title: Short-term Forecasting of the Prevalence of Trachoma: Expert Opinion, Statistical Regression, versus Transmission Models.
abstract: BACKGROUND
  Trachoma 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.
  
  
  METHODS
  The 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.
  
  
  RESULTS
  Regression 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.
  
  
  CONCLUSIONS
  Regression 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.
  
  
  BACKGROUND
  Clinicaltrials.gov NCT00792922.
authors: Francis I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America.
authors: Fengchen
authors: F
authors: Liu
authors: Francis I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America; Department of Ophthalmology, University of California San Francisco, San Francisco, California, United States of America; Department of Epidemiology & Biostatistics, University of California San Francisco, San Francisco, California, United States of America.
authors: Travis C
authors: TC
authors: Porco
authors: Programme FSS/Université Abdou Moumouni de Niamey, Programme National de Santé Oculaire, Niamey, Niger.
authors: Abdou
authors: A
authors: Amza
authors: Programme FSS/Université Abdou Moumouni de Niamey, Programme National de Santé Oculaire, Niamey, Niger.
authors: Boubacar
authors: B
authors: Kadri
authors: Programme FSS/Université Abdou Moumouni de Niamey, Programme National de Santé Oculaire, Niamey, Niger.
authors: Baido
authors: B
authors: Nassirou
authors: Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors: Sheila K
authors: SK
authors: West
authors: Clinical Research Unit, Department of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors: Robin L
authors: RL
authors: Bailey
authors: Francis I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America; Department of Ophthalmology, University of California San Francisco, San Francisco, California, United States of America.
authors: Jeremy D
authors: JD
authors: Keenan
authors: Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland.
authors: Anthony W
authors: AW
authors: Solomon
authors: International Trachoma Initiative, Atlanta, Georgia, United States of America.
authors: Paul M
authors: PM
authors: Emerson
authors: Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
authors: Manoj
authors: M
authors: Gambhir
authors: Francis I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America; Department of Ophthalmology, University of California San Francisco, San Francisco, California, United States of America; Department of Epidemiology & Biostatistics, University of California San Francisco, San Francisco, California, United States of America.
authors: Thomas M
authors: TM
authors: Lietman
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D019353:Endemic Diseases / Q000706:statistics & numerical data*; D005544:Forecasting / Q000379:methods; D006801:Humans; D007223:Infant; D008954:Models, Biological; D009548:Niger / Q000453:epidemiology; D015995:Prevalence; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*; D012044:Regression Analysis; D014141:Trachoma / Q000188:drug therapy* / Q000453:epidemiology* / Q000635:transmission
chemical_list: D000900:Anti-Bacterial Agents