Dataset Information

Modeling Long-Term Graft Survival With Time-Varying Covariate Effects: An Application to a Single Kidney Transplant Centre in Johannesburg, South Africa.

ABSTRACT: Objectives: Patients' characteristics that could influence graft survival may also exhibit non-constant effects over time; therefore, violating the important assumption of the Cox proportional hazard (PH) model. We describe the effects of covariates on the hazard of graft failure in the presence of long follow-ups. Study Design and Settings: We studied 915 adult patients that received kidney transplant between 1984 and 2000, using Cox PH, a variation of the Aalen additive hazard and Accelerated failure time (AFT) models. Selection of important predictors was based on the purposeful method of variable selection. Results: Out of 915 patients under study, 43% had graft failure by the end of the study. The graft survival rate is 81, 66, and 50% at 1, 5, and 10 years, respectively. Our models indicate that donor type, recipient age, donor-recipient gender match, delayed graft function, diabetes and recipient ethnicity are significant predictors of graft survival. However, only the recipient age and donor-recipient gender match exhibit constant effects in the models. Conclusion: Conclusion made about predictors of graft survival in the Cox PH model without adequate assessment of the model fit could over-estimate significant effects. The additive hazard and AFT models offer more flexibility in understanding covariates with non-constant effects on graft survival. Our results suggest that the period of follow-up in this study is long to support the proportionality assumption. Modeling graft survival at different time points may restrain the possibility of important covariates showing time-variant effects in the Cox PH model.

SUBMITTER: Achilonu OJ

PROVIDER: S-EPMC6669915 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundSequelae post-SARS-CoV-2 infection, including lung and functional impairment, pose a significant challenge post-recovery. We explored the burden and risk factors for post-COVID-19 sequelae in an African population with prevalent comorbidities including tuberculosis (TB) and HIV.MethodsWe conducted an observational cohort study on hospitalised adults with confirmed SARS-CoV-2 infection from 20 March to 06 October 2021 at Chris Hani Baragwanath Academic Hospital, South Africa. We collected data on comorbidities, and COVID-19 severity using the World Health Organization (WHO) clinical progression scale. Prospectively, we followed up all participants within 40-days post-discharge to assess body mass index (BMI), COVID-19 symptoms and quality of life using St George's Respiratory Questionnaire (SGRQ), 6-min walking-test (6MWT), and spirometry. A subsequent in-depth visit assessed plethysmography, diffusing capacity for the lung for carbon monoxide (DLCO), and high-resolution chest-CT.FindingsWe followed up 111 participants, where 65.8% were female, median age 50.5 years, and predominantly black-African (92.8%). Relevant comorbidities included TB disease (18.9%) and HIV infection (36%). SGRQ total scores were elevated in 78.9%, median 6MWT distance was reduced at 300 m (IQR 210-400), and nearly half (49.5%) exhibited spirometry findings below the lower limit of normal (LLN). In-depth pulmonary assessment for 61 participants revealed abnormalities in total lung capacity (31.6% <80% predicted), DLCO (53.4% <80% predicted), and chest-CT (86.7% abnormal). Significant risk factors for individual abnormal outcomes, adjusted for age and sex, were TB disease, HIV with CD4 <200 cells/mm3, BMI <18.5 kg/m2 and >35 kg/m2, and initial COVID-19 severity.InterpretationThis study demonstrates substantial lung and functional morbidity within the first weeks post-COVID-19, particularly in individuals with pre-existing comorbidities including TB, HIV, and low or high BMI. Chest-CT and DLCO show best early potential at reflecting COVID-19-related pathologies.FundingThe Bavarian State Ministry of Science and Arts.

Project description:Background Depression is associated with high rates of morbidity and mortality. Globally, depression is higher among university students than the general population—making it a significant public health problem. Despite this, there is limited data on the prevalence in university students in the Gauteng province, South Africa. This study determined the prevalence of screening positive for probable depression and its correlates among undergraduate students at the university of the Witwatersrand, Johannesburg, South Africa. Methods A cross-sectional study, using an online survey was conducted among undergraduate students at the University of the Witwatersrand in 2021. Patient Health Questionnaire (PHQ-2) was used to assess the prevalence of probable depression. Descriptive statistics was computed and conducted bivariate and multivariable logistic regression to identify factors associated with probable depression. Age, marital status, substance use (alcohol use, cannabis use, tobacco use, and other substance use) were included in the multivariable model apriori determined confounders and other factors were only added if they had a p-value <0.20 in the bivariate analysis. A p-value of 0.05 was considered statistically significant. Results The response rate was 8.4% (1046/12404). The prevalence of screening positive for probable depression was 48% (439/910). Race, substance use, and socio-economic status were associated with odds of screening positive for probable depression. Specifically reporting white race (adjusted OR (aOR) = 0.64, 95% CI: 0.42, 0.96), no cannabis use (aOR = 0.71, 95% CI: 0.44–0.99), higher spending power in the form of having the most important things but few luxury goods (aOR = 0.50, 95% CI: 0.31, 0.80) and having enough money for luxury goods and extra things (aOR = 0.44, 95% CI: 0.26–0.76) were associated with lower odds of screening positive for probable depression. Discussion: In this study, screening positive for probable depression was common among undergraduate students at the University of the Witwatersrand, Johannesburg, South Africa and associated with sociodemographic and selected behavioral factors. These findings call for strengthening the awareness and use of counselling services among undergraduate students.

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Modeling Long-Term Graft Survival With Time-Varying Covariate Effects: An Application to a Single Kidney Transplant Centre in Johannesburg, South Africa.

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