Browsing by Author "Fielding, Katherine"

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    Predictors of silicosis and variation in prevalence across mines among employed gold miners in South Africa
    (2020-06-01) Knight, Dave; Ehrlich, Rodney; Cois, Annibale; Fielding, Katherine; Grant, Alison D; Churchyard, Gavin
    Background The stated intention to eliminate silicosis from the South African goldmining industry as well as current programmes to find and compensate ex-miners with silicosis require an understanding of variation in silicosis prevalence across the industry. We aimed to identify the predictors of radiological silicosis in a large sample of working miners across gold mines in South Africa. Methods Routine surveillance chest radiographs were collected from 15 goldmine “clusters” in a baseline survey undertaken in preparation for a separate tuberculosis isoniazid prophylaxis trial. All images were read for silicosis by a health professional experienced in using the International Labour Organisation (ILO) classification. Profusion thresholds of > 1/0 and > 1/1 were used. Demographic and occupational information was obtained by questionnaire. Predictors of silicosis were examined in a multivariable logistic regression model, including age, gender, racial ascription, country of origin, years since starting mine employment, mine shaft, skill category, underground work status and tuberculosis. Results The crude silicosis prevalence at ILO > 1/1 was 3.8% [95% confidence interval (CI) 3.5–4.1%]. The range across mine shafts was 0.8–6.9%. After adjustment for covariates, the interquartile range across shafts was reduced from 2.4 to 1.2%. Black miners [adjusted odds ratio (aOR) 2.8; 95% CI 1.1–7.2] and miners in full-time underground work (aOR 2.1; 95% CI 1.3–3.4) had substantially elevated odds of silicosis, while workers from Mozambique had lower odds (aOR 0.54; 95% CI 0.38–0.77). Silicosis odds rose sharply with both age and years since starting in the industry (p for linear trend < 0.005), with 95.5% of affected miners having > 15 years since first exposure and 2.2% < 10 years. Conclusions In surveillance of silicosis in working gold miners time since first exposure remains a powerful predictor. Age appears to be an independent predictor, while the detection of radiological silicosis in short-service miners requires attention. Public risk reporting by mines should include factors bearing on silicosis prevalence, specifically dust concentrations, with independent verification. Studies of silicosis and tuberculosis in ex-miners are needed, supported by an accessible electronic database of the relevant medical and dust exposure records of all gold miners.
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    Pregnancy incidence and correlates during the HVTN 503 Phambili HIV vaccine trial conducted among South African women
    (Public Library of Science, 2012) Latka, Mary H; Fielding, Katherine; Gray, Glenda E; Bekker, Linda-Gail; Nchabeleng, Maphoshane; Mlisana, Koleka; Nielson, Tanya; Roux, Surita; Mkhize, Baningi; Mathebula, Matsontso
    BACKGROUND: HIV prevention trials are increasingly being conducted in sub-Saharan Africa. Women at risk for HIV are also at risk of pregnancy. To maximize safety, women agree to avoid pregnancy during trials, yet pregnancies occur. Using data from the HVTN 503/"Phambili" vaccine trial, we report pregnancy incidence during and after the vaccination period and identify factors, measured at screening, associated with incident pregnancy. METHODS: To enrol in the trial, women agreed and were supported to avoid pregnancy until 1 month after their third and final vaccination ("vaccination period"), corresponding to the first 7 months of follow-up. Unsterilized women, pooled across study arms, were analyzed. Poisson regression compared pregnancy rates during and after the vaccination period. Cox proportional hazards regression identified associations with first pregnancy. RESULTS: Among 352 women (median age 23 yrs; median follow-up 1.5 yrs), pregnancy incidence was 9.6/100 women-years overall and 6.8/100 w-yrs and 11.3/100 w-yrs during and after the vaccination period, respectively [Rate Ratio = 0.60 (0.32-1.14), p = 0.10]. In multivariable analysis, pregnancy was reduced among women who: enrolled at sites providing contraception on-site [HR = 0.43, 95% CI (0.22-0.86)]; entered the trial as injectable contraceptive users [HR = 0.37 (0.21-0.67)] or as consistent condom users (trend) [HR = 0.54 (0.28-1.04)]. Compared with women with a single partner of HIV-unknown status, pregnancy rates were increased among women with: a single partner whose status was HIV-negative [HR = 2.34(1.16-4.73)] and; 2 partners both of HIV-unknown status [HR = 4.42(1.59-12.29)]. Women with 2 more of these risk factors: marijuana use, heavy drinking, or use of either during sex, had increased pregnancy incidence [HR = 2.66 (1.24-5.72)]. CONCLUSIONS: It is possible to screen South African women for pregnancy risk at trial entry. Providing injectable contraception for free on-site and supporting consistent condom use may reduce incident pregnancy. Screening should determine the substance use, partnering, and HIV status of both members of the couple for both pregnancy and HIV prevention. Trial Registration SA National Health Research Database DOH-27-0207-1539; Clinicaltrials.gov NCT00413725
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    Risk factors for poor virological outcome at 12 months in a workplace-based antiretroviral therapy programme in South Africa: A cohort study
    (BioMed Central Ltd, 2008) Fielding, Katherine; Charalambous, Salome; Stenson, Amy; Pemba, Lindiwe; Martin, Des; Wood, Robin; Churchyard, Gavin; Grant, Alison
    BACKGROUND: Reasons for the variation in reported treatment outcomes from antiretroviral therapy (ART) programmes in developing countries are not clearly defined. METHODS: Among ART-naive individuals in a workplace ART programme in South Africa we determined virological outcomes at 12 months, and risk factors for suboptimal virological outcome, defined as plasma HIV-1 viral load >= 400 copies/ml. RESULTS: Among 1760 individuals starting ART before July 2004, 1172 were in follow-up at 12 months of whom 953 (81%) had a viral load measurement (median age 41 yrs, 96% male, median baseline CD4 count 156 x 106/l). 71% (681/953) had viral load < 400 copies/ml at 12 months. In a multivariable analysis, independent predictors of suboptimal virological outcome at 12 months were <1 log decrease in viral load at six weeks (odds ratio [OR] 4.71, 95% confidence interval [CI] 2.56-8.68), viral load at baseline (OR 3.63 [95% CI 1.88-7.00] and OR 3.54 [95% CI 1.79-7.00] for 10,001-100,000 and >100,000 compared to <= 10,000 copies/ml, respectively), adherence at six weeks (OR 3.50 [95% CI 1.92-6.35]), WHO stage (OR 2.08 [95% CI 1.28-3.34] and OR 2.03 [95% CI 1.14-3.62] for stage 3 and 4 compared to stage 1-2, respectively) and site of ART delivery. Site of delivery remained an independent risk factor even after adjustment for individual level factors. At 6 weeks, of 719 patients with self-reported adherence and viral load, 72 (10%) reported 100% adherence but had <1 log decrease in viral load; conversely, 60 (8%) reported <100% adherence but had >= 1 log decrease in viral load. CONCLUSION: Virological response at six weeks after ART start was the strongest predictor of suboptimal virological outcome at 12 months, and may identify individuals who need interventions such as additional adherence support. Self reported adherence was less strongly associated but identified different patients compared with viral load at 6 weeks. Site of delivery had an important influence on virological outcomes; factors at the health system level which influence outcome need further investigation to guide development of effective ART programmes.