OBJECTIVES: State Transition Models (STMs) are the most common type of models used in the economic evaluation of health technologies. Transition probabilities (TPs) are central to the STMs which determine the movement of patients between the health states. This study aims to identify and summarize the existing Health Technology Assessment (HTA) guidelines around estimating TPs.

METHODS: A targeted literature review was conducted to study the national HTA guidelines around TP estimation across the world. Existing national pharmacoeconomic guidelines were identified by manual search on websites of HTA agencies and referring to the Professional Society for Health Economics and Outcomes Research (ISPOR’s) ‘Pharmacoeconomic Guidelines Around the World’. Guidelines available in English, Dutch, Portuguese, German, Spanish, Persian, and Russian were included. In addition, National Institute for Health and Care Excellence (NICE) UK technical support documents (TSDs) were also reviewed.

RESULTS: Overall, 45 national pharmacoeconomic guidelines were included. Most of the guidance found was from Europe (n = 26; 58%) followed by Asia and Oceania (n = 9; 20%), North America and Latin America (both; n = 7; 15%), and Africa (n = 3; 7%). None of the HTA agencies provided proper guidance on TP estimation methods that need to be employed in STMs. The guidelines mostly focused on the presentation of TPs (in a matrix form), nature of the TPs (constant or time-varying) and differentiation between rates and probabilities. In addition to the pharmacoeconomic guidelines, 21 TSDs were retrieved from the NICE Decision Support Unit website. None of the TSDs focused on TPs estimation method guidance or framework. However, four TSDs covered TPs briefly (TSD 5, TSD 15, TSD 17, and TSD19).

CONCLUSIONS: Mostly, the HTA guidelines are silent on TP estimation. Further research is warranted to develop more detailed guidelines on TP estimation.