An investigation of a critically low glucose result of an ambulatory, non-hospitalized patient must include:
- Confirmation of the patient identification, including name, medical record number, and date of birth.
- Examination of the date and time of collection on the laboratory requisition and collection tube(s).
- Examination of the original serum tube for evidence of intact gel barrier.
- Confirmation of the sample type of serum or plasma, as urine, spinal fluid, and other body fluids most likely have lower glucose levels than that of serum.
- Rule out evidence of contamination of the blood sample with intravenous (IV) fluids.
In this case, the observant technologist noted that the date of collection had been the previous day, and that the requisition time stamp indicated a collection time of 5:05 PM. She later noted that the receipt time stamp in the laboratory information system (LIS) was 8:10 AM, which indicates an extended transport time of approximately 15 hours. The core laboratory receiving staff had received the sample via pneumatic tube system, which had misdirected the collected sample to the radiology department. Upon discovery on the weekend morning, radiology forwarded the carrier to the laboratory. Glucose is known to decrease 7-10% per hour in a non-centrifuged whole blood sample, which could certainly account for this critically low level. The test request was cancelled, and a redraw requested. The laboratory manager was notified to further investigate the pneumatic tube manifest, and end-of-day protocols for sample transportation.