Which statement about the index test in a diagnostic study is true?

Which statement about the index test in a diagnostic study is true?

• A. The reference standard
• B. The diagnostic test being studied
• C. The patient-reported outcome
• D. The imaging modality used in routine care

Answer: (B)

In diagnostic accuracy research, the central idea is evaluating a specific test’s ability to classify disease status. The index test is precisely that: the diagnostic test being studied to determine how well it detects or rules out the disease. Its results are compared to the reference standard, which is the best available method for establishing the true disease status. The patient-reported outcome reflects the patient’s experience or symptoms rather than the actual disease status, and the imaging modality used in routine care isn’t inherently the test under evaluation unless it is the test being studied.

In diagnostic accuracy research, the central idea is evaluating a specific test’s ability to classify disease status. The index test is precisely that: the diagnostic test being studied to determine how well it detects or rules out the disease. Its results are compared to the reference standard, which is the best available method for establishing the true disease status. The patient-reported outcome reflects the patient’s experience or symptoms rather than the actual disease status, and the imaging modality used in routine care isn’t inherently the test under evaluation unless it is the test being studied.