Table 2.

Data extraction variables.

Variable	Standardized method
First author and year of publication	Identify the first author and year of publication of the study
Objective	Detail the study objective
Study design	Detail the study design described by the author or authors
Data collection procedures	List the data collection technique or techniques used
Geographic extent	Identify the city, state, region, or country where the study was conducted
Syphilis, gestational syphilis, congenital syphilis	Identify the classification of syphilis
Period (in years) of the collected data	Identify the period of data collection
Visualization software	Identify the geographic visualization software
Spatial analysis method	Describe the methodology developed in the spatial analysis
Results	Describe the main study results
Challenges and limitations	Describe the main study challenges and limitations mentioned by the authors related to using spatial analysis