Bayesian semiparametric model for sequential treatment decisions with informative timing.

We develop a Bayesian semiparametric model for the impact of dynamic treatment rules on survival among patients diagnosed with pediatric acute myeloid leukemia (AML). The data consist of a subset of patients enrolled in a phase III clinical trial in which patients move through a sequence of four treatment courses. At each course, they undergo treatment that may or may not include anthracyclines (ACT). While ACT is known to be effective at treating AML, it is also cardiotoxic and can lead to early death for some patients. Our task is to estimate the potential survival probability under hypothetical dynamic ACT treatment strategies, but there are several impediments. First, since ACT is not randomized, its effect on survival is confounded over time. Second, subjects initiate the next course depending on when they recover from the previous course, making timing potentially informative of subsequent treatment and survival. Third, patients may die or drop out before ever completing the full treatment sequence. We develop a generative Bayesian semiparametric model based on Gamma Process priors to address these complexities. At each treatment course, the model captures subjects' transition to subsequent treatment or death in continuous time. G-computation is used to compute a posterior over potential survival probability that is adjusted for time-varying confounding. Using our approach, we estimate the efficacy of hypothetical treatment rules that dynamically modify ACT based on evolving cardiac function.

Decreased Emergency Cholecystectomy and Case Fatality Rate, Not Explained by Expansion of Medicaid.

INTRODUCTION: Population data on longitudinal trends for cholecystectomies and their outcomes are scarce. We evaluated the incidence and case fatality rate of emergency and ambulatory cholecystectomies in New Jersey (NJ) and whether the Medicaid expansion changed trends. MATERIALS AND METHODS: A retrospective population cohort design was used to study the incidence of cholecystectomies and their case fatality rate from 2009 to 2018. Using linear and logistic regression we explored the trends of incidence and the odds of case fatality after versus before the January 1, 2014 Medicaid expansion. RESULTS: Overall, 93,423 emergency cholecystectomies were performed, with 644 fatalities; 87,239 ambulatory cholecystectomies were performed, with fewer than 10 fatalities. The 2009 to 2018 annual incidence of emergency cholecystectomies dropped markedly from 114.8 to 77.5 per 100,000 NJ population (P < 0.0001); ambulatory cholecystectomies increased from 93.5 to 95.6 per 100,000 (P = 0.053). The incidence of emergency cholecystectomies dropped more after than before Medicaid expansion (P < 0.0001). The odds ratio for case fatality among those undergoing emergency cholecystectomies after versus before expansion was 0.85 (95% CI, 0.72-0.99). This decrease in case fatality, apparent only in those over age 65, was not explained by the addition of Medicaid. CONCLUSIONS: A marked decrease in the incidence of emergency cholecystectomies occurred after Medicaid expansion, which was not accounted for by a minimal increase in the incidence of ambulatory cholecystectomies. Case fatality from emergency cholecystectomy decreased over time due to factors other than Medicaid. Further work is needed to reconcile these findings with the previously reported lack of decrease in overall gallstone disease mortality in NJ.

Respiratory Microbiome Disruption and Risk for Ventilator-Associated Lower Respiratory Tract Infection.

BACKGROUND: Ventilator-associated lower respiratory tract infection (VA-LRTI) is common among critically ill patients and has been associated with increased morbidity and mortality. In acute critical illness, respiratory microbiome disruption indices (MDIs) have been shown to predict risk for VA-LRTI, but their utility beyond the first days of critical illness is unknown. We sought to characterize how MDIs previously shown to predict VA-LRTI at initiation of mechanical ventilation change with prolonged mechanical ventilation, and if they remain associated with VA-LRTI risk. METHODS: We developed a cohort of 83 subjects admitted to a long-term acute care hospital due to their prolonged dependence on mechanical ventilation; performed dense, longitudinal sampling of the lower respiratory tract, collecting 1066 specimens; and characterized the lower respiratory microbiome by 16S rRNA sequencing as well as total bacterial abundance by 16S rRNA quantitative polymerase chain reaction. RESULTS: Cross-sectional MDIs, including low Shannon diversity and high total bacterial abundance, were associated with risk for VA-LRTI, but associations had wide posterior credible intervals. Persistent lower respiratory microbiome disruption showed a more robust association with VA-LRTI risk, with each day of (base e) Shannon diversity <2.0 associated with a VA-LRTI odds ratio of 1.36 (95% credible interval, 1.10-1.72). The observed association was consistent across multiple clinical definitions of VA-LRTI. CONCLUSIONS: Cross-sectional MDIs have limited ability to discriminate VA-LRTI risk during prolonged mechanical ventilation, but persistent lower respiratory tract microbiome disruption, best characterized by consecutive days with low Shannon diversity, may identify a population at high risk for infection and may help target infection-prevention interventions.

Risk of HCC With Hepatitis B Viremia Among HIV/HBV-Coinfected Persons in North America.

BACKGROUND AND AIMS: Chronic HBV is the predominant cause of HCC worldwide. Although HBV coinfection is common in HIV, the determinants of HCC in HIV/HBV coinfection are poorly characterized. We examined the predictors of HCC in a multicohort study of individuals coinfected with HIV/HBV. APPROACH AND RESULTS: We included persons coinfected with HIV/HBV within 22 cohorts of the North American AIDS Cohort Collaboration on Research and Design (1995-2016). First occurrence of HCC was verified by medical record review and/or cancer registry. We used multivariable Cox regression to determine adjusted HRs (aHRs [95% CIs]) of factors assessed at cohort entry (age, sex, race, body mass index), ever during observation (heavy alcohol use, HCV), or time-updated (HIV RNA, CD4+ percentage, diabetes mellitus, HBV DNA). Among 8,354 individuals coinfected with HIV/HBV (median age, 43 years; 93% male; 52.4% non-White), 115 HCC cases were diagnosed over 65,392 person-years (incidence rate, 1.8 [95% CI, 1.5-2.1] events/1,000 person-years). Risk factors for HCC included age 40-49 years (aHR, 1.97 [1.22-3.17]), age ≥50 years (aHR, 2.55 [1.49-4.35]), HCV coinfection (aHR, 1.61 [1.07-2.40]), and heavy alcohol use (aHR, 1.52 [1.04-2.23]), while time-updated HIV RNA >500 copies/mL (aHR, 0.90 [0.56-1.43]) and time-updated CD4+ percentage <14% (aHR, 1.03 [0.56-1.90]) were not. The risk of HCC was increased with time-updated HBV DNA >200 IU/mL (aHR, 2.22 [1.42-3.47]) and was higher with each 1.0 log10 IU/mL increase in time-updated HBV DNA (aHR, 1.18 [1.05-1.34]). HBV suppression with HBV-active antiretroviral therapy (ART) for ≥1 year significantly reduced HCC risk (aHR, 0.42 [0.24-0.73]). CONCLUSION: Individuals coinfected with HIV/HBV on ART with detectable HBV viremia remain at risk for HCC. To gain maximal benefit from ART for HCC prevention, sustained HBV suppression is necessary.

A Bayesian nonparametric model for zero-inflated outcomes: Prediction, clustering, and causal estimation.

Researchers are often interested in predicting outcomes, detecting distinct subgroups of their data, or estimating causal treatment effects. Pathological data distributions that exhibit skewness and zero-inflation complicate these tasks-requiring highly flexible, data-adaptive modeling. In this paper, we present a multipurpose Bayesian nonparametric model for continuous, zero-inflated outcomes that simultaneously predicts structural zeros, captures skewness, and clusters patients with similar joint data distributions. The flexibility of our approach yields predictions that capture the joint data distribution better than commonly used zero-inflated methods. Moreover, we demonstrate that our model can be coherently incorporated into a standardization procedure for computing causal effect estimates that are robust to such data pathologies. Uncertainty at all levels of this model flow through to the causal effect estimates of interest-allowing easy point estimation, interval estimation, and posterior predictive checks verifying positivity, a required causal identification assumption. Our simulation results show point estimates to have low bias and interval estimates to have close to nominal coverage under complicated data settings. Under simpler settings, these results hold while incurring lower efficiency loss than comparator methods. We use our proposed method to analyze zero-inflated inpatient medical costs among endometrial cancer patients receiving either chemotherapy or radiation therapy in the SEER-Medicare database.

A practical introduction to Bayesian estimation of causal effects: Parametric and nonparametric approaches.

Substantial advances in Bayesian methods for causal inference have been made in recent years. We provide an introduction to Bayesian inference for causal effects for practicing statisticians who have some familiarity with Bayesian models and would like an overview of what it can add to causal estimation in practical settings. In the paper, we demonstrate how priors can induce shrinkage and sparsity in parametric models and be used to perform probabilistic sensitivity analyses around causal assumptions. We provide an overview of nonparametric Bayesian estimation and survey their applications in the causal inference literature. Inference in the point-treatment and time-varying treatment settings are considered. For the latter, we explore both static and dynamic treatment regimes. Throughout, we illustrate implementation using off-the-shelf open source software. We hope to leave the reader with implementation-level knowledge of Bayesian causal inference using both parametric and nonparametric models. All synthetic examples and code used in the paper are publicly available on a companion GitHub repository.

Validation of a claims-based algorithm for identifying non-infectious pneumonitis in patients diagnosed with lung cancer.

PURPOSE: Non-infectious pneumonitis (NIP) is a common complication of treatments for lung cancer. We know of no existing validated algorithm for identifying NIP in claims databases, limiting our ability to understand the morbidity and mortality of this toxicity in real-world data. METHODS: Electronic health records (EHR), cancer registry, and administrative data from a National Cancer Institute-designated comprehensive cancer center were queried for patients diagnosed with lung cancer between 10/01/2015-12/31/2020. Health insurance claims were searched for ICD-10-CM codes that indicate an inpatient or outpatient diagnosis with possible NIP. A 20-code (Algorithm A) and 11-code (Algorithm B) algorithm were tested with and without requiring prescription with corticosteroids. Cases with a diagnosis of possible NIP in the 6 months before their first lung cancer diagnosis were excluded. The algorithms were validated by reviewing the EHR. The positive predictive value (PPV) for each algorithm was computed with 95% confidence intervals (CI). RESULTS: Seventy patients with lung cancer had a diagnosis code compatible with NIP: 36 (51.4%) inpatients and 34 (48.6%) outpatients. The PPV of Algorithm A was 77.1% (95% CI: 65.6-86.3). The PPV of Algorithm B was 86.9% (95% CI: 75.8-94.2). Requiring a documented prescription for a systemic corticosteroid improved the PPV of both Algorithm A and Algorithm B: 92.5% (95% CI: 79.6-98.4) and 100.0% (95% CI: 90.0-100.0), respectively. CONCLUSIONS: This study validated ICD-10-CM and prescription-claims-based definitions of NIP in lung cancer patients. All algorithms have at least reasonable performance. Enriching the algorithm with corticosteroid prescription records results in excellent performance.

Concordance of hospitalizations between Clinical Practice Research Datalink and linked Hospital Episode Statistics among patients treated with oral antidiabetic therapies.

PURPOSE: The ability of the Clinical Practice Research Datalink (CPRD) to ascertain all-cause hospitalizations remains unknown. We determined the proportion of hospitalizations in CPRD that were also recorded in Hospital Episode Statistics (HES), and vice versa, among patients initiating oral antidiabetic (OAD) therapy. METHODS: We conducted a retrospective cohort study from October 2009 to September 2012 among OAD-treated patients registered with general practitioners who contribute to CPRD and consent to HES linkage. In CPRD, we identified initial hospitalizations for each calendar year by an Inpatient Referral, Consultation Type code, or Read code indicating an inpatient episode and determined if an admission date was recorded in HES within ±30 days. We then identified initial HES admission dates and determined if a hospitalization was documented in CPRD within ±30 days. Sensitivity analyses were conducted utilizing HES discharge, rather than admission, dates. RESULTS: Among 8574 OAD-treated HES-linked patients in CPRD, 6574 initial hospitalizations across the study period were identified in CPRD, and 5188 (78.9% [95% CI, 77.9%-79.9%]) were confirmed by a HES admission date within ±30 days (median difference, ±3 days [IQR, 1-7 days]). Among 8609 initial hospital admissions in HES, 4803 (55.7% [95% CI, 54.7%-56.8%]) hospitalizations were recorded in CPRD within ±30 days (median difference, ±4 days [IQR, 1-9 days]). Similar results were observed using HES discharge dates. CONCLUSION: A substantial minority of patient-level hospitalization data are nonconcordant between HES and CPRD. Pharmacoepidemiologic studies within CPRD that seek to identify hospitalizations should consider linkage with HES to ensure adequate ascertainment of inpatient events.

Increased Mortality Rates With Prolonged Corticosteroid Therapy When Compared With Antitumor Necrosis Factor-α-Directed Therapy for Inflammatory Bowel Disease.

OBJECTIVES: Crohn's disease (CD) and ulcerative colitis (UC) are inflammatory bowel diseases (IBD) that compromise quality of life and may increase mortality. This study compared the mortality risk with prolonged corticosteroid use vs. antitumor necrosis factor-α (anti-TNF) drugs in IBD. METHODS: A retrospective cohort study was conducted among Medicaid and Medicare beneficiaries from 2001 to 2013 with IBD prescribed either >3,000 mg of prednisone or equivalent within a 12-month period or new initiation of anti-TNF therapy, each treated as time-updating exposures. The primary outcome was all-cause mortality. Secondary outcomes included common causes of death. Marginal structural models were used to determine odds ratios (ORs) and 95% confidence intervals (CIs) for anti-TNF use relative to corticosteroids. RESULTS: Among patients with CD, 7,694 entered the cohort as prolonged corticosteroid users and 1,879 as new anti-TNF users. Among patients with UC, 3,224 and 459 entered the cohort as prolonged CS users and new anti-TNF users, respectively. The risk of death was statistically significantly lower in patients treated with anti-TNF therapy for CD (21.4 vs. 30.1 per 1,000 person-years, OR 0.78, 0.65-0.93) but not for UC (23.0 vs. 30.9 per 1,000 person-years, OR 0.87, 0.63-1.22). Among the CD cohort, anti-TNF therapy was also associated with lower rates of major adverse cardiovascular events (OR 0.68, 0.55-0.85) and hip fracture (OR 0.54, 0.34-0.83). CONCLUSIONS: Compared with prolonged corticosteroid exposure, anti-TNF drug use was associated with reduced mortality in patients with CD that may be explained by lower rates of major adverse cardiovascular events and hip fracture.

Validity of diagnostic codes to identify hospitalizations for infections among patients treated with oral anti-diabetic drugs.

PURPOSE: Identification of hospitalizations for infection is important for post-marketing surveillance of drugs, but the validity of using diagnosis codes to identify these events is unknown. Differentiating between hospitalization for and with infection is important, as the latter is common and less likely to arise from pre-admission exposure to drugs. We determined positive predictive values (PPVs) of diagnostic coding-based algorithms to identify hospitalization for infection among patients prescribed oral anti-diabetic drugs (OADs). METHODS: We identified patients initiating OADs within 2 United States claims databases (Medicare, HealthCore Integrated Research DatabaseSM [HIRDSM ]) and 2 United Kingdom electronic medical record databases (Clinical Practice Research Datalink [CPRD], The Health Improvement Network [THIN]) from 2009 to 2014. To identify potential hospitalizations for infection, we selected patients with a hospital diagnosis of infection and, within 7 days prior to hospitalization, either an outpatient/emergency department visit with an infection diagnosis or outpatient antimicrobial treatment. Hospital records were reviewed by infectious disease specialists to adjudicate hospital admissions for infection. PPVs for confirmed outcomes were determined for each database. RESULTS: Code-based algorithms to identify hospitalization for infection had PPVs exceeding 80% within Medicare (PPV, 83% [90/109]; 95% CI, 74-89%), HIRDSM (PPV, 89% [73/82]; 95% CI, 80-95%), and THIN (PPV, 86% [12/14]; 95% CI, 57-98%) but not within CPRD (PPV, 67% [14/21]; 95% CI, 43-85%). CONCLUSIONS: Algorithms identifying hospitalization for infection utilizing hospital diagnoses along with antecedent outpatient/emergency infection diagnoses or antimicrobial therapy had sufficiently high PPVs for confirmed events within Medicare, HIRDSM , and THIN to enable their use for pharmacoepidemiologic research.

Risk of Acute Liver Injury After Statin Initiation by Human Immunodeficiency Virus and Chronic Hepatitis C Virus Infection Status.

BACKGROUND: Patients with human immunodeficiency virus (HIV) and/or chronic hepatitis C virus (HCV) infection may be prescribed statins as treatment for metabolic/cardiovascular disease, but it remains unclear if the risk of acute liver injury (ALI) is increased for statin initiators compared to nonusers in groups classified by HIV/HCV status. METHODS: We conducted a cohort study to compare rates of ALI in statin initiators vs nonusers among 7686 HIV/HCV-coinfected, 8155 HCV-monoinfected, 17739 HIV-monoinfected, and 36604 uninfected persons in the Veterans Aging Cohort Study (2000-2012). We determined development of (1) liver aminotransferases >200 U/L, (2) severe ALI (coagulopathy with hyperbilirubinemia), and (3) death, all within 18 months. Cox regression was used to determine propensity score-adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) of outcomes in statin initiators compared to nonusers across the groups. RESULTS: Among HIV/HCV-coinfected patients, statin initiators had lower risks of aminotransferase levels >200 U/L (HR, 0.66 [95% CI, .53-.83]), severe ALI (HR, 0.23 [95% CI, .12-.46]), and death (HR, 0.36 [95% CI, .28-.46]) compared with statin nonusers. In the setting of chronic HCV alone, statin initiators had reduced risks of aminotransferase elevations (HR, 0.57 [95% CI, .45-.72]), severe ALI (HR, 0.15 [95% CI, .06-.37]), and death (HR, 0.42 [95% CI, .32-.54]) than nonusers. Among HIV-monoinfected patients, statin initiators had lower risks of aminotransferase increases (HR, 0.52 [95% CI, .40-.66]), severe ALI (HR, 0.26 [95% CI, .13-.55]), and death (HR, 0.19 [95% CI, .16-.23]) compared with nonusers. Results were similar among uninfected persons. CONCLUSIONS: Regardless of HIV and/or chronic HCV status, statin initiators had a lower risk of ALI and death within 18 months compared with statin nonusers.

A framework for Bayesian nonparametric inference for causal effects of mediation.

We propose a Bayesian non-parametric (BNP) framework for estimating causal effects of mediation, the natural direct, and indirect, effects. The strategy is to do this in two parts. Part 1 is a flexible model (using BNP) for the observed data distribution. Part 2 is a set of uncheckable assumptions with sensitivity parameters that in conjunction with Part 1 allows identification and estimation of the causal parameters and allows for uncertainty about these assumptions via priors on the sensitivity parameters. For Part 1, we specify a Dirichlet process mixture of multivariate normals as a prior on the joint distribution of the outcome, mediator, and covariates. This approach allows us to obtain a (simple) closed form of each marginal distribution. For Part 2, we consider two sets of assumptions: (a) the standard sequential ignorability (Imai et al., 2010) and (b) weakened set of the conditional independence type assumptions introduced in Daniels et al. (2012) and propose sensitivity analyses for both. We use this approach to assess mediation in a physical activity promotion trial.

Evaluation of methods to estimate missing days' supply within pharmacy data of the Clinical Practice Research Datalink (CPRD) and The Health Improvement Network (THIN).

PURPOSE: The extent to which days' supply data are missing in pharmacoepidemiologic databases and effective methods for estimation is unknown. We determined the percentage of missing days' supply on prescription and patient levels for oral anti-diabetic drugs (OADs) and evaluated three methods for estimating days' supply within the Clinical Practice Research Datalink (CPRD) and The Health Improvement Network (THIN). METHODS: We estimated the percentage of OAD prescriptions and patients with missing days' supply in each database from 2009 to 2013. Within a random sample of prescriptions with known days' supply, we measured the accuracy of three methods to estimate missing days' supply by imputing the following: (1) 28 days' supply, (2) mode number of tablets/day by drug strength and number of tablets/prescription, and (3) number of tablets/day via a machine learning algorithm. We determined incidence rates (IRs) of acute myocardial infarction (AMI) using each method to evaluate the impact on ascertainment of exposure time and outcomes. RESULTS: Days' supply was missing for 24 % of OAD prescriptions in CPRD and 33 % in THIN (affecting 48 and 57 % of patients, respectively). Methods 2 and 3 were very accurate in estimating days' supply for OADs prescribed at a consistent number of tablets/day. Method 3 was more accurate for OADs prescribed at varying number of tablets/day. IRs of AMI were similar across methods for most OADs. CONCLUSIONS: Missing days' supply is a substantial problem in both databases. Method 2 is easy and very accurate for most OADs and results in IRs comparable to those from method 3.

High fluoroquinolone MIC is associated with fluoroquinolone treatment failure in urinary tract infections caused by fluoroquinolone susceptible Escherichia coli.

BACKGROUND: Suboptimal clinical response to fluoroquinolone (FQ) therapy has been clearly documented in patients with Salmonella typhi infection with reduced FQ susceptibility. However, the clinical impact of reduced FQ susceptibility on other infections including E. coli urinary tract infections (UTIs) has never been evaluated. METHODS: We conducted a retrospective cohort study of female patients with fluoroquinolone susceptible E. coli (FQSEC) UTIs who received FQ therapy at outpatient services within University of Pennsylvania Health System, Philadelphia. Exposed patients were those with high MIC-FQSEC UTIs (the levofloxacin MIC > 0.12 but ≤ 2 mg/L) while unexposed patients were those with low MIC-FQSEC UTIs (the levofloxacin MIC ≤ 0.12 mg/L). The primary treatment outcome was treatment failure within 10 weeks after initiation of FQ therapy. RESULTS: From May 2008 to April 2011, we enrolled 29 exposed patients and 246 unexposed patients. Two patients in each group experienced treatment failure; exposed vs. unexposed (6.9 vs. 0.8%; p = 0.06). Risk difference and risk ratio (RR) for treatment failure were 0.06 [95% CI -0.03-0.15; exact-p = 0.06] and 8.48 [95% CI 1.24-57.97; exact-p = 0.06], respectively. After adjusting for underlying cerebrovascular disease, the RR was 7.12 (95% CI 1.20-42.10; MH-p = 0.04). CONCLUSION: Our study demonstrated the negative impact of reduced FQ susceptibility on the treatment response to FQ therapy in FQSEC UTIs. This negative impact may be more intensified in other serious infections. Future studies in other clinical situations should be conducted to fill the gap of knowledge.

Risk of liver decompensation with cumulative use of mitochondrial toxic nucleoside analogues in HIV/hepatitis C virus coinfection.

PURPOSE: Among patients dually infected with human immunodeficiency virus (HIV) and chronic hepatitis C virus (HCV), use of antiretroviral therapy (ART) containing mitochondrial toxic nucleoside reverse transcriptase inhibitors (mtNRTIs) might induce chronic hepatic injury, which could accelerate HCV-associated liver fibrosis and increase the risk of hepatic decompensation and death. METHODS: We conducted a cohort study among 1747 HIV/HCV patients initiating NRTI-containing ART within the Veterans Aging Cohort Study (2002-2009) to determine if cumulative mtNRTI use increased the risk of hepatic decompensation and death among HIV-/HCV-coinfected patients. Separate marginal structural models were used to estimate hazard ratios (HRs) of each outcome associated with cumulative exposure to ART regimens that contain mtNRTIs versus regimens that contain other NRTIs. RESULTS: Over 7033 person-years, we observed 97 (5.6%) decompensation events (incidence rate, 13.8/1000 person-years) and 125 (7.2%) deaths (incidence rate, 17.8 events/1000 person-years). The risk of hepatic decompensation increased with cumulative mtNRTI use (1-11 mo: HR, 1.79 [95% confidence interval (CI), 0.74-4.31]; 12-35 mo: HR, 1.39 [95% CI, 0.68-2.87]; 36-71 mo: HR, 2.27 [95% CI, 0.92-5.60]; >71 mo: HR, 4.66 [95% CI, 1.04-20.83]; P = .045) versus nonuse. Cumulative mtNRTI use also increased risk of death (1-11 mo: HR, 2.24 [95% CI, 1.04-4.81]; 12-35 mo: HR, 2.05 [95% CI, 0.68-6.20]; 36-71 mo: HR, 3.04 [95% CI, 1.12-8.26]; >71 mo: HR, 3.93 [95% CI, 0.75-20.50]; P = .030). CONCLUSIONS: These findings suggest that cumulative mtNRTI use may increase the risk of hepatic decompensation and death in HIV/HCV coinfection. These drugs should be avoided when alternatives exist for HIV/HCV patients.

Disparities in Absolute Denial of Modern Hepatitis C Therapy by Type of Insurance.

BACKGROUND & AIMS: The high costs of direct-acting antiviral (DAA) agents to treat chronic hepatitis C virus (HCV) infection have resulted in denials of treatment, but it is not clear whether patients' access to these therapies differs with their type of insurance. METHODS: We conducted a prospective cohort study among all patients who had a DAA prescription submitted between November 1, 2014 and April 30, 2015 to Burman's Specialty Pharmacy, which provides HCV pharmacy services to patients in Delaware, Maryland, New Jersey, and Pennsylvania. We determined the incidence of absolute denial of DAA prescription, defined as a lack of approval of a prescription fill by the insurer, according to type of insurance (US Medicaid, US Medicare, or commercial insurance). Multivariable Poisson regression was used to estimate adjusted relative risks of absolute denial associated with patient characteristics. RESULTS: Among 2321 patients prescribed a DAA regimen (503 covered by Medicaid, 795 covered by Medicare, and 1023 covered by commercial insurance), 377 (16.2%) received an absolute denial. The most common reasons for absolute denial were insufficient information to assess medical need (134 [35.5%]) and lack of medical necessity (132 [35.0%]). A higher proportion of patients covered by Medicaid received an absolute denial (233 [46.3%]) than those covered by Medicare (40 [5.0%]; P < .001) or commercial insurance (104 [10.2%]; P < .001). Medicaid insurance (adjusted relative risk, 4.14; 95% confidence interval, 3.38-5.08) and absence of cirrhosis (adjusted relative risk, 1.96; 95% confidence interval, 1.53-2.50) were associated with absolute denial. CONCLUSIONS: There are significant disparities in access to DAA-based treatments for HCV infection among patients with different types of insurance. Nearly half of Medicaid beneficiaries in Delaware, Maryland, New Jersey, and Pennsylvania were denied access to these drugs for chronic HCV infection.

Acute Kidney Injury in Pediatric Severe Sepsis: An Independent Risk Factor for Death and New Disability.

OBJECTIVES: The prevalence of septic acute kidney injury and impact on functional status of PICU survivors are unknown. We used data from an international prospective severe sepsis study to elucidate functional outcomes of children suffering septic acute kidney injury. DESIGN: Secondary analysis of patients in the Sepsis PRevalence, OUtcomes, and Therapies point prevalence study: acute kidney injury was defined on the study day using Kidney Disease Improving Global Outcomes definitions. Patients with no acute kidney injury or stage 1 acute kidney injury ("no/mild acute kidney injury") were compared with those with stage 2 or 3 acute kidney injury ("severe acute kidney injury"). The primary outcome was a composite of death or new moderate disability at discharge defined as a Pediatric Overall Performance Category score of 3 or higher and increased by 1 from baseline. SETTING: One hundred twenty-eight PICUs in 26 countries. PATIENTS: Children with severe sepsis in the Sepsis PRevalence, OUtcomes, and Therapies study. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: One hundred two (21%) of 493 patients had severe acute kidney injury. More than twice as many patients with severe acute kidney injury died or developed new moderate disability compared with those with no/mild acute kidney injury (64% vs 30%; p < 0.001). Severe acute kidney injury was independently associated with death or new moderate disability (adjusted odds ratio, 2.5; 95% CI, 1.5-4.2; p = 0.001) after adjustment for age, region, baseline disability, malignancy, invasive mechanical ventilation, albumin administration, and the pediatric logistic organ dysfunction score. CONCLUSIONS: In a multinational cohort of critically ill children with severe sepsis and high mortality rates, septic acute kidney injury is independently associated with further increased death or new disability.

Abrupt Decline in Kidney Function Before Initiating Hemodialysis and All-Cause Mortality: The Chronic Renal Insufficiency Cohort (CRIC) Study.

BACKGROUND: It is not clear whether the pattern of kidney function decline in patients with chronic kidney disease (CKD) may relate to outcomes after reaching end-stage renal disease (ESRD). We hypothesize that an abrupt decline in kidney function prior to ESRD predicts early death after initiating maintenance hemodialysis therapy. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: The Chronic Renal Insufficiency Cohort (CRIC) Study enrolled men and women with mild to moderate CKD. For this study, we studied 661 individuals who developed chronic kidney failure that required hemodialysis therapy initiation. PREDICTORS: The primary predictor was the presence of an abrupt decline in kidney function prior to ESRD. We incorporated annual estimated glomerular filtration rates (eGFRs) into a mixed-effects model to estimate patient-specific eGFRs at 3 months prior to initiation of hemodialysis therapy. Abrupt decline was defined as having an extrapolated eGFR≥30mL/min/1.73m(2) at that time point. OUTCOMES: All-cause mortality within 1 year after initiating hemodialysis therapy. MEASUREMENTS: Multivariable Cox proportional hazards. RESULTS: Among 661 patients with CKD initiating hemodialysis therapy, 56 (8.5%) had an abrupt predialysis decline in kidney function and 69 died within 1 year after initiating hemodialysis therapy. After adjustment for demographics, cardiovascular disease, diabetes, and cancer, abrupt decline in kidney function was associated with a 3-fold higher risk for death within the first year of ESRD (adjusted HR, 3.09; 95% CI, 1.65-5.76). LIMITATIONS: Relatively small number of outcomes; infrequent (yearly) eGFR determinations; lack of more granular clinical data. CONCLUSIONS: Abrupt decline in kidney function prior to ESRD occurred in a significant minority of incident hemodialysis patients and predicted early death in ESRD.

Influence of Nephrologist Care on Management and Outcomes in Adults with Chronic Kidney Disease.

BACKGROUND: Predialysis nephrology care for adults with late stage chronic kidney disease (CKD) is associated with improved outcomes. Less is known about the effects of nephrology care in earlier stages of CKD. OBJECTIVE: We aimed to evaluate the effect of nephrology care on management of CKD risk factors and complications, CKD progression, incident cardiovascular disease (CVD), and death. DESIGN: This was a prospective cohort study. PARTICIPANTS: Participants included 3855 men and women aged 21 to 74 years enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study with a mean (SD) estimated glomerular filtration rate (eGFR) at entry of 45 (17) ml/min/1.73 m(2), followed for a median of 6.6 years. MAIN MEASURES: The main predictor was self-reported prior contact with a nephrologist at study enrollment. Outcomes evaluated included CKD progression (≥ 50 % eGFR loss or end-stage renal disease), incident CVD, and death. RESULTS: Two-thirds (67 %) of the participants reported prior contact with a nephrologist at study enrollment. They were younger, more likely to be male, non-Hispanic white, and had lower eGFR and higher urine protein (p < 0.05). A subgroup with eGFR 30- < 60 ml/min/1.73 m(2) and prior contact with a nephrologist were more likely to receive pharmacologic treatment for CKD-related complications and to report angiotensin-converting enzyme inhibitor or angiotensin receptor blocker (ACEi/ARB) use. After propensity score matching (for reporting prior contact with a nephrologist vs. not) and adjusting for demographic and clinical variables, prior contact with a nephrologist was not significantly associated with CKD progression, incident CVD or death (p > 0.05). CONCLUSIONS: One-third of CRIC participants had not seen a nephrologist before enrollment, and this prior contact was subject to age, sex, and ethnic-related disparities. While prior nephrology care was associated with more frequent treatment of CKD complications and use of ACEi/ARB medications, there was neither an association between this care and achievement of guideline-recommended intermediate measures, nor long-term adverse outcomes.

Global epidemiology of pediatric severe sepsis: the sepsis prevalence, outcomes, and therapies study.

RATIONALE: Limited data exist about the international burden of severe sepsis in critically ill children. OBJECTIVES: To characterize the global prevalence, therapies, and outcomes of severe sepsis in pediatric intensive care units to better inform interventional trials. METHODS: A point prevalence study was conducted on 5 days throughout 2013-2014 at 128 sites in 26 countries. Patients younger than 18 years of age with severe sepsis as defined by consensus criteria were included. Outcomes were severe sepsis point prevalence, therapies used, new or progressive multiorgan dysfunction, ventilator- and vasoactive-free days at Day 28, functional status, and mortality. MEASUREMENTS AND MAIN RESULTS: Of 6,925 patients screened, 569 had severe sepsis (prevalence, 8.2%; 95% confidence interval, 7.6-8.9%). The patients' median age was 3.0 (interquartile range [IQR], 0.7-11.0) years. The most frequent sites of infection were respiratory (40%) and bloodstream (19%). Common therapies included mechanical ventilation (74% of patients), vasoactive infusions (55%), and corticosteroids (45%). Hospital mortality was 25% and did not differ by age or between developed and resource-limited countries. Median ventilator-free days were 16 (IQR, 0-25), and vasoactive-free days were 23 (IQR, 12-28). Sixty-seven percent of patients had multiorgan dysfunction at sepsis recognition, with 30% subsequently developing new or progressive multiorgan dysfunction. Among survivors, 17% developed at least moderate disability. Sample sizes needed to detect a 5-10% absolute risk reduction in outcomes within interventional trials are estimated between 165 and 1,471 [corrected] patients per group. CONCLUSIONS: Pediatric severe sepsis remains a burdensome public health problem, with prevalence, morbidity, and mortality rates similar to those reported in critically ill adult populations. International clinical trials targeting children with severe sepsis are warranted.