Liu et al. BMC Public Health 2010, 10:82 http://www.biomedcentral.com/1471-2458/10/82 Page 7 of 9 Table 3 Optimal waist circumference thresholds for cardiovascular risk factors clustering in boys (n = 982) and girls (n = 863) Boys Girls Area under the curve (95% confidence interval) 0.814 (0.761-0.866) 0.810 (0.720-0.899) Sensitivity (%) 83.3 75.0 Specificity (%) 73.7 67.2 Threshold (percentiles) 90 84 Odds ratio (95% confidence interval) 10.349 (4.466-23.979) 8.084 (3.147-20.767) Figure 3 The 50th percentiles for waist circumference in seven studies for boys and girls. Data in the present study were collected among children aged 6-12 years in 2008; Data from Australian children aged 7-15 years were collected in 1985 [18]; Data of children aged 7-18 years from Xinjiang province, China were collected in 2005 [25]; Data from Turkish children aged 7-17 years were collected in 2005 [17]; Data from British children aged 5-16 years were collected in 1990 [21]; Data from Hong Kong Chinese children aged 6-18 years was collected in 2002- 2004 [24]; Data from Mexican children aged 6-10 years (collection date unknown) [23]. Table 4 Optimal age- and gender-specific waist circumference cut-off values for Chinese children Age (years) 6 7 8 9 10 11 12 Girls 57.2 59.3 62.6 65.7 68.5 71.8 76.3 Boys 62.7 66.1 70.0 75.5 79.9 83.1 88.0 tend to cluster together for individuals among both chil- dren and adults. The cluster of risk factors and thresh- olds with the strongest predictive relationship to cardiovascular disease should be identified for both clinical practice and prevention-oriented research and practice for the whole population, especially when devel- oping universal cut-off points to predict it. Conclusions The present study provides waist circumference percen- tiles for Chinese children aged 6-12 years living in the