When should sensitivity be prioritized over specificity in medical diagnostics?

From the Guidelines

Sensitivity should be prioritized over specificity in medical diagnostics when the consequences of missing a diagnosis are severe and potentially life-threatening. This approach is supported by the American College of Physicians, which recommends using age-adjusted d-dimer thresholds to determine whether imaging is warranted for patients with suspected acute pulmonary embolism 1. The use of sensitivity-focused tests is particularly important when testing for life-threatening diseases like cancer, HIV, tuberculosis, or conditions requiring immediate intervention such as meningitis or pulmonary embolism. In these scenarios, it's better to accept some false positives (which can be ruled out with follow-up testing) than to miss cases that require urgent treatment. The underlying principle is that the harm of missing a serious condition typically outweighs the temporary anxiety and resource utilization associated with false positives, especially when confirmatory testing is available to refine the diagnosis. Some key points to consider when prioritizing sensitivity over specificity include:

• The disease being tested for should have severe consequences if left untreated or if treatment is delayed
• The test should be able to identify a significant proportion of true cases (high sensitivity)
• The consequences of false positives should be minimal and manageable with follow-up testing
• The disease should be treatable, and early detection should significantly improve outcomes. For example, in the diagnosis of tuberculosis, performing a second diagnostic test when the initial test is negative is a strategy to increase sensitivity, even if it reduces specificity, as the consequences of missing a diagnosis of latent tuberculosis infection (LTBI) can be severe 1. Overall, the decision to prioritize sensitivity over specificity should be made on a case-by-case basis, taking into account the specific disease being tested for, the consequences of missing a diagnosis, and the availability of follow-up testing to refine the diagnosis.

From the Research

Sensitivity vs Specificity in Medical Diagnostics

• Sensitivity and specificity are two fundamental concepts in medical diagnostics that help evaluate the accuracy of a diagnostic test 2, 3.
• Sensitivity refers to the ability of a test to correctly identify individuals with a disease, while specificity refers to the ability of a test to correctly identify individuals without the disease 3, 4.
• In general, sensitivity and specificity are considered fixed properties of a diagnostic test, but they can be influenced by various factors such as disease prevalence and population case mix 5, 6.

Prioritizing Sensitivity over Specificity

• Sensitivity should be prioritized over specificity in medical diagnostics when the consequences of missing a true case are more severe than the consequences of falsely identifying a healthy individual as diseased 3, 4.
• For example, in screening tests for life-threatening diseases, sensitivity is often prioritized to ensure that as many cases as possible are detected, even if it means that some healthy individuals are falsely identified as diseased 2, 5.
• However, prioritizing sensitivity over specificity can lead to an increase in false positives, which can result in unnecessary further testing, treatment, and anxiety for patients 3, 6.

Disease Prevalence and Diagnostic Test Accuracy

• Disease prevalence can affect the accuracy of diagnostic tests, with higher prevalence often associated with higher sensitivity and lower specificity 5.
• Clinicians should consider the implications of disease prevalence and spectrum when interpreting the results from studies of diagnostic test accuracy 5, 6.
• Understanding the relationship between disease prevalence and diagnostic test accuracy can help clinicians make more informed decisions about test selection and interpretation 3, 4.