What is the ideal measurement time after collection for chemistry assays?

• A. 30 minutes after collection
• B. 1 hour after collection
• C. 2 hours after collection
• D. 4 hours after collection

Answer: (B)

Prompt processing of specimens is crucial because blood cells stay metabolically active after collection, which can alter the sample's composition. Glycolysis continues in whole blood, so glucose and lactate levels can change, and cells may release or take up ions and enzymes, shifting potassium, pH, and other analytes. Separating serum or plasma and measuring soon after collection minimizes these pre-analytical changes, keeping the result closer to the patient’s true value. About one hour after collection is the practical target for the measurement time, balancing the need to run tests promptly with typical lab workflows. Delays beyond this window can lead to noticeable shifts in many common chemistry analytes, reducing accuracy. If immediate processing isn’t possible, cooling or other preservation methods can help some tests, but the general guideline remains to aim for measurement within roughly one hour.