Lab Med Qual Assur.  2020 Sep;42(3):140-149. 10.15263/jlmqa.2020.42.3.140.

Comparison of Preanalytical Sample Stability between Serum and Ethylenediaminetetraacetic Acid Plasma for the Measurement of Biological Analytes

• Lee J
• Jeon K
• Lee T
• Lee J
• Kim M
• Kim HS
• Lee YK
• Kang HJ

• KMID: 2506966
• DOI: http://doi.org/10.15263/jlmqa.2020.42.3.140

Abstract

Background
In this study, we aim to examine the effects of pre-analytical factors such as specimen type (serum or plasma), collection and storage conditions, and time, on the results of chemiluminescence immunoassay.
Methods
Blood samples were collected from 10 individuals and aliquoted into two sets of K3-ethylenediaminetetraacetic acid (EDTA) and serumseparating tubes (SST) each, for plasma and serum collection, respectively. For all the samples, one set of tubes was centrifuged within 1 hour and other set was centrifuged after 4 hours, followed by cell separation. Chemiluminescence assay was performed for adrenocorticotropic hormone (ACTH), parathyroid hormone (PTH), osteocalcin, C-telopeptide, and insulin at 0, 6, 24, and 48 hours after centrifugation; all the samples were assayed in duplicate. The samples were stored at 4℃ before the assay.
Results
The results obtained showed that the levels detected in plasmas were more consistent and stable as compared to serum. After a 6-hour storage at 4℃, a significant decrease was observed in the levels of ACTH and osteocalcin in plasma and serum; whereas, PTH and C-telopeptide levels were stable in plasma but decreased significantly in serum. Insulin levels in serum showed a decrease after a 6-hour storage while the levels in plasma were found to be stable until 24-hour storage. Serum samples separated after 4 hours showed a significant decrease in all hormone levels, while C-telopeptide and insulin levels were stable in plasma samples separated after 4 hours.
Conclusions
The results were found to be more stable in plasma samples from K3-EDTA tubes as compared to serum samples from SST in the measurement of unstable biological analytes. These results suggest that K3-EDTA tubes are preferable in the specimen collection for assaying biological analytes.

Keyword

Plasma; Serum; Delayed centrifugation; Stability of analytes