Critical analytical evaluation of promising markers for sarcopenia

We tested and validated irisin (IRI), myostatin (MYO), PIIINP, osteoglycin (OGN), TMEM119 (TMEM) and activin A (AA) and established the analytical performance, reference range and stability (considered unstable if more than 20% increase/decrease in the levels was observed in more than 10% of the samples). We were unable to obtain a valuable calibration curve with the Cusabio kits (TMEME and OGN). Coefficient of variation (CV) was too high for IRI (CV 17-30%), but were <= 10% for the 3 other analytes. AA and MYO were stable up to 3 months at -20 degrees C and -80 degrees C in serum or EDTA plasma and up to 6 months at -80 degrees C. PIIINP was stable only 1 month in EDTA plasma (but not in serum) at -20 degrees C or -80 degrees C. After 3 months of storage, PIIINP was not stable anymore, in serum or EDTA plasma, at -20 degrees C or -80 degrees C. Surprisingly, after 6 months at -80 degrees C, results returned in the +/- 20% for both serum and EDTA plasma. PIIINP levels did not differ between men and women and the RR was (median, 90% CI) 1.2 (0.8-1.6)-6.0 (5.6-6.4) mu g/L. The RR for MYO was 845 (437-1312)-6067 (5524-6552) pg/mL for men and 600 (268-1027)-4438 (4026-4837) pg/mL for women and the RR for AA was 177 (132-210)-622 (580-661) pg/mL for men and 98 (49-147)-480 (430-525) pg/mL for women. PIIINP and AA but not MYO accumulated in CKD as values observed in 10 hemodialyzed patients were higher than in normal individuals. (C) 2015 Published by Elsevier Masson SAS.