Objectives: We evaluated whether and how the effects of risk factors on periodontal disease (PD) were modified by measurement errors using community periodontal index (CPI) and loss attachment (LA) in the community-based survey. Methods: A pilot validation study was performed to estimate the rates of false negative and false positive for both CPI and LA in 31 subjects from different regions using measurements from 12 well-trained dentists and a senior periodontist as a gold standard. Afterward, a Taiwanese nationwide survey was conducted by enrolling 3,860 participants to estimate the effect of each risk factor on PD calibrated with both sensitivity and specificity of two indices. Results: The values obtained for the sensitivity to false-positive ratio for CPI ranged widely from 1.12 to 7.71, indicating regional variation in both errors. The calibrated adjusted odds ratio for smoking vs non-smoking was higher than the uncalibrated odds ratio for PD defined by CPI (2.75 (2.01, 3.77) vs 2.02 (1.63, 2.52)) and LA (3.85 (2.44, 6.13) vs 1.93 (1.47, 2.54)) scores. Similar underestimation was noted for other risk factors. Conclusion: The effects of risk factors on PD measured using CPI and LA in a large population-based survey were underestimated without correcting for measurement errors.
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