Two-stage lot quality assurance sampling framework for monitoring and evaluation of neglected tropical diseases, allowing for imperfect diagnostics and spatial heterogeneity
Fig 2
Program decision-making process based on 2-stage LQAS framework allowing for an imperfect diagnostic test.
Panel A illustrates the risk of making a wrong program decision (εovertreat and εundertreat) for a given true prevalence πi and decision cut-off c = 90 was applied. The vertical straight line indicates the program prevalence threshold T = 50%, whereas the horizontal dotted lines represent the εovertreat and εundertreat for πi = 37.5% and πi = 62.5%, respectively. Panel B represents the decision cut-off c for a choice of grey zone width (lower limit (LL) = 37.5% and upper limit (UL) = 62.5%) and acceptable risk levels (Eovertreat = 25% and εundertreat = 5%) for a particular of range of πi. The solid sigmoid curves (in red and blue) indicate the values of c that satisfy the conditions and
, whereas the dotted sigmoid curves (green and purple) do not satisfy the conditions mentioned above. All graphs are based on the same theoretical diagnostic test D (sed = 80% and spd = 98%), survey design (nclust = 5 and nsub = 50), an intra-cluster correlation ρi = 0.02 and 10,000 Monte Carlo simulations.