A Comparison of Point-of-Care Instruments Designed for Monitoring Oral Anticoagulation with Standard Laboratory Methods

Summary

Our study compared point-of-care (POC) device monitoring with traditional clinical laboratory methods device of patients on oral anticoagulant therapy. The POC devices used in the study were Coumatrak, CoaguChek, CoaguChek Plus, Thrombolytic Assessment System (TAS) PT-One, TAS PTNC, TAS PT, Hemachron Jr. Signature, Protime Microcoagulation System, and Medtronics ACT II. The clinical laboratory method used thromboplastins with different ISI values: Innovin and Thromboplastin C Plus (TPC). All POC INRs showed strong correlation with both laboratory methods, with correlation coefficients of >0.900. All POC methods demonstrated a significant (p <0.05) difference in INR values, except the TAS PTNC and ACT II INRs (p: 0.12 and 0.71 respectively) when compared with Innovin INRs. All POC INRs were significantly different from TPC generated INRs (p <0.05). Comparisons of the POC INRs to the group mean of the POC methods, show higher correlation (R>0.93), but there were still significant (p<0.05) differences noted between the POC group INR mean and CoaguChek Plus, ACT II, TAS PT-One, TAS PTNC, and Hemachron Jr Signature INRs. These data indicate that POC INR biases exist between laboratory methods and POC devices. Until a suitable whole blood INR standardization method is available, we conclude that clinicians using point-of-care anticoagulation monitoring should be aware of differences between POC and parent laboratory values.

Key words

International Normalized Ratio (INR) - point-of-care devices - coumadin monitoring

• References

• 1 Poller L. INR-Calibration of the therapeutic range. Adv Exper Med Biol 1987; 214: 95-112.
• 2 Hirsh J, Dalen JE, Deykin D, Poller L, Bussey H. Oral Anticoagulants. Mechanism of action, clinical effectiveness, and optimal therapeutic range. Chest 1995; 108 (Suppl): 231S-46S.
• 3 Schmitz LL, Olson SL, Shapiro RS, McCormick SR, Kubic VL. Failure to generate comparable International Normalized Ratio values using five different thromboplastin reagents in parallel studies of patient receiving warfarin. Clin Appl Thrombosis/Hemostasis 1995; 01: 142-50.
• 4 Ts’ao C, Swedlund J, Neofotistos D. Implications of use of low International Sensitivity Index thromboplastins in prothrombin time testing. Arch Pathol Lab Med 1994; 118: 1183-7.
• 5 Gosselin RC, Owings JT, Larkin E, White RH, Hutchinson R, Branch J. Monitoring oral anticoagulant therapy with point-of-care devices: correlations and caveats. Clin Chem 1997; 43: 1785-6.
• 6 Adcock D. The use of commercially prepared frozen coumadin plasma calibrants to establish a localized INR reporting scheme. Oral presentation, Temple University Hemostasis Update. Philadelphia, PA: April 16, 1999
• 7 McCurdy SA, White RH. Accuracy and precision of a portable anticoagulation monitor in a clinical setting. Arch Intern Med 1992; 152: 589-92.
• 8 Yano Y, Kambayashi J, Murata K, Shiba E, Sakon M, Kawasaki T, Mori T. Bedside monitoring of warfarin therapy by a whole blood capillary coagulation monitor. Thromb Res 1992; 66: 583-90.
• 9 College of American Pathologist (CAP) Whole blood coagulation survey. 1997 participant summary.
• 10 Oberhardt BJ, Dermott SC, Taylor M, Alkadi ZY, Abruzzini AF, Gresalfi NJ. Dry reagent technology for rapid, convenient measurements of blood coagulation and fibrinolysis. Clin Chem 1991; 37: 520-6.
• 11 Rose VL, Dermott SC, Murray BF, McIver MM, High KA, Oberhardt BJ. Decentralized testing for prothrombin time and activated partial thromboplastin time using a dry chemistry portable analyzer. Arch Pathol Lab Med 1993; 117: 611-7.
• 12 Pan CM, Jobes D, Van Riper D, Ogilby JD, Lin CY, Horrow J, Blumenthal R, Mendoza M, LaDuca F. A modified microsample ACT assay for heparin monitoring. ISCH Poster session. June 12, 1995; Israel 73, 6: 976.
• 13 Andrew M, MacIntyre B, MacMillan J, Williams WG, Gruenwald C, Johnston M, Burrows F, Wang E, Adams M. Heparin therapy during cardiopulmonary bypass in children requires ongoing quality control. Thromb Haemost 1993; 70: 937-41.
• 14 Tripodi A, Chantarangkul V, Negri B, Clerici M, Mannucci PM. International collaborative study for the calibration of a proposed reference preparation for thromboplastin, human recombinant, plain. Thromb Haemost 1998; 79: 439-43.
• 15 Poller L, van den Besselaar AMHP, Jespersen J, Tripodi A, Houghton D. Correction for lack of coincidence of normal and abnormal calibration slopes in ISI determination. Thromb Haemost 1999; 81: 935-9.
• 16 Poller L, van den Besselaar AMHP, Jespersen J, Tripodi A, Houghton D. The European concerted action on anticoagulation (ECAA): Field study of coagulometer effects on the ISI of ECAA thromboplastins. Thromb Haemost 1998; 80: 615-23.
• 17 Kitchen S, Jennings I, Woods AL, Preston FE. Local calibration of international normalized ratio improves between laboratory agreement: results from the UK national external quality assessment scheme. Thromb Haemost 1999; 81: 60-5.
• 18 Eckman MH, Levine HJ, Pauker SG. Effect of laboratory variation in the prothrombin-time ratio on the results of oral anticoagulant therapy. NEJM 1993; 329: 696-702.
• 19 Gosselin RC, Owings JT, Lin L, Wong L, Larkin EC. Failure of the International Normalized Ratio to mitigate system and reagent biases. Blood 1997; 90 (Suppl. 10) 94b-5b.
• 20 Andrews TC, Peterson DW, Doeppenschmidt D, Foster JS, Lucca MJ, Deering JA, LaVeau PJ. Complications of warfarin therapy monitored by the International Normalized Ratio versus the prothrombin time ratio. Clin Cardiol 1995; 18: 80-2.
• 21 Palareti G, Leali N, Coccheri S, Poggi M, Manotti C, D’Angelo A, Pengo V, Erba N, Mola M, Ciavarella N, Devoto G, Berrenttini M, Musolesi S. Bleeding complications of oral anticoagulant therapy treatment: an inception-cohort, prospective collaborative study (ISCOAT). Lancet 1996; 348: 423-8.
• 22 Massicotte P, Marzinotto V, Vegh P, Adams M, Andrew M. Home monitoring of warfarin therapy in children with a whole blood prothrombin time monitor. J Pediatr 1995; 127: 389-94.
• 23 Tripodi A, Chantarangkul V, Clerici M, Negri B, Mannucci PM. Determination of the international sensitivity index of a new near-patient testing device to monitor oral anticoagulant therapy. Thromb Haemost 1997; 78: 855-8.