Browsing by Subject "Confidence intervals"

Now showing 1 - 8 of 8
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    Anaemia, haemoglobin level and cause-specific mortality in people with and without diabetes
    (Public Library of Science, 2012) Kengne, Andre Pascal; Czernichow, Sébastien; Hamer, Mark; Batty, G David; Stamatakis, Emmanuel
    BACKGROUND: Both anaemia and cardiovascular disease (CVD) are common in people with diabetes. While individually both characteristics are known to raise mortality risk, their combined influence has yet to be quantified. In this pooling project, we examined the combined impact of baseline haemoglobin levels and existing CVD on all-cause and CVD mortality in people with diabetes. We draw comparison of these effects with those apparent in diabetes-free individuals. Methods/Principal FINDINGS: A combined analyses of 7 UK population-based cohorts resulted in 26,480 study members. There were 946 participants with physician-diagnosed diabetes, 2227 with anaemia [haemoglobin<13 g/dl (men) or <12 (women)], 2592 with existing CVD (stroke, ischaemic heart disease), and 21,396 with none of the conditions. Across diabetes and anaemia subgroups, and using diabetes-free, non-anaemic participants as the referent group, the adjusted hazard ratios (HR) were 1.46 (95% CI: 1.30-1.63) for anaemia, 1.67 (1.45-1.92) for diabetes, and 2.10 (1.55-2.85) for diabetes and anaemia combined. Across combined diabetes, anaemia and CVD subgroups, and compared with non-anaemic, diabetes-free and CVD-free participants, HR (95% CI) for all-cause mortality were 1.49 (1.32-1.69) anaemia, 1.60 (1.46-1.76) for existing CVD, and 1.66 (1.39-1.97) for diabetes alone. Equivalents were 2.13 (1.48-3.07) for anaemia and diabetes, 2.68 (2.14-3.36) for diabetes and existing CVD, and 3.25 (1.88-5.62) for the three combined. Patterns were similar for CVD mortality. Conclusions/Significance Individually, anaemia and CVD confer similar mortality risks in people with diabetes, and are excessively fatal in combination. Screening for anaemia would identify vulnerable diabetic patients whose outcomes can potentially be improved.
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    Correcting for mortality among patients lost to follow up on antiretroviral therapy in South Africa: a cohort analysis
    (Public Library of Science, 2011) Van Cutsem, Gilles; Ford, Nathan; Hildebrand, Katherine; Goemaere, Eric; Mathee, Shaheed; Abrahams, Musaed; Coetzee, David; Boulle, Andrew
    BACKGROUND: Loss to follow-up (LTF) challenges the reporting of antiretroviral treatment (ART) programmes, since it encompasses patients alive but lost to programme and deaths misclassified as LTF. We describe LTF before and after correction for mortality in a primary care ART programme with linkages to the national vital registration system. Methods and FINDINGS: We included 6411 patients enrolled on ART between March 2001 and June 2007. Patients LTF with available civil identification numbers were matched with the national vital registration system to ascertain vital status. Corrected mortality and true LTF were determined by weighting these patients to represent all patients LTF. We used Kaplan-Meier estimates and Cox regression to describe LTF, mortality among those LTF, and true LTF. Of 627 patients LTF, 85 (28.8%) had died within 3 months after their last clinic visits. Respective estimates of LTF before and after correction for mortality were 6.9% (95% confidence interval [CI] 6.2-7.6) and 4.3% (95% CI 3.5-5.3) at one year on ART, and 23.9% (95% CI 21.0-27.2) and 19.7% (95% CI 16.1-23.7) at 5 years. After correction for mortality, the hazard of LTF was reversed from decreasing to increasing with time on ART. Younger age, higher baseline CD4 count, pregnancy and increasing calendar year were associated with higher true LTF. Mortality of patients LTF at 1, 12 and 24 months after their last visits was respectively 23.1%, 30.9% and 43.8%; 78.0% of deaths occurred during the first 3 months after last visit and 45.0% in patients on ART for 0 to 3 months. CONCLUSIONS: Mortality of patients LTF was high and occurred early after last clinic visit, especially in patients recently started on ART. Correction for these misclassified deaths revealed that the risk of true LTF increased over time. Research targeting groups at higher risk of LTF (youth, pregnant women and patients with higher CD4 counts) is needed.
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    Differing patterns of overweight and obesity among black men and women in Cape Town: the CRIBSA study
    (Public Library of Science, 2014) Peer, Nasheeta; Lombard, Carl; Steyn, Krisela; Gwebushe, Nomonde; Levitt, Naomi
    Objectives To ascertain the prevalence and determinants of overweight/obesity in the 25-74-year-old urban black population of Cape Town and examine the changes between 1990 and 2008/09. METHODS: In 2008/09, a representative cross-sectional sample, stratified for age and sex, was randomly selected from the same townships sampled in 1990. Data were collected by questionnaires, clinical measurements and biochemical analyses. Gender-specific linear regression models evaluated the associations with overweight/obesity. RESULTS: There were 1099 participants, 392 men and 707 women (response rate 86%) in 2008/09. Mean body mass index (BMI) and waist circumference (WC) were 23.7 kg/m 2 (95% confidence interval (CI): 23.1-24.2) and 84.2 cm (95% CI: 82.8-85.6) in men, and 33.0 kg/m 2 (95% CI: 32.3-33.7) and 96.8 cm (95% CI: 95.5-98.1) in women. Prevalence of BMI ≥25 kg/m 2 and raised WC were 28.9% (95% CI: 24.1-34.3) and 20.1% (95% CI: 15.9-24.9) in men, and 82.8% (95% CI: 79.3-85.9) and 86.0% (95% CI: 82.9-88.6) in women. Among 25-64-year-olds, BMI ≥25 kg/m 2 decreased between 1990 (37.3%, 95% CI: 31.7-43.1) and 2008/09 (27.7%, 95% CI: 22.7-33.4) in men but increased from 72.7% (95% CI: 67.6-77.2) to 82.6% (95% CI: 78.8-85.8) in women. In the regression models for men and women, higher BMI was directly associated with increasing age, wealth, hypertension and diabetes but inversely related to daily smoking. Also significantly associated with rising BMI were raised low-density lipoprotein cholesterol and being employed compared to unemployed in men, and having >7 years of education in women. CONCLUSIONS: Overweight/obesity, particularly in urban black women, requires urgent action because of the associations with cardiovascular disease risk factors and their serious consequences.
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    Gauging the threat: the first population estimate for white sharks in South Africa using photo identification and automated software
    (Public Library of Science, 2013) Towner, Alison V; Wcisel, Michelle A; Reisinger, Ryan R; Edwards, David; Jewell, Oliver J D
    South Africa is reputed to host the world’s largest remaining population of white sharks, yet no studies have accurately determined a population estimate based on mark-recapture of live individuals. We used dorsal fin photographs (fin IDs) to identify white sharks in Gansbaai, South Africa, from January 2007 - December 2011. We used the computer programme DARWIN to catalogue and match fin IDs of individuals; this is the first study to successfully use the software for white shark identification. The programme performed well despite a number of individual fins showing drastic changes in dorsal fin shape over time. Of 1682 fin IDs used, 532 unique individuals were identified. We estimated population size using the open-population POPAN parameterisation in Program MARK, which estimated the superpopulation size at 908 (95% confidence interval 808-1008). This estimated population size is considerably larger than those described at other aggregation areas of the species and is comparable to a previous South African population estimate conducted 16 years prior. Our assessment suggests the species has not made a marked recovery since being nationally protected in 1991. As such, additional international protection may prove vital for the long-term conservation of this threatened species.
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    Increasing transfers-out from an antiretroviral treatment service in South Africa: patient characteristics and rates of virological non-suppression
    (Public Library of Science, 2013) Nglazi, Mweete D; Kaplan, Richard; Orrell, Catherine; Myer, Landon; Wood, Robin; Bekker, Linda-Gail; Lawn, Stephen D
    Objectives: To determine the proportion, characteristics and outcomes of patients who transfer-out from an antiretroviral therapy (ART) service in a South African township. METHODS: This retrospective cohort study included all patients aged ≥15 years who enrolled between September 2002 and December 2009. Follow-up data were censored in December 2010. Kaplan-Meier survival analysis was used to describe time to transfer-out and cox proportional hazard analysis was used to determine associated risk factors. RESULTS: 4511 patients (4003 ART-naïve and 508 non-naïve at baseline) received ART during the study period. Overall, 597 (13.2%) transferred out. The probability of transferring out by one year of ART steadily increased from 1.4% in 2002/2004 cohort to 8.9% for the 2009 cohort. Independent risk factors for transfer-out were more recent calendar year of enrolment, younger age (≤25 years) and being ART non-naïve at baseline (i.e., having previously transferred into this clinic from another facility). The proportions of patients transferred out who had a CD4 cell count <200 cells/µL and/or a viral load ≥1000 copies/mL were 19% and 20%, respectively. CONCLUSIONS: With scale-up of ART over time, an increasing proportion of patients are transferring between ART services and information systems are needed to track patients. Approximately one-fifth of these have viral loads >1000 copies/mL around the time of transfer, suggesting the need for careful adherence counseling and assessment of medication supplies among those planning transfer.
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    Mycobactericidal activity of sutezolid (PNU-100480) in sputum (EBA) and blood (WBA) of patients with pulmonary tuberculosis
    (Public Library of Science, 2014) Wallis, Robert S; Dawson, Rodney; Friedrich, Sven O; Venter, Amour; Paige, Darcy; Zhu, Tong; Silvia, Annette; Gobey, Jason; Ellery, Craig; Zhang, Yao
    Rationale: Sutezolid (PNU-100480) is a linezolid analog with superior bactericidal activity against Mycobacterium tuberculosis in the hollow fiber, whole blood and mouse models. Like linezolid, it is unaffected by mutations conferring resistance to standard TB drugs. This study of sutezolid is its first in tuberculosis patients. METHODS: Sputum smear positive tuberculosis patients were randomly assigned to sutezolid 600 mg BID (N = 25) or 1200 mg QD (N = 25), or standard 4-drug therapy (N = 9) for the first 14 days of treatment. Effects on mycobacterial burden in sputum (early bactericidal activity or EBA) were monitored as colony counts on agar and time to positivity in automated liquid culture. Bactericidal activity was also measured in ex vivo whole blood cultures (whole blood bactericidal activity or WBA) inoculated with M. tuberculosis H37Rv. RESULTS: All patients completed assigned treatments and began subsequent standard TB treatment according to protocol. The 90% confidence intervals (CI) for bactericidal activity in sputum over the 14 day interval excluded zero for all treatments and both monitoring methods, as did those for cumulative WBA. There were no treatment-related serious adverse events, premature discontinuations, or dose reductions due to laboratory abnormalities. There was no effect on the QT interval. Seven sutezolid-treated patients (14%) had transient, asymptomatic ALT elevations to 173±34 U/L on day 14 that subsequently normalized promptly; none met Hy's criteria for serious liver injury. CONCLUSIONS: The mycobactericidal activity of sutezolid 600 mg BID or 1200 mg QD was readily detected in sputum and blood. Both schedules were generally safe and well tolerated. Further studies of sutezolid in tuberculosis treatment are warranted. Trial Registration ClinicalTrials.gov NCT01225640
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    Revisiting the effect of capture heterogeneity on survival estimates in capture-mark-recapture studies: does it matter?
    (Public Library of Science, 2013) Abadi, Fitsum; Botha, Andre; Altwegg, Res
    Recently developed capture-mark-recapture methods allow us to account for capture heterogeneity among individuals in the form of discrete mixtures and continuous individual random effects. In this article, we used simulations and two case studies to evaluate the effectiveness of continuously distributed individual random effects at removing potential bias due to capture heterogeneity, and to evaluate in what situation the added complexity of these models is justified. Simulations and case studies showed that ignoring individual capture heterogeneity generally led to a small negative bias in survival estimates and that individual random effects effectively removed this bias. As expected, accounting for capture heterogeneity also led to slightly less precise survival estimates. Our case studies also showed that accounting for capture heterogeneity increased in importance towards the end of study. Though ignoring capture heterogeneity led to a small bias in survival estimates, such bias may greatly impact management decisions. We advocate reducing potential heterogeneity at the sampling design stage. Where this is insufficient, we recommend modelling individual capture heterogeneity in situations such as when a large proportion of the individuals has a low detection probability (e.g. in the presence of floaters) and situations where the most recent survival estimates are of great interest (e.g. in applied conservation).
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    TB incidence in an adolescent cohort in South Africa
    (Public Library of Science, 2013) Mahomed, Hassan; Ehrlich, Rodney; Hawkridge, Tony; Hatherill, Mark; Geiter, Lawrence; Kafaar, Fazlin; Abrahams, Deborah Ann; Mulenga, Humphrey; Tameris, Michele; Geldenhuys, Hennie
    BACKGROUND: Tuberculosis (TB) is a major public health problem globally. Little is known about TB incidence in adolescents who are a proposed target group for new TB vaccines. We conducted a study to determine the TB incidence rates and risk factors for TB disease in a cohort of school-going adolescents in a high TB burden area in South Africa. METHODS: We recruited adolescents aged 12 to 18 years from high schools in Worcester, South Africa. Demographic and clinical information was collected, a tuberculin skin test (TST) performed and blood drawn for a QuantiFERON TB Gold assay at baseline. Screening for TB cases occurred at follow up visits and by surveillance of registers at public sector TB clinics over a period of up to 3.8 years after enrolment. RESULTS: A total of 6,363 adolescents were enrolled (58% of the school population targeted). During follow up, 67 cases of bacteriologically confirmed TB were detected giving an overall incidence rate of 0.45 per 100 person years (95% confidence interval 0.29-0.72). Black or mixed race, maternal education of primary school or less or unknown, a positive baseline QuantiFERON assay and a positive baseline TST were significant predictors of TB disease on adjusted analysis. CONCLUSION: The adolescent TB incidence found in a high burden setting will help TB vaccine developers plan clinical trials in this population. Latent TB infection and low socio-economic status were predictors of TB disease.