A primary care evaluation of three near patient coagulometers

Aim-To compare the reliability and relative costs of three international no rmalised ratio (INR) near patient tests. Materials-Protime (ITC Technidyne) , Coaguchek (Boehringer Mannheim), and TAS (Diagnostic Testing). Methods-All patients attending one inner city general practice anticoagulat ion clinic were asked to participate, with two samples provided by patients not taking warfarin. A 5 mi sample of venous whole blood was taken from ea ch patient and a drop immediately added to the prepared Coaguchek test stri p followed by the Protime cuvette. The remainder was added to a citrated bo ttle. A drop of citrated blood was then placed on the TAS test card and the remainder sent to the reference laboratory for analysis. Parallel INR esti mation was performed on the different near patient tests at each weekly ant icoagulation clinic from July to December 1997. Results-19 patients receiving long term warfarin treatment provided 62 INR results. INR results ranged from 0.8-8.2 overall and 1.0-5.7 based on the l aboratory method. Taking the laboratory method as the gold standard, 12/62 results were < 2.0 and 2/62 were > 4.5. There were no statistical or clinic ally significant differences between results from the three systems, althou gh all near patient tests showed slightly higher mean readings than the lab oratory, and 19-24% of tests would have resulted in different management de cisions based on the machine used in comparison with the laboratory INR val ue. The cost of the near patient test systems varied substantially. Conclusions-All three near patient test systems are safe and efficient for producing acceptable and reproducible INR results within the therapeutic ra nge in a primary care setting. All the systems were, however, subject to op erator dependent variables at the time of blood letting. Adequate training in capillary blood sampling, specific use of the machines, and quality assu rance procedures is therefore essential.