Dependence of TIMP-1 plasma levels on preanalytical specimen handling.

BACKGROUND Tissue inhibitor of metalloproteinases-1 (TIMP-1) in blood might be a helpful biomarker in various diseases. However, various authors report that TIMP-1 is dependent on preanalytical procedures. Our study was performed to determine how storage conditions and time to centrifugation influence TIMP-1. MATERIALS AND METHODS Twenty-six blood specimens were collected from each of 20 volunteers. Two specimens from each person were centrifuged/measured within 1 h after venipuncture and frozen at -80 degrees C. They were thawed once or twice within 72 h. Eight specimens were stored at 20 degrees C in daylight, 8 at 20 degrees C covered and 8 at 4 degrees C in daylight. Four of each of these 8 specimens were mixed once a day until centrifugation. A mixed and an unmixed specimen of each group was centrifuged/measured after 3, 6, 24 and 72 h. RESULTS TIMP-1 increased after freeze/thaw (p < 0.001). Mixing blood specimens more than once caused increased TIMP-1 (p < 0.001). TIMP-1 increased within 3 h of storage (p < 0.001). The increase was lower in specimens covered and refrigerated (p < 0.001). CONCLUSION TIMP-1 is unstable and has to be evaluated carefully. Blood should be centrifuged directly after venipuncture. For routine application, specimen handling must be standardized and carefully followed. Research should be done on specimens handled identically.