Classification error rates of NAT2PRED in the 56 worldwide samples. The classification accuracy of NAT2PRED was evaluated using either three phenotypic classes (slow, intermediate and rapid acetylators; hatched area) or two phenotypic classes (slow and other acetylators; black area) for the acetylation status. Single populations are reported on the left side of the plot, with sample sizes (number of individuals) in brackets. Geographic areas are indicated on the right side, as follows: SSAFRICA, sub-Saharan Africa; EUROPE/NORTH AFRICA, Europe and North Africa; CSASIA, Central and South Asia; EAST ASIA, East Asia; AME, America. The assignment of populations to one of the five world regions was based on the origin of the population, in effect ignoring the past 1,000 years of known human migration (e.g., people of European descent in the United States were assigned to Europe).