Diagnostic Accuracy of Raman Spectroscopy Integrated With Polarized Light Microscopy for Calcium...

Area of Science:

• Rheumatology
• Crystallography
• Spectroscopy

Background:

• Calcium pyrophosphate (CPP) crystal deposition is a key factor in diagnosing certain types of arthritis.
• Accurate identification of CPP crystals in synovial fluid is crucial for effective patient management.
• Traditional polarized light microscopy (PLM) can face challenges in specificity, particularly in complex cases.

Purpose of the Study:

• To evaluate the diagnostic performance of integrated Raman polarized light microscopy (iRPolM) for identifying CPP crystals.
• To compare the accuracy of iRPolM against established diagnostic methods, including PLM and the 2023 ACR/EULAR criteria.
• To assess the interrater reliability of iRPolM in the context of rheumatological practice.

Main Methods:

• A diagnostic accuracy study was conducted on 400 synovial fluid samples.
• iRPolM was utilized for crystal identification and compared with PLM.
• The 2023 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) criteria served as a benchmark for CPPD diagnosis.

Main Results:

• iRPolM demonstrated strong interrater reliability (κ = 0.88) when compared to the 2023 ACR/EULAR criteria.
• High diagnostic performance metrics were observed for iRPolM: 86.0% sensitivity, 99.1% specificity, and 97.5% accuracy.
• The study identified novel particles in synovial fluid, including calcium carbonate crystals and microplastics, and showed iRPolM's utility in confirming uncertain CPP identifications.

Conclusions:

• iRPolM is a highly effective tool for identifying CPP crystals, offering strong diagnostic performance.
• The integration of Raman spectroscopy into rheumatology practice can significantly benefit patients suspected of having CPPD.
• iRPolM provides a more specific and reliable method for diagnosing CPPD compared to PLM alone, especially in challenging cases.