The partial thromboplastin time in the CAP survey program.

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Hematology

Background:

• Proficiency testing is crucial for ensuring accurate laboratory measurements.
• Partial thromboplastin time (PTT) is a key diagnostic test in coagulation analysis.
• Previous studies highlighted the need for standardization in PTT testing.

Purpose of the Study:

• To analyze the variability of partial thromboplastin time (PTT) measurements.
• To compare the performance of activated versus non-activated PTT methods.
• To identify factors contributing to PTT measurement variability in clinical laboratories.

Main Methods:

• Analysis of data from the College of American Pathologists (CAP) Surveys conducted between 1969 and 1973.
• Statistical comparison of interlaboratory variability for different PTT methodologies.
• Review of laboratory adherence to manufacturer guidelines for PTT assays.

Main Results:

• Significant variability in PTT determination was observed across participating laboratories.
• Non-activated PTT procedures exhibited greater interlaboratory variability compared to activated methods.
• Many laboratories failed to establish specific upper limits of normal for their PTT systems.
• Non-adherence to manufacturer instructions, particularly regarding incubation times and calcium concentrations, was common.

Conclusions:

• Activated PTT methods may be preferable for routine laboratory use due to lower variability.
• Establishing laboratory-specific upper limits of normal is essential for accurate PTT interpretation.
• Improved adherence to manufacturer protocols is necessary to reduce PTT measurement variability and enhance diagnostic accuracy.