A laboratory evaluation into the short activated partial thromboplastin time.

Area of Science:

• Hematology
• Clinical Pathology
• Cardiovascular Medicine

Background:

• Short activated partial thromboplastin times (APTTs) are often dismissed as laboratory artifacts.
• Emerging evidence suggests short APTTs may signal an in-vivo hypercoagulable state.
• This state is potentially linked to heightened thrombotic risk and cardiovascular events.

Purpose of the Study:

• To prospectively investigate the clinical significance of short APTTs.
• To compare coagulation parameters in patients with short APTTs versus those with normal APTTs.
• To determine the prevalence of in-vivo hypercoagulability associated with short APTTs.

Main Methods:

• Prospective evaluation of 113 consecutive samples with short APTTs.
• Comparison with an equal number of age- and sex-matched normal APTT samples.
• Analysis of various coagulation parameters including PT, Factors V, VIII, XI, XII, VWF antigen and activity, and procoagulant phospholipids using the XACT assay.

Main Results:

• Significant differences observed in PT, Factor V, VIII, XI, XII, VWF antigen and activity, and procoagulant phospholipids between short and normal APTT groups.
• A significant negative association was found for fibrinogen.
• Approximately 20% or more of laboratory-defined short APTTs were found to represent an in-vivo phenomenon.

Conclusions:

• Plasma from patients with short APTTs reflects a complex hypercoagulant milieu.
• This hypercoagulable state may contribute to thrombotic risk.
• A significant proportion of short APTTs are indicative of an in-vivo condition rather than a mere laboratory artifact.