Comparative study of blood collection tubes and thromboplastin reagents for correction of INR discrepancies: a proposal for maximum allowable magnesium contamination in sodium citrate anticoagulant solutions.

Author(s): van den Besselaar AM, Van Zanten AP, Brantjes HM, Elisen MG, van der Meer FJ, Poland DC, Sturk A, Leyte A, Castel A

Publication: Am J Clin Pathol, 2012, Vol. 138, Page 248-54

PubMed ID: 22904137 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 collection tube type, reagent, and analyzer on PT and INR in plasma from outpatients receiving vitamin K antagonist treatment. After collection into sodium citrate Vacutainers or Monovettes, plasma was transferred into new plastic tubes and transported by car at room temperature to 3 different laboratories for PT analysis within 5 hours. Frozen pooled citrate plasma was used for analyzer calibration.

   Summary of Findings:

   For specimens collected in Vacutainers, very strong correlations were observed between INR for all reagent/instrument combinations, but INR were significantly different between the three reagent/instrument combinations with a maximum mean bias of 14% observed between the ACL-9000 and STA-R Evolution analyzers. This INR bias was reduced along with the number of discrepant cases (INR of 2 was the threshold) when local PT system calibration was performed. For specimens collected in Monovettes, some significant differences in INR were observed between the reagent/instrument combinations, but the maximum mean bias of 4.9% was much lower than that observed with specimens collected in Vacutainers. Again the maximum mean bias for all specimens and the number of discrepant cases decreased after local PT system calibration was performed. INR calculated using the STA Hepato Quick assay with the STA-R Evolution analyzer were systematically higher than those calculated with the other 2 instrument/reagent combinations, regardless of collection tube type. The authors point to the higher levels of magnesium contamination in Vacutainer tubes as accounting for the larger INR discrepancies.

   Biospecimens

   • Bodily Fluid - Plasma
   • Bodily Fluid - Blood

   Preservative Types

   • None (Fresh)
   • Frozen

   Diagnoses:

   • Not specified

   Platform:

   Analyte	Technology Platform
   Morphology	Hematology/ auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Acquisition	Type of collection container/solution	Vacutainer Monovette
   Hematology/ auto analyzer Specific	Reaction solution	STA Hepato Quick Innovin HemosIL RecombiPlasTin 2G
   Hematology/ auto analyzer Specific	Technology platform	STA-R Evolution Sysmex CA-1500 ACL-9000

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