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Are tube fill volumes below 90% a rejection criterion for all coagulation tests?

Author(s): Odabasi MS, Yalcinkaya Kara ZM

Publication: Lab Med, 2023, Vol. , Page

PubMed ID: 38104249 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   This study compared PT, APTT, and fibrinogen levels in plasma obtained from the blood of healthy volunteers and patients taking oral anticoagulants in partially filled (50%, 60%, 70%, 80% or 90%) and completely filled tubes.  Venous blood was collected using syringes from ten healthy volunteers and ten patients receiving oral vitamin K antagonist anticoagulant therapy.  Blood was immediately transferred into Sarstedt 0.2% buffered sodium citrate tubes. Tubes were filled to the fill line (2.7 mL blood, 100%), and to a volume of 90% (2.4 mL blood), 80% (2.1 mL blood), 70% (1.8 mL blood), 60% (1.5 mL blood), and 50 % (1.2 mL). All tubes were mixed by inversion. Blood was centrifuged at 2000 x g for 10 min at room temperature immediately before analysis. The normalized PT and APTT as well as fibrinogen levels were measured using a Stago Compact Max 3 coagulation analyzer. The reference change value was calculated based on the analytical and previously reported biological variation. The total allowable error was 15% for PT and APTT and 20% for fibrinogen.

   Summary of Findings:

   When all specimens were considered, changes in the PT and APTT were within allowable the reference change value and total allowable error when the tubes were filled to ≥70%; but when filled to tube volume that was ≤60%, PT and APTT were prolonged, and the percent error exceeded the total allowable error of 15%. Among healthy patients, PT was longer in tubes that were filled ≤70% (P≤0.014), and APTT was prolonged in tubes that were filled to ≤80% (P≤ 0.019). Among specimens collected from patients taking an oral anticoagulant, n increase APTT was observed when tubes were filled ≤60% (P=0.019), whereas PT was not significantly affected by fill volumes as low as 50%. Generally, fibrinogen levels were not significantly affected by tube fill volume and for all specimens remained within the acceptable reference change value and total allowable error (20%) for all fill volumes investigated, but for specimens from patients on an oral anticoagulant, the fibrinogen level was reduced when the fill volume was 50% (P=0.02). The authors conclude that a tube fill volume of ≥70% meets the specifications for PT and APTT and a fill volume of ≥50% is sufficient for fibrinogen.

   Biospecimens

   • Bodily Fluid - Plasma
   • Bodily Fluid - Blood

   Preservative Types

   • None (Fresh)

   Diagnoses:

   • Not specified
   • Normal

   Platform:

   Analyte	Technology Platform
   Glycoprotein	Hematology/ auto analyzer
   Morphology	Hematology/ auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Preaquisition	Other drugs	Oral anticoagulants None
   Biospecimen Aliquots and Components	Aliquot size/volume	50% full 60% full 70% full 80% full 90% full 100% full
   Biospecimen Acquisition	Method of fluid acquisition	Properly filled tube Improperly filled tube

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