Difference in activated partial thromboplastin time values with two different reagents according to C-reactive...

Area of Science:

• Clinical Chemistry
• Hematology
• Diagnostic Reagents

Background:

• Activated partial thromboplastin time (APTT) assay results are influenced by reagent composition.
• Discrepancies in APTT measurements necessitate investigation into underlying causes.

Purpose of the Study:

• To investigate a large cohort of specimens to identify the causes of discrepancies in APTT measurements between different reagents.
• To determine the correlation between APTT variations and clinical parameters such as C-reactive protein (CRP).

Main Methods:

• Analysis of 18,994 coagulation tests performed between May 2020 and December 2020.
• Comparison of APTT results using two different reagents: HemosIL SynthASil APTT (APTT-SS) and Coagpia APTT-N (APTT-N).
• Cross-mixing tests (CMT) were performed on selected subjects to investigate potential lupus anticoagulant (LA) interference.

Main Results:

• 451 patients showed prolonged APTT-N with an APTT-N/SS ratio >1.3.
• A significant positive correlation was observed between C-reactive protein (CRP) levels (≥1.4 mg/L) and the APTT-N/SS ratio.
• Cross-mixing tests suggested transient lupus anticoagulant (LA) involvement in 17 out of 28 non-anticoagulated subjects, potentially linked to CRP levels.

Conclusions:

• Prolongation of APTT-N is correlated with CRP levels and may involve transient lupus anticoagulant (LA) interference.
• Assay reagent reactivity varies, impacting APTT results.
• Further investigation for LA is recommended when suspected, considering patient background and CRP levels.