Photo Credit: Md Saiful Islam
The following is a summary of “Significance of Intracellular versus Extracellular Calcium Pyrophosphate Crystals in Diagnosing Calcium Pyrophosphate Crystal Arthritis.,” published in the October 2024 issue of Rheumatology by Harris et al.
Acute and chronic calcium pyrophosphate (CPP) crystal arthritis is characterized by synovial CPP crystals in inflamed joints. The clinical significance of the intracellular or extracellular location of these crystals remains underexplored.
Researchers conducted a retrospective study to assess the relevance of CPP crystal location in diagnosing acute and chronic CPP crystal arthritis.
They collected data from Waikato District Health Board to identify a study population with synovial fluid samples positive for CPP crystals. The cohort was stratified into intracellular and extracellular groups, comparing the proportion of acute and chronic CPP crystal arthritis cases. Diagnosis required the presence of synovial CPP crystals, objective evidence of joint inflammation, and exclusion of alternative diagnoses. Further analysis included demographics, laboratory results, and cartilage calcification.
The results showed that 134 patients were included, with 108 having intracellular CPP crystals and 26 having extracellular CPP crystals. Acute/chronic CPP crystal arthritis was diagnosed in 85% of the intracellular group and 50% of the extracellular group (P<0.001). After excluding septic arthritis cases, acute/chronic CPP crystal arthritis was diagnosed in 97% of the intracellular group and 62% of the extracellular group (P<0.001).
The study concluded that intracellular CPP crystals were more strongly associated with acute and chronic CPP crystal arthritis, while extracellular locations were less specific.
Source: jrheum.org/content/early/2024/09/24/jrheum.2024-0469
