGlycemic control improved similarly in all treatment groups. There were no differences in the mean daily BG after the 1st day of treatment (P = 0.23), number of readings within a BG target of 70 and 140 mg/dL (P = 0.53), number of BG readings >200 mg/dL (P = 0.23), and number of treatment failures (P > 0.99). The total daily insulin dose and number of insulin injections were significantly less in the sitagliptin groups compared with the basal bolus group (both P < 0.001). There were no differences in length of hospital stay (P = 0.78) or in the number of hypoglycemic events between groups (P = 0.86)CONCLUSIONS Results of this pilot indicate that treatment with sitagliptin alone or in combination with basal insulin is safe and effective for the management of hyperglycemia in general medicine and surgery patients with T2D.
    Diabetes care 07/2013; 36(11). DOI:10.2337/dc13-0277 · 8.57 Impact Factor
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    ABSTRACT: The need to assess agreement arises in many scenarios in biomedical sciences when measurements were taken by different methods on the same subjects. When the endpoints are survival outcomes, the study of agreement becomes more challenging given the special characteristics of time-to-event data. In this article, we propose a new framework for assessing agreement based on survival processes that can be viewed as a natural representation of time-to-event outcomes. Our new agreement measure is formulated as the chance-corrected concordance between survival processes. It provides a new perspective for studying the relationship between correlated survival outcomes and offers an appealing interpretation as the agreement between survival times on the absolute distance scale. We provide a multivariate extension of the proposed agreement measure for multiple methods. Furthermore, the new framework enables a natural extension to evaluate time-dependent agreement structure. We develop nonparametric estimation of the proposed new agreement measures. Our estimators are shown to be strongly consistent and asymptotically normal. We evaluate the performance of the proposed estimators through simulation studies and then illustrate the methods using a prostate cancer data example.
    Biometrics 07/2013; 69(4):1-9. DOI:10.1111/biom.12063 · 1.52 Impact Factor
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    ABSTRACT: OBJECTIVE Effective and easily implemented insulin regimens are needed to facilitate hospital glycemic control in general medical and surgical patients with type 2 diabetes (T2D).RESEARCH DESIGN AND METHODS This multicenter trial randomized 375 patients with T2D treated with diet, oral antidiabetic agents, or low-dose insulin (≤0.4 units/kg/day) to receive a basal bolus regimen with glargine once daily and glulisine before meals, a basal plus regimen with glargine once daily and supplemental doses of glulisine, and sliding scale regular insulin (SSI).RESULTSImprovement in mean daily blood glucose (BG) after the first day of therapy was similar between basal bolus and basal plus groups (P = 0.16), and both regimens resulted in a lower mean daily BG than did SSI (P = 0.04). In addition, treatment with basal bolus and basal plus regimens resulted in less treatment failure (defined as >2 consecutive BG >240 mg/dL or a mean daily BG >240 mg/dL) than did treatment with SSI (0 vs. 2 vs. 19%, respectively; P < 0.001). A BG <70 mg/dL occurred in 16% of patients in the basal bolus group, 13% in the basal plus group, and 3% in the SSI group (P = 0.02). There was no difference among the groups in the frequency of severe hypoglycemia (<40 mg/dL; P = 0.76).CONCLUSIONS The use of a basal plus regimen with glargine once daily plus corrective doses with glulisine insulin before meals resulted in glycemic control similar to a standard basal bolus regimen. The basal plus approach is an effective alternative to the use of a basal bolus regimen in general medical and surgical patients with T2D.
    Diabetes care 02/2013; 36(8). DOI:10.2337/dc12-1988 · 8.57 Impact Factor
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    ABSTRACT: Objective: To compare the response to different insulin regimens for management of hyperglycemia in diabetic patients with hematological malignancies receiving dexamethasone.Methods: Retrospective analysis to determine whether basal bolus insulin (BBI) regimen with detemir and aspart is superior to the use of sliding scale regular insulin (SSI) in the management of hyperglycemia in hospitalized diabetic patients receiving dexamethasone.Results: Forty patients with hematological malignancies were treated with intravenous (8-12 mg/day) or oral (40 mg/day) dexamethasone for 3 days. In the SSI group (n=28), the average day 1-3 BG was 301±57 mg/dL while in the BBI group (n=12) it was 219±51 mg/dL (P<0.001). The BBI regimen resulted in BG reduction throughout the course of dexamethasone therapy that averaged -52±82 mg/dL while in the SSI mean daily BG increased on average by +128±77 mg/dL (P<0.001). On the last day of dexamethasone administration, insulin requirements were 49±29 units/day in SSI group and 122±39 units/day in BBI group (P<0.001). Three patients in the SSI group developed diabetic ketoacidosis or hyperosmolar hyperglycemic state during steroid therapy. No hypoglycemia was observed in either group. The length of stay and infection rates were similar between groups.Conclusion: Basal and bolus insulin regimen is an effective and safe approach for the management of dexamethasone-induced hyperglycemia in hospitalized patients with hematological malignancies.
    Endocrine Practice 01/2013; 19(2):1-14. DOI:10.4158/EP12256.OR · 2.59 Impact Factor
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    ABSTRACT: Thiazolidinedione (TZD) therapy has been associated with an increased risk of bone fractures. Studies in rodents have led to a model in which decreased bone quality in response to TZDs is due to a competition of lineage commitment between osteoblasts (OBs) and adipocytes (ADs) for a common precursor cell, resulting in decreased OB numbers. Our goal was to investigate the effects of TZD exposure on OB-AD lineage determination from primary human bone marrow stromal cells (hBMSCs) both in vitro and in vivo from nondiabetic subjects and patients with type 2 diabetics. Our experimental design included 2 phases. Phase 1 was an in vitro study of TZD effects on the differentiation of hBMSCs into OBs and ADs in nondiabetic subjects. Phase 2 was a randomized, placebo-controlled trial to determine the effects of 6-month pioglitazone treatment in vivo on hBMSC differentiation using AD/OB colony forming unit assays in patients with type 2 diabetes. In vitro, TZDs (pioglitazone and rosiglitazone) enhanced the adipogenesis of hBMSCs, whereas neither altered OB differentiation or function as measured by alkaline phosphatase activity, gene expression, and mineralization. The ability of TZDs to enhance adipogenesis occurred at a specific time/stage of the differentiation process, and pretreating with TZDs did not further enhance adipogenesis. In vivo, 6-month TZD treatment decreased OB precursors, increased AD precursors, and increased total colony number in patients with type 2 diabetes. Our results indicate that TZD exposure in vitro potently stimulates adipogenesis but does not directly alter OB differentiation/mineralization or lineage commitment from hBMSCs. However, TZD treatment in type 2 diabetic patients results in decreased osteoblastogenesis from hBMSCs compared with placebo, indicating an indirect negative effect on OBs and suggesting an alternative model by which TZDs might negatively regulate bone quality.
    09/2012; 161(3). DOI:10.1016/j.trsl.2012.08.006
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    ABSTRACT: Objective: We aimed to determine risk factors associated with hypoglycemia during subcutaneous insulin therapy in non-critically ill patients with type 2 diabetes. Methods: We conducted an analysis of three randomized control trials using basal/bolus regimen and regular sliding scale insulin (SSI) in patients with diabetes admitted to medical and surgical settings. Results: We analyzed medical records of 261 general medicine and 211 noncardiac surgery patients treated with basal/bolus regimen with glargine/glulisine (n = 169), detemir/aspart (n = 67), neutral protamine Hagedorn/regular (n = 63), or with SSI (n = 173). The overall frequency of mild and severe hypoglycemia (<70 and <40 mg/dl) was 19% and 2%, respectively. During treatment, medical patients experienced a higher number of hypoglycemia than surgical patients (23% versus 13%; p = .005), but the rate of severe hypoglycemia was similar between groups (1.9% versus 1.9%; p = not significant). Increasing age, impaired kidney function (glomerular filtration rate < 60 ml/min), total daily insulin dose, and type of insulin regimen (basal/bolus versus SSI) during hospitalization were important contributors for hypoglycemia in both medical and surgical patients. Among these variables, increasing age and type of insulin regimen (basal/bolus versus SSI) were found to be independent predictors of hypoglycemic events. Conclusions: Mild hypoglycemic events are common during subcutaneous insulin therapy in medical and surgical patients with type 2 diabetes. Increasing age, impaired renal function, daily insulin dose, and insulin regimen (basal/bolus versus SSI) are important predictors of hypoglycemia during insulin therapy in patients with type 2 diabetes mellitus.
    Journal of diabetes science and technology 09/2012; 6(5):1022-9. DOI:10.1177/193229681200600505
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    ABSTRACT: Parenteral nutrition has been associated with metabolic and infectious complications in intensive care unit patients. The underlying mechanism for the high risk of complications is not known but may relate to the proinflammatory effects of soybean oil-based lipid emulsions, the only Food and Drug Administration-approved lipid formulation for clinical use. Prospective, double-blind, randomized, controlled trial. Medical-surgical intensive care units from a major urban teaching hospital and a tertiary referral university hospital. Adult medical-surgical intensive care unit patients. Parenteral nutrition containing soybean oil-based (Intralipid) or olive oil-based (ClinOleic) lipid emulsions. Differences in hospital clinical outcomes (nosocomial infections and noninfectious complications), hospital length of stay, glycemic control, inflammatory and oxidative stress markers, and granulocyte and monocyte functions between study groups. A total of 100 patients were randomized to either soybean oil-based parenteral nutrition or olive oil-based parenteral nutrition for up to 28 days. A total of 49 patients received soybean oil-based parenteral nutrition (age 51 ± 15 yrs, body mass index 27 ± 6 kg/m2, and Acute Physiology and Chronic Health Evaluation II score 15.5 ± 7 [±SD]), and a total of 51 patients received olive oil-based lipid emulsion in parenteral nutrition (age 46 ± 19 yrs, body mass index 27 ± 8 kg/m2, and Acute Physiology and Chronic Health Evaluation II score 15.1 ± 6 [±SD]) for a mean duration of 12.9 ± 8 days. The mean hospital blood glucose concentration during parenteral nutrition was 129 ± 14 mg/dL, without differences between groups. Patients treated with soybean oil-based and olive oil-based parenteral nutrition had a similar length of stay (47 ± 47 days and 41 ± 36 days, p = .49), mortality (16.3% and 9.8%, p = .38), nosocomial infections (43% vs. 57%, p = .16), and acute renal failure (26% vs. 18%, p = .34). In addition, there were no differences in inflammatory and oxidative stress markers or in granulocyte and monocyte functions between groups. The administration of parenteral nutrition containing soybean oil-based and olive oil-based lipid emulsion resulted in similar rates of infectious and noninfectious complications and no differences in glycemic control, inflammatory and oxidative stress markers, and immune function in critically ill adults.
    Critical care medicine 04/2012; 40(6):1792-8. DOI:10.1097/CCM.0b013e3182474bf9 · 6.15 Impact Factor
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    ABSTRACT: Hyperglycemia and elevated free fatty acids (FFA) are implicated in the development of endothelial dysfunction. Infusion of soy-bean oil-based lipid emulsion (Intralipid®) increases FFA levels and results in elevation of blood pressure (BP) and endothelial dysfunction in obese healthy subjects. The effects of combined hyperglycemia and high FFA on BP, endothelial function and carbohydrate metabolism are not known. Twelve obese healthy subjects received four random, 8-h IV infusions of saline, Intralipid 40 mL/h, Dextrose 10% 40 mL/h, or combined Intralipid and dextrose. Plasma levels of FFA increased by 1.03±0.34 mmol/L (p=0.009) after Intralipid, but FFAs remained unchanged during saline, dextrose, and combined Intralipid and dextrose infusion. Plasma glucose and insulin concentrations significantly increased after dextrose and combined Intralipid and dextrose (all, p<0.05) and were not different from baseline during saline and lipid infusion. Intralipid increased systolic BP by 12±9 mmHg (p<0.001) and diastolic BP by 5±6 mmHg (p=0.022),and decreased flow-mediated dilatation (FMD) from baseline by 3.2%±1.4% (p<0.001). Saline and dextrose infusion had neutral effects on BP and FMD. The co-administration of lipid and dextrose decreased FMD by 2.4%±2.1% (p=0.002) from baseline, but did not significantly increase systolic or diastolic BP. Short-term Intralipid infusion significantly increased FFA and BP; in contrast, FFA and BP were unchanged during combined infusion of Intralipid and dextrose. Combined Intralipid and dextrose infusion resulted in endothelial dysfunction similar to Intralipid alone.
    Metabolism: clinical and experimental 04/2012; 61(10):1370-6. DOI:10.1016/j.metabol.2012.03.006 · 3.61 Impact Factor
  • Limin Peng
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    ABSTRACT: The principle of self-consistency has been employed to estimate regression quantile with randomly censored response. The asymptotic studies for this type of approach was established only recently, partly due to the complex forms of the current self-consistent estimators of censored regression quantiles. Of interest, how the self-consistent estimation of censored regression quantiles is connected to the alternative martingale-based approach still remains uncovered. In this paper, we propose a new formulation of self-consistent censored regression quantiles based on stochastic integral equations. The proposed representation of censored regression quantiles entails a clearly defined estimation procedure. More importantly, it greatly simplifies the theoretical investigations. We establish the large sample equivalence between the proposed self-consistent estimators and the existing estimator derived from martingale-based estimating equations. The connection between the new self-consistent estimation approach and the available self-consistent algorithms is also elaborated.
    Journal of Multivariate Analysis 02/2012; 105(1):368-379. DOI:10.1016/j.jmva.2011.10.005 · 0.94 Impact Factor
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    ABSTRACT: Many obese children with unprovoked diabetic ketoacidosis (DKA) display clinical features of type 2 diabetes during follow up. We describe the clinical presentation, autoimmune markers and the long-term course of obese and lean children with DKA. We reviewed the medical records on the initial acute hospitalization and outpatient follow-up care of 21 newly diagnosed obese and 20 lean children with unprovoked DKA at Emory University affiliated children's hospitals between 1/2003 and 12/2006. Obese children with DKA were older and predominantly male, had acanthosis nigricans, and had lower prevalence of autoantibodies to islet cells and glutamic acid decarboxylase than lean children. Half of the obese, but none of the lean children with DKA achieve near-normoglycemia remission and discontinued insulin therapy during follow-up. Time to achieve remission was 2.2±2.3 months. There were no differences on clinical presentation between obese children who achieved near-normoglycemia remission versus those who did not. The addition of metformin to insulin therapy shortly after resolution of DKA resulted in lower hemoglobin A1c (HbA1c) levels, higher rates of near-normoglycemia remission, and lower frequency of DKA recurrence. Near-normoglycemia remission, however, was of short duration and the majority of obese patients required reinstitution of insulin treatment within 15 months of follow-up. In contrast to lean children with DKA, many obese children with unprovoked DKA display clinical and immunologic features of type 2 diabetes during follow-up. The addition of metformin to insulin therapy shortly after resolution of DKA improves glycemic control, facilitates achieving near-normoglycemia remission and prevents DKA recurrence in obese children with DKA.
    01/2012; 6(1):61-5. DOI:10.1016/j.pcd.2011.11.001
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    ABSTRACT: Conventional agreement studies have been confined to addressing the sense of reproducibility, and therefore are limited to assessing measurements on the same scale. In this work, we propose a new concept, called "broad sense agreement," which extends the classical framework of agreement to evaluate the capability of interpreting a continuous measurement in an ordinal scale. We present a natural measure for broad sense agreement. Nonparametric estimation and inference procedures are developed for the proposed measure along with theoretical justifications. We also consider longitudinal settings which involve agreement assessments at multiple time points. Simulation studies have demonstrated good performance of the proposed method with small sample sizes. We illustrate our methods via an application to a mental health study.
    Journal of the American Statistical Association 12/2011; 106(496):1592-1601. DOI:10.1198/jasa.2011.tm10483 · 2.11 Impact Factor

Publication Stats

692 Citations
170.33 Total Impact Points

Institutions

  • 2007–2015
    • Emory University
      • • Department of Biostatistics and Bioinformatics
      • • School of Medicine
      Atlanta, Georgia, United States
    • University of Wisconsin–Madison
      • Department of Biostatistics and Medical Informatics
      Madison, Wisconsin, United States
  • 2006–2008
    • UK Department of Health
      Londinium, England, United Kingdom