Stability of YKL-40 concentration in blood samples

The stability of YKL-40, a mammalian member of the family of 18 glycosylhyd rolases, in blood samples handled under different temperatures and differen t time intervals before centrifugation was studied in paired serum and plas ma samples from 25 healthy premenopausal Danish women. Significant elevatio ns of YKL-40 were found in 8 paired serum samples left on the clot for more than 3 h at room temperature compared to paired serum samples left on the clot for 3 h or less. Significant elevations of YKL-40 were found in 8 pair ed plasma (EDTA) samples left on the blood cells for more than 8 h at room temperature compared to paired plasma (EDTA) samples left on the blood cell s for 8 h or less. No elevations were found in YKL-40 levels in serum sampl es left on the clot at 4 degrees C for 24 h or in plasma (EDTA) samples lef t on the blood cells for 72 h before centrifugation. Significantly lower co ncentrations of YKL-40 were measured in plasma (EDTA) compared with paired serum samples with a serum/plasma ratio of 1.4 in samples left on the clot or on blood cells at 4 degrees C for up to 24 h. Repetitive freezing and th awing had no significant effect on the measured YKL-40 concentrations. In c onclusion, we have shown that YKL-40 is very dependent on the handling proc edures. All the blood samples must be processed into plasma (EDTA) within 8 h at room temperature or into serum in less than 3 h at room temperature. If this is not possible, the blood samples must be stored at 4 degrees C un til processed.