The Extended Log-Logistic Distribution: Properties, Inference, and Applications in Medicine and Geology

In this paper, a new flexible extension of the log-logistic model called the extended odd Weibull log-logistic (EOWLL) distribution is studied. The EOWLL density can be expressed as a mixture of Dagum densities. The EOWLL distribution provides decreasing, increasing, upside-down bathtub, and reversed-J-shaped hazard rates, and right-skewed, symmetrical, and left-skewed densities. Its mathematical properties are derived. The EOWLL parameters are estimated via eight classical methods of estimation. Additionally, extensive simulations are obtained to explore the performance of the proposed methods for small and large samples. Two real-life sets of data from medicine and geology are analyzed, showing the flexibility of the EOWLL distribution as compared to other log-logistic extensions. The results show that the EOWLL distribution is more appropriate as compared to the Kumaraswamy transmuted log-logistic, alpha-power transformed log-logistic, and additive Weibull log-logistic distributions, among others

A New Generalized Family of Distributions for Lifetime Data

A new class of continuous distributions called the generalized Burr X-G family is introduced. Some special models of the new family are provided. Some of its mathematical properties including explicit expressions for the quantile and generating functions, ordinary and incomplete moments, order statistics and Rényi entropy are derived. The maximum likelihood is used for estimating the model parameters. The flexibility of the generated family is illustrated by means of two applications to real data sets

Inference on Constant Stress Accelerated Life Tests Under Exponentiated Exponential Distribution

Accelerated life tests have become increasingly important because of highercustomer expectations for better reliability, more complicated products withmore components, rapidly changing technologies advances, and the clear needfor rapid product development. Hence, accelerated life tests have been widelyused in manufacturing industries, particularly to obtain timely informationon the reliability. Maximum likelihood estimation is the starting point whenit comes to estimating the parameters of the model. In this paper, besides themethod of maximum likelihood, nine other frequentist estimation methodsare proposed to obtain the estimates of the exponentiated exponential distribution parameters under constant stress accelerated life testing. We considertwo parametric bootstrap confedence intervals based on different methods ofestimation. Furthermore, we use the different estimates to predict the shapeparameter and the reliability function of the distribution under the usualconditions. The performance of the ten proposed estimation methods isevaluated via an extensive simulation study. As an empirical illustration,the proposed estimation methods are applied to an accelerated life test dataset

Peguero Electrocardiographic Left Ventricular Hypertrophy Criteria and Risk of Mortality

Background: Peguero electrocardiographic left ventricular hypertrophy (ECG-LVH) criteria are newly developed criteria that have shown better diagnostic performance than the traditional Cornell-voltage and Sokolow-Lyon criteria. However, prediction of poor outcomes rather than detection of increased left ventricular mass is becoming the primary use for ECG-LVH criteria which requires investigating any new ECG-LVH criteria in terms of prediction.Aims: To examine the prognostic significance of the newly developed Peguero ECG-LVH criteria.Methods: We compared the prognostic significance of Peguero ECG-LVH with Cornell-voltage and Sokolow-Lyon ECG-LVH criteria in 7,825 participants (age 59.8 ± 13.4 years; 52.7% women) from the third National Health and Nutrition Examination Survey who were free of major intraventricular conduction defects. ECG-LVH criteria were derived from digital ECG tracings processed at a central core laboratory.Results: At baseline, ECG-LVH was detected in 11.8% by Peguero; in 4.3% by Cornell voltage and in 6.4% by Sokolow-Lyon. During a median follow up of 13.8 years, 2,796 all-cause mortality events occurred. In multivariable models adjusted for demographics and cardiovascular risk factors, presence of Peguero ECG-LVH was associated with increased risk of all-cause mortality [HR (95% CI): 1.29 (1.16, 1.44)]. This association was not significantly different from the associations of Cornell voltage-LVH or Sokolow-Lyon LVH with all-cause mortality [HR (95%CI): 1.32 (1.12, 1.55) and 1.24 (1.07, 1.43), respectively; p-values for comparisons of these HRs with the HR of Peguero ECG-LVH 0.817 and 0.667, respectively]. Similar patterns of associations were observed with cardiovascular, ischemic heart disease and heart failure mortalities.Conclusion: Peguero ECG-LVH is predictive of increased risk of death similar to the traditional ECG-LVH criteria

Diagnostic yield of colonoscopy in patients with symptoms compatible with Rome IV functional bowel disorders

Background There is little data on the diagnostic yield of colonoscopy in patients with symptoms compatible with functional bowel disorders (FBDs). Previous studies have only focused on diagnostic outcomes of colonoscopy in those with suspected irritable bowel syndrome using historic Rome I-III criteria, whilst having partially assessed for alarm features and shown markedly conflicting results. There is also no colonoscopy outcome data for other FBDs, such as functional constipation or functional diarrhea. Aims Using the contemporaneous Rome IV criteria we determined the diagnostic yield of colonoscopy in patients with symptoms compatible with a FBD, stratified diligently according to the presence or absence of alarm features Methods Basic demographics, alarm features, and bowel symptoms using the Rome IV diagnostic questionnaire were collected prospectively from adults attending out-patient colonoscopy in 2019. Endoscopists were blinded to the questionnaire data. Organic disease was defined as the presence of inflammatory bowel disease, colorectal cancer, or microscopic colitis. Results 646 patients fulfilled symptom-based criteria for the following Rome IV FBDs: IBS (56%), functional diarrhea (27%) and functional constipation (17%). Almost all had alarm features (98%). The combined prevalence of organic disease was 12%, being lowest for functional constipation and IBS-constipation (∼6% each), followed by IBS-mixed (∼9%), and highest amongst functional diarrhea and IBS-diarrhea (∼17% each); p=0.005. The increased prevalence of organic disease in diarrheal versus constipation disorders was accounted for by microscopic colitis (5.7% vs. 0%, p<0.001) but not inflammatory bowel disease (7.2% vs. 4.0%, p=0.2) or colorectal cancer (4.2% vs. 2.3%, p=0.2). However, one-in-four chronic diarrhea patients - conceivably at risk for microscopic colitis - did not have colonic biopsies taken. Finally, only 11 of 646 (2%) patients were without alarm features, in whom colonoscopy was normal. Conclusion Most patients with symptoms of FBDs who are referred for colonoscopy have alarm features. The presence of organic disease is significantly higher in diarrheal versus constipation disorders, with microscopic colitis largely accounting for the difference whilst also being a missed diagnostic opportunity. In those patients without alarm features, the diagnostic yield of colonoscopy was nil

Increased psychological distress and somatization in patients with irritable bowel syndrome compared with functional diarrhea or functional constipation, based on Rome IV criteria

Background The Rome IV criteria for disorders of gut‐brain interaction define irritable bowel syndrome (IBS) as a functional bowel disorder associated with frequent abdominal pain of at least 1 day per week. In contrast, functional diarrhea (FD) and functional constipation (FC) are relatively painless. We compared differences in mood and somatization between Rome IV IBS and FC/FD. Methods A total of 567 patients with Rome IV defined IBS or FD/FC completed a baseline questionnaire on demographics, abdominal pain frequency, mood (hospital anxiety and depression scale, HADS), and somatization (patient health questionnaire, PHQ‐12). The primary analysis compared differences in mood and somatization between IBS and FC/FD, and the relative influence of abdominal pain frequency on these extra‐intestinal symptoms. The secondary analysis evaluated differences across individual IBS subtypes, and also between FC and FD. Key Results Patients with IBS—in comparison to those with FC/FD—had significantly higher mean PHQ‐12 somatization scores (9.1 vs. 5.4), more somatic symptoms (6.0 vs. 4.3), abnormally high somatization levels (16% vs. 3%), higher HADS score (15.0 vs. 11.7), and clinically abnormal levels of anxiety (38% vs. 20%) and depression (17% vs. 10%). Increasing abdominal pain frequency correlated positively with PHQ‐12, number of somatic symptoms, and HADS; p < 0.001. No differences in mood and somatization scores were seen between individual IBS subtypes, and nor between FC and FD. Conclusion & Inferences Based on the Rome IV criteria, IBS is associated with increased levels of psychological distress and somatization compared with FD or FC. Patients reporting frequent abdominal pain should be comprehensively screened for psychosomatic disorders, with psychological therapies considered early in the disease course

Etiological spectrum and treatment outcome of Obstructive jaundice at a University teaching Hospital in northwestern Tanzania: A diagnostic and therapeutic challenges

Obstructive jaundice poses diagnostic and therapeutic challenges to general surgeons practicing in resource-limited countries. This study was undertaken to highlight the etiological spectrum, treatment outcome of obstructive jaundice in our setting and to identify prognostic factors for morbidity and mortality. This was a descriptive prospective study which was conducted at Bugando Medical Centre between July 2006 and June 2010. All patients with a clinical diagnosis of obstructive jaundice were, after informed consent for the study, consecutively enrolled into the study. Data were collected using a pre-tested structured questionnaire and analyzed using SPSS computer software version 11.5. A total of 116 patients were studied. Females outnumbered males by a ratio of 1.3:1. Patients with malignant obstructive jaundice were older than those of benign type. Ca head of pancreas was the commonest malignant cause of jaundice where as choledocholithiasis was the commonest benign cause. Abdominal ultrasound was the only diagnostic imaging done in all patients and revealed dilated intra and extra-hepatic ducts, common bile stones and abdominal masses in 56.2%, 78.9%, 58.1% and 72.4% of the cases respectively. A total of 110 (94.8%) patients underwent surgical treatment and the remaining 6 (5.2%) patients were unfit for surgery. The complication rate was 22.4% mainly surgical site infections. The mean hospital stay and mortality rate were 14.54 days and 15.5% respectively. A low haematocrit and presence of postoperative sepsis were the main predictors of the hospital stay (P < 0.001), whereas age > 60 years, prolonged duration of jaundice, malignant causes and presence of postoperative complications mainly sepsis significantly predicted mortality (P < 0.001). Obstructive jaundice in our setting is more prevalent in females and the cause is mostly malignant. The result of this study suggests that early diagnosis and treatment plays an important role in the prognosis of patients with obstructive jaundice

The role of grass volatiles on oviposition site selection by Anopheles arabiensis and Anopheles coluzzii

Background: The reproductive success and population dynamics, of Anopheles malaria mosquitoes is strongly influenced by the oviposition site selection of gravid females. Mosquitoes select oviposition sites at different spatial scales, starting with selecting a habitat in which to search. This study utilizes the association of larval abundance in the field with natural breeding habitats, dominated by various types of wild grasses, as a proxy for oviposition site selection by gravid mosquitoes. Moreover, the role of olfactory cues emanating from these habitats in the attraction and oviposition stimulation of females was analysed. Methods: The density of Anopheles larvae in breeding sites associated with Echinochloa pyramidalis, Echinochloa stagnina, Typha latifolia and Cyperus papyrus, was sampled and the larvae identified to species level. Headspace volatile extracts of the grasses were collected and used to assess behavioural attraction and oviposition stimulation of gravid Anopheles arabiensis and Anopheles coluzzii mosquitoes in wind tunnel and two-choice oviposition assays, respectively. The ability of the mosquitoes to differentiate among the grass volatile extracts was tested in multi-choice tent assays. Results: Anopheles arabiensis larvae were the most abundant species found in the various grass-associated habitats. The larval densities described a hierarchical distribution, with Poaceae (Echinochloa pyramidalis and Echinochloa stagnina)-associated habitat sites demonstrating higher densities than that of Typha-associated sites, and where larvae were absent from Cyperus-associated sites. This hierarchy was maintained by gravid An. arabiensis and An. coluzzii mosquitoes in attraction, oviposition and multi-choice assays to grass volatile extracts. Conclusions: The demonstrated hierarchical preference of gravid An. coluzzii and An. arabiensis for grass volatiles indicates that vegetation cues associated with larval habitats are instrumental in the oviposition site choice of the malaria mosquitoes. Identifying volatile cues from grasses that modulate gravid malaria mosquito behaviours has distinct potential for the development of tools to be used in future monitoring and control methods

Overexpression of CD44 accompanies acquired tamoxifen resistance in MCF7 cells and augments their sensitivity to the stromal factors, heregulin and hyaluronan

Background: Acquired resistance to endocrine therapy in breast cancer is a significant problem with relapse being associated with local and/or regional recurrence and frequent distant metastases. Breast cancer cell models reveal that endocrine resistance is accompanied by a gain in aggressive behaviour driven in part through altered growth factor receptor signalling, particularly involving erbB family receptors. Recently we identified that CD44, a transmembrane cell adhesion receptor known to interact with growth factor receptors, is upregulated in tamoxifen-resistant (TamR) MCF7 breast cancer cells. The purpose of this study was to explore the consequences of CD44 upregulation in an MCF7 cell model of acquired tamoxifen resistance, specifically with respect to the hypothesis that CD44 may influence erbB activity to promote an adverse phenotype. Methods: CD44 expression in MCF7 and TamR cells was assessed by RT-PCR, Western blotting and immunocytochemistry. Immunofluorescence and immunoprecipitation studies revealed CD44-erbB associations. TamR cells (± siRNA-mediated CD44 suppression) or MCF7 cells (± transfection with the CD44 gene) were treated with the CD44 ligand, hyaluronon (HA), or heregulin and their in vitro growth (MTT), migration (Boyden chamber and wound healing) and invasion (Matrigel transwell migration) determined. erbB signalling was assessed using Western blotting. The effect of HA on erbB family dimerisation in TamR cells was determined by immunoprecipitation in the presence or absence of CD44 siRNA. Results: TamR cells overexpressed CD44 where it was seen to associate with erbB2 at the cell surface. siRNA-mediated suppression of CD44 in TamR cells significantly attenuated their response to heregulin, inhibiting heregulin-induced cell migration and invasion. Furthermore, TamR cells exhibited enhanced sensitivity to HA, with HA treatment resulting in modulation of erbB dimerisation, ligand-independent activation of erbB2 and EGFR and induction of cell migration. Overexpression of CD44 in MCF7 cells, which lack endogenous CD44, generated an HA-sensitive phenotype, with HA-stimulation promoting erbB/EGFR activation and migration. Conclusions: These data suggest an important role for CD44 in the context of tamoxifen-resistance where it may augment cellular response to erbB ligands and HA, factors that are reported to be present within the tumour microenvironment in vivo. Thus CD44 may present an important determinant of breast cancer progression in the setting of endocrine resistance