Balancing Test Sensitivity and Specificity to Cut RA Diagnostic Costs

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To maximize RA diagnostic test cost-effectiveness,balancing sensitivity and specificity, add-on tests with high specificity (high true negative rate) should be favored
To maximize RA diagnostic test cost-effectiveness,balancing sensitivity and specificity, add-on tests with high specificity (high true negative rate) should be favored

Add-on diagnostic testing favoring specificity over sensitivity are cost effective, with the largest benefit occurring in patients at an intermediate risk of developing rheumatoid arthritis (RA), according to research published in Arthritis Care & Research.

Jolanda J Luime, PhD, Erasmus Medical Center and Erasmus University, Rotterdam, the Netherlands, and colleagues, modeled 4 diagnostic add-on tests to the American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) 2010 RA classification criteria, using data from the Rotterdam Early Arthritis Cohort.

High Yield Data Summary

  • To maximize RA diagnostic test cost-effectiveness, while balancing sensitivity and specificity, add-on tests with high specificity (high true negative rate) should be favored 

“Sensitivity, specificity, and costs were assigned to the magnetic resonance imaging of hands and feet, interleukin-6 (IL-6) serum level tests, B cell-related gene expression, and gene assay for RA,” said Dr Luime. Sensitivity, specificity, and costs were 0.90, 0.60, €756; 0.70, 0.53, €50; 0.60, 0.90, €150; and 0.40, 0.85, €750, respectively, for each procedure.

Outcomes were evaluated in 552 patients; 263 were intermediate-risk patients and 329 were seronegative patients. 

The highest unweighted diagnostic net benefit (UDNB) was found when using the B cell assay in patients at intermediate risk (43%, incremental cost effectiveness ratio [ICER] €5,314); the lowest UDNB was found with the IL-6 test in seroengative patients (-11.4%, ICER €7,650).

“In this early health technology assessment study, we modeled the short-term cost effectiveness of 4 new diagnostic pathways,” said Dr Luime. “If a threshold of €20,000 is applied, the B cell assay would be preferred over other alternatives with a 78% probability of being cost effective for intermediate-risk patients, 57% for all patients, and 73% for seronegative patients.”

Summary and Clinical Applicability

To maximize RA diagnostic test cost-effectiveness (while balancing sensitivity and specificity) add-on tests with high specificity, and hence a high true negative rate, should be favored as the current American College of Rheumatology and EULAR 2010 RA classification criteria have been shown to effectively rule out disease.

“Add-on tests … with a headroom less than €370 per test are cost effective, with the largest diagnostic benefit occurring in intermediate-risk patients,” Dr Luime concluded.

Limitations and Disclosures

“With new diagnostic biomarkers in the pipeline, our decision model is able to determine the maximum increase in diagnostic cost for which reclassification of patients is still likely to be cost effective,” said Dr Luime. “A limitation of performing early health technology assessment is that there is only a limited amount of clinical data available with which to populate the decision models.”

This study was supported by the Center for Translational Molecular Medicine and the Dutch Arthritis Foundation, project TRACER (grant O41-202). 

Reference

Luime JJ, Buisman LR, Oppe M, et al. Cost-Effectiveness Model for Evaluating New Diagnostic Tests in the Evaluation of Patients With Inflammatory Arthritis at Risk of Having Rheumatoid Arthritis. Arthritis Care Res. 2016;68(7):927-935; doi: 10.1002/acr.22776

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