Serum, plasma, and dried blood spot high-sensitivity C-reactive protein enzyme immunoassay for population research.

Author(s): Brindle E, Fujita M, Shofer J, O'Connor KA

Publication: J Immunol Methods, 2010, Vol. 362, Page 112-20

PubMed ID: 20850446 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   The purpose of this study was to determine the effects of analysis of DBS versus liquid serum or plasma and collection of venous versus capillary blood on CRP levels. Plasma was prepared from venous blood collected into K2EDTA tubes. Serum was prepared from venous blood collected into plain tubes. A second plain tube of venous blood was used to prepare venous DBS, while a fingerprick specimen was used to prepare capillary DBS. Both DBS were dried at room temperature for 3-5 hours, stored in sealed bags with desiccant, and frozen at -20 degrees C along with serum and plasma specimens.

   Summary of Findings:

   Significant correlations were observed between CRP measurements from plasma, serum, venous DBS, and capillary DBS (0.974-0.995). Plasma levels of CRP were on average 7% lower than those in serum. CRP levels were only an average of 1% lower in venous DBS than capillary DBS, but they were 33% and 31% lower, on average, respectively, than CRP levels measured in serum. The authors report that their CRP assay results did not differ significantly from those determined with a previously published assay method.

   Biospecimens

   • Bodily Fluid - Blood
   • Bodily Fluid - Plasma
   • Bodily Fluid - Serum

   Preservative Types

   • Frozen
   • Other Preservative

   Diagnoses:

   • Not specified

   Platform:

   Analyte	Technology Platform
   Protein	ELISA

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Preservation	Type of fixation/preservation	Air-dried Frozen
   Biospecimen Aliquots and Components	Blood and blood products	Plasma Serum Whole blood
   Biospecimen Acquisition	Anatomical location of blood draw	Capillary Vein

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2. Study Purpose

   The purpose of this study was to determine the stability of CRP in DBS (venous or capillary blood) and liquid serum stored at various temperatures and durations and subjected to freeze-thaw cycling (22 degrees C, then -20 degrees C) or hot-cool cycling (37 degrees C, then 15-17 degrees C). All of these specimens were frozen at -20 degrees C prior to and after experimental storage. A separate group of matched serum and venous DBS specimens was field-collected in northern Kenya and subjected to slightly different preanalytical storage conditions. These venous DBS were stored in sealed bags at ambient temperatures (12-28 degrees C) for 13-42 d while serum was frozen and stored in liquid nitrogen for 13-42 d. Then both types of specimens were transported and frozen at -20 degrees C in a laboratory for an undisclosed amount of time, shipped via air express on dry ice to Seattle, Washington, and stored at -20 degrees C until assay (approximately 8-12 months after collection).

   Summary of Findings:

   CRP levels showed significant declines after capillary DBS were subjected to 8 freeze-thaw cycles (p=0.013) or after they were stored at 22 degrees C for 14 d or more, 37 degrees C for 7 d or more, or during hot cycling after 12 h at 37 degrees C followed by 12 h at 15 degrees C. On the other hand, CRP was stable in capillary DBS stored at -20 degrees C for up to 42 d. During long-term frozen storage (lasting between 161 and 1026 d at -20 degrees C), CRP declined significantly in venous DBS (p<0.0001) but not in serum. CRP levels in venous DBS and serum specimens that were field-collected were significantly correlated with one another. However, for DBS that spent 20 days or less at ambient temperatures before frozen storage, CRP levels averaged 76% of those in serum, and for DBS that spent more than 20 days at ambient temperatures before frozen storage, CRP levels averaged 51% of those in serum, demonstrating that ambient temperature storage prior to frozen storage had a detrimental effect on CRP levels in DBS.

   Biospecimens

   • Bodily Fluid - Blood
   • Bodily Fluid - Serum

   Preservative Types

   • Frozen
   • Other Preservative

   Diagnoses:

   • Not specified

   Platform:

   Analyte	Technology Platform
   Protein	ELISA

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Preservation	Type of fixation/preservation	Air-dried Frozen
   Biospecimen Aliquots and Components	Blood and blood products	Serum Whole blood
   Storage	Storage temperature	-20 degrees C 15-17 degrees C 22 degrees C 37 degrees C
   Storage	Freeze/thaw cycling	1 cycle 2 cycles 4 cycles 8 cycles
   Storage	Storage duration	7 d 14 d 28 d 42 d 161 d 374 d 764 d 1026 d
   Biospecimen Acquisition	Anatomical location of blood draw	Capillary Vein

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