There are several evaluation strategies that assess the quality of epidemiological studies. In general, these methodologies are oriented towards determining the degree of evidence contributed by these studies, most of them clinical<sup>(5)</sup> . In this type of evaluation, clinical trials and cohort studies are considered to be the best methodological route to generate evidence—mostly because of causality issues, such as those that arise in the study of the efficiency and effectiveness of interventions and/or treatments. By contrast, crosssectional studies are considered exploratory and only capable of generating hypotheses. The particular situation under which research is done on the HIV epidemic (prevalence, determination of knowledge and behavior levels) limits the possibility of implementing experimental studies; HIV-related research is based mainly on the application of crosssectional studies or surveys. For this reason, the UNAIDS Triangulation Resource Guide states that priority, or the highest level of trust, must be given to the data obtained by large-scale, standardized, cross-sectional epidemiological studies, such as National Demographic and Health Surveys (DHS)<sup>(6)</sup> .

The literature notes several questionnaires and checklists that create a framework to assess the methodological quality of studies, but most of them are designed to be applied to randomized clinical trials and not to observational studies<sup>(7)</sup> . The methodology described in this paper was developed and implemented so that it is mostly applicable to cross-sectional studies. In a practical way, this new tool aims to determine which studies utilize strategies and designs that increase the reliability of the results. The ASAP questionnaire is based on an extensive analysis that includes the World Health Organization’s normative guidelines on the implementation of prevalence studies for sexually transmitted infections<sup>(8)</sup> , as well as several published materials—including books and scientific journals—which form the basis for evaluation of the methodological quality of epidemiological studies<sup>(9, 10, 11, 12, 13, 14)</sup> .

# **Methodology for the Assessment of Data Quality**

Since 2009, Ministries of Health in several Latin American countries—with help from UNAIDS and ASAP—have compiled the main findings of HIV studies done over the past fifteen years. The data for each country was then integrated into a document called “ _Database and References for an Evidence-Based Strategy”_ . Criteria for the studies to be included were simple: (i) they had to represent a primary source of data; and (ii) they had to contain quantitative data. Through this process, a great number of documents have been compiled by local, national and international research groups. The resulting databases are a robust collection of studies categorized by type, methodological characteristics and status of publication.

The methodology of analysis for data quality has two phases. The first phase characterizes each of the documents to be included in the database, and the second phase analyzes the methodological context. This analysis is carried out following an evaluation guideline (included in the Annex), whose main sections are detailed below.

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