Outdoor Courier Lockboxes in Summer Are a Significant Source of Preanalytical Error

Megan E. Dibbern, MD; Christina C. Pierre, PhD; Joesph R. Wiencek, PhD


Am J Clin Pathol. 2021;156(5):866-870. 

In This Article


Courier lockboxes are critical components of the external sample transport process. Unfortunately, this frequently used step is not being adequately investigated.6 In our study, we showed that short-term sample exposure inside an outdoor lockbox can lead to error. Significant analyte-specific changes were noted as early as 1 hour depending on the conditions. Guidance is available for sample collection and common clinical laboratory storage conditions, but guidance remains unspecific for lockbox use.[8–16] In addition, basic storage requirements are listed in the package inserts for testing laboratories, but the current state of lockbox guidance and their general, most common design make it difficult to monitor and ensure that samples are stored appropriately.

Preanalytical testing errors are estimated to account for 0.23% to 1.2% of total hospital operating costs and remain a major challenge in laboratory medicine.[17] For a US hospital with approximately 650 beds, this cost can be extrapolated to approximately $1,199,122 per year.[17] Therefore, from a cost perspective, reduction of known or often-overlooked sources of preanalytical error, such as lockboxes, can benefit a health institution financially. Furthermore, targeting error reduction in the preanalytical phase can decrease patient inconvenience and reduce the potential harm associated with acting on inaccurate results, which lead to sample re-collection or even a misdiagnosis leading to unnecessary treatments.[18–20]

There are several limitations of this study. First, we used samples from healthy donors, and therefore the range of assay results is narrow. It is possible that more significant variation in results may have been observed in additional analytes if the samples had had higher concentrations of those analytes. In addition, samples were noted to be outside SCLs for several analytes at varying time points and conditions, which could have been the result of sample placement within the lockboxes or other, undetermined factors. Lastly, we did not separate the plasma from gel barrier. The increased temperatures in the warm lockbox may have led to deterioration of the gel separators that led to blood cell (eg, erythrocyte) contamination or potentially other interferences.[19,21]

Immediate efforts at standardization and to increase quality assurance should be made for lockboxes used in external sample transport. Time, temperature, location, and shock events are several quality indicators that can be monitored to determine the integrity of samples stored in outside lockboxes.[5,22–25] Two recent studies demonstrated the feasibility of an integrated monitoring system in external sample transport as well as a state-of-the-art temperature-controlled transport container.[24,25] Our study further provides evidence of the need to create universal lockbox guidance as well as the need to implement affordable, climate-proof or refrigerator-like lockboxes that can be adequately monitored.