Bedside heparin monitoring by activated partial thromboplastin time measured with a dry reagent.

Activated partial thromboplastin time (APTT; also coagulation surface induced time [ID is a routine method for monitoring heparin treatment [2-5]. This time is influenced by the type of reagent, the method of analysis, and the laboratory instrument used; thus, the result will vary from one laboratory to another [6, 7]. Variation in heparin sensitivity between batches of re-agents produced from the same manufacturer has been reported [8], and attempts to standardize AP'TT reagents have not been entirely successful [9, 10]. Temperature and duration of sample storage until centrifugation and analysis also affect the APYT' [Ii]. The APTT in whole blood decreases with time if left without centrifugation [12] because the heparin is neutralized by plasma proteins, the most important of which is considered to be platelet factor 4. Among the bedside methods developed for APTT' measurement, some appear to be reliable alternatives to a central laboratory method [12, 13]. Here we compare a dry-reagent bedside system for APTT analysis with a central laboratory method for monitoring patients treated with heparin for unstable angina or after percutaneous transluminal coronary angioplasty (PTCA). Seventy-five patients (ages 36-84 years) treated with heparin at the Department of Cardiology, Karolinska Hospital, Stock-holm, Sweden, for either unstable angina (n = 54) or after P'FCA (n = 21) were included in the study between November 1994 and April 1995. We also sampled healthy volunteers (n = 15) and patients without heparin treatment (n = 10) to compare the two AP'TT methods at values near the reference interval. The procedure followed was part of the routine care and in accordance with the ethical standards of our institution. Samples from all patients were taken only once, by a well-trained nurse applying minimum stasis. Venous blood from either an intravenous catheter or from a disposable needle was drawn into two 5-mL Vacutainer Tubes (Becton Dickinson, Rutherford, NJ) containing 0.5 mL of 129 mmol/L trisodium citrate (pH 7.4). One tube was sent for AP1IT analysis to the central laboratory at the hospital and one tube was used for APTI' analysis by the Thrombolytic Assessment System (TAS; Cardiovascular Diag-nostics, Raleigh, NC). The latter analysis was performed within 15 mm by one specially trained research nurse, who had performed >100 analyses with the TAS before the study. The TAS is a portable instrument designed for bedside monitoring of AP1T with a dry reagent system. The dry reagent contains phospholipids derived from a chlorofrom extract …