Abstract
INTRODUCTIONGrading the strength of a body of diagnostic test evidence involves challenges over and above those related to grading the evidence from health care intervention studies. This chapter identifies challenges and outlines principles for grading the body of evidence related to diagnostic test performance.CHALLENGESDiagnostic test evidence is challenging to grade because standard tools for grading evidence were designed for questions about treatment rather than diagnostic testing; and the clinical usefulness of a diagnostic test depends on multiple links in a chain of evidence connecting the performance of a test to changes in clinical outcomes.PRINCIPLESReviewers grading the strength of a body of evidence on diagnostic tests should consider the principle domains of risk of bias, directness, consistency, and precision, as well as publication bias, dose response association, plausible unmeasured confounders that would decrease an effect, and strength of association, similar to what is done to grade evidence on treatment interventions. Given that most evidence regarding the clinical value of diagnostic tests is indirect, an analytic framework must be developed to clarify the key questions, and strength of evidence for each link in that framework should be graded separately. However if reviewers choose to combine domains into a single grade of evidence, they should explain their rationale for a particular summary grade and the relevant domains that were weighed in assigning the summary grade.
Highlights
Grading the strength of a body of diagnostic test evidence involves challenges over and above those related to grading the evidence from health care intervention studies
The greatest challenge appears to be assessing multiple links in a chain of evidence connecting the performance of a test to changes in clinical outcomes
We focused primarily on grading the body of evidence related to a crucial link in the chain—diagnostic test performance—and described less fully the challenges involved in assessing other links in the chain
Summary
“Grading” refers to the assessment of the strength of the body of evidence supporting a given statement or conclusion rather than to the quality of an individual study.[1]. Note that an individual woman’s risk may be different from these estimates depending on her own individual characteristics[11] outcomes can be assessed in very much the same way as a body of evidence evaluating outcomes of therapeutic interventions Grading issues in this type of diagnostic test study are more straightforward than in studies measuring accuracy outcomes. Reviewers should comment on publication bias when circumstances suggest that relevant empirical findings, negative or no-difference findings, have not been published or are unavailable The dose-response association may support an underlying mechanism of detection and potential relevance for some tests that have continuous outcomes and possibly multiple cutoffs [e.g., gene expression, serum PSA (prostate-specific antigen) levels, and ventilation/perfusion scanning] The impact of plausible unmeasured confounders may be relevant to testing strategies that predict outcomes.
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