Abstract Background Identification of underfilled sodium citrate tubes is paramount to avoid inaccurate results for coagulation testing. The conventional process entails manual checking of blood fill volumes before sample analysis, but this workflow is not possible if instruments are placed on an automation line. Individual tube weight can be collected using scales underneath the Aptio® centrifuge buckets and used as a proxy for measurement of tube fill volume. Our lab defined initial minimum weights for both 1.8 mL and 2.7 mL sodium citrate tubes as 10,000 mg. However, retrospective data review revealed an approximate 50% increase in QNS cancellations after automation implementation. The goal of this study was to refine minimum weight limit requirements for 1.8 mL and 2.7mL sodium citrate tubes on the Aptio® to reduce QNS cancelation rates for suspected overcitration. Methods Four 1.8 mL and 2.7 mL 3.2% Beckton Dickinson (BD) sodium citrate tubes were collected from a female donor with normal hematocrit to create a range of sub aliquots tubes. For the 1.8 mL size, 6 sodium citrate tubes were created with blood volumes ranging from 1.8 to 0.3 mL (1.8, 1.5, 1.2, 0.9, 0.6, 0.3). For the 2.7 mL size, 6 tubes were created with blood volumes ranging from 2.7 to 0.45 mL (2.7, 2.25, 1.8, 1.35, 0.9, 0.45). Tubes were weighed by the Aptio® automation centrifuge scales followed by manual assessment of adequate filling using a citrated plasma nomogram. Empty tubes were also weighed by the Aptio®. Following preliminary results, a 7th 2.7mL tube was made to further refine the weight cutoff for minimum volume. Manual assessment for minimum volume was compared with the tube weights to identify the defined minimum weight limit for each tube size. Results Surprisingly, empty tubes without any blood showed inversely proportional weights. The smaller 1.8 mL tube weighed 8,800 mg and the larger 2.7 mL tube weighed 8,000 mg. Weights for the 2.7 mL tubes ranged from 10,600 mg (2.7 mL blood volume) to 8,300 mg (0.45 mL blood volume). Weights for the 1.8 mL tubes ranged from 10,600 mg (1.8 mL blood volume) to 9,100 mg (0.3 mL blood volume). Manual determination of an underfilled 2.7 mL tube corresponded with a weight of 9,500 mg (1.8 mL of blood volume). Manual determination of an underfilled 1.8 mL tube corresponded with a weight of 9,900 mg (1.2 mL blood volume). Weight limits for 1.8mL tubes stayed at 10,000mg and were adjusted to 9,700mg for 2.7mL tubes. Conclusion Centrifuge scales on the Aptio Automation can be leveraged to detect and sort underfilled tubes for coagulation testing for normal hematocrit populations prior to analysis. Blood volume capacity alone should not be used to set thresholds for weight limits due to smaller tubes weighing more than larger tubes. For BD sodium citrate 1.8 mL and 2.7 mL tubes, weight thresholds of 10,000 mg and 9,700 mg matched our laboratory’s existing criteria for rejection of underfilled tubes for coagulation testing. Future work seeks to monitor cancelation rates with these updated rules.
Reschly et al. (Wed,) studied this question.