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 °C and -80 °C in serum or EDTA plasma and up to 6 months at -80 8C. PIIINP was stable only 1 month in EDTA plasma (but not in serum) at -20 °C or -80 8C. After 3 months of storage, PIIINP was not stable anymore, in serum or EDTA plasma, at -20 °C or -80 8C. Surprisingly, after 6 months at -80 8C, 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) μg/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. © 2015 Elsevier Masson SAS and European Union Geriatric Medicine Society. All rights reserved.