APTT critical value establishment in four different reagent/instrument systems based on single factor deficiencies

Area of Science:

• Clinical Chemistry
• Hematology
• Diagnostic Laboratory Science

Background:

• Activated partial thromboplastin time (APTT) critical values vary significantly across studies, lacking standardization for specific detection systems.
• The International Council for Standardization in Hematology (ICSH) recommends establishing APTT critical values considering reagent type, coagulation factor sensitivity, and heparin response.

Purpose of the Study:

• To establish reagent-specific APTT critical values.
• To evaluate these values based on single coagulation factor deficiencies (FVIII, FIX, FXI).

Main Methods:

• APTT values were measured in factor-deficient plasma across four assay systems at various concentrations.
• Retrospective data from patients with isolated FVIII, FIX, or FXI deficiencies were analyzed.
• Receiver operating characteristic (ROC) curves assessed diagnostic accuracy for factor activity < 5 IU/dL.

Main Results:

• Significant differences in APTT values were observed among the four assay systems (P < 0.001).
• Reagent-specific critical APTT values were proposed: 40.0 s (Sysmex CS5100/Actin FSL), 58.0 s (Sysmex CS5100/Actin), 51.8 s (STA-R Evolution/STA-PTTA), and 64.8 s (ACL TOP 700/HemosIL SynthasIL).
• Optimal ROC-derived thresholds for STA-PTTA were 55.8 s (FVIII), 54.3 s (FIX), and 71.7 s (FXI), demonstrating high sensitivity and specificity.

Conclusions:

• APTT critical values must be established for specific reagents.
• These values should be determined considering the presence of single coagulation factor deficiencies for accurate diagnostic interpretation.