Evaluation of sample handling in relation to levels of tissue inhibitor of metalloproteinases-1 measured in blood by immunoassay.
BACKGROUND
The possible effect of preanalytical conditions such as blood sample preparation and handling on TIMP-1 levels in blood needs thorough investigation.


METHODS
Blood was collected in dry tubes and tubes containing EDTA and kept at 4 degrees C or 20 degrees C for 1, 3, 8, 24 or 72 hours before processing into serum or EDTA plasma. In addition, serum and EDTA plasma samples were frozen and thawed 1-8 times. TIMP-1 was measured by ELISA.


RESULTS
Time to processing for up to 72 hours did not significantly affect TIMP-1 levels in serum. In EDTA plasma, TIMP-1 levels were stable for up to eight hours; however, if samples were kept for 24 hours or longer the TIMP-1 levels increased (p < 0.0001). Repeated freezing and thawing had a significant effect on TIMP-1 levels in serum (p = 0.04). In plasma, repeated freezing and thawing for up to six times did not influence TIMP-1. However, in plasma samples exposed to seven or eight freeze/thaw cycles TIMP-1 levels decreased, although not significantly (p = 0.23).


CONCLUSIONS
Handling and processing of blood samples is crucial for TIMP-1 measurement by immunoassay. In serum, TIMP-1 levels are unaffected by time to processing. Plasma samples should be processed within eight hours to avoid a TIMP-1 increase. For the measurement of TIMP-1 in archival material, serum should not be used because TIMP-1 levels are significantly affected by repeated freezing and thawing; archival plasma can readily be used provided that samples have not been frozen and thawed more than six times.
Holten-Andersen
M N
MN
Institute for Pharmacology and Pathobiology, The Royal Veterinary and Agricultural University, Frederiksberg C, Copenhagen, Denmark. mholten@dadlnet.dk
Schrohl
A S
AS
Brünner
N
N
Nielsen
H J
HJ
Høgdall
C K
CK
Høgdall
E V S
EV
D014408:Biomarkers, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005615:Freezing; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D009369:Neoplasms / Q000097:blood / Q000175:diagnosis*; D013048:Specimen Handling / Q000379:methods*; D013696:Temperature; D013997:Time Factors; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000097:blood*
D014408:Biomarkers, Tumor; D002614:Chelating Agents; D019715:Tissue Inhibitor of Metalloproteinase-1; D004492:Edetic Acid