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Abstract
OBJECTIVE To examine changes in quality of life (QoL) after an eight-week period of robotic exoskeleton training in a homogeneous group of patients with chronic complete spinal cord injury (SCI). DESIGN Prospective single-group pre-post study. SETTING Rehabilitation center. PARTICIPANTS Patients with a chronic (>6 months) motor complete SCI (T1-L1). INTERVENTION Twenty-four training sessions with the ReWalk exoskeleton over an eight-week period. MAIN OUTCOME MEASURE QoL, assessed with the sum score of the Short Form-36 with Walk Wheel modification (SF-36ww). Secondary outcome measures were the eight SF-36ww subdomains, satisfaction with bladder and bowel management, lower extremity joint passive range of motion (pROM), and lower extremity spasticity. RESULTS Twenty-one participants completed the training. QoL significantly improved after the training period (average SF-36 sum score 621 ± 90) compared to baseline (571 ± 133) (t(20)=-2.5, P=.02). Improvements were seen on the SF-36ww subdomains for pain (P=.003), social functioning (P=.03), mental health (P=.02), and general health perception (P=.01). Satisfaction with bladder management (range 1-5) improved from median 3 at baseline to 4 after exoskeleton training (P=0.01). No changes in satisfaction with bowel management (P=.11), pROM (hip-extension (P=.49), knee-extension (P=.36), ankle dorsiflexion (P=.69)), or spasticity (P=.94) were found. CONCLUSION Even in patients with chronic motor complete SCI and a relatively high level of QoL at baseline, a short-term exoskeleton training improved their QoL, pain and satisfaction with bladder management; findings that warrant further controlled studies in this specific SCI population.
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Determination of quality of life-related health utilities for surgical complications in ovarian cancer. Gynecol Oncol 2024; 185:101-107. [PMID: 38377761 DOI: 10.1016/j.ygyno.2024.01.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 01/25/2024] [Accepted: 01/27/2024] [Indexed: 02/22/2024]
Abstract
OBJECTIVE To assess the health state utilities of ovarian cancer patients, clinicians, and non-cancer controls regarding surgical complications in ovarian cancer. METHODS Utilities for 14 surgical complications were assessed from patients with recently diagnosed or recurrent ovarian cancer, clinicians, and non-cancer controls using the visual analog scale (VAS) and time trade-off (TTO) methods. Health state utilities were converted to a 0-to-1 scale, where 0 represents the least favorable outcome and 1 represents the most favorable outcome. RESULTS Fifty patients, 50 clinicians, and 50 controls participated. Median VAS scores were lower than TTO scores across all groups (p < 0.01). Patients viewed 'bleeding requiring transfusion' most favorably (VAS utility 0.75), followed in order by less favorable utility scores for hernia, thromboembolism, pleural effusion, abscess, ileus/bowel obstruction, wound infection, bowel obstruction requiring surgery, anastomotic leak requiring drain, temporary ostomy, anastomotic leak requiring surgery, genito-urinary fistula, permanent ostomy, and genito-intestinal fistula (VAS utility 0.2). Overall, clinicians perceived complications more favorably than patients by VAS (overall utility score 0.49 vs 0.43, p < 0.01), but not by the TTO. There were no differences in overall utility scores between patients and controls. Patients who had not experienced certain surgical complications had less favorable scores than patients who did (utility score for ostomy = 0.2 for patients without ostomy vs. 0.7 for patients with ostomy, p = 0.02). CONCLUSIONS This study establishes health state utilities for surgical complications associated with ovarian cancer. These utilities can be used in future cost-effectiveness evaluations to determine quality-adjusted outcomes and may help in counseling patients during the shared decision-making process.
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Population norms in France with EQ-5D-5L: health states, value indexes, and VAS. THE EUROPEAN JOURNAL OF HEALTH ECONOMICS : HEPAC : HEALTH ECONOMICS IN PREVENTION AND CARE 2023; 24:1517-1530. [PMID: 36625971 DOI: 10.1007/s10198-022-01559-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 12/16/2022] [Indexed: 06/17/2023]
Abstract
PURPOSE To provide EuroQoL EQ-5D-5L French population norms based on a sample of 15,000 responders. METHODS Based on the National Health and Wellness Survey, an international, annual, selfadministered Internet-based survey, this study extracted data from France for 2018 involving a sample of 15,000 respondents stratified by age and gender. Responses to the EQ-5D-5L questionnaire and the Visual Analog Scale (VAS) score, together with sociodemographic, health behavior, and disease status variables were collected. VAS, value indexes, the level sum score, and the distribution of levels per dimension were described. Multivariate regression analyses were performed to identify covariates with a statistically significant effect on the five dimensions and the three scores. RESULTS The mean [standard deviation (SD)] VAS was 73.4 (22.2) for the entire sample (male 74.8 vs female 72.2, p < 0.0001). The Mean SD value index was 0.905 (0.158) (male 0.915 vs female 0.895, p < 0.0001). The mean SD level sum score was 7.6 (3.0) (7.4 for males vs. 7.9 for females p < 0.0001). Health state 11,111 (no problem in any dimension) represented 25.1% of all responses. "No problem" responses' proportions were Self Care (91.3%), Usual Activities (74.2%), Mobility (72.4%), Anxiety/Depression (52.6%) and Pain/Discomfort (37.7%). Multivariate regressions revealed a significant relationship for health states, value indexes, and VAS with age, income, employment, marital status, smoking and alcohol consumption, obesity, and the presence of one or more health problems. CONCLUSION Based on a large sample, this study is the first to report EQ-5D-5L population norms for France.
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Disability weight measurement for the severity of different diseases in Wuhan, China. Popul Health Metr 2023; 21:5. [PMID: 37143047 PMCID: PMC10157574 DOI: 10.1186/s12963-023-00304-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 04/16/2023] [Indexed: 05/06/2023] Open
Abstract
BACKGROUND Measurement of the Chinese burden of disease with disability-adjusted life-years (DALYs) requires disability weight (DW) that quantify health losses for all non-fatal consequences of disease and injury. The Global Burden of Disease (GBD) 2013 DW study indicates that it is limited by lack of geographic variation in DW data and by the current measurement methodology. We aim to estimate DW for a set of health states from major diseases in the Wuhan population. METHODS We conducted the DW measurement study for 206 health states through a household survey with computer-assisted face-to-face interviews and a web-based survey. Based on GBD 2013 DW study, paired comparison (PC) and Population health equivalence (PHE) method was used and different PC/PHE questions were randomly assigned to each respondent. In statistical analysis, the PC data was analyzed by probit regression. The probit regression results will be anchored by results from the PHE data analyzed by interval regression on the DW scale units between 0 (no loss of health) and 1 (loss equivalent to death). RESULTS A total of 2610 and 3140 individuals were included in the household and web-based survey, respectively. The results from the total pooled data showed health state "mild anemia" (DW = 0.005, 95% UI 0.000-0.027) or "allergic rhinitis (hay fever)" (0.005, 95% UI 0.000-0.029) had the lowest DW and "heroin and other opioid dependence, severe" had the highest DW (0.699, 95% UI 0.579-0.827). A high correlation coefficient (Pearson's r = 0.876; P < 0.001) for DWs of same health states was observed between Wuhan's survey and GBD 2013 DW survey. Health states referred to mental symptom, fatigue, and the residual category of other physical symptoms were statistically significantly associated with a lower Wuhan's DWs than the GBD's DWs. Health states with disfigurement and substance use symptom had a higher DW in Wuhan population than the GBD 2013 study. CONCLUSIONS This set of DWs could be used to calculate local diseases burden for health policy-decision in Wuhan population. The DW differences between the GBD's survey and Wuhan's survey suggest that there might be some contextual or culture factors influencing assessment on the severity of diseases.
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Can global or national disability weights represent provincial level? BMC Public Health 2023; 23:461. [PMID: 36899365 PMCID: PMC9999537 DOI: 10.1186/s12889-022-14347-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Accepted: 10/11/2022] [Indexed: 03/12/2023] Open
Abstract
BACKGROUND A universal set of disability weights(DWs) is mainly based on the survey of North America, Australia and Europe, whereas the participants in Asia was limited. The debate hasn't yet settled whether a universal DW is desirable or useful.The focus of the debate is its representativenes-s.After all, the DWs come from people's subjective evaluation of pain, and they may vary according to cultural background.The differences of the DWs could have implications for the magnitude or ranking of disease burdens.The DWs of Anhui Province has not been completely presented.This paper aims to obtain the DWs suitable for the general population of Anhui Province of China, and attempts to explore the differences between different DWs by comparing the DWs with the similar-cultural background and the DWs with cross-cultural background. METHODS A web-based survey was conducted to estimate the DWs for 206 health states of Anhui province in 2020. Paired comparison (PC) data were analyzed and anchored by probit regression and fitting loess model. We compared the DWs in Anhui with other provinces in China and those in Global burden of disease (GBD) and Japan. RESULTS Compared with Anhui province, the proportion of health states which showed 2 times or more differences ranged from 1.94% (Henan) to 11.17% (Sichuan) in China and domestic provinces. It was 19.88% in Japan and 21.51% in GBD 2013 respectively. In Asian countries or regions, most of the health states with top 15 DWs belonged to the category of mental, behavioral, and substance use disorders. But in GBD, most were infectious diseases and cancer. The differences of DWs in neighboring provinces were smaller than other geographically distant provinces or countries. CONCLUSION PC responses were largely consistent across very distinct settings,but the exceptions do need to be faced squarely.The differences of DWs among similar-cultural regions were smaller than cross-cultural regions. There is an urgent need for relevant gold standards.
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Accounting for delayed entry into observational studies and clinical trials: length-biased sampling and restricted mean survival time. LIFETIME DATA ANALYSIS 2022; 28:637-658. [PMID: 35778643 DOI: 10.1007/s10985-022-09562-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 06/09/2022] [Indexed: 06/15/2023]
Abstract
Individuals in many observational studies and clinical trials for chronic diseases are enrolled well after onset or diagnosis of their disease. Times to events of interest after enrollment are therefore residual or left-truncated event times. Individuals entering the studies have disease that has advanced to varying extents. Moreover, enrollment usually entails probability sampling of the study population. Finally, event times over a short to moderate time horizon are often of interest in these investigations, rather than more speculative and remote happenings that lie beyond the study period. This research report looks at the issue of delayed entry into these kinds of studies and trials. Time to event for an individual is modelled as a first hitting time of an event threshold by a latent disease process, which is taken to be a Wiener process. It is emphasized that recruitment into these studies often involves length-biased sampling. The requisite mathematics for this kind of sampling and delayed entry are presented, including explicit formulas needed for estimation and inference. Restricted mean survival time (RMST) is taken as the clinically relevant outcome measure. Exact parametric formulas for this measure are derived and presented. The results are extended to settings that involve study covariates using threshold regression methods. Methods adapted for clinical trials are presented. An extensive case illustration for a clinical trial setting is then presented to demonstrate the methods, the interpretation of results, and the harvesting of useful insights. The closing discussion covers a number of important issues and concepts.
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Eliciting national and subnational sets of disability weights in mainland China: Findings from the Chinese disability weight measurement study. THE LANCET REGIONAL HEALTH. WESTERN PACIFIC 2022; 26:100520. [PMID: 35910433 PMCID: PMC9335373 DOI: 10.1016/j.lanwpc.2022.100520] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
BACKGROUND The disability weight (DW) quantifies the severity of health states from disease sequela and is a pivotal parameter for disease burden calculation. We conducted a national and subnational DW measurement in China. METHODS In 2020-2021, we conducted a web-based survey to assess DWs for 206 health states in 31 Chinese provinces targeting health workers via professional networks. We fielded questions of paired comparison (PC) and population health equivalence (PHE). The PC data were analysed by probit regression analysis, and the regression results were anchored by results from the PHE responses on the DW scale between 0 (no loss of health) and 1 (health loss equivalent to death). FINDINGS We used PC responses from 468,541 respondents to estimate DWs of health states. Eight of 11 domains of health had significantly negative coefficients in the regression of the difference between Chinese and Global Burden of Disease (GBD) DWs, suggesting lower DW values for health states with mention of these domains in their lay description. We noted considerable heterogeneity within domains, however. After applying these Chinese DWs to the 2019 GBD estimates for China, total years lived with disability (YLDs) increased by 14·9% to 177 million despite lower estimates for musculoskeletal disorders, cardiovascular diseases, mental disorders, diabetes and chronic kidney disease. The lower estimates of YLDs for these conditions were more than offset by higher estimates of common, low-severity conditions. INTERPRETATION The differences between the GBD and Chinese DWs suggest that there might be some contextual factors influencing the valuation of health states. While the reduced estimates for mental disorders, alcohol use disorder, and dementia could hint at a culturally different valuation of these conditions in China, the much greater shifts in YLDs from low-severity conditions more likely reflects methodological difficulty to distinguish between health states that vary a little in absolute DW value but a lot in relative terms. FUNDING This work was supported by the National Natural Science Foundation of China [grant number 82173626], the National Key Research and Development Program of China [grant numbers 2018YFC1315302], Wuhan Medical Research Program of Joint Fund of Hubei Health Committee [grant number WJ2019H304], and Ningxia Natural Science Foundation Project [grant number 2020AAC03436].
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Characterizing health state utilities associated with Duchenne muscular dystrophy: a systematic review. Qual Life Res 2019; 29:593-605. [PMID: 31811595 PMCID: PMC7028804 DOI: 10.1007/s11136-019-02355-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/30/2019] [Indexed: 01/14/2023]
Abstract
Background Preferences for health states for Duchenne muscular dystrophy (DMD) are necessary to assess costs and benefits of novel therapies. Because DMD progression begins in childhood, the impact of DMD on health-related quality-of-life (HRQoL) affects preferences of both DMD patients and their families. The objective of this review was to synthesize published evidence for health state utility from the DMD patient and caregiver perspectives. Methods A systematic review was performed using MEDLINE and Embase, according to best practices. Data were extracted from studies reporting DMD patient or caregiver utilities; these included study and patient characteristics, health states considered, and utility estimates. Quality appraisal of studies was performed. Results From 888 abstracts, eight publications describing five studies were identified. DMD utility estimates were from preference-based measures presented stratified by ambulatory status, ventilation, and age. Patient (or patient–proxy) utility estimates ranged from 0.75 (early ambulatory DMD) to 0.05 (day-and-night ventilation). Caregiver utilities ranged from 0.87 (for caregivers of adults with DMD) to 0.71 (for caregivers of predominantly childhood patients). Both patient and caregiver utilities trended lower with higher disease severity. Variability in utilities was observed based on instrument, respondent type, and country. Utility estimates for health states within non-ambulatory DMD are under reported; nor were utilities for DMD-related health states such as scoliosis or preserved upper limb function identified. Conclusion Published health state utilities document the substantial HRQoL impacts of DMD, particularly with disease progression. Additional research in patient utilities for additional health states, particularly in non-ambulatory DMD patients, is warranted. Electronic supplementary material The online version of this article (10.1007/s11136-019-02355-x) contains supplementary material, which is available to authorized users.
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Should the EuroQol-Five Dimensions Replace the Oswestry Disability Index When Tracking Lumbar Tubular Microdecompression Outcomes? World Neurosurg 2019; 134:e566-e571. [PMID: 31678442 DOI: 10.1016/j.wneu.2019.10.124] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Revised: 10/20/2019] [Accepted: 10/21/2019] [Indexed: 11/23/2022]
Abstract
OBJECTIVE Patient-reported outcomes measures (PROMs) are critical in evaluating the effectiveness of surgical spine interventions. The Oswestry Disability Index (ODI) is commonly used but tedious to administer routinely. The EuroQol-5 Dimensions (EQ-5D) questionnaire is easier to administer but not traditionally used to measure spine surgical results. This study aimed to investigate the correlation of commonly administered PROMs in lumbar tubular microdecompression patients, and to consider whether ODI could be predicted from remaining PROMs. METHODS This study examined 304 index lumbar tubular microdecompression patients with PROMs collected at routine intervals. Spearman correlation coefficients were calculated for each pairwise combination of the following PROMs: ODI, EQ-5D index, leg pain visual analog scale (VAS), low back pain VAS, health state item. Linear regression modeling was conducted to predict ODI from the remaining four PROMs. RESULTS The patients had a mean age of 65.55 ± 12.97 years and 46.4% were male. Each combination of PROMs demonstrated a statistically significant pairwise correlation (P < 0.001). ODI showed strong correlation with EQ-5D index (r = -0.77), leg pain VAS (r = 0.73), and back pain VAS (r = 0.65), but weak correlation with health state item (r = -0.33). Forwards stepwise model selection yielded a multiple linear regression model including all four PROMs predictors, with an adjusted R2 of 0.690. There was strong correlation between predicted and observed ODI (r = 0.83, P < 0.001). CONCLUSIONS ODI can be predicted from EQ-5D, leg and low back pain VAS, and health state items with moderate accuracy. The added utility of capturing ODI routinely may not out-weigh the challenges in doing so.
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Assessing utility values for treatment-related health states of acute myeloid leukemia in the United States. Health Qual Life Outcomes 2018; 16:193. [PMID: 30241538 PMCID: PMC6151058 DOI: 10.1186/s12955-018-1013-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 09/06/2018] [Indexed: 01/09/2023] Open
Abstract
Background Preference valuations of health status are essential in health technology and economic appraisal. This study estimated utilities for treatment-related health states of acute myeloid leukemia (AML) and disutilities of severe adverse events (SAEs) using a representative sample of adults from the general population in the United States (US). Methods Treatment-related AML health states, defined based on literature and interviews with clinicians, included complete remission (CR), no CR, relapse, stem cell transplant (SCT), and post SCT short-term recovery. Six attributes with varying levels, including fever, lack of energy, problems with daily function, anxiety/depression, blood transfusions, and hospitalization, were used to define health states. An online survey using discrete choice experiment methodology was designed to capture preferences for health status scenarios including the identified attributes and key grade 3/4 chemotherapy-related SAEs. Health state utilities and SAE disutilities were generated from a conditional logistic regression with generalized estimating equations. Results Of the 300 survey participants, the demographic distributions were within a 3% margin of those in the 2010 US Census. CR had the highest utility value (0.875), followed by post-SCT short-term recovery (0.398), relapse (0.355), no CR (0.262), and SCT (0.158). Of the SAEs, serious infection had the highest decline in utility (0.218), followed by severe diarrhea (0.176), abnormally low blood cell counts (0.100), and severe redness/skin peeling (0.060). Conclusions AML and treatments can result in reduced quality of life and impaired ability to perform daily activities. Findings of this study underline the value that society places on treatment-related AML health states and SAEs.
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Abstract
Burden and vulnerability factors after the genocide by ISIS accumulate to a high risk of health for displaced Yezidi women having survived or escaped the "ISIS" persecutions and massacres 2014. In May 2017, standardized interviews, including tests for the acquisition of healthrelated quality of life (SF12), stress (PSS10) and experienced trauma were performed with 29 and a medical anamnesis with 10 displaced female Yezidi in camps for internally displaced people (IDP) and unofficial settlements in Northern Iraq. 58, 62% stated their general health as "poor", 17.24% each as "fair" or "good" and 3.45% each as "very good" or "excellent". In the assessment of health-related quality of life, physical as well as mental health showed significantly reduced values, while simultaneously a high level of stress was recorded. 79.3% reported about having experienced at least one traumatic event. Chronic stress due to living conditions and traumatization is most likely responsible for the recorded poor health.
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Utility values associated with advanced or metastatic non-small cell lung cancer: data needs for economic modeling. Expert Rev Pharmacoecon Outcomes Res 2017; 17:153-164. [PMID: 28335636 DOI: 10.1080/14737167.2017.1311210] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
INTRODUCTION Cost-effectiveness analyses often inform healthcare reimbursement decisions. The preferred measure of effectiveness is the quality adjusted life year (QALY) gained, where the quality of life adjustment is measured in terms of utility. Areas covered: We assessed the availability and variation of utility values for health states associated with advanced or metastatic non-small cell lung cancer (NSCLC) to identify values appropriate for cost-effectiveness models assessing alternative treatments. Our systematic search of six electronic databases (January 2000 to August 2015) found the current literature to be sparse in terms of utility values associated with NSCLC, identifying 27 studies. Utility values were most frequently reported over time and by treatment type, and less frequently by disease response, stage of disease, adverse events or disease comorbidities. Expert commentary: In response to rising healthcare costs, payers increasingly consider the cost-effectiveness of novel treatments in reimbursement decisions, especially in oncology. As the number of therapies available to treat NSCLC increases, cost-effectiveness analyses will play a key role in reimbursement decisions in this area. Quantifying the relationship between health and quality of life for NSCLC patients via utility values is an important component of assessing the cost effectiveness of novel treatments.
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Assessment of health status over time by Prevalence and Weighted Prevalence functions: Interface in R. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2015; 118:298-308. [PMID: 25622568 DOI: 10.1016/j.cmpb.2014.12.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 12/10/2014] [Accepted: 12/30/2014] [Indexed: 06/04/2023]
Abstract
The importance of evaluating complications and toxicity during and following treatment has been stressed in many publications. In most studies, these endpoints are presented descriptively and summarized by numbers and percentages but descriptive methods are rarely sufficient to evaluate treatment-related complications. Pepe and Lancar developed Prevalence and Weighted Prevalence functions which take into account the duration and the severity of complication unlike conventional methods of survival analysis or competing risks which are limited to the time to first event. The purpose of this paper is to describe features and use of two R functions, main.preval.func and main.wpreval.func, which were designed for the analysis of survival adjusted for quality of life. These functions compute descriptive statistics, survival and competing risks analysis and especially Prevalence and Weighted Prevalence estimations with confidence intervals and associated test statistics. The use of these functions is illustrated by several examples.
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Condition-dependent chemosignals in reproductive behavior of lizards. Horm Behav 2015; 68:14-24. [PMID: 24952102 DOI: 10.1016/j.yhbeh.2014.06.009] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 06/07/2014] [Accepted: 06/10/2014] [Indexed: 10/25/2022]
Abstract
This article is part of a Special Issue "Chemosignals and Reproduction". Many lizards have diverse glands that produce chemosignals used in intraspecific communication and that can have reproductive consequences. For example, information in chemosignals of male lizards can be used in intrasexual competition to identify and assess the fighting potential or dominance status of rival males either indirectly through territorial scent-marks or during agonistic encounters. Moreover, females of several lizard species "prefer" to establish or spend more time on areas scent-marked by males with compounds signaling a better health or body condition or a higher genetic compatibility, which can have consequences for their mating success and inter-sexual selection processes. We review here recent studies that suggest that the information content of chemosignals of lizards may be reliable because several physiological and endocrine processes would regulate the proportions of chemical compounds available for gland secretions. Because chemosignals are produced by the organism or come from the diet, they should reflect physiological changes, such as different hormonal levels (e.g. testosterone or corticosterone) or different health states (e.g. parasitic infections, immune response), and reflect the quality of the diet of an individual. More importantly, some compounds that may function as chemosignals also have other important functions in the organism (e.g. as antioxidants or regulating the immune system), so there could be trade-offs between allocating these compounds to attending physiological needs or to produce costly sexual "chemical ornaments". All these factors may contribute to maintain chemosignals as condition-dependent sexual signals, which can inform conspecifics on the characteristics and state of the sender and allow making behavioral decisions with reproductive consequences. To understand the evolution of chemical secretions of lizards as sexual signals and their relevance in reproduction, future studies should examine what information the signals are carrying, the physiological processes that can maintain the reliability of the message and how diverse behavioral responses to chemosignals may influence reproductive success.
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Population modelling of patient responses in antidepressant studies: a stochastic approach. Math Biosci 2014; 261:37-47. [PMID: 25481225 DOI: 10.1016/j.mbs.2014.11.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 10/09/2014] [Accepted: 11/22/2014] [Indexed: 11/29/2022]
Abstract
This paper addresses the problem of modelling longitudinal data describing patients' responses in clinical trials. In particular, a systematic approach relying on a system theoretic paradigm is proposed to deal with contexts where limited physiopathological knowledge is available on disease, drug response, and patients' characteristics. The model relies on the notion of patient's health state which summarizes the patient's condition. In order to cope with the limited number of clinical data usually available, the paper considers a very parsimonious realization where the two state variables are the clinical endpoint and its derivative. Within a population framework, the individual response is modelled as the sum of an individual shift and the average response of subjects belonging to the same study, both described as Markovian processes and identified by empirical Bayes techniques. The proposed approach is validated with experimental data from a Phase II, flexible-dose, depression trial. The dose changes due to the flexible-dose scheme are handled as perturbations on the state. The connection between inter-individual variability and model stability is evaluated showing that the introduction of stable poles helps to describe populations whose range of individual responses does not diverge with time. In this way, good individual fittings and visual predictive checks were obtained for the clinical data. The proposed analysis provides a systematic approach to semi-mechanistic modelling when a precise knowledge of the physiological mechanisms of the disease is incomplete or missing.
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