Accuracy and precision of 3 multidose vial tracking methods to inform controlled drug tracking in practice.

Objective: To evaluate the precision and accuracy of 3 common methods (method 1, actual draws of the volume remaining; method 2, weight tracking of the volume remaining and/or the volume removed; and method 3, discrepancy percentage at the end of each vial) for monitoring volumes in vials of injectable controlled drugs.

Methods: For methods 1 and 2, doses were drawn from a vial containing a known amount of sterile water. For method 1, after each dose was removed, the remaining quantity of liquid was withdrawn, measured, and reinjected into the vial. The estimated and actual hub loss were calculated. For method 2, the syringe with the needle attached was weighed immediately prior to each draw and reweighed after the draw. The vial was weighed after each draw and compared to the expected weight of 1 g/mL. For method 3, the total discrepancy volume per vial was determined for vials used from January 1, 2022, through March 31, 2023. The discrepancy percentage between the calculated amount remaining and 0 mL was determined for each vial. Accuracy and precision were determined for each method.

Results: Method 2 was more accurate than method 1. Precision was equal for methods 1 and 2, with method 3 having the lowest precision.

Conclusions: Methods 1 and 2 have accuracy and precision sufficient to justify their use in practice. Method 3 is not sufficiently precise to be used alone.

Clinical relevance: The method(s) chosen should be based on accuracy and precision as well as the pros and cons of each method.