Monitoring Heparin Therapy by the Activated Partial Thromboplastin Time - The Effect of Pre-Analytical Conditions

Abstract

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.

Antibodies to non‐bilayer phospholipid arrangements induce a murine autoimmune disease resembling human lupus

“…Positive results had values n 1.9 AU for IgG, as established in humans [26]. A modification of kaolin-activated partial thromboplastin time was used to determine lupus anticoagulant antibodies [21,27]. Hep-2 cells incubated with mice sera at different dilutions were used to determine antinuclear antibodies and FITC-conjugated goat anti-mouse antibodies were used as secondary reagents [28].…”

CTAD as a universal anticoagulant

“…To reduce sample blood volume for laboratory testing, various kinds of universal anticoagulants have been proposed, but most are not satisfactory for universal use [2][3][4][5]. On the other hand, CTAD, a mixture of sodium citrate, citric acid, theophylline, adenosine and dipyridamole was first developed for use in blood coagulation tests with less effect on coexisting platelets [6,7]. CTAD blood can be used for coagulation tests.…”

The Optimum Number and Types of Plasma Samples Necessary for an Accurate Activated Partial Thromboplastin Time–Based Heparin Therapeutic Range

“…4,7 However with the ex vivo method, significant drawbacks can be encountered: difficulty in obtaining an adequate number of samples, use of the proper types of samples, and integrity of the range, based on a ''best-fit'' linear regression statistical model. [7][8][9] In addition, significant variation can be due to both the heparin and aPTT values. The causes of variation include (1) differences in the heparin sources (preparation and content), (2) biological variation (heparin binding proteins, coagulation factor levels, and in vivo heparin processing), (3) clinical parameters (international normalized ratio [INR] and optimum clinical concentration), (4) preanalytic variation (sample collection, processing, and storage), and (5) analytic variables (different aPTT reagent sensitivities, components, and concentrations).…”

“…[4][5][6][7]10,11 Based on these issues, aPTT monitoring of UFH is difficult to standardize even using the ex vivo HTR method. 4,7,8 Many factors can influence both aPTT and heparin values. Few systematic investigations have evaluated the parameters of the ex vivo HTR model.…”

“…Several groups have proposed criteria and procedures for performing the ex vivo method but in fact did not scientifically establish their guidelines. 4,8,9 The purpose of this study is to evaluate the number and type of samples affecting the ex vivo HTR method. Since this report is not a comparison of specific reagents per se, the commercial reagents are not identified within the data sets.…”