2.2 Data Extraction
The data extracted from studies that met the inclusion criteria included
the location of the study, the year of the study, sample size, mean age
of the respondents, GFR-formular used, prevalence and risk factors, (in
studies that carried out multiple logistic regression). In case the full
text revealed that not all requirements were present, the paper was
excluded. Additional literature was obtained through searching
references in the manuscript (snowball method). An individual paper was
categorized into different areas. The review was further elaborated by
addressing each area separately and rereading all article that were
relevant for that area.