Doctor using digital tablet to discuss results of diagnostic tests with senior cancer patient

Assessing the Value of Diagnostic Tests

The merit of diagnostic tests may extend beyond measurable clinical outcomes. In pursuit of diagnostic excellence, evaluation of diagnostic tests should consider 3 aspects: accuracy, clinical utility, and patient benefit. In a JAMA Viewpoint article, Ashley Graham Kennedy, PhD, outlined the main factors that should be considered when assessing the true value of a diagnostic test.

The first determination is whether the test can be used to accurately diagnose the suspected condition. It must be technically accurate in order to detect or quantify what it is intended to measure. In clinical use, this is determined via sensitivity and specificity. To have meaning, the test results must always be interpreted in a clinical setting, taking into account the patient’s history and physical examination findings when applicable. Without clinical interpretation of the results, even if they are technically accurate, they may not have meaning for the patient or practitioner.

An effective diagnostic test must also have clinical utility, with a probability of leading to a measurable improvement in the patient’s health once applied. Information from a diagnostic test does not have a direct effect on clinical outcomes—it is the subsequent diagnostic, therapeutic, and preventive decisions that are made on the basis of the results that can affect clinical outcomes.

Beyond accuracy and clinical utility, there are times when patient benefit prevails in determining the value of a diagnostic test. Even if a disease is not treatable or preventable, many patients still want to have knowledge of their diagnosis to help them understand or make sense of their condition. In such cases, the diagnosis can empower the patient by reducing uncertainty and enabling them to focus on strategies for maintaining quality of life. Others may find the diagnosis unsettling, anxiety provoking, or depressing, so the decision of whether to perform a test that will not have measurable clinical benefit for the patients should be made with careful consideration on an individual basis.

High level
As the author stated, “Patients who desire more information should generally be allowed to have it. However, when a patient wants less information, this, too should be respected.” Protocols and pathways should factor accuracy, clinical utility, and patient benefit into decisions about diagnostic tests, with flexibility to allow clinicians to make the best decision for each individual patient.

Ground level
While diagnostic test results are undeniably an important part of clinical decision making, clinicians must also consider the interpretation of the results and probability of improving the patient’s health once applied. The decision of whether to perform a diagnostic test should be shared with the patient, especially in cases where the disease cannot be treated or prevented. To be clinically effective, a diagnostic test should be technically accurate, have a measurable net-positive effect on a patient’s clinical outcome, and positively affect the patient’s health or well-being in some way.