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Using patient management as a surrogate for patient health outcomes in diagnostic test evaluation.

Staub LP, Lord SJ, Simes RJ, Dyer S, Houssami N, Chen RY, Irwig L - BMC Med Res Methodol (2012)

Bottom Line: Patient management can be measured as a surrogate outcome for test evaluation if its limitations are recognised.The potential consequences of a positive and negative test result on patient management should be pre-specified and the potential patient benefits of these management changes clearly stated.Regardless of the study design used, the critical assumption that patient management is a valid surrogate for downstream patient benefits or harms must be discussed in these studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: NHMRC Clinical Trials Centre, The University of Sydney, Sydney, Australia. lukas.staub@ctc.usyd.edu.au

ABSTRACT

Background: Before a new test is introduced in clinical practice, evidence is needed to demonstrate that its use will lead to improvements in patient health outcomes. Studies reporting test accuracy may not be sufficient, and clinical trials of tests that measure patient health outcomes are rarely feasible. Therefore, the consequences of testing on patient management are often investigated as an intermediate step in the pathway. There is a lack of guidance on the interpretation of this evidence, and patient management studies often neglect a discussion of the limitations of measuring patient management as a surrogate for health outcomes.

Methods: We discuss the rationale for measuring patient management, describe the common study designs and provide guidance about how this evidence should be reported.

Results: Interpretation of patient management studies relies on the condition that patient management is a valid surrogate for downstream patient benefits. This condition presupposes two critical assumptions: the test improves diagnostic accuracy; and the measured changes in patient management improve patient health outcomes. The validity of this evidence depends on the certainty around these critical assumptions and the ability of the study design to minimise bias. Three common designs are test RCTs that measure patient management as a primary endpoint, diagnostic before-after studies that compare planned patient management before and after testing, and accuracy studies that are extended to report on the actual treatment or further tests received following a positive and negative test result.

Conclusions: Patient management can be measured as a surrogate outcome for test evaluation if its limitations are recognised. The potential consequences of a positive and negative test result on patient management should be pre-specified and the potential patient benefits of these management changes clearly stated. Randomised comparisons will provide higher quality evidence about differences in patient management using the new test than observational studies. Regardless of the study design used, the critical assumption that patient management is a valid surrogate for downstream patient benefits or harms must be discussed in these studies.

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Related in: MedlinePlus

Study designs to assess the impact of tests on patient management. Abbreviations: RCT = randomised controlled trial, R = randomise, PET = positron emission tomography, MRI = magnetic resonance imaging
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Figure 3: Study designs to assess the impact of tests on patient management. Abbreviations: RCT = randomised controlled trial, R = randomise, PET = positron emission tomography, MRI = magnetic resonance imaging

Mentions: RCTs with patient management as a primary endpoint are the optimal design to minimise bias for measurement of the consequences of alternative test strategies (Figure 3A), because they do not rely on assumptions of planned management. Such RCTs are suitable for replacement, add-on or triage tests and can also measure any other important intermediate consequences of the test procedure, such as test safety or patient acceptability. This evidence may be instrumental in the planning of definitive trials of a test. Rules developed for the design and reporting of treatment trials also apply to trials reporting on patient management [23]. An example is the ongoing POC-OP trial, which measures the effectiveness of point-of-care prothrombin time testing to reduce the administration of blood products during and after surgery [18]. Patients are randomised to usual care plus point-of-care testing or usual care only, and the primary outcome is the relative risk of receiving any fresh frozen plasma perioperatively. If point-of-care prothrombin time testing in the operation theatre proves to reduce the administration of fresh frozen plasma, this may lead to decreased costs and avoid complications associated with the administration of allogenic blood products.


Using patient management as a surrogate for patient health outcomes in diagnostic test evaluation.

Staub LP, Lord SJ, Simes RJ, Dyer S, Houssami N, Chen RY, Irwig L - BMC Med Res Methodol (2012)

Study designs to assess the impact of tests on patient management. Abbreviations: RCT = randomised controlled trial, R = randomise, PET = positron emission tomography, MRI = magnetic resonance imaging
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3313870&req=5

Figure 3: Study designs to assess the impact of tests on patient management. Abbreviations: RCT = randomised controlled trial, R = randomise, PET = positron emission tomography, MRI = magnetic resonance imaging
Mentions: RCTs with patient management as a primary endpoint are the optimal design to minimise bias for measurement of the consequences of alternative test strategies (Figure 3A), because they do not rely on assumptions of planned management. Such RCTs are suitable for replacement, add-on or triage tests and can also measure any other important intermediate consequences of the test procedure, such as test safety or patient acceptability. This evidence may be instrumental in the planning of definitive trials of a test. Rules developed for the design and reporting of treatment trials also apply to trials reporting on patient management [23]. An example is the ongoing POC-OP trial, which measures the effectiveness of point-of-care prothrombin time testing to reduce the administration of blood products during and after surgery [18]. Patients are randomised to usual care plus point-of-care testing or usual care only, and the primary outcome is the relative risk of receiving any fresh frozen plasma perioperatively. If point-of-care prothrombin time testing in the operation theatre proves to reduce the administration of fresh frozen plasma, this may lead to decreased costs and avoid complications associated with the administration of allogenic blood products.

Bottom Line: Patient management can be measured as a surrogate outcome for test evaluation if its limitations are recognised.The potential consequences of a positive and negative test result on patient management should be pre-specified and the potential patient benefits of these management changes clearly stated.Regardless of the study design used, the critical assumption that patient management is a valid surrogate for downstream patient benefits or harms must be discussed in these studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: NHMRC Clinical Trials Centre, The University of Sydney, Sydney, Australia. lukas.staub@ctc.usyd.edu.au

ABSTRACT

Background: Before a new test is introduced in clinical practice, evidence is needed to demonstrate that its use will lead to improvements in patient health outcomes. Studies reporting test accuracy may not be sufficient, and clinical trials of tests that measure patient health outcomes are rarely feasible. Therefore, the consequences of testing on patient management are often investigated as an intermediate step in the pathway. There is a lack of guidance on the interpretation of this evidence, and patient management studies often neglect a discussion of the limitations of measuring patient management as a surrogate for health outcomes.

Methods: We discuss the rationale for measuring patient management, describe the common study designs and provide guidance about how this evidence should be reported.

Results: Interpretation of patient management studies relies on the condition that patient management is a valid surrogate for downstream patient benefits. This condition presupposes two critical assumptions: the test improves diagnostic accuracy; and the measured changes in patient management improve patient health outcomes. The validity of this evidence depends on the certainty around these critical assumptions and the ability of the study design to minimise bias. Three common designs are test RCTs that measure patient management as a primary endpoint, diagnostic before-after studies that compare planned patient management before and after testing, and accuracy studies that are extended to report on the actual treatment or further tests received following a positive and negative test result.

Conclusions: Patient management can be measured as a surrogate outcome for test evaluation if its limitations are recognised. The potential consequences of a positive and negative test result on patient management should be pre-specified and the potential patient benefits of these management changes clearly stated. Randomised comparisons will provide higher quality evidence about differences in patient management using the new test than observational studies. Regardless of the study design used, the critical assumption that patient management is a valid surrogate for downstream patient benefits or harms must be discussed in these studies.

Show MeSH
Related in: MedlinePlus