Distance from main arteries influences microstructural and functional brain tissue characteristics.

Given the substantial dependence of neurons on continuous supply of energy, the distribution of major cerebral arteries opens a question whether the distance from the main supply arteries constitutes a modulating factor for the microstructural and functional properties of brain tissue. To tackle this question, multimodal MRI acquisitions of 102 healthy volunteers over the full adult age span were utilised. Relaxation along a fictitious field in the rotating frame of rank n = 4 (RAFF4), adiabatic T1ρ, T2ρ,  and intracellular volume fraction (fICVF) derived from diffusion-weighted imaging were implemented to quantify microstructural (cellularity, myelin density, iron concentration) tissue characteristics and degree centrality and fractional amplitude of low-frequency fluctuations to probe for functional metrics. Inverse correlation of arterial distance with robust homogeneity was detected for T1ρ, T2ρ and RAFF4 for cortical grey matter and white matter, showing substantial complex microstructural differences between brain tissue close and farther from main arterial trunks. Albeit with wider variability, functional metrics pointed to increased connectivity and neuronal activity in areas farther from main arteries. Surprisingly, multiple of these microstructural and functional distance-based gradients diminished with higher age, pointing to uniformization of brain tissue with ageing. All in all, this pilot study provides a novel insight on brain regionalisation based on artery distance, which merits further investigation to validate its biological underpinnings.

Elucidating vaccine efficacy using a correlate of protection, demographics, and logistic regression.

BACKGROUND: Vaccine efficacy (VE) assessed in a randomized controlled clinical trial can be affected by demographic, clinical, and other subject-specific characteristics evaluated as baseline covariates. Understanding the effect of covariates on efficacy is key to decisions by vaccine developers and public health authorities. METHODS: This work evaluates the impact of including correlate of protection (CoP) data in logistic regression on its performance in identifying statistically and clinically significant covariates in settings typical for a vaccine phase 3 trial. The proposed approach uses CoP data and covariate data as predictors of clinical outcome (diseased versus non-diseased) and is compared to logistic regression (without CoP data) to relate vaccination status and covariate data to clinical outcome. RESULTS: Clinical trial simulations, in which the true relationship between CoP data and clinical outcome probability is a sigmoid function, show that use of CoP data increases the positive predictive value for detection of a covariate effect. If the true relationship is characterized by a decreasing convex function, use of CoP data does not substantially change positive or negative predictive value. In either scenario, vaccine efficacy is estimated more precisely (i.e., confidence intervals are narrower) in covariate-defined subgroups if CoP data are used, implying that using CoP data increases the ability to determine clinical significance of baseline covariate effects on efficacy. CONCLUSIONS: This study proposes and evaluates a novel approach for assessing baseline demographic covariates potentially affecting VE. Results show that the proposed approach can sensitively and specifically identify potentially important covariates and provides a method for evaluating their likely clinical significance in terms of predicted impact on vaccine efficacy. It shows further that inclusion of CoP data can enable more precise VE estimation, thus enhancing study power and/or efficiency and providing even better information to support health policy and development decisions.

Utility of quantitative MRI metrics in brain ageing research.

The advent of new, advanced quantitative MRI metrics allows for in vivo evaluation of multiple biological processes highly relevant for ageing. The presented study combines several MRI parameters hypothesised to detect distinct biological characteristics as myelin density, cellularity, cellular membrane integrity and iron concentration. 116 healthy volunteers, continuously distributed over the whole adult age span, underwent a multi-modal MRI protocol acquisition. Scatterplots of individual MRI metrics revealed that certain MRI protocols offer much higher sensitivity to early adulthood changes while plateauing in higher age (e.g., global functional connectivity in cerebral cortex or orientation dispersion index in white matter), while other MRI metrics provided reverse ability-stable levels in young adulthood with sharp changes with rising age (e.g., T1ρ and T2ρ). Nonetheless, despite the previously published validations of specificity towards microstructural biology based on cytoarchitectonic maps in healthy population or alterations in certain pathologies, several metrics previously hypothesised to be selective to common measures failed to show similar scatterplot distributions, pointing to further confounding factors directly related to age. Furthermore, other metrics, previously shown to detect different biological characteristics, exhibited substantial intercorrelations, be it due to the nature of the MRI protocol itself or co-dependence of relevant biological microstructural processes. All in all, the presented study provides a unique basis for the design and choice of relevant MRI parameters depending on the age group of interest. Furthermore, it calls for caution in simplistic biological inferences in ageing based on one simple MRI metric, even though previously validated under other conditions. Complex multi-modal approaches combining several metrics to extract the shared subcomponent will be necessary to achieve the desired goal of histological MRI.

Randomized comparison of 9-month stent strut coverage of biolimus and everolimus drug-eluting stents assessed by optical coherence tomography in patients with ST-segment elevation myocardial infarction. Long-term (5-years) clinical follow-up (ROBUST trial).

BACKGROUND: The aim of the study was to compare healing (assessed by optical coherence tomography [OCT]) of biolimus A9 (BES) and everolimus drug-eluting stents (EES) at 9-month follow-up in patients with ST-segment elevation myocardial infarction (STEMI) treated by primary percutaneous coronary intervention (pPCI). Nine-month clinical and angiographic data were also compared in both groups as well as clinical data at 5 years of follow-up. METHODS: A total of 201 patients with STEMI were enrolled in the study and randomized either to pPCI with BES or EES implantation. All patients were scheduled for 9 months of angiographic and OCT follow-up. RESULTS: The rate of major adverse cardiovascular events (MACE) was comparable at 9 months in both groups (5% in BES vs. 6% in the EES group; p = 0.87). Angiographic data were also comparable between both groups. The main finding at 9-month OCT analysis was the greatly reduced extent of mean neointimal area at the cost of a higher proportion of uncovered struts in the BES group (1.3 mm² vs. 0.9 mm²; p = 0.0001 and 15.9% vs. 7.0%; p = 0.0001, respectively). At 5 years of clinical follow-up the rate of MACE was comparable between both groups (16.8% vs. 14.0%, p = 0.74). CONCLUSIONS: The study demonstrates a very low rate of MACE and good 9-month stent strut coverage of second-generation BES and EES in patients with STEMI. BES showed greatly reduced extent of mean neointimal hyperplasia area at the cost of a higher proportion of uncovered struts when compared to EES. The rate of MACE was low and comparable in both groups at 5 years.

Kidney Graft Failure and Patient Survival Modelling Based on Competing Risks Under Nonproportional Hazards.

We analyze data on Silesian patients after kidney transplantation under competing events scenarios where time to death and time to graft failure are considered as absorbing competing events. Our objectives are to use model diagnostics in identifying violations of proportionality assumption under the framework of subdistribution and cause-specific hazards. We use the Fine-Gray proportional hazards model for the subdistribution. Under the cause-specific hazards (CSH) scenario we use the Cox proportional hazards model and Gray's time-varying coefficients model and available model diagnostics. We show that violation of proportional subdistribution hazards assumption may be conveniently identified using residual diagnostics and properly accounted for by involving time interactions with appropriate model predictors. We also show that although the nonproportional effects on cumulative incidence do not necessarily translate in those on cause-specific hazards, they often take place simultaneously, and a violation of the proportionality assumption needs to be checked rigorously. Time-varying effects have a profound impact on clinical inference under competing risks. They do not translate directly between the frameworks of subdistribution and cause-specific hazards because the cumulative incidence is obtained via integrating the cause-specific hazard weighted by the overall survival function. Also, a different definition of the risk set is in place under the cumulative incidence and CSH framework, respectively. However, a simultaneous violation of the proportionality assumption under both frameworks is still possible. Clinical inference may change considerably when such a violation occurs. Nonproportional effects may be properly identified under each framework using available model diagnostics.

Tremor associated with similar structural networks in Parkinson's disease and essential tremor.

INTRODUCTION: Despite substantial clinical and pathophysiological differences, the characteristics of tremor in Parkinson's disease (PD) and essential tremor (ET) patients bear certain similarities. The presented study delineates tremor-related structural networks in these two disorders. METHODS: 42 non-advanced PD patients (18 tremor-dominant, 24 without substantial tremor), 17 ET, and 45 healthy controls underwent high-angular resolution diffusion-weighted imaging acquisition to reconstruct their structural motor connectomes as a proxy of the anatomical interconnections between motor network regions, implementing state-of-the-art globally optimised probabilistic tractography. RESULTS: When compared to healthy controls, ET patients exhibited higher structural connectivity in the cerebello-thalamo-cortical network. Interestingly, the comparison of tremor-dominant PD patients and PD patients without tremor yielded very similar results - higher structural connectivity in tremor-dominant PD sharing multiple nodes with the tremor network detected in ET, despite the generally lower structural connectivity between basal ganglia and frontal cortex in the whole PD group when compared to healthy controls. CONCLUSION: The higher structural connectivity of the cerebello-thalamo-cortical network seems to be the dominant tremor driver in both PD and ET. While it appears to be the only tremor-related network in ET, its combination with large scale hypoconnectivity in the frontal cortico-subcortical network in PD may explain different clinical features of tremor in these two disorders.

Analysis of Complications and Recipients' and Graft Survival in Patients 60 Years of Age and Older in the Long-Term Follow-up Period After Kidney Transplant: A Single-Center, Paired Kidney Analysis.

BACKGROUND: Long-term results of kidney transplant (KTx) in older patients may differ from younger recipients owing to increased cardiovascular comorbidities. The study aimed to analyze surgical and nonsurgical complications that develop in the long-term follow-up period after KTx, and factors that influence results of KTx in recipients aged 60 years and older (≥60) compared with younger recipients (<60). METHODS: One hundred seventy-five patients aged ≥60 years and 175 patients aged <60 years who received a kidney graft from the same deceased donor were enrolled in the study. In the long-term follow-up period (3 months to 5 years after KTx) the incidence of surgical and nonsurgical complications, as well as patient and kidney graft survival, were compared. Additionally, the influence of early complications on patients and kidney graft survival was assessed. RESULTS: There were no differences between recipients aged ≥60 years compared with recipients aged <60 years in occurrence of surgical complications (graft artery stenosis: 0.6% vs 2.3%; ureter stenosis: 3.4% vs 1.1%; lymphocele: 6.9% vs 3.4%) and nonsurgical complications (urinary tract infection: 19.4% vs 23.4%; pneumonia: 8.6% vs 8.6%; cytomegalovirus infection: 6.3% vs 8%; new-onset diabetes after transplant: 16.6% vs 17.1%; cancer incidence: 5.7% vs 4.6%; acute rejection episode: 13.1% vs 17.1%). Five-year recipient survival was lower in a group of patients aged ≥60 years (death, 15.4% vs 8%; death with functioning graft, 12% vs 5.1%). CONCLUSIONS: The incidence of surgical and nonsurgical complications, as well as kidney-graft survival, in recipients aged ≥60 years in a 5-year follow-up period is comparable to younger recipients aged <60 years.

Effect of early postnatal supplementation of newborns with probiotic strain E. coli O83:K24:H31 on allergy incidence, dendritic cells, and microbiota.

Introduction: Probiotic administration seems to be a rational approach to promote maturation of the neonatal immune system. Mutual interaction of the microbiota with the host immune system is critical for the setting of appropriate immune responses including a tolerogenic one and thevmaintenance of homeostasis. On the other hand, our knowledge on the modes of actions of probiotics is still scarce. Methods: In our study, probiotic strain Escherichia coli O83:K24:H31 (EcO83) was administered to neonates of allergic mothers (AMs; neonates with increased risk for allergy development) within 48 h after the delivery, and the impact of this early postnatal supplementation on allergy incidence and selected immune markers has been analyzed 10 years after the primary EcO83 administration. Results: We have observed decreased allergy incidence in 10-year-old children supplemented with EcO83 (13 of 52 children were allergic) in comparison with non-supplemented children of AMs (16 of 42 children were allergic). The early postnatal EcO83 supplementation appeared to limit the allergy in the high-risk group (children of AMs) compared to that in the low-risk group (children of healthy mothers). Dendritic cells (DCs) in the peripheral blood of EcO83-supplemented children do not differ significantly in cell surface presence of CD83. The immunomodulatory capacity of EcO83 on DCs was tested in vitro as well. Both directly isolated myeloid and in vitro monocyte-derived DCs from cord blood increased CD83 expression together with interleukin (IL)-10 secretion after EcO83 stimulation. The effect of early postnatal EcO83 supplementation on the microbiota composition of 10-year-old children was characterized by next-generation sequencing, and we have not observed significant changes in the microbiota composition of EcO83-supplemented and non-supplemented children at the age of 10 years. Conclusions: Early postnatal EcO83 supplementation appears to lower allergy incidence in children of AMs. It seems that the beneficial effect of EcO83 is mediated via modulation of DC functional capacities without impacting the microbiota composition. Larger-scale studies will be necessary to confirm these preliminary findings.

[Comparison of results of two serological methods for diagnosing leptospirosis - microagglutination test and ELISA]. / Porovnání výsledku dvou metod sérologických diagnostiky leptospirózy - mikroaglutinacniho testu a metody ELISA.

BACKGROUND: The aim of this study was to evaluate diagnostic sensitivity and specificity of the SERION ELISA classic IgM and SERION ELISA classic IgG kits and to confirm the results by the microagglutination test (MAT). MATERIAL AND METHODS: A total of 45 blood serum samples from 45 patients, 30 from males and 15 from females (mean age 44.24 ± 15.56 range 19-82 year), were included in our study. Blood serum samples were examined using the ELISA and MAT methods and diagnostic sensitivity and specificity of both methods were calculated. RESULTS: The MAT was shown to have 100 % diagnostic sensitivity and specificity. The ELISA kits for detecting IgM and IgG antibodies against pathogenic leptospires had diagnostic sensitivity of 100 % and diagnostic specificity of 88.6 % and 54.3 %, respectively. CONCLUSION: The above results suggest that the MAT with diagnostic sensitivity and specificity of 100 % remains the gold standard for detection of specific antibodies against pathogenic leptospires. The diagnostic sensitivity of both ELISA kits is high but due to their low diagnostic specificity, especially in the case of IgG antibodies, the kits are inappropriate for use in routine clinical practice.

[Incidence of leptospirosis in Pardubice and Hradec Králové region and a part of Vysocina region in the years 2002-2009]. / Výskyt leptospirózy v Kralovehradeckem a Pardubické m kraji a v cásti kraje Vysocina v letech 2002-2009.

BACKGROUND: The aim of this study was to evaluate the incidence of leptospirosis in Pardubice and Hradec Králové regions and a part of Vysocina region in 2002-2009. A group of patients was statistically analyzed and the incidence rates of leptospirosis in individual months and years were calculated. MATERIAL AND METHODS: A group of 4,813 patients with suspected leptospirosis from Pardubice and Hradec Králové regions and a part of Vysocina region were examinated in our centre in 2002-2009. A total of 5,366 biological samples were studied. From 4,625 blood samples, 3,958 were examinated with the serological microagglutination-lysis method and the remaining 667 with the PCR method. RESULTS: From 4,813 patients suspected to have leptospirosis, 89 were found to be leptospirosis-positive. Leptospirosis was diagnosed in 63 males (70.7 %) a 26 females (29.3 %); the mean age were 39.52 ± 17.67 years in males and 46.85 ± 18.34 years in females; the mean age men + women was 41.66 ± 18.13 years (range 3-78 years). Most positive male patients (n = 28) were in 26-45 age group; the findings were similar in females (n = 10). The highest number of leptospirosis cases was noted in 2005. Most frequently, infection caused by pathogenic leptospires was diagnosed in November. CONCLUSION: The incidence rates of leptospirosis in Pardubice and Hradec Králové regions and a part of Vysocina region in 2002-2009 (with the exception of 2008) exceeded the overall reported levels 0.4/100,000 population.

Early Complications After Kidney Transplantation in Patients Aged 60 Years and Older: A Single-Center, Paired-Kidney Analysis.

OBJECTIVES: As the population ages, the number of people suffering from cardiovascular diseases (CVD) and diabetes mellitus (DM) increases. The coexistence of these diseases can affect the results of kidney transplantation (KT) in the elderly. The aim of this study was to analyze surgical and nonsurgical complications in the early period after KT and to identify the factors that influence their development in recipients aged ≥ 60 years compared to younger recipients < 60 years. METHODS: One hundred seventy-five recipients of KT ≥ 60 years and 175 recipients of KT < 60 years who received kidneys from the same deceased donor were enrolled into the study. The incidence of surgical and nonsurgical complications, factors that may influence their development, early graft function, and patient and kidney-graft survival were analyzed during a 3-month follow-up period. Donor sources complied with the Helsinki Congress and Istanbul Declaration and organs were not procured from prisoners and individuals who were coerced or paid. RESULTS: Older recipients were characterized by higher body mass index ± SD (26.1 ± 3.5 vs 24.7 ± 3.4 kg/m2) and suffered more often from pretransplant DM (20.6% vs 11.4%) and CVD (34.3% vs 10.3%) and less frequently underwent previous KT (6.3% vs 20.0%). There were no differences between the ≥ 60 year old and < 60 year old groups in reference to surgical (20.6% vs 24%) and nonsurgical complications (28.6% vs 27.4%), early graft function, serum creatinine, and proteinuria. Recipients (95.4% vs 97.1%) and kidney-graft survival (93.1% vs 95.4%) were similar in both groups. The recipient factors that influenced the development of infectious complications were age, dialysis duration, pretransplant DM, and CVD. CONCLUSIONS: Despite higher co-incidence of CVD and DM, the risk of surgical and nonsurgical complications in elderly recipients is comparable to younger recipients in the early period after KT.

OCT guidance during stent implantation in primary PCI: A randomized multicenter study with nine months of optical coherence tomography follow-up.

AIMS: To assess the possible merits of optical coherence tomography (OCT) guidance in primary percutaneous coronary intervention (pPCI). METHODS AND RESULTS: 201 patients with ST-elevation myocardial infarction (STEMI) were enrolled in this study. Patients were randomized either to pPCI alone (angio-guided group, n=96) or to pPCI with OCT guidance (OCT-guided group, n=105) and also either to biolimus A9 or to everolimus-eluting stent implantation. All patients were scheduled for nine months of follow-up angiography and OCT study. OCT guidance led to post-pPCI optimization in 29% of cases (59% malapposition and 41% dissections). No complications were found related to the OCT study. OCT analysis at nine months showed significantly less in-segment area of stenosis (6% [-11, 19] versus 18% [3, 33]; p=0.0002) in favor of the OCT-guided group. The rate major adverse cardiovascular events were comparable at nine months in both groups (3% in the OCT group versus 2% in the angio-guided group; p=0.87). CONCLUSIONS: This study demonstrates the safety of OCT guidance during pPCI. The use of OCT optimized stent deployment in 1/3 of patients in this clinical scenario and significantly reduced in-segment area of stenosis at nine months of follow-up. Whether such improvements in OCT endpoints will have a positive impact on late clinical outcomes, they demand both a larger and longer-term follow-up study.

Active transforming growth factor-ß2 in the aqueous humor of posterior polymorphous corneal dystrophy patients.

PURPOSE: Posterior polymorphous corneal dystrophy (PPCD) is characterized by abnormal proliferation of corneal endothelial cells. It was shown that TGF-ß2 present in aqueous humor (AH) could help maintaining the corneal endothelium in a G1-phase-arrest state. We wanted to determine whether the levels of this protein are changed in AH of PPCD patients. METHODS: We determined the concentrations of active TGF-ß2 in the AH of 29 PPCD patients (42 samples) and 40 cadaver controls (44 samples) by ELISA. For data analysis the PPCD patients were divided based on either the molecular genetic cause of their disease as PPCD1 (37 samples), PPCD3 (1 sample) and PPCDx (not linked to a known PPCD loci, 4 samples) or on the presence (17 samples) or absence (25 samples) of secondary glaucoma or on whether they had undergone penetrating keratoplasty (PK, 32 samples) or repeated PK (rePK, 7 samples). RESULTS: The level of active TGF-ß2 in the AH of all PPCD patients (mean ± SD; 386.98 ± 114.88 pg/ml) in comparison to the control group (260.95 ± 112.43 pg/ml) was significantly higher (P = 0.0001). Compared to the control group, a significantly higher level of active TGF-ß2 was found in the PPCD1 (P = 0.0005) and PPCDx (P = 0.0022) groups. Among patients the levels of active TGF-ß2 were not significantly affected by gender, age, secondary glaucoma or by the progression of dystrophy when one or repeated PK were performed. CONCLUSION: The levels of active TGF-ß2 in the AH of PPCD patients are significantly higher than control values, and thus the increased levels of TGF-ß2 could be a consequence of the PPCD phenotype and can be considered as another feature characterizing this disease.

The decrease in C-reactive protein concentration after diet and physical activity induced weight reduction is associated with changes in plasma lipids, but not interleukin-6 or adiponectin.

Subclinical inflammation is a risk factor for cardiovascular disease. The mechanisms underlying increased levels of inflammatory markers and their changes in response to weight loss are not fully understood yet. It has been proposed that elevated concentrations of C-reactive protein (CRP) are mediated by cytokines produced in adipose tissue. We investigated the changes in circulating CRP after weight reduction, in relation to parameters relevant to the metabolic syndrome. Forty 25- to 35-year-old obese female volunteers participated in an intervention program of dietary education and supervised physical activity for a period of 9 weeks. Anthropological parameters and biochemical measurements (high-sensitivity CRP [hsCRP], plasma lipoproteins, interleukin 6 [IL-6], adiponectin) were analyzed before and after the intervention. Body mass index decreased by more than 7% from 31.5 +/- 4.1 to 29.1 +/- 3.9. Plasma free fatty acid (FFA) concentrations decreased by 30%, high-density lipoprotein cholesterol increased by 8%, and fasting insulin concentrations decreased by 15%. There were no significant changes in either low-density lipoprotein cholesterol or triacylglycerol concentrations. Subcutaneous and visceral adipose tissue mass decreased by 12% and 18%. High-sensitivity CRP concentrations decreased by 30%; however, mean plasma IL-6 and adiponectin concentrations remained unchanged. In linear regression analysis, the changes in plasma hsCRP concentrations were associated with baseline hsCRP concentration, change in triacylglycerols and FFA concentrations, and in waist circumference. The decrease in hsCRP concentration after weight reduction does not appear to be mediated by decreases in circulating IL-6 or adiponectin concentrations; however, change in hsCRP concentration is related to changes in waist circumference and lipid metabolism, reflected by plasma triacylglycerol and FFA levels.

Effectiveness of transoral laser microsurgery for precancerous lesions and early glottic cancer guided by analysis of voice quality.

BACKGROUND: The purpose of this study was to show our comparison of the quality of voice obtained after superficial transoral endoscopic cordectomies (types I, II, and III) according to the European Laryngological Society classification versus the more extended cordectomy (types IV and V) among patients with glottic precancerous lesions or early glottic cancer. METHODS: Sixty-two patients underwent vocal assessment after cordectomy (types I-V) for dysplasia, Tis, T1a, T1b, and T2 lesions. RESULTS: Cordectomy (types I-III) had good vocal outcomes. Cordectomy (types IV-V) showed less favorable outcomes, p < .005 in common parameters of voice range profile and symmetry in stroboscopy after cordectomy (types IV-V), with significant voice handicap index. Recurrences were found in 4 patients with T1b and T2 cancer. Two cases were managed by a higher type of cordectomy, and the other 2 by total laryngectomy. CONCLUSION: Effect of transoral laser microsurgery on quality of voice depends on the type of cordectomy and the site of the lesion.

Patient and physician perception of natural orifice transluminal endoscopic appendectomy.

AIM: To investigate perception of natural orifice transluminal endoscopic surgery (NOTES) as a potential technique for appendectomy. METHODS: One hundred patients undergoing endoscopy and 100 physicians were given a questionnaire describing in detail the techniques of NOTES and laparoscopic appendectomy. They were asked about the reasons for their preference, choice of orifice, and extent of complication risk they were willing to accept. RESULTS: Fifty patients (50%) and only 21 physicians (21%) preferred NOTES (P < 0.001). Patients had previously heard of NOTES less frequently (7% vs 73%, P < 0.001) and had undergone endoscopy more frequently (88% vs 36%, P < 0.001) than physicians. Absence of hernia was the most common reason for NOTES preference in physicians (80% vs 44%, P = 0.003), whereas reduced pain was the most common reason in patients (66% vs 52%). Physicians were more likely to refuse NOTES as a novel and unsure technique (P < 0.001) and having an increased risk of infection (P < 0.001). The preferred access site in both groups was colon followed by stomach, with vagina being rarely preferred. In multivariable modeling, those with high-school education [odds ratio (OR): 2.68, 95% confidence interval (CI): 1.23-5.83] and prior colonoscopy (OR: 2.10, 95% CI: 1.05-4.19) were more likely to prefer NOTES over laparoscopic appendectomy. There was a steep decline in NOTES preference with increased rate of procedural complications. Male patients were more likely to consent to their wives vaginal NOTES appendectomy than male physicians (P = 0.02). CONCLUSION: The preference of NOTES for appendectomy was greater in patients than physicians and was related to reduced pain and absence of hernia rather than lack of scarring.

Proportional odds logistic regression--effective means of dealing with limited uncertainty in dichotomizing clinical outcomes.

Classifying a measurable clinical outcome as a dichotomous variable often involves difficulty with borderline cases that could fairly be assigned either of the two binary class memberships. In such situations the indicated class membership is often highly subjective and subject to, for instance, a measurement error. In other situations the intermediate level of a three-level ordinal factor may sometimes be explicitly reserved for cases which could likely belong to either of the two binary classes. Such indefinite readings are often eliminated from the statistical analysis. In this article we review conceptual and methodological aspects of employing proportional odds logistic regression for a three level ordinal factor as a suitable alternative to ordinary logistic regression when dealing with limited uncertainty in classifying clinical outcome as a binary variable.

Estimation of the survival function for Gray's piecewise-constant time-varying coefficients model.

Gray's extension of Cox's proportional hazards (PH) model for right-censored survival data allows for a departure from the PH assumption via introduction of time-varying regression coefficients (TVC). For this model estimation of the conditional hazard rate relies on the inclusion of penalized splines. Cubic penalized splines tend to be unstable in the right tail of the distribution and thus quadratic, linear and piecewise-constant penalized splines may be a favourable choice. We derive a survival function estimator for one important member of the class of TVC models--a piecewise-constant time-varying coefficients (PC-TVC) model. Using the first-order Taylor series approximation we also derive an estimate for the variance of the log-transformed and log(-log)-transformed survival function, which in turn leads to estimated confidence limits on the corresponding scales of the survival function. Accuracy in estimating underlying survival times and survival quantiles is assessed for both Cox's and Gray's PC-TVC model using a simulation study featuring scenarios violating the PH assumption. Finally, an example of the estimated survival functions and the corresponding confidence limits derived from Cox's PH and Gray's PC-TVC model, respectively, is presented for a liver transplant data set.

Survival after liver transplantation in the United States: a disease-specific analysis of the UNOS database.

Our goal was to describe disease-specific survival and the clinical variables that predict survival in a large national cohort of adult liver transplant recipients. Data on 17,044 adult patients who received an initial orthotopic liver transplant between 1990 and 1996 with follow-up through 1999 was obtained from the United Network for Organ Sharing (UNOS). Disease-specific Kaplan-Meier survival plots and Cox Proportional Hazards models were estimated, and differences in the clinical characteristics of patients at the time of transplantation by disease were examined. Overall posttransplant survival currently exceeds 85% in the first year and is approaching 75% at 5 years. Unadjusted Kaplan-Meier survival is improved for recipients who are younger, female, and in better clinical condition. Survival is a function of disease and level of illness: cancer, fulminant liver failure, alcoholic liver disease, and the hepatitidies have the poorest prognosis, while primary billiary cirrohsis and sclerosing cholangitis have the best. Recipients who were outpatients before transplantation have longer survival than those transplanted from the hospital or intensive care unit. Although the model for end-stage liver disease (MELD) score was designed to predict pretransplant survival, patients with higher MELD scores have poorer posttransplant survival, but the MELD score is less predictive than the specific disease. Differences in disease-specific survival are partially explained by differences in disease severity at the time of transplantation. In conclusion, Disease-specific survival models indicate that there remains tremendous variability in survival as a function of underlying liver disease. However, a significant portion of the difference in survival between diseases arises from differences in clinical characteristics at the time of transplantation.