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The present paper has three objectives. First, methods for comparing alternative tests for the purpose of replacement of one test with a second presumably superior test are described. Second, problems in the interpretation of the relevance of different diagnostic thresholds (thresholds of positivity) that define who is and who is not a disordered gambler are examined and a potential solution offered in the form of a common quantitative measure of the risk of being a disordered gambler. Third, alternative methodologies are described as potential solutions to the lack of a gold or reference standard in the evaluation of new tests. [ABSTRACT FROM AUTHOR]

The present paper is the third in a series on the evaluation of new tests designed to detect the disordered gambler. The present paper has two objectives. First, the observed variation in test performance between settings and populations is described in general terms and an explanation of the observed variation is presented in terms of what is referred to as spectrum effects. Second the expected variation in test performance between settings and populations is illustrated with several examples and the implications emphasized for the purpose of test evaluation. [ABSTRACT FROM AUTHOR]

Much of the debate over how best to estimate the prevalence of problem gambling in the general population is driven by a number of misconceptions, misinterpretations, and questionable, sometimes erroneous assumptions. Among the latter is the failure to understand that what is being validated is not the test but the interpretation of test scores for a specific purpose. In addition there has been a lack of attention to defining the clinical and/or epidemiologic relevance of case definitions in terms of severity and other clinical attributes, a misunderstanding of how test values are interpreted when criterion thresholds or cut-off points are selected, and a failure to replicate the validation of criterion thresholds for defining cases of problem gambling. It is argued further that the distinction between dichotomy and continuum is a false choice, and any emphasis on overestimation is misdirected. Alternative methods for evaluating tests and estimating prevalence are described and a pragmatic empirical approach to the interpretation of prevalence estimates is recommended. [ABSTRACT FROM AUTHOR]

The focus of this report is to examine the process of validation of new screening tests designed to detect the problem gambler in research and practice settings. A hierarchical or phases of evaluation model is presented as a conceptual framework to describe the basic features of the validation process and its implications for application and interpretation of test results. The report describes a number of threats to validity in the form of sources of unintended bias that when unrecognized may lead to incorrect interpretations of study results and the drawing of incorrect conclusions about the usefulness of the new screening tests. Examples drawn from the gambling literature on problem gambling are used to illustrate some of the more important concepts including spectrum bias and clinical variation in test accuracy. The concept of zones of severity and the bias inherent in selecting criterion thresholds are reviewed. A definition of reference or study gold standard is provided. The use of 2-stage designs to establish validity by efficiently using reference standards to determine indices of accuracy and prevalence is recommended. [ABSTRACT FROM AUTHOR]

Much of the debate over how best to estimate the prevalence of problem gambling in the general population is driven by a number of misconceptions, misinterpretations, and questionable, sometimes erroneous assumptions. Among the latter is the failure to understand that what is being validated is not the test but the interpretation of test scores for a specific purpose. In addition there has been a lack of attention to defining the clinical and/or epidemiologic relevance of case definitions in terms of severity and other clinical attributes, a misunderstanding of how test values are interpreted when criterion thresholds or cut-off points are selected, and a failure to replicate the validation of criterion thresholds for defining cases of problem gambling. It is argued further that the distinction between dichotomy and continuum is a false choice, and any emphasis on overestimation is misdirected. Alternative methods for evaluating tests and estimating prevalence are described and a pragmatic empirical approach to the interpretation of prevalence estimates is recommended. [ABSTRACT FROM AUTHOR]

Two-stage designs offer several advantages for purposes of test validation and prevalence estimation. These include enhanced precision and increased cost-efficiency. Cost efficiency is obtained when the best available verification criterion is too expensive to employ in a large-scale epidemiologic study. The use of two-stage (or double-sampling) designs permit the same inferences from application to only a subset of those who were screened (with the less expensive criterion) during stage one. The retesting of only some of the first stage respondents introduces a bias, however, if these are sampled on the basis of first stage screening results. The form of this bias is described and solutions for correcting estimates are provided. These solutions are applied to the data reported by Abbott and Volberg (1996) in their study of the New Zealand general population. Corrected estimates of the sensitivity and specificity of the South Oaks Gambling Screen are obtained and used to adjust the reported lifetime and current prevalence estimates. The value of multi-stage designs for validity assessment and prevalence estimation are briefly described. [ABSTRACT FROM AUTHOR]

The concern that the South Oaks Gambling Screen (SOGS) and other screening tests have a relatively high rate of false positive errors which results in overestimation of the true prevalence in general population studies is shown to be unfounded. False positives are seen to be a necessary but not sufficient condition for overestimation. It is demonstrated that the proper research question is whether the sample prevalence estimator is biased, and, if so, in which direction. One solution to the problem of bias is shown to depend on the availability of estimates of the error rates of the test. [ABSTRACT FROM AUTHOR]

Theorists and practitioners are separated by a gap that reflects an unnatural concern with their respective tasks. As a consequence, practitioners lack theories that are grounded in the best of practice, nor do they engage in practice that is guided by the kind of prescriptive theory from which it can benefit from systematic feedback. The reasons for this predicament can be traced to the structural and personal characteristics of the current knowledge generation, knowledge transfer, and knowledge utilization system. It is recommended that practitioners in the addictions rely more on their own resources in order to explicate the systems under which they practice in order to develop theories of practice. This includes the use of systematic observation, hypothesis testing, and evaluating research as major tools in the construction of prescriptive theories of practice in the addictions. [ABSTRACT FROM PUBLISHER]

In response to Abbott and Volberg's (in press) rejoinder to my epidemiologic note on verification bias and estimation of prevalence rates (Gambino, in press), I provide the formulas for computing confidence intervals for the results of second-stage verification. In addition, I provide the appropriate equation for determining confidence intervals when prevalence is near zero or one. Finally, we present formulas for determining the most efficient sample sizes needed to minimize second-stage variance estimates. These allow the investigator working under a fixed budget to determine the relative value of sampling negative screens to test for false negatives. We close with an observation on the interpretability of evidence. [ABSTRACT FROM AUTHOR]