Abstract
Clinicians, patients, governments, third-party payers, and the public take for granted that diagnostic tests are accurate, safe and effective. However, we may be seriously misled if we are relying on robust study design to ensure accurate, safe, and effective diagnostic tests. Properly conducted, randomized controlled trials are the gold standard for assessing the effectiveness and safety of interventions, yet are rarely conducted in the assessment of diagnostic tests. Instead, diagnostic cohort studies are commonly performed to assess the characteristics of a diagnostic test including sensitivity and specificity. While diagnostic cohort studies can inform us about the relative accuracy of an experimental diagnostic intervention compared to a reference standard, they do not inform us about whether the differences in accuracy are clinically important, or the degree of clinical importance (in other words, the impact on patient outcomes). In this commentary we provide the advantages of the diagnostic randomized controlled trial and suggest a greater awareness and uptake in their conduct. Doing so will better ensure that patients are offered diagnostic procedures that will make a clinical difference.
Highlights
The cohort design The prevailing study design for investigating a new diagnostic test is a prospective blind comparison of the experimental test and the diagnostic reference standard (“gold standard”) in a consecutive series of patients from a representative clinical population [2,3,4]
In order to adequately assess the diagnostic characteristics, as well as the impact on clinical outcomes without bias, we suggest that the evaluation of diagnostic interventions move beyond traditional diagnostic study designs to diagnostic randomized controlled trials
Not Reported diagnostic cohort studies); 3) diagnostic randomized controlled trials can be conducted where there is no accepted reference standard; 4) test properties can still be calculated in diagnostic randomized controlled trials if the reference standard is conducted and the results kept blinded in the experimental group and the results of the experimental tests are conducted but kept blinded in the reference group; and 5) diagnostic technologies could be compared across disciplines to help policy makers decide in which new diagnostic technologies to invest
Summary
The cohort design The prevailing study design for investigating a new diagnostic test is a prospective blind comparison of the experimental test and the diagnostic reference standard (“gold standard”) in a consecutive series of patients from a representative clinical population [2,3,4]. The advantages of a diagnostic accuracy cohort study include their simplicity to perform, they are relatively inexpensive, and they are well accepted among the medical research community. They are appropriate for the early investigation of an experimental diagnostic test to determine if it is appropriate to continue investigating the experimental diagnostic test. Reasons for their lack of conduct have not been explored but may include the resources, sample size, and interdisciplinary teamwork
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