The main purpose of the paper is to present some theoretical approaches and some methods providing assessment optimization in specialists' accreditation in area of public health services. The results of research presented in this paper, include the model of multistage adaptive measurements and two methods for reliability and validity analysis,
providing high justice decisions in accreditation and corresponding to requirements in High-Stakes Testing procedures. The assessment optimization intends for minimization time of assessment and for reliability and validity data increasing. For optimization the special model of measurements based on multistage adaptive testing is offered. The using
of offered model in assessment design allows to realize the advantages of traditional adaptive testing and linear testing, while minimizing their disadvantages. So, this model is recommended as dominating for assessment in accreditation