Long-term stability of frozen pooled plasmas stored at -70°C, -40°C, and -20°C for prothrombin time and International Normalized Ratio (INR) assessment.

Background: Frozen pooled plasmas may be used for quality assessment and local calibration of prothrombin time (PT) and International Normalized Ratio (INR) measurement systems. The purpose of the present study is to estimate the long-term stability of frozen pooled plasmas stored for at least three years.

Methods: Six pooled plamas with different INR levels were stored at -70°C, -40°C, and -20°C for various time periods up to 1453days.

Point-of-care monitoring of vitamin K-antagonists: validation of CoaguChek XS test strips with International Standard thromboplastin.

Aims: Many patients treated with vitamin K-antagonists (VKA) use point-of-care (POC) whole blood coagulometers for self-testing. The majority of patients in the Netherlands use one type of POC coagulometer, that is, the CoaguChek XS. Each new lot of test strips for the CoaguChek XS is validated by a group of collaborating thrombosis centres.

Influence of haematocrit on international normalised ratio (INR) differences between a whole blood point-of-care coagulation monitor and reference prothrombin time in plasma.

The CoaguChek S system is designed for use in patient self-testing. In this system a whole blood sample without sodium citrate is applied to a test strip containing thromboplastin and iron oxide particles. The detection principle is based on fibrin formation which inhibits and finally stops the movement of the iron oxide particles.

Influence of blood collection systems on the prothrombin time and international sensitivity index determined with human and rabbit thromboplastin reagents.

Three brands of blood collection tubes were studied for their influence on the prothrombin time (PT) and international sensitivity index (ISI) for 5 commercial thromboplastin reagents. With all reagents, PTs were shorter in Vacutainer (Becton Dickinson Vacutainer Systems, Plymouth, England) samples than in S-Monovette (Sarstedt, Nümbrecht, Germany) or Venosafe (Terumo Europe, Leuven, Belgium) samples. ISI values were higher with Vacutainer samples than with S-Monovette or Venosafe samples.

The influence of exogenous magnesium chloride on the apparent INR determined with human, rabbit, and bovine thromboplastin reagents.

Magnesium ions can shorten the tissue factor-induced coagulation time. Some blood collection systems with sodium citrate are contaminated with variable amounts of magnesium and influence the results of the prothrombin time (PT) test. The aim of the study was to determine the dose-response relationship between exogenous magnesium chloride added to blood and the PT and the international normalized ratio (INR).