PT  - JOURNAL ARTICLE
AU  - Weidong Zhang
AU  - Sergei Likhodii
AU  - Erfan Aref-Eshghi
AU  - Yuhua Zhang
AU  - Patricia E. Harper
AU  - Edward Randell
AU  - Roger Green
AU  - Glynn Martin
AU  - Andrew Furey
AU  - Guang Sun
AU  - Proton Rahman
AU  - Guangju Zhai
TI  - Relationship Between Blood Plasma and Synovial Fluid Metabolite Concentrations in Patients with Osteoarthritis
AID  - 10.3899/jrheum.141252
DP  - 2015 May 01
TA  - The Journal of Rheumatology
PG  - 859--865
VI  - 42
IP  - 5
4099  - http://www.jrheum.org/content/42/5/859.short
4100  - http://www.jrheum.org/content/42/5/859.full
SO  - J Rheumatol2015 May 01; 42
AB  - Objective. To investigate the relationship between plasma and synovial fluid (SF) metabolite concentrations in patients with osteoarthritis (OA). Methods. Blood plasma and SF samples were collected from patients with primary knee OA undergoing total knee arthroplasty. Metabolic profiling was performed by electrospray ionization tandem mass spectrometry using the AbsoluteIDQ kit. The profiling yielded 168 metabolite concentrations. Correlation analysis between SF and plasma metabolite concentrations was done on absolute concentrations as well as metabolite concentration ratios using Spearman’s rank correlation (ρ) method. Results. A total of 69 patients with knee OA were included, 30 men and 39 women, with an average age of 66 ± 8 years. For the absolute metabolite concentrations, the average ρ was 0.23 ± 0.13. Only 8 out of 168 metabolite concentrations had a ρ ≥ 0.45, with a p value ≤ 2.98 × 10−4, statistically significant after correcting multiple testing with the Bonferroni method. For the metabolite ratios (n = 28,056), the average ρ was 0.29 ± 0.20. There were 4018 metabolite ratios with a ρ ≥ 0.52 and a p value ≤ 1.78 × 10−6, significant after correcting multiple testing. Sex-separate analyses found no difference in ρ between men and women. Similarly, there was no difference in ρ between people younger and older than 65 years. Conclusion. Correlation between blood plasma and SF metabolite concentrations are modest. Metabolite ratios, which are considered proxies for enzymatic reaction rates and have higher correlations, should be considered when using blood plasma as a surrogate of SF in OA biomarker identification.