Minimal Residual Disease (MRD) tests are powerful tools for detecting tiny amounts of myeloma cells that remain after treatment. Their accuracy and reliability depend on the method used, the quality of the sample, and how the results are interpreted.

Key Factors Influencing Accuracy and Reliability

Testing Method:

• Next-Generation Sequencing (NGS): Highly sensitive (detects 1 in 1 million cells), FDA-approved (clonoSEQ®), and widely used in clinical trials.
• Flow Cytometry: Sensitive and FDA-approved, but may miss very low levels of disease.
• Blood-Based MRD Tests (Liquid Biopsy): Less invasive but currently less sensitive than bone marrow-based tests.

Sample Quality:

• High-quality bone marrow samples are crucial for accurate results. Poor sampling may lead to false negatives.
• Blood-based tests offer easier sampling but may not detect very low disease levels.

Testing Environment:

• MRD testing in academic centers and clinical trials often uses standardized methods, ensuring more consistent results.
• Community oncology centers may have limited access to the most advanced testing options, potentially affecting accuracy.

Detection Limits (Sensitivity):

• The most sensitive tests (NGS) can detect disease at a level of 10⁻⁶.
• Flow cytometry typically detects down to 10⁻⁵, while blood-based tests are improving but are not yet as sensitive.

Clinical Interpretation:

• MRD-negative results mean no disease was detected at the test’s sensitivity limit, but do not guarantee the disease is completely gone.
• MRD-positive results indicate residual disease, guiding doctors in adjusting treatment plans.

Are MRD Tests 100% Accurate?

No test is perfect. False negatives (missing residual disease) and false positives (detecting cells that may not cause relapse) can occur. That’s why MRD testing is often combined with imaging (PET-CT, MRI) and other clinical assessments for a more complete picture.

Why Reliability Matters

Consistent MRD testing over time helps doctors track how well treatment is working and predict the risk of relapse, making it a valuable tool in managing multiple myeloma.