Reliability analysis for continuous measurements: equivalence test for agreement.

In tandem with the rapid development of medical technology, methods for assessing intrarater and interrater reliability or agreement across tools for continuous measurements have become an increasingly important research topic. Thus far, a number of reliability assessment methods have been proposed. Among them, the limits of agreement and repeatability coefficients were found to be the most useful tools for assessing reliability when measurements are on a continuous scale. However, both are considered as descriptive methods. The concepts of consistency or conformity require an equivalence test without which judgment would be subjective. In this paper we will extend the repeatability coefficient approach and propose an equivalence test that can be used to confirm the agreement between two or more measurement tools or assess interrater and intrarater reliability. Using this approach, a formula to calculate sample size will also be suggested and examples will be provided to illustrate the method.

Comparison of surgical outcomes for small hepatocellular carcinoma in patients with hepatitis B versus hepatitis C: a Chinese experience.

BACKGROUND: Although both hepatitis B virus (HBV) and hepatitis C virus (HCV) infection are well recognized risk factors for hepatocellular carcinoma (HCC), little is known with respect to how HBV and HCV infection affect HCC recurrence in postoperative HCC Chinese patients. The objective of this study was to determine if differences exist in preoperative characteristics and postoperative HCC recurrence in patients with different HBV and HCV infection status. METHODS: The study population consisted of 413 patients undergoing a curative resection at Tianjin Cancer Hospital for small HCC (< or =3 cm) from January 1997 to December 2003. The patients were divided into four groups: HCV only (n = 75), HBV only (n = 251), HBV and HCV (n = 33), and neither HBV nor HCV (NBNC, n = 54). The preoperative status and postoperative HCC recurrence were recorded. Survival analyses were used to assess the impact of HBV/HCV status on HCC recurrence. RESULTS: Patients with HCV had a significant association with older age, lower mean preoperative platelet counts and albumin levels, higher mean prothrombin time, alanine aminotransferase and total bilirubin levels and multinodular tumors during diagnosis. Patients with HCV also had significantly less differentiated tumors and a higher incidence of vascular invasion and cirrhosis when compared to the other groups. During the follow-up, the HCV group showed a higher incidence of intrahepatic recurrence and multiple recurrent lesions than the other patients. CONCLUSIONS: Patients with HCV infection tended to be older, and were characterized by more severe cirrhosis and higher incidence of tumor multicentricity. The statistically significant determinants for reoccurrence in patients with small HCC were HCV infection, presence of vascular invasion and multiple tumors.

Factors associated with disease survival after surgical resection in Chinese patients with hepatocellular carcinoma.

OBJECTIVE: The aim of this cohort study was to investigate clinical outcome and prognostic factors after surgical resection for hepatocellular carcinoma (HCC). MATERIALS AND METHODS: A total of 1,157 HCC patients undergoing hepatic resection between 1998 and 2003 were included in this study. Univariate and multivariate analyses were performed to examine factors affecting clinical outcome and recurrence. RESULTS: Surgical procedures consisted of 1,011 (87.4%) anatomical resections, including 205 (17.7%) extended hepatectomies, 324 (28.0%) hemihepatectomies, 482 (41.7%) segmental resections, and 146 (12.6%) local resections. The results suggest that 56.6% of patients had a recurrence of HCC during the study period and the main recurrence type was intrahepatic (542; 83.1%). The median survival time was 45 months. The 1-, 3- and 5-year overall disease-free survival rates for the study population were 74%, 47%, and 39% respectively. CONCLUSIONS: The results of proportional hazard analyses suggest that tumor size, number of nodules and vascular invasion were significant predictors for poor survival rates.

Exploring the role of contextual factors in disability models.

PURPOSE: The objective of this paper is to define and categorize the types of relationships that contextual factors have within models of disability according to the WHO International Classification of Disability, Functioning, and Health (ICF) conceptual scheme. METHOD: A conceptual analysis building on the disability literature specifies the causal relationships for contextual factors in relation to the association between activity limitation and participation using a person with arthritis as an example. RESULTS: From a statistical point of view, in relation to disability process, contextual factors can act as an independent factor, confounding factor, moderating factor, and mediating factor. How the role of a particular contextual factor is specified depends on the researcher's hypothesized disability framework and research goals. Moderating and mediating contextual factors are of particular importance in disability model specification. Various sub-types of moderating contextual factors are also identified. CONCLUSION: This paper provides a framework for the conceptualization of contextual factors in the examination of disability models. This framework has implications in constructing conceptual models as well as for setting up analytical plans. In light of the increasing awareness and application of the ICF model, we intend this work to stimulate additional discussion on this topic.

Activity limitation, coping efficacy and self-perceived physical independence in people with disability.

OBJECTIVE: This study examines whether the relationships between activity limitations and independence are mediated by coping efficacy. METHOD: Data come from a cross-sectional survey of 286 adults, aged 55 or older, with osteoarthritis (OA) and/or osteoporosis (OP). Physical independence was assessed by asking to what extent respondents' OA/OP had affected their independence on a 5-point scale from 'not at all' to 'a great deal'. Activity limitations were examined in three domains: personal care, community mobility, and household activity. A coping efficacy scale was derived from three items scored on a 5-point Likert-type scale from strongly disagree to strongly agree. Structural equation modelling was used to test the model. RESULTS: Activity limitation in household activities was directly associated with perceptions of independence, with a statistically significant standardized path coefficients of -0.32. The effect of activity limitation in personal care was partially mediated by coping efficacy with a direct effect of -0.41 which was partially offset by coping efficacy to give a net effect of -0.308. The effect of community mobility on independence was completely mediated through coping efficacy with significant standardized path coefficients of -0.85 (community mobility to coping efficacy) and -0.14 (coping efficacy to independence). The overall model's goodness of fit was excellent (R =0.59, ch-square/df=1.4, CFI=0.97, and NNFI=0.97). CONCLUSION: Activity limitation had a detrimental effect on the level of self-perceived independence. Coping efficacy showed a significant mediating effect between activity limitation and self-perceived independence for the domains of personal care and community mobility, but not household tasks. This study suggests that how activity limitation affects perceptions of independence varies across activity limitation domains, and indicates the importance of incorporating activity limitation domains in future studies.