American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

If a blood sample tested for liver enzymes shows elevated levels except for lactate dehydrogenase (LDH), what may be the cause?

1. Improper collection technique

2. Refrigeration of the blood sample

3. Prolonged delay before analysis

4. Insufficient sample volume

The correct answer is: Refrigeration of the blood sample

The elevated liver enzymes in a blood sample, coupled with an unchanged lactate dehydrogenase (LDH) level, suggests that the enzymatic activities of other liver enzymes may be influenced by certain conditions while LDH remains stable. Refrigeration of the blood sample can impact the activity of certain enzymes, potentially stabilizing their levels while preventing enzyme degradation or alterations due to temperature fluctuations. In the context of liver function tests, proper temperature management is crucial because enzymes can be sensitive to heat and may denature or lose activity when not stored correctly. Refrigeration tends to keep the enzymes from degrading as rapidly, while some enzymes could see activity changes depending on their stability at different temperatures. Therefore, if a sample is refrigerated properly, it's less likely to exhibit elevated levels due to conditions during transport, which is consistent with the scenario where other liver enzymes are elevated except for LDH. On the other hand, factors such as improper collection technique, prolonged delay before analysis, or insufficient sample volume would typically lead to problems with all enzyme levels, not just affecting the liver enzymes selectively while sparing LDH. This context helps clarify why refrigeration is recognized as the relevant factor affecting the observed enzyme levels in this case.