| Summary: | 碩士 === 國立臺灣大學 === 流行病學與預防醫學研究所 === 101 === Background: Community Periodontal Index (CPI) has been recommended in epidemiological studies on periodontal disease (PD). However, there are several thorny issues when this indicator is applied to a community-based epidemiological study. The validity and the reliability of its measurement across examiners are often criticized. The correlation between teeth and sextant in the same individual or same district characterized by multilevel data further complicates the accuracy of measurement of CPI and the analysis of the correlates accounting for the condition of PD. It is of great interest to do calibration of CPI measurement making allowance for such multi-level data. The measurement errors obtained from the calibration study were further applied to calibrating the odds ratio for the association between certain risk factor (such as smoking) andPD.
Aim: The calibration study before a nationwide survey of CPI was conducted to assess the reliability and validity on the periodontal disease measurement taking the correlated property of CPI into account. Theses measurement errors were incorporated into Bayesian hierarchical model to correct the magritude of odds ratio between smoking and PD.
Methods and Materials: Thirteen examiners were involved in intra- and inter-rater measurement of site-level on thirty-one subjects with CPI index at individual, sextant, and tooth level from different districts. The validity with sensitivity and specificity was conducted to compare the results from these rates against a gold standard senior specialist in periodontology. The reliability with Kappa and correlation coefficient was also assessed. We applied a series of random effect mixed model to assess the validity and reliability making allowance for correlated data. We develop a Bayesian hierarchical model with the consideration of validity and correlation arising from hierarchical data structure.
Results: The total of 28,008 repeated measure site data were available for analysis. Without stratifying the districts, as far as the reliability is concerned, the kappa values for site, tooth and sextant level, respectively, were 0.71 (95% CI: 0.69, 0.74), 0.78(0.74, 0.80) and 0.78(0.72, 0.83). Accounting for subject effect, the estimate and 95% confidence interval of intra-examiner based on the gold standard using a generalized linear mixed-effect model were 0.01 (95% CI: -0.35, 0.37), -0.15 (95% CI:-0.54, 0.25) and -0.29(95% CI: -0.93, 0.35) at site, tooth and sextant level, respectively, indicating a lack of statistical significance. The sensitivity and the specificity based on the gold standard sample at site, tooth and sextant level, respectively, were as follows: 0.44 and 0.96; 0.57 and 0.90; 0.73 and 0.82. Using the generalized linear mixed-effect model, the estimate and 95% confidence interval adjusted subject effect of validity at site, tooth and sextant level, respectively, were -0.11 (95% CI: -0.51, 0.30), -0.16(95% CI:-0.58, 0.26) and -0.12(95% CI:-0.49, 0.25), without statistical significance. However, the reliability and validity of examiners measurement varied with districts. After accounting for correlation, the estimates of reliability for the examiners of Taipei at site level and the estimates of validity for the examiners of Tainan(I) at site and tooth level were statistical significance.
After the calibration of measurement error and the consideration of correlation resulting from hierarchical data structure with Bayesian DAG model, the adjusted odds ratio was inflated from 1.60(1.44, 1.78) to 3.11(2.14, 4.38).
Conclusion: The calibration study on PD shows that reliability and validity was in poor at site level but acceptable at sextant level. The reliability varied with districts after taking correlation into account. However, the validity of CPI has a large variation and requires for calibration, but the overall difference was not statistically significant. The results of calibration would provide the basis for calibrating the association between correlates and the condition of PD.
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