Working the emergency-department specimen set

Return to the 09:00 collection. Four tests were ordered from the same draw: plasma glucose by an enzymatic method, whole-blood lactate by an enzymatic method, plasma ammonia by an enzymatic method, and total bilirubin by a diazo method. The adult reference intervals below do not substitute for your laboratory's verified intervals; each laboratory establishes and verifies its own reference intervals. The transport log records 23 C to 25 C for the full 42 minutes, no ice, and no light cover. Time to separation was not documented.

Plasma glucose measured 62 mg/dL against a fasting reference interval of 70-99 mg/dL. Given 42 minutes unseparated at ambient temperature with no inhibitor declared, a decline in this range is consistent with ongoing glycolysis at the guideline's cited 5% to 7% per hour. That is a plausible explanation for the low result, not proof, because the exact starting glucose, leukocyte count, and true separation time are not known from this log.

Whole-blood lactate measured 3.0 mmol/L against a reference interval of 0.5-2.0 mmol/L. The same unseparated, ambient, 42-minute condition is a known driver of lactate increase, so this elevated value cannot be read as reflecting the patient's true circulating lactate at 09:00 without knowing whether ice-slush handling was used, which the log does not show.

Plasma ammonia measured 76 µmol/L against a reference interval of 11-35 µmol/L. Ammonia is vulnerable to exactly this kind of processing delay, but the direction and size of any bias for this specific local method cannot be reconstructed from a transport log alone; that requires the assay's own validated interval and the actual separation time.

Total bilirubin measured 1.1 mg/dL against a reference interval of 0.2-1.2 mg/dL, inside the interval. The specimen was not light-protected, which is a real excursion for this analyte, but a short delay without light protection does not by itself prove this particular result is biased; a peer-reviewed study found bilirubin stable for 24 hours at either 3 C or 22 C when light-protected, which only tells you what happens when light protection is present.

The preferred bench action is not to guess a correction factor for any of these four results. It is to check the assay-specific local procedure and the actual separation time if it can be recovered, document the temperature and light excursion, and follow the laboratory's accept, reject, recollect, or qualified-release policy. Do not release a comment stating that transport caused a specific bias unless the local procedure or validation supports that exact statement.

An unseparated, warm, light-uncovered 42-minute delay is enough to explain low glucose and high lactate and ammonia here, but explaining a pattern is not the same as quantifying its size for this method.