Agreement Among Multiple Observers on Crystal Identification by Synovial Fluid Microscopy
Authors' conclusion
Compensated polarized microscopy remained consistent in detecting and identifying crystals in synovial fluid, even when examined among multiple observers, confirming its high utility for clinical practice.
Study context
- Population
- Consecutive synovial fluid samples analysed by compensated polarized microscopy (400×) by 5 observers250 observations · 50 samples
- Outcome
- Interrater agreement on crystal identification (no crystals, MSU, CPP), Cohen's kappa
Methodological detailsobservational, consecutive synovial fluid sampling, 5 observers blinded to clinical data
- Observational
- Consecutive synovial fluid sampling
- 5 observers blinded to clinical data
Main finding
As reported in the abstract
Interrater agreement (Cohen's kappa)
Overall κ (95% CI 0.64-0.84), good agreement
0.74
Crystal detection κ
0.71
95% CI 0.59–0.82
MSU κ
0.88
95% CI 0.75–1.0
CPP κ
0.69
95% CI 0.56–0.82
Observational data: associations, not effects.
Further findings
Agreement by visualization delay (before vs after 24 hours)
- No differences (P = 0.859)
Agreement by expertise in crystal analysis
- No differences (P = 0.989)
Ordinary-light observations matching final diagnosis
- Matched in 242 of 250 cases
- 96.8%
- Most crystal identifications already made by ordinary light
Original publication
Agreement Among Multiple Observers on Crystal Identification by Synovial Fluid Microscopy. Arthritis Care Res (Hoboken). Published 25 November 2022. doi:10.
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