SummaryBlood and plasma specimens from patients receiving heparin were collected and stored under various conditions. The effect of these conditions on the activated partial thromboplastin time (APTT) was assessed. Four APTT reagents were used. Blood samples centrifuged at 600 × g gave slightly shorter APTTs than samples centrifuged at 940 × g and 2200 × g. Storage of uncentrifuged citrated-blood at room temperature resulted in 15-29% shortening of the APTT, depending on the reagent used. Storage of the same blood samples at 4° C resulted in 6-19% lengthening of the APTT. The presence of HEPES-buffer in citrated-blood shortened the APTT of heparinized patient specimens, but not of normal specimens. When blood was collected in a mixture of citric acid, theophylline, adenosine and dipyridamole (CTAD-mix-ture), storage at room temperature induced 0-11% decrease of the APTT, depending on the reagent used. Storage of CTAD-blood at 4° C resulted in 7-19% lengthening of the APTT. Shortening of the APTT could be explained by release of platelet factor 4 (PF4). Release of PF4 could be inhibited by CTAD-mixture. These data suggest that storage of CTAD-blood at room temperature is the best pre-analytical condition for reliable monitoring of heparin therapy by the APTT.
Background: To simplify International Sensitivity Index (ISI) calibration, the possibility of substituting fresh plasma for fresh whole-blood samples with point-of-care testing (POCT) whole-blood monitors was investigated in a three-center study of three different POCT systems.
Methods: A modified full WHO calibration procedure based on 20 healthy controls and 60 coumarin-treated patients was performed on three monitoring systems with whole-blood and plasma samples against plasma tested using the European Concerted Action on Anticoagulation (ECAA) rabbit reference plain thromboplastin and the manual prothrombin time (PT) method.
Results: With one of the three systems, the mean ISI was 1.51 for whole blood and 1.49 for plasma; with the second system, the mean ISI was 1.08 for both whole blood and plasma. With the third system, however, the difference between the mean ISI for whole blood and that for plasma was greater (1.15 and 1.01, respectively). Overall, the precision of the calibrations was less than with traditional manual plasma PT testing.
Conclusions: Provided that an appropriate calcium chloride concentration is used, the plasma PT results can be used for accurate ISI calibration of two of these three whole-blood POCT systems. Precision criteria need to be modified for POCT monitors.
To contribute to the development of a reference reagent for monitoring heparin therapy, a lyophilized partial thromboplastin time (PTT) reagent was prepared from synthetic dioleoylphosphatidylcholine, dioleoylphosphatidylserine, and dioleoylphosphatidylethanolamine, with colloidal silica as activator. The reagent, coded 91/558, was contained in sealed glass ampoules; it deteriorated in a heat degradation experiment, but its activity remained constant for at least 4 years when stored at −70 °C. Within- and between-run precision with this reagent complied with the requirements proposed by the International Committee for Standardization in Haematology (ICSH) Panel on PTT. The response of this reagent and of two other reagents to heparin added to pooled normal plasma was nonlinear. Citrated samples from 58 patients receiving intravenous heparin and from 24 apparently healthy volunteers were tested with reagent 91/558, with Automated APTT (Organon Teknika), with Manchester APTT reagent, with an anti-factor Xa assay, and with an anti-factor IIa assay. The correlation of APTT with anti-Xa and anti-IIa activity was poor. The best correlation was observed between reagent 91/558 and the Organon Teknika reagent. Correlations were improved when individual patients’ samples were replaced by pooled plasmas from heparinized patients, in whom the effect of oral anticoagulation was minimal. These results suggest that preparation of a lyophilized synthetic phospholipid reagent is feasible for use in monitoring heparin therapy.
Ihrombosis and Haemostasis-@ E K. SchattauerVerlagsgesellschaft mbH (Stuttgart) 67 (6) 725 (1992) Artificial Prolongation of the Prothrombin Time of Lyophilized Plasma lnduced by Transportation with Solid Garbon Dioxide Dear Sir, In The Netherlands, external quality assessment (EOA) of coagulation assays (prothrombin time, activated partial thromboplastin time, fibrinogetr, factor VIII) is performed by a national committee. In bimonthly surv€yS, sets of three lyophilized citrate plasma samples are mailed to 120 participants. The samples are Lyophilized plasma samples could be shipped without dry ice altogether.
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