Cox Proportional Hazards Frailty Models Research Articles

Patient and implant-related risk factors for implant failure of one-stage lateral sinus floor elevation: A 2- to 10-year retrospective study.

This retrospective study aimed to evaluate the early and late implant failure rates of one-stage lateral sinus floor elevation (LSFE)and to identify the patient and implant-related risk factors associated with these failures. All patients treated with one-stage LSFE from January 2014 to December 2021 were evaluated for inclusion. A total of 618 patients with 936 implants met the inclusion criteria. Clinical and radiographic information about patient and implants was collected. Univariate and multivariate Cox proportional hazards frailty regression models were performed to identify risk factors for early and late implant failure. The cumulative implant survival rate was 95.62% (95% CI 93.90%-97.68%), with 16 early implant failures and 25 late implant failures. The Cox analysis indicated that ≤3 mm residual bone height (RBH) was associated with a higher early failure rate. For late implant failure, smoking habit, ≤3 mm RBH, and certain implant brand were independent risk factors. Narrow sinus ostium, long infundibulum, and flat thickening of Schneiderian membrane might be non-independent risk factors for late implant failure. No significance was found in other variables, including age, periodontitis history, implant characteristics (position, diameter, length, protrusion length, marginal bone loss), surgeon experience, healing time, opposing dentition, and prosthesis. One-stage LSFE is a predictable treatment for patients with atrophic maxilla. ≤3 mm RBH increased the risk of early implant failure, while smoking habit, ≤3 mm RBH, and certain implant brand were independent risk factors for late implant failure.

P158 Cutaneous vasculitis in systemic lupus erythematosus: trends of incidence and risk factors

Abstract Background/Aims Cutaneous vasculitis (CV) is the most common form of vasculitis observed in patients with SLE; however, the precise epidemiological trends and underlying risk factors remain uncertain. The aim of this study was to define the incidence, prevalence, and risk factors of CV in systemic lupus erythematosus (SLE) patients over a period of 20 years. Methods The Birmingham Lupus Cohort is a longitudinal observational cohort of patients with SLE. All patients fulfilled the 1997 ACR Updated Classification Criteria for SLE. Inception patients were recruited within three years of their fourth ACR criterion. Disease activity was assessed using the classic BILAG index and laboratory results recorded. The BILAG vascular domain was used to determine the incidence rate, which refers to the rate at which new cases of minor and major CV attributed to active SLE occur. Cox proportional hazards frailty models were developed to identify clinical and laboratory variables associated with development of CV. Results We analysed 392 patients, of whom 375 (92.5%) were females. There were 213 (55.0%) White, 72 (18.6%) African-Caribbean, 82 (21.1%) South Asian, 9 (2.3%) East Asian, and 11 (2.8%) other ethnicities. The median (IQR) age at enrolment was 33 (26 - 44) years and the median duration of follow up was 9.2 (5.1 - 14.7) years. The incidence rates of minor and major CV were reported in Table 1. In Cox proportional hazards models, there was a positive association between CV and discoid rash (hazard ratio [HR] 2.16 [95% CI: 1.01, 4.61]), Raynaud’s phenomenon (HR 5.67 [95% CI: 4.11, 7.81]), livedo reticularis (HR = 4.69 [95% CI: 1.83, 12.0]), arthritis (HR 3.02 [95% CI: 2.20, 4.15]), renal involvement (OR 2.40 [95% CI: 1.55, 3.71]), haematological involvement (HR = 2.46 [95% CI: 1.80, 3.36]), and Afro-Caribbean descent (HR 1.96 [95% CI: 1.03, 3.74]). In addition, CV was positively associated with anti-dsDNA (HR = 2.33 [95% CI: 1.67, 3.27]), low C3 or C4 (HR 2.29 [95% CI: 2.18, 4.10]), and history of anti-Ro or anti-La (HR = 1.92 [95% CI: 1.15, 3.21]). Conclusion The incidence rates of CV decrease over the duration of follow-up and are associated with defined clinical and serological features. Disclosure A. Saleh: Grants/research support; A.S. is a sponsored PhD student by the Egyptian ministry of higher education represented by The Egyptian Bureau for Cultural & Educational Affairs in London. C. Gordon: None. J. Reynolds: None.

Spatial Survival Model for COVID-19 in México

A spatial survival analysis was performed to identify some of the factors that influence the survival of patients with COVID-19 in the states of Guerrero, México, and Chihuahua. The data that we analyzed correspond to the period from 28 February 2020 to 24 November 2021. A Cox proportional hazards frailty model and a Cox proportional hazards model were fitted. For both models, the estimation of the parameters was carried out using the Bayesian approach. According to the DIC, WAIC, and LPML criteria, the spatial model was better. The analysis showed that the spatial effect influences the survival times of patients with COVID-19. The spatial survival analysis also revealed that age, gender, and the presence of comorbidities, which vary between states, and the development of pneumonia increase the risk of death from COVID-19.

Fast and accurate recurrent event analysis for genome-wide association studies.

Many diseases recur after recovery, for example, recurrences in cancer and infections. However, research is often focused on analysing only time-to-first recurrence, thereby ignoring any subsequent recurrences that may occur after the first. Statistical models for the analysis of recurrent events are available, of which the extended Cox proportional hazards frailty model is the current state-of-the-art. However, this model is too statistically complex for computationally efficient application in high-dimensional data sets, including genome-wide association studies (GWAS). Here, we develop an application for fast and accurate recurrent event analysis in GWAS, called SPARE (SaddlePoint Approximation for Recurrent Event analysis). In SPARE, every DNA variant is tested for association with recurrence risk using a modified score statistic. A saddlepoint approximation is implemented to achieve statistical accuracy. SPARE controls the Type I error, and its statistical power is similar to existing recurrent event models, yet SPARE is significantly faster. An application of SPARE in a recurrent event GWAS on bladder cancer for 6.2 million DNA variants in 1,443 individuals required less than 15 min, whereas existing recurrent event methods would require several weeks.

Associations of outdoor fine particulate air pollution and cardiovascular disease: Results from the Prospective Urban and Rural Epidemiology Study in China (PURE-China)

BackgroundEvidence on whether an excess risk of incidence and mortality of cardiovascular disease (CVD) among people exposed to a high level of ambient PM2.5 in low- and middle-income countries (LMICs) is lacking. This study aimed to investigate the associations between long-term exposure to ambient fine particulate matter<2.5 µm (PM2.5) concentrations and the risk of incidence and mortality of CVD in a large cohort study from 115 communities. MethodsIn this cohort study, we followed 42 160 adults aged 35–75 years at baseline who enrolled in the Prospective Urban and Rural Epidemiology Study conducted in China (PURE-China) between 2005 and 2009 with ambient PM2.5 estimates, and followed up until August 2021. Cox proportional hazards frailty models were used to estimate the associations between long-term mean outdoor PM2.5 concentrations and CVD events, CVD mortality, and all-cause mortality. FindingsDuring a median follow-up period of 11.8 years, we documented 2 190 deaths, including 732 CVD deaths. There were 4 559 (10.8 %) of 42 160 participants who experienced incident total CVD, among them there were 861 myocardial infarctions (MI) and 2 338 S. The 3-year median concentration of ambient PM2.5 before the cohort commencement was 52.7 µg/m3 (interquartile range [IQR] 30.3–74.6). In full adjusted model, a 10 µg/m3 increase in PM2.5 was associated with a hazard ratio (HR) of 1.12 (95 % CI 1.11–1.14) for major CVD and 1.03 (95 % CI 1.01–1.05) for all-cause mortality. Besides, long-term PM2.5 concentrations had a significantly positive gradient association with total CVD and a similar pattern of associations with other CVD outcomes was observed. InterpretationThis study demonstrated that long-term ambient PM2.5 concentrations is positively associated with increased risks of CVD in adults aged 35–70 years from China. This finding reinforces the need for policymakers to adopt more effective strategies to improve air quality.

Implant failure and associated risk factors of transcrestal sinus floor elevation: A retrospective study.

This retrospective study aimed to evaluate early and late implant loss rates after transcrestal sinus floor elevation (TSFE) and to identify the risk factors related to these failures. All patients treated with TSFE and simultaneous implant placement during October 2015 to March 2019 were evaluated for inclusion. A total of 802 patients with 976 implants met the inclusion criteria. Clinical and radiographic information was collected from medical records and image software. Univariate and multivariate Cox proportional hazards frailty regression models were performed to identify potential risk factors associated with early and late implant loss after TSFE. The 3-year cumulative implant survival rate was 96.9% (95% CI 95.8%-98.0%). Twelve implants in 12 patients were lost before or at the abutment connection, while 24 implants in 24 patients were lost after functional loading. The Cox frailty regression analyses indicated that two factors were correlated with early implant loss: TSFE with grafting materials, and operators with less clinical experience. As for late implant loss, RBH ≤6 mm, male sex, and certain implant brands were associated with a significantly increased failure rate. Transcrestal sinus floor elevation with simultaneous implant placement is a predictable treatment option in the atrophic maxilla. The presence of grafting materials and the lack of clinical experience of the surgeon were possibly associated with early implant loss, while low RBH, male sex, and certain implant brands tended to increase late implant loss.

The Impact of Preventive Dental Services on Subsequent Dental Treatment for Children in Medicaid.

The goal of this study was to use claims data linked with community-level measures to evaluate the impact of preventive services on the time to subsequent restorative, advanced restorative, and complex dental treatment among children enrolled in the Virginia Medicaid program. Four data sources were used (dental claims, eligibility files, American Community Survey, and Area Health Resource Files) for fiscal years 2011 to 2018. The outcomes of interest were time to first treatment services from birth. The treatment outcomes were basic restorative treatment, advanced restorative treatment, or complex treatment. The independent variable was a preventive service prior to a treatment service. Time-to-event curves were estimated and compared using a log-rank test. Propensity score-matched univariate and multivariate Cox proportional hazards frailty models with an inverse probability censoring weighting correction estimated hazard ratios (HRs) for treatment outcomes comparing use of preventive services while controlling for patient demographic, geospatial, and county-level socioeconomic status measures. The analysis included 430,594 children (10,204,182 claims). A log-rank test showed significant differences (P < 0.001) between the times to treatment of those who had a preventive service and those who did not have a preventive service prior to a treatment service. Both Kaplan-Meier curves and the adjusted HR (1.88; 95% confidence interval [CI], 1.46-2.15) indicated that children without preventive services were more likely to have basic restorative treatment at an earlier age along with advanced restorative treatment (HR, 1.52; 95% CI, 1.28-1.80) and complex treatment (HR, 2.13; 95% CI, 1.68-2.61). In a population of Medicaid-enrolled children, children who did not receive preventive services were significantly more likely to have treatment at an earlier age than those who did receive preventive services. This study examines the impact of the utilization of preventive dental services since birth and the subsequent dental treatment for children enrolled in a dental Medicaid program. This study also examines the influence of preventive care on dental complexity of treatment for these children. Findings can inform federal and state policy planning of dental Medicaid programs as well as interventions to improve referral systems for the early use of preventive dental services and the establishment of a dental home.

Long-term exposure to PM2.5 and cardiovascular disease incidence and mortality in an Eastern Mediterranean country: findings based on a 15-year cohort study

BackgroundEvidence concerning the impact of long-term exposure to fine Particulate Matter ≤2.5 μm (PM2.5) on Cardio-Vascular Diseases (CVDs) for those people subject to ambient air pollution in developing countries remains relatively scant. This study assessed the relationship of 15-year PM2.5 exposure with cardiovascular incidence and mortality rate in Isfahan province, Iran.MethodsThe cohort comprised 3081 participants over 35 years old who were free of CVDs. They were selected through multi-stage cluster sampling in Isfahan, Iran. PM2.5 exposure was determined separately for each individual via satellite-based spatiotemporal estimates according to their residential addresses. In this context, CVD is defined as either fatal and non-fatal Acute Myocardial Infarctions (AMI) or stroke and sudden cardiac death. The incidence risk for CVD and the ensuing mortality was calculated based on the average PM2.5 exposure within a study period of 15 years using the Cox proportional hazards frailty model upon adjusting individual risk factors. The mean annual rate of PM2.5 and the follow-up data of each residential area were combined.ResultsMean three-year PM2·5 exposure for the cohort was measured at 45.28 μg/m3, ranging from 20.01 to 69.80 μg/m3. The median time period for conducting necessary follow-ups was 12.3 years for the whole population. Notably, 105 cardiovascular and 241 all-cause deaths occurred among 393,786 person-months (27 and 61 per 100,000 person-months, respectively). In well-adjusted models, 10 μg/m3 increase in PM2.5 corresponded to a 3% increase in the incidence rate of CVDs [0.95 CI = 1.016, 1.036] (in case of p = 0.000001 per 10 μg/m3 increase in PM2.5, the Hazard Ratio (HR) for AMI and Ischemic Heart Disease (IHD) was 1.031 [0.95 CI = 1.005, 1.057] and 1.028 [0.95 CI = 1.017, 1.039]), respectively. No consistent association was observed between PM2.5 concentration and fatal CVD (fatal AMI, fatal stroke, SCD (Sudden Cardiac Death)) and all-cause mortality.ConclusionsResults from analyses suggest that the effect of PM2.5 on cardiovascular disease occurrence was stronger in the case of older people, smokers, and those with high blood pressure and diabetes. The final results revealed that long-term exposure to ambient PM2.5 with high concentrations positively correlated with IHD incidence and its major subtypes, except for mortality. The outcome accentuates the need for better air quality in many countries.

Assessing the determinants of completing OAT induction and long-term retention: A population-based study in British Columbia, Canada

BackgroundPharmacological treatments for opioid use disorder are essential, life-saving medications, yet successful induction of them and long-term retention on them is limited in many settings. Induction into opioid agonist treatment (OAT) features the highest risk of mortality throughout the treatment course, and greatest risk of discontinuation. We aimed to identify determinants of completing OAT induction and, among those completing induction, time to OAT discontinuation in British Columbia (BC), Canada. MethodsWe conducted a retrospective study using linked population-level health administrative databases to capture all individuals in BC receiving at least one OAT dispensation from January 1, 2008, to September 30, 2018. We constructed covariates capturing client demographics, clinical history, and characteristics of the treatment episode and the primary prescribing physician. We estimated a two-part model to identify determinants of the probability of completing induction using a generalized linear mixed model with logit link and the time to OAT discontinuation among those completing induction using a Cox proportional hazards frailty model. ResultsWe observed 220,474 OAT episodes (73.9% initiated with methadone, 24.7% with buprenorphine, and 1.4% with slow-release oral morphine) among 45,608 individuals over the study period. Less than 60% of all OAT episodes completed induction (59.0% for methadone episodes, 56.7% for buprenorphine/naloxone, 41.0% for slow-release oral morphine) and half of all episodes that completed induction reached the minimum effective dosage (51.0% for methadone episodes [60 mg/day], 48.2% for buprenorphine/naloxone [12 mg/day], 59.4% for slow-release oral morphine [240 mg/day]). In multiple regression analysis, the adjusted odds of completing induction with buprenorphine improved over time, exceeding that of methadone in 2018: 1.46 (1.40, 1.51). For those who completed induction, buprenorphine use was associated with shorter times to discontinuation throughout the study period, but the estimated rate of discontinuation decreased over time (adjusted hazard ratio, vs. methadone in 2008: 2.50 (2.35, 2.66); in 2018: 1.79 (1.74, 1.85)). ConclusionWe found low rates of completing OAT induction and, for those who did complete it, low rates of reaching the minimum effective dose.

PENALIZED LOG-LIKELIHOOD ESTIMATION FOR COX-FRAILTY MODEL WITH NONINFORMATIVE BIVARIATE CURRENT STATUS DATA

A Penalized Maximum Likelihood Estimation (PMLE) procedure is proposed for Cox proportional hazards frailty model with noninformative bivariate current status data. An integrated splines (I-splines) was used to approximate the two unknown baseline cumulative hazard functions of the failure times. The one-parameter gamma frailty distribution was used to model the correlation between the two failure times. An easy to implement computational algorithm is proposed to estimate the regression and splines parameters. Bayesian technique as proposed by Wahba (1983) was employed for the variance estimation. The statistical properties of the estimated parameters were studied through extensive simulation and it was observed that the PMLEs were consistent, asymptotically normal and efcient. In addition, the estimators were robust to the choice of knots, censoring rates and type of frailty distribution used. The proposed methodology is further demonstrated through the analysis of the tumorigenicity experiment data by Lindsey and Ryan (1994).

Nurse staffing practices and adverse events in acute care hospitals: The research protocol of a multisite patient-level longitudinal study.

AimsWe describe an innovative research protocol to: (a) examine patient‐level longitudinal associations between nurse staffing practices and the risk of adverse events in acute care hospitals and; (b) determine possible thresholds for safe nurse staffing.DesignA dynamic cohort of adult medical, surgical and intensive care unit patients admitted to 16 hospitals in Quebec (Canada) between January 2015–December 2019.MethodsPatients in the cohort will be followed from admission until 30‐day postdischarge to assess exposure to selected nurse staffing practices in relation to the subsequent occurrence of adverse events. Five staffing practices will be measured for each shift of an hospitalization episode, using electronic payroll data, with the following time‐varying indicators: (a) nursing worked hours per patient; (b) skill mix; (c) overtime use; (d) education mix and; and (e) experience. Four high‐impact adverse events, presumably associated with nurse staffing practices, will be measured from electronic health record data retrieved at the participating sites: (a) failure‐to‐rescue; (b) in‐hospital falls; (c) hospital‐acquired pneumonia and; and (d) venous thromboembolism. To examine the associations between the selected nurse staffing exposures and the risk of each adverse event, separate multivariable Cox proportional hazards frailty regression models will be fitted, while adjusting for patient, nursing unit and hospital characteristics, and for clustering. To assess for possible staffing thresholds, flexible non‐linear spline functions will be fitted. Funding for the study began in October 2019 and research ethics/institutional approval was granted in February 2020.DiscussionTo our knowledge, this study is the first multisite patient‐level longitudinal investigation of the associations between common nurse staffing practices and the risk of adverse events. It is hoped that our results will assist hospital managers in making the most effective use of the scarce nursing resources and in identifying staffing practices that minimize the occurrence of adverse events.

Cox regression of clustered event times with covariates missing not at random

AbstractMotivated by a recent tuberculosis (TB) study, this paper is concerned with covariates missing not at random (MNAR) and models the potential intracluster correlation by a frailty. We consider the regression analysis of right‐censored event times from clustered subjects under a Cox proportional hazards frailty model and present the semiparametric maximum likelihood estimator (SPMLE) of the model parameters. An easy‐to‐implement pseudo‐SPMLE is then proposed to accommodate more realistic situations using readily available supplementary information on the missing covariates. Algorithms are provided to compute the estimators and their consistent variance estimators. We demonstrate that both the SPMLE and the pseudo‐SPMLE are consistent and asymptotically normal by the arguments based on the theory of modern empirical processes. The proposed approach is examined numerically via simulation and illustrated with an analysis of the motivating TB study data.

Increasing Bovine leukemia virus (BLV) proviral load is a risk factor for progression of Enzootic bovine leucosis: A prospective study in Japan

Bovine leukemia virus (BLV) belongs to the genus Deltaretrovirus in the family Retroviridae, and is etiologically associated with Enzootic Bovine Leukosis (EBL). The majority of BLV-infected cattle remain asymptomatic throughout their productive lives, whereas approximately 5%–10% of infected cattle develop EBL. Data accumulated recently indicate that whole blood proviral load (PVL) levels of BLV-infected cattle could be an indicator of disease progression in the field. However, a few cross-sectional studies have been reported. Here, we prospectively evaluated 866 cattle enrolled between August 2015 and December 2015, and followed until November 2018, identifying 407 asymptomatic BLV-infected cattle. There were no significant differences in the median PVL level among the category of herd seroprevalence (p = 0.57), herd size (p = 0.19), nor among the category of past EBL history in the herd (p = 0.31). During the study period, 12 cattle developed EBL. The PVL levels of EBL cattle at the time of enrollment were significantly higher than that of cattle that did not progress to EBL (median, 90,695 vs 39,139 copies/105 cells, p = 0.0005). Moreover, the adjusted hazard ratio for the increase in PVL was 2.61 (95% CI, 1.51–4.53) as estimated by the Cox proportional hazards frailty model. These results indicate that a high PVL level is a significant risk factor for progression to EBL, and could potentially be used as an indicator for the identification of cattle to be culled from the herd long before the progression of EBL. This knowledge might be useful to design a strategy for decreasing economic loss from EBL or even eradicating it from herds.

Depression and long-term prognostic outcomes following peripheral endovascular interventions in the VA Healthcare System.

The association between depression and peripheral artery disease (PAD) outcomes remains widely understudied. In patients with PAD undergoing a peripheral vascular intervention (PVI) who have a recent diagnosis of depression, it is unknown what their long-term outcomes are and what factors may mediate an adverse risk. We therefore studied 797 consecutive patients undergoing PVI across 33 Veterans Affairs (VA) centers. Depression and outcomes were documented from patients' medical records. Outcomes included: (1) all-cause death; (2) non-fatal cardiovascular events (myocardial infarction, stroke); and (3) PAD-related events (including repeat PVI or amputation). Cox proportional hazards frailty models were constructed, adjusting for age. Additional covariates were selected if they resulted in at least 5% change in the age-adjusted hazard ratio (HR) for depression on outcomes. Overall, 265 (33%) patients had a diagnosis of depression. After a median follow-up of 955 days (range 1-6.25 years), 52 (6.5%) patients died, 30 (3.8%) experienced non-fatal cardiovascular events, and 176 (22.1%) had PAD-related events. Compared to patients without depression, depressed patients had higher rates of non-fatal cardiovascular events (6.4% vs 2.4%, p-value 0.0055). No differences for the other outcomes were noted. Higher risk for non-fatal cardiovascular events persisted after adjustment for age (HR 1.6, 95% CI 1.05-2.47). The only additional covariate that met our selection criteria was hypertension. After adjusting for hypertension, the association between depression and non-fatal cardiovascular outcomes attenuated (HR 1.53, 95% CI 0.99-2.35). In conclusion, a diagnosis of depression in veterans undergoing PVI was associated with increased risk of non-fatal cardiovascular events, mediated by age and hypertension.

Factors Influencing Time to Adoption for Dogs in a Provincial Shelter System in Canada

ABSTRACTMillions of companion animals are relinquished to shelters each year. For each dog entering, their characteristics and the characteristics of the shelter holding him/her influence their time to adoption. Using a Cox proportional hazards frailty model, these issues were explored using data from 31 shelters within the British Columbia Society for the Prevention of Cruelty to Animals shelter system. Results indicated that surrender reason, age, original source, coat color, breed, human population density of the shelter location, and year the nonhuman animal entered the shelter significantly influenced time to adoption. This study identified characteristics of dogs that make them less likely to be adopted quickly. Given limited resources, these results may help inform shelters on how to best allocate resources, particularly in interventions to improve adoption rates in shelters.

Assessing the effectiveness of adjuvant chemoradiotherapy after cholecystectomy in patients with gallbladder cancer.

455 Background: The study was conducted to compare the overall survival for patients receiving concurrent chemoradiotherapy (CCRT) versus radiotherapy (RT) or chemotherapy (CT) alone after cholecystectomy in patients with gallbladder cancer. Methods: Patients with gallbladder cancer who had surgical resection from 2004 to 2015 were identified in the National Cancer Database. The proportional hazards assumption for each predictor was assessed using Martingale residuals. Significance was then determined using univariable and multivariable Cox proportional hazards frailty models that allow for clustering of patients within their treatment facility type. Results: A total of 7,258 gallbladder cancer patients who had undergone cholecystectomy met eligibility criteria: 1,509 (20.8%) received CCRT, 283 (3.9%) received RT alone, 1,368 (18.9%) received CT alone, and 4,098 (56.5%) received no adjuvant therapy. The median survival for this patient sample was 29.11 months with median follow-up of 59.10 months. On multivariable analysis, the hazard of death at any given time for patients who received adjuvant CCRT following surgery was 20% (HR = 0.80, 95 CI: 0.73-0.87) lower than those who only underwent surgery alone (p &lt; .0001). By contrast, the hazard of death at any given time for patients who received CT following surgery was 33% (HR = 1.33, 95 CI: 1.22-1.44) higher than those who only underwent surgery (p &lt;.0001). Conclusions: CCRT is associated with improved OS compared with CT or RT alone after cholecystectomy in patients with gallbladder cancer, suggesting that adjuvant CCRT should be used in this population although prospective data is needed to validate these findings.

Association of Citizenship Status With Kidney Transplantation in Medicaid Patients

Although individuals classified as nonresident aliens, including undocumented immigrants, are entitled to receive emergency dialysis in the United States regardless of their ability to pay, most states do not provide them with subsidized care for maintenance dialysis or kidney transplantation. We explored whether nonresident aliens have similar outcomes to US citizens after receiving kidney transplants covered by Medicaid, a joint federal and state health insurance program. Retrospective observational cohort study. All adult Medicaid patients in the US Renal Data System who received their first kidney transplant from 1990 to2011. Citizenship status, categorized as UScitizen, nonresident alien, or permanent resident. All-cause transplant loss. HRs and 95% CIs estimated by applying Cox proportional hazards frailty models with transplantation center as a random effect. Of 10,495 patients, 8,660 (82%) were US citizens, 1,489 (14%) were permanent residents, and 346 (3%) were nonresident aliens, whom we assumed were undocumented immigrants. Nonresident aliens were younger, healthier, receiving dialysis longer, and more likely to have had a living donor. 71% underwent transplantation in California, and 61% underwent transplantation after 2005. Nonresident aliens had a lower unadjusted risk for transplant loss compared with US citizens (HR, 0.48; 95% CI, 0.35-0.65). Results were attenuated but still significant when adjusted for demographics, comorbid conditions, dialysis, and transplant-related factors (HR, 0.67; 95% CI, 0.46-0.94). Citizenship status was self-reported, possible residual confounding. Our study suggests that the select group of insured nonresident aliens who undergo transplantation with Medicaid do just as well as US citizens with Medicaid. Policymakers should consider expanding coverage for kidney transplantation in nonresident aliens, including undocumented immigrants, given the associated high-quality outcomes in these patients.

Liver Transplantation for Hepatocellular Carcinoma in Young Adults: A United Network for Organ Sharing Study.

Orthotopic liver transplantation (OLT) is curative for hepatocellular carcinoma (HCC). HCC is typically a disease of older adults (OAs); therefore, characteristics and outcomes of OLT for young adults (YAs) (ages 18-40) are not described. The objective of this study was to assess the characteristics and outcomes of YAs with HCC receiving OLT and compare these to OAs (ages >40 years). YAs with HCC who had OLT from the United Network for Organ Sharing (UNOS) database were included in this study. As a comparison group, OAs with HCC were matched 4:1 to the YA group. Descriptive statistics of demographics, comorbidities, and outcomes were generated. Kaplan-Meier product limit estimates were used to assess patient and graft survival. Conditional logistic regression and Cox proportional hazards frailty models were used to compare the groups. A total of 464 YAs received OLT for HCC. The most common underlying liver diseases were hepatitis C virus (21.3%), hepatitis B virus (HBV, 15.5%), and autoimmune/cholestatic disease (12.3%). An increased number of YAs received OLT for HCC after implementation of model for end-stage liver disease scoring. One thousand two hundred eighty OAs served as the comparison group. Post-transplant 5-year survival was 73.1% in YAs with a retransplantation rate of 7.8%. In OAs, survival and retransplantation rates were lower (68.6% p = 0.093; 4.3% p = 0.001). Four hundred sixty-four YAs with HCC received OLT in the UNOS database. Compared to the older population, survival and retransplantation rates were higher. HBV, which is vaccine preventable, is a frequent contributor to HCC in YAs.

Effect of Catheter Dwell Time on Risk of Central Line-Associated Bloodstream Infection in Infants.

Central venous catheters in the NICU are associated with significant morbidity and mortality because of the risk of central line-associated bloodstream infections (CLABSIs). The purpose of this study was to determine the effect of catheter dwell time on risk of CLABSI. Retrospective cohort study of 13,327 infants with 15,567 catheters (93% peripherally inserted central catheters [PICCs], 7% tunneled catheters) and 256,088 catheter days cared for in 141 NICUs. CLABSI was defined using National Health Surveillance Network criteria. We defined dwell time as the number of days from line insertion until either line removal or day of CLABSI. We generated survival curves for each week of dwell time and estimated hazard ratios for CLABSI at each week by using a Cox proportional hazards frailty model. We controlled for postmenstrual age and year, included facility as a random effect, and generated separate models by line type. Median postmenstrual age was 29 weeks (interquartile range 26-33). The overall incidence of CLABSI was 0.93 per 1000 catheter days. Increased dwell time was not associated with increased risk of CLABSI for PICCs. For tunneled catheters, infection incidence was significantly higher in weeks 7 and 9 compared with week 1. Clinicians should not routinely replace uninfected PICCs for fear of infection but should consider removing tunneled catheters before week 7 if no longer needed. Additional studies are needed to determine what daily maintenance practices may be associated with decreased risk of infection, especially for tunneled catheters.

Characterizing retention in HAART as a recurrent event process: insights into 'cascade churn'.

The benefits of HAART rely on continuous lifelong treatment retention. We used linked population-level health administrative data to characterize durations of HAART retention and nonretention. This is a retrospective cohort study. We considered individuals initiating HAART in British Columbia (1996-2012). An HAART episode was considered discontinued if individuals had a gap of at least 30 days between days in which medication was prescribed. We considered durations of HAART retention and nonretention separately, and used Cox proportional hazards frailty models to identify demographic and treatment-related factors associated with durations of HAART retention and nonretention. Six thousand one hundred fifty-two individuals were included in the analysis; 81.2% were male, 40.6% were people who inject drugs, and 42.8% initiated treatment with CD4 cell count less than 200 cells/μl. Overall, 29% were continuously retained on HAART through the end of follow-up. HAART episodes were a median 6.8 months (25th, 75th percentile: 2.3, 19.5), whereas off-HAART episodes lasted a median 1.9 months (1.2, 4.5). In Cox proportional hazards frailty models, durations of HAART retention improved over time. Successive treatment episodes tended to decrease in duration among those with multiple attempts, whereas off-HAART episodes remained relatively stable. Younger age, earlier stages of disease progression, and injection drug use were all associated with shorter durations of HAART retention and longer off-HAART durations. Metrics to monitor HAART retention, dropout, and reentry should be prioritized for HIV surveillance. Clinical strategies and public health policies are urgently needed to improve HAART retention, particularly among those at earlier stages of disease progression, the young, and people who inject drugs.