Erratum to: Short-term forecasting of the prevalence of clinical trachoma: utility of including delayed recovery and tests for infection.
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SUBMITTER: Liu F
PROVIDER: S-EPMC4901435 | biostudies-literature | 2016 Jun
REPOSITORIES: biostudies-literature
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Erratum to: Short-term forecasting of the prevalence of clinical trachoma: utility of including delayed recovery and tests for infection.
Liu Fengchen F Porco Travis C TC Amza Abdou A Kadri Boubacar B Nassirou Baido B West Sheila K SK Bailey Robin L RL Keenan Jeremy D JD Lietman Thomas M TM
Parasites & vectors 20160609 1
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Project description:BackgroundThe World Health Organization aims to control blinding trachoma by 2020. Decisions on whether to start and stop mass treatments and when to declare that control has been achieved are currently based on clinical examination data generated in population-based surveys. Thresholds are based on the district-level prevalence of trachomatous inflammation-follicular (TF) in children aged 1-9 years. Forecasts of which districts may and may not meet TF control goals by the 2020 target date could affect resource allocation in the next few years.MethodsWe constructed a hidden Markov model fit to the prevalence of two clinical signs of trachoma and PCR data in 24 communities from the recent PRET-Niger trial. The prevalence of TF in children in each community at 36 months was forecast given data from earlier time points. Forecasts were scored by the likelihood of the observed results. We assessed whether use of TF with additional TI and PCR data rather than just the use of TF alone improves forecasts, and separately whether incorporating a delay in TF recovery is beneficial.ResultsIncluding TI and PCR data did not significantly improve forecasts of TF. Forecasts of TF prevalence at 36 months by the model with the delay in TF recovery were significantly better than forecasts by the model without the delay in TF recovery (p = 0.003). A zero-inflated truncated normal observation model was better than a truncated normal observation model, and better than a sensitivity-specificity observation model.ConclusionThe results in this study suggest that future studies could consider using just TF data for forecasting, and should include a delay in TF recovery.Trial registrationClinicaltrials.gov NCT00792922.
| S-EPMC4618840 | biostudies-literature
Project description:BackgroundTrachoma programs rely on guidelines made in large part using expert opinion of what will happen with and without intervention. Large community-randomized trials offer an opportunity to actually compare forecasting methods in a masked fashion.MethodsThe Program for the Rapid Elimination of Trachoma trials estimated longitudinal prevalence of ocular chlamydial infection from 24 communities treated annually with mass azithromycin. Given antibiotic coverage and biannual assessments from baseline through 30 months, forecasts of the prevalence of infection in each of the 24 communities at 36 months were made by three methods: the sum of 15 experts' opinion, statistical regression of the square-root-transformed prevalence, and a stochastic hidden Markov model of infection transmission (Susceptible-Infectious-Susceptible, or SIS model). All forecasters were masked to the 36-month results and to the other forecasts. Forecasts of the 24 communities were scored by the likelihood of the observed results and compared using Wilcoxon's signed-rank statistic.FindingsRegression and SIS hidden Markov models had significantly better likelihood than community expert opinion (p = 0.004 and p = 0.01, respectively). All forecasts scored better when perturbed to decrease Fisher's information. Each individual expert's forecast was poorer than the sum of experts.InterpretationRegression and SIS models performed significantly better than expert opinion, although all forecasts were overly confident. Further model refinements may score better, although would need to be tested and compared in new masked studies. Construction of guidelines that rely on forecasting future prevalence could consider use of mathematical and statistical models.Trial registrationClinicaltrials.gov NCT00792922.
| S-EPMC4547743 | biostudies-literature
Project description:BackgroundTremendous progress towards elimination of trachoma as a public health problem has been made. However, there are areas where the clinical indicator of disease, trachomatous inflammation-follicular (TF), remains prevalent. We quantify the progress that has been made, and forecast how TF prevalence will evolve with current interventions. We also determine the probability that a district is a transmission-hotspot based on its TF prevalence (ie, reproduction number greater than one).MethodsData on trachoma prevalence come from the GET2020 global repository organized by the World Health Organization and the International Trachoma Initiative. Forecasts of TF prevalence and the percent of districts with local control is achieved by regressing the coefficients of a fitted exponential distribution for the year-by-year distribution of TF prevalence. The probability of a district being a transmission-hotspot is extrapolated from the residuals of the regression.ResultsForecasts suggest that with current interventions, 96.5% of surveyed districts will have TF prevalence among children aged 1-9 years <5% by 2030 (95% CI: 86.6%-100.0%). Districts with TF prevalence < 20% appear unlikely to be transmission-hotspots. However, a district having TF prevalence of over 28% in 2016-2019 corresponds to at least 50% probability of being a transmission-hotspot.ConclusionsSustainable control of trachoma appears achievable. However there are transmission-hotspots that are not responding to annual mass drug administration of azithromycin and require enhanced treatment in order to reach local control.
| S-EPMC8201580 | biostudies-literature
Project description:BackgroundTrachoma is the leading infectious cause of blindness worldwide and is nearing elimination as a public health problem in Guinea Bissau. It is imperative that elimination is followed by a successful postvalidation surveillance programme. The aim of this study was to determine the acceptability and perceived utility of different diagnostic tests and sample types that could be used for postvalidation trachoma surveillance in the Bijagos Islands, Guinea Bissau.MethodsSemistructured interviews with community members and stakeholders involved in trachoma elimination were followed by focus group discussions with community members, covering experiences with trachoma and views on trachoma diagnostic methods and sample types.ResultsIn this setting, all diagnostic tests and sample types used for trachoma surveillance were generally considered acceptable by communities. A preference for laboratory-based testing and finger-prick blood samples was expressed as these results were considered more accurate and applicable to a range of diseases beyond trachoma.ConclusionsAppropriate community and stakeholder engagement and communication regarding the purpose and processes around diagnostic practice prior to trachoma programme implementation are crucial for long-term successful disease-elimination efforts.
| S-EPMC8382514 | biostudies-literature
Project description:We assessed trachoma grading agreement among field graders using photographs that included the complete spectrum of disease and compared it with cases where there was consensus among experienced graders. Trained photographers took photographs of children's conjunctiva during a clinical trial in Ethiopia. We calculated κ-agreement statistics using a complete set of 60 cases and then recalculated the κ using a consensus set where cases were limited to those cases with agreement among experienced graders. When the complete set of 60 cases was used, agreement was moderate (κ = 0.61, 95% confidence interval [95% CI] = 0.56-0.67). When the consensus set was used, agreement improved significantly (κ = 0.75, 95% CI = 0.68-0.80). The κ of the consensus set was higher than the complete set by 0.14 (95% CI = 0.12-0.16) (P < 0.001). If testing sets remove difficult-to-grade cases, agreement in trachoma grading may be higher than actually seen in population-based trachoma surveys.
| S-EPMC4155563 | biostudies-literature
Project description:Robust surveillance methods are needed for trachoma control and recrudescence monitoring, but existing methods have limitations. Here, we analyse data from nine trachoma-endemic populations and provide operational thresholds for interpretation of serological data in low-transmission and post-elimination settings. Analyses with sero-catalytic and antibody acquisition models provide insights into transmission history within each population. To accurately estimate sero-conversion rates (SCR) for trachoma in populations with high-seroprevalence in adults, the model accounts for secondary exposure to Chlamydia trachomatis due to urogenital infection. We estimate the population half-life of sero-reversion for anti-Pgp3 antibodies to be 26 (95% credible interval (CrI): 21-34) years. We show SCRs below 0.015 (95% confidence interval (CI): 0.0-0.049) per year correspond to a prevalence of trachomatous inflammation-follicular below 5%, the current threshold for elimination of active trachoma as a public health problem. As global trachoma prevalence declines, we may need cross-sectional serological survey data to inform programmatic decisions.
| S-EPMC6303365 | biostudies-literature
Project description:Tests for ocular Chlamydia trachomatis have not been well characterized, because there is no gold standard test. Latent class analysis (LCA) was performed to estimate the sensitivity and specificity of laboratory and clinical tests for trachoma in the absence of a gold standard.Individual data from pretreatment, hyperendemic areas in Ethiopia were used. A clustered LCA was performed for three diagnostic tests: PCR and WHO simplified criteria grades of follicular trachoma (TF) and intense trachomatous inflammation (TI).Data from 2111 subjects in 40 villages were available. TF was estimated to be 87.3% (95% CI, 83.3-90.1) sensitive and 36.6% (95% CI, 23.6-40.3) specific; TI was estimated to be 53.6% (95% CI, 46.1-88.0) sensitive and 88.3% (95% CI, 83.3-92.0) specific, and PCR was estimated to be 87.5% (95% CI, 79.9-97.2) sensitive and 100% (95% CI 69.3-100) specific.LCA allows for an estimate of test characteristics without prior assumption of their performance. TF and TI were found to act in a complementary manner: TF is a sensitive test and TI is a specific test. PCR is highly specific but lacks sensitivity. The performance of these tests may be due to the time course of ocular chlamydial infection, and for this reason, results may differ in areas of low prevalence or recent mass treatment (ClinicalTrials.gov number, NCT00221364).
| S-EPMC3176003 | biostudies-literature
Project description:BackgroundBased on previous studies, historical records and risk factors, trachoma was suspected to be endemic in 31 health districts (HDs) in Guinea. To facilitate planning for the elimination of trachoma as a public health problem, national trachoma surveys were conducted between 2011 and 2016 to determine the prevalence of trachomatous inflammation-follicular (TF) and trachomatous trichiasis (TT) in all 31 endemic HDs.Methodology/principal findingsA total of 27 cross-sectional surveys were conducted, each using two-stage cluster sampling (one survey in 2011 covered five HDs). Children aged 1-9 years and adults aged ≥15 years were examined for TF and TT, respectively, using the World Health Organization (WHO) simplified grading system. Indicators of household access to water, sanitation and hygiene (WASH) were also collected. A total of 100,051 people from 13,725 households of 556 clusters were examined, of whom 44,899 were male and 55,152 were female. 44,209 children aged 1-9-years and 48,745 adults aged ≥15 years were examined. The adjusted prevalence of TF varied between 1.0% (95%CI: 0.6-1.5%) to 41.8% (95%CI: 39.4-44.2%), while the adjusted prevalence of TT ranged from 0.0% (95%CI: 0.0-0.2%) to 2.8% (95%CI: 2.3-3.5%) in the 27 surveys. In all, 18 HDs had a TF prevalence ≥5% in children aged 1-9 years and 21 HDs had a TT prevalence ≥0.2% in adults aged ≥15 years. There were an estimated 32,737 (95% CI: 19,986-57,811) individuals with TT living in surveyed HDs at the time of surveys.Conclusions/significanceTrachoma is a public health problem in Guinea. 18 HDs required intervention with at least one round of mass drug administration and an estimated 32,737 persons required TT surgery in the country. The results provided clear evidence for Guinea to plan for national trachoma elimination.
| S-EPMC6013237 | biostudies-literature
Project description: Not available
| S-EPMC10316972 | biostudies-literature
Project description:BackgroundAs the World Health Organization seeks to eliminate trachoma by 2020, countries are beginning to control the transmission of trachomatous inflammation-follicular (TF) and discontinue mass drug administration (MDA) with oral azithromycin. We evaluated the effect of MDA discontinuation on TF1-9 prevalence at the district level.MethodsWe extracted from the available data districts with an impact survey at the end of their program cycle that initiated discontinuation of MDA (TF1-9 prevalence <5%), followed by a surveillance survey conducted to determine whether TF1-9 prevalence remained below the 5% threshold, warranting discontinuation of MDA. Two independent analyses were performed, 1 regression based and 1 simulation based, that assessed the change in TF1-9 from the impact survey to the surveillance survey.ResultsOf the 220 districts included, TF1-9 prevalence increased to >5% from impact to surveillance survey in 9% of districts. Regression analysis indicated that impact survey TF1-9 prevalence was a significant predictor of surveillance survey TF1-9 prevalence. The proportion of simulations with >5% TF1-9 prevalence in the surveillance survey was 2%, assuming the survey was conducted 4 years after MDA.ConclusionAn increase in TF1-9 prevalence may represent disease resurgence but could also be due to measurement error. Improved diagnostic tests are crucial to elimination of TF1-9 as a public health problem.
| S-EPMC7289551 | biostudies-literature