Measurement of the Activated Partial Thromboplastin Time from a Capillary (fingerstick) Sample of Whole Blood: A New Method for Monitoring Heparin Therapy

The monitoring of heparin anticoagulation is fraught with difficulties because of the need for repetitive venipunctures and the vagaries of sample handling and processing. The authors evaluated a new aPTT monitoring system with the potential to eliminate many of these difficulties. The Ciba Corning Diagnostics 512 Coagulation Monitor (CCD monitor) is a hand-held portable instrument that can measure an aPTT from a fingerstick sample of capillary whole blood. Fingerstick aPTTs from 319 subjects (including controls and individuals on heparin and/or warfarin) were compared to venipuncture-derived standard laboratory plasma aPTTs using different aPTT reagents on conventional instruments. The correlation coefficients between fingerstick and standard aPTTs (0.79-0.83) were the same as the correlation coefficient between standard laboratory aPTTs using different reagents (0.79). When venipuncture-derived whole blood was compared to fingerstick samples on the new instrument, the correlation coefficient was excellent (0.93). A high degree of precision, as demonstrated by low coefficients of variations, was shown for within-day and between-day testing using the CCD monitor and normal controls. This capillary whole blood, aPTT system is the first to provide the clinician with a means of rapidly and reliably assessing the anticoagulant response to heparin therapy at the bedside, and its use may ultimately lead to more efficient and effective therapy overall.