A common cause of a falsely elevated LD1 fraction is which of the following?

• A. Specimen hemolysis
• B. Liver disease
• C. Congestive heart failure
• D. Drug toxicity

Answer: (A)

LDH isoenzyme patterns are used to help interpret LDH elevations, and LD1 is the isoenzyme most abundant in red blood cells and heart tissue. In a clean serum sample, the LD1 fraction is typically not markedly higher than LD2, but when red blood cells hemolyze, they release large amounts of LDH, especially LD1 and LD2, into the serum. This releases a falsely elevated LD1 fraction, which can mimic patterns seen with cardiac injury but is actually a problem with the specimen quality. Among the options, specimen hemolysis is the classic cause of a falsely elevated LD1 fraction. The other conditions can raise overall LDH or specific isoforms due to true pathology, but they do not produce the spurious rise in LD1 caused by rupture of red blood cells.