Is a screening test with sensitivity above 90% (ninety percent) a good indicator of its effectiveness?

From the Guidelines

A screening test with sensitivity above 90% is generally considered effective for detecting disease, but sensitivity alone is not sufficient to determine overall effectiveness. A highly sensitive test is good at identifying people who truly have the condition (few false negatives), meaning it rarely misses cases. However, complete evaluation of a screening test's effectiveness also requires consideration of specificity (ability to correctly identify those without the disease), positive and negative predictive values (which depend on disease prevalence), and the test's practical implementation factors.

Key Considerations

• A test with high sensitivity but poor specificity may lead to many false positives, resulting in unnecessary anxiety, follow-up testing, and potential harm.
• The ideal screening test balances high sensitivity with acceptable specificity while being cost-effective, acceptable to patients, and leading to interventions that improve outcomes.
• The clinical context, disease prevalence, and consequences of false results must all be considered when determining if a screening test with >90% sensitivity is truly effective for its intended purpose. As noted in a recent study 1, for use as a triaging test, a sensitivity ≥90% is recommended, but the specificity should be ≥75–85%, depending on the availability of follow-up testing. This highlights the importance of considering both sensitivity and specificity in the context of resource availability and the potential consequences of false results.

Balancing Sensitivity and Specificity

• High sensitivity is crucial for minimizing false negatives, but it must be balanced with adequate specificity to avoid excessive false positives.
• The choice of cutoff points can significantly influence the sensitivity and specificity of a test, as seen in a study on heart failure syndromes 1, where different cutoff points yielded varying levels of sensitivity and specificity.
• Recent guidelines for laboratory analysis in diabetes mellitus 1 also emphasize the importance of balancing sensitivity and specificity, recommending that semiquantitative or qualitative screening tests should be positive in >85% of individuals with moderately increased albuminuria to be useful for assessment of cardiovascular risk and progression of kidney disease.

Practical Implementation

• The practical implementation of a screening test, including its cost-effectiveness, patient acceptability, and the potential for interventions to improve outcomes, is critical to its overall effectiveness.
• As discussed in the context of blood biomarker tests for amyloid pathology 1, the availability of follow-up testing and the potential consequences of false results can significantly impact the choice of screening test and its implementation.

Conclusion Not Applicable - Answer Continues

Given these considerations, a screening test with sensitivity above 90% can be a good indicator of its effectiveness, but only when balanced with adequate specificity and considered within the context of its practical implementation and the potential consequences of its use. This balanced approach ensures that the test is not only effective at detecting disease but also minimizes harm and maximizes benefit for patients.

From the Research

Screening Test Effectiveness

A screening test with sensitivity above 90% can be considered a good indicator of its effectiveness, but it is not the only factor to consider.

• The test's specificity, disease prevalence, and positive predictive value also play a crucial role in determining its overall effectiveness 2.
• A high sensitivity test may still generate many false-positive results, leading to unnecessary procedures and anxiety, while a test with many false-negative results may worsen outcomes due to delayed diagnosis and treatment 2.

Key Characteristics of a Useful Screening Test

For a screening test to be useful, it must have:

• High sensitivity and specificity for the disease being screened
• Be cost-effective
• Be acceptable to patients
• Have a high positive predictive value, which is influenced by disease prevalence and test sensitivity and specificity 2, 3

Limitations and Biases

Screening tests can be subject to various biases, including:

• Screening bias, where the sample population is not representative of the target population
• Length bias, where indolent disease is more likely to be detected than aggressive disease
• Lead-time bias, where survival is measured from the date of screening rather than detection of symptomatic disease 2
• The accuracy assessment interval, which can affect estimates of sensitivity and specificity 3