Table 2.

Main study designs on costs.

Approaches	Description	Advantages	Disadvantages
Prevalence	Frequency measure It evaluates all existing cases in a given period	Ample results Specific policy planning Fast study and recommended for chronic diseases	Considered weak at estimating the risk of developing disease
Incidence	Frequency measure Assesses the number of new cases in a given period	Implementation of measures to reduce new cases It is used more for acute diseases, since it estimates the risk of developing the disease	Not recommended for chronic diseases
Top-down	It measures the proportion of a disease attributed to several risk factors. It involves a study directed from total to lower levels	When the scope of study is well understood	More comprehensive, it hampers the study on the details of the disease
Bottom-up	Related to the unit costs of inputs used. It involves the study directed from individual levels to the total.	More detailed	Risk of double counting
Prospective	Temporal study, performed during disease. Probes the effect through the cause	Used in chronic diseases	Time-consuming and expensive
Retrospective	Temporal study performed with preexisting data. Probes the cause through the effect	Quick and cheaper	Risk of memory bias
Econometric	Comparison of groups	Minor amount of data required Cost difference between the two populations	Long study, requiring that the control group be paired to the study group
Markov models	Stochastic process Used in prospective studies. Patients stratified in stages of disease	Dynamic model aiming at studying the transition from one stage to another, evaluating the costs of each step	Transition of stages is independent, without considering the previous one