TY - JOUR
T1 - Intraclass correlation coefficient and outcome prevalence are associated in clustered binary data
AU - Gulliford, M C
AU - Adams, G
AU - Ukoumunne, O C
AU - Latinovic, R
AU - Chinn, S
AU - Campbell, M J
PY - 2005/3
Y1 - 2005/3
N2 - Background and Objective: To describe the association between values for a proportion and the intraclass correlation coefficient (ICC). Methods: Analysis of data obtained from the General Practice Research Database (GPRD) for variation between United Kingdom general practices and results from a Health Technology Assessment (HTA) review for a range of outcomes in community and health services settings. Results: There were 188 ICCs from the GPRD, the median prevalence was 13.1% (interquartile range IQR 3.5 to 28.4%) and median ICC 0.051 (IQR 0.011 to 0.094). There were 136 ICCs from the HTA review, with median prevalence 6.5% (IQR 0.4 to 20.7%) and median ICC 0.006 (IQR 0.0003 to 0.036). There was a linear association of log ICC with log prevalence in both datasets (GPRD, regression coefficient 0.61, 95% confidence interval 0.53 to 0.69, P <0.001; HTA, 0.91, 0.81 to 1.01, P <0.001). When the prevalence was 1% the predicted ICC was 0.008 from the GPRD or 0.002 from the HTA, but when the prevalence was 40% the predicted ICC was 0.075 (GPRD) or 0.046 (HTA). Conclusion: The prevalence of an outcome may be used to make an informed assumption about the magnitude of the intraclass correlation coefficient. (C) 2005 Elsevier Inc. All rights reserved
AB - Background and Objective: To describe the association between values for a proportion and the intraclass correlation coefficient (ICC). Methods: Analysis of data obtained from the General Practice Research Database (GPRD) for variation between United Kingdom general practices and results from a Health Technology Assessment (HTA) review for a range of outcomes in community and health services settings. Results: There were 188 ICCs from the GPRD, the median prevalence was 13.1% (interquartile range IQR 3.5 to 28.4%) and median ICC 0.051 (IQR 0.011 to 0.094). There were 136 ICCs from the HTA review, with median prevalence 6.5% (IQR 0.4 to 20.7%) and median ICC 0.006 (IQR 0.0003 to 0.036). There was a linear association of log ICC with log prevalence in both datasets (GPRD, regression coefficient 0.61, 95% confidence interval 0.53 to 0.69, P <0.001; HTA, 0.91, 0.81 to 1.01, P <0.001). When the prevalence was 1% the predicted ICC was 0.008 from the GPRD or 0.002 from the HTA, but when the prevalence was 40% the predicted ICC was 0.075 (GPRD) or 0.046 (HTA). Conclusion: The prevalence of an outcome may be used to make an informed assumption about the magnitude of the intraclass correlation coefficient. (C) 2005 Elsevier Inc. All rights reserved
U2 - 10.1016/j.jclinepi.2004.08.012
DO - 10.1016/j.jclinepi.2004.08.012
M3 - Article
VL - 58
SP - 246
EP - 251
JO - Journal of Clinical Epidemiology
JF - Journal of Clinical Epidemiology
IS - 3
ER -