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

Materials and Methods

This study was approved by the institutional review board at the University of Virginia under protocol IRB-HSR # 21030.

To evaluate the effect of short-term (<4-hour) storage on either uncentrifuged or centrifuged samples stored in courier lockboxes, 2 dates were selected in summer 2019, when outdoor temperatures were predicted to exceed 32°C. At approximately 11:00 AM on each preselected day, 2 medium-sized, insulated (0.5-in expanded-polystyrene foam) LabLocker-KF300 lockboxes (20-gauge galvanized steel) were placed on the cement ground outside, side by side, with adequate space in between and in direct sunlight. One lockbox contained the standard number (n = 2) of frozen (−20°C) Nordic NI24 24-oz cold packs (cold lockbox) recommended by the institution's outreach program. The second lockbox used in the study did not contain cold packs (warm lockbox). The temperature in each lockbox, next to the samples, was monitored every 5 minutes using an Elitech GSP-6 temperature data logger.

Seven samples in lithium heparin BD PST Vacutainer tubes were drawn from healthy volunteers (n = 4, study 1) under standard conditions. In the uncentrifuged study, 1 sample from each participant was immediately centrifuged, and plasma was left on gel barrier. These samples were then analyzed on the Abbott Architect c16000 analyzer to determine C-reactive protein, comprehensive metabolic panel, lactate dehydrogenase (LDH), lipid panel, magnesium, and phosphorus concentrations. This sample served as a baseline (t0), within-subject control for each participant. The remaining samples (n = 6 per participant) were then split equally (3 per cold and warm storage conditions in the lockboxes, as described), wrapped in several layers of paper towels, and placed in Ziploc bags within the lockbox. The cold packs did not come in direct contact with the samples. At specific time points (1, 2, and 4 hours) after initial collection, 1 sample from each participant was removed from the cold and warm lockboxes, immediately centrifuged, left on gel barrier, and analyzed. Lastly, in the second study, all samples (n = 7) were centrifuged and left on gel barrier before placement in the 2 described lockbox conditions. Otherwise, study design, participants (n = 4), and outdoor temperatures for the centrifuged study were comparable to the uncentrifuged study.

An online search was performed to identify US clinical laboratories that provided publicly available instructions for courier lockboxes. Information from private (n = 3), academic (n = 2), and reference (n = 2) laboratories were reviewed for specific instructions (n = 7) relating to courier lockboxes . If specific instructions were included on each individual clinical laboratory's website, it was marked as "Yes" or "No" if limited or no information was provided Table 1.