COMPARISON OF PT, APTT, AND FACTOR-VII VALUES OBTAINED BY CONCURRENT SAMPLE COLLECTION BY DIRECT VENIPUNCTURE AND PERIPHERAL VENOUS CATHETERS

Study Objective. To compare prothrombin time (PT), activated partial t hromboplastin time (aPTT), and factor VII values in concurrent blood s amples obtained by direct venipuncture and from a peripheral venous ca theter. Design. Concurrent samples obtained from catheters and by dire ct venipuncture were studied. In a separate crossover bioequivalence a ssessment of DNA-derived factor VIIa (rFVIIa) from two different batch es, samples results of each technique were compared. Setting. Universi ty hospital clinical research unit. Patients. Six patients with hemoph ilia A under nonbleeding conditions. Interventions. The patients recei ved a single dose of rFVIIa 70 mug/kg administered by intravenous push over 2 minutes. Concurrent blood samples were collected at 2, 3, 4, 6 , 8, 10, and 12 hours after rFVIIa administration. Catheter blood samp les were drawn from a three-way stopcock attached to an 18-gauge perip heral venous catheter in the patient's forearm and connected to an int ravenous solution of 5% dextrose with half normal saline maintained at a rate of 30 ml/hour. Venipuncture samples were drawn from the opposi te arm. Measurements and Main Results. The PT and aPTT values were det ermined by using a BBL Fibrometer (PT) and a Coagamate X-2 with automa ted aPTT reagent. Blood samples were analyzed for factor VII concentra tion using the Novo Clot assay. The mean venipuncture-obtained PT (8.9 +/- 1.0 sec) and aPTT (48.7 +/- 13.6 sec) values were numerically equ ivalent to mean catheter-derived PT (9.0 +/- 1.0 sec) and aPTT (48.3 /- 12.5 sec) results, as were mean venipuncture and catheter-obtained FVII:C values. Conclusions. The PT and aPTT values determined after ve nipuncture and through the peripheral catheter were not statistically different (p>0.05) when compared by paired or unpaired analysis. Simil arly, values of FVII:C measured after venipuncture were statistically equivalent to those after sampling through the peripheral catheter. Al l six patients preferred the catheter method of blood collection over venipuncture.