This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
“Flipping effect” is ? 
Select and explain. 
A. LDH 1> LDH 2, B. LDH2>LDH1, C. LDH 2> LDH 3, D. LDH 3>LDH 2
A: LDH 1> LDH 2
Answer: A: LDH 1> LDH 2 
Explanation: Ref. API Textbook of Medicine. Pg. 798
 
Lactate dehydrogenase, tetrameric enzyme with 4 subunits,

4 Subunits with 2 isoforms - H isoform (Heart) & M isoform (Muscle)
Heart & RBCs - LDH-1 (4H);
Reticuloendothelial system - LDH-2 (3H1M)
Lungs - LDH-3 (2H2M)
Kidneys, placenta, & pancreas - LDH-4 (1H3M)
Liver & striated muscle - LDH-5 (4M)

Flipping effect

Usually LDH 2 in predominant in serum & LDH 1 is predominant in heart
Higher levels of LDH 1 than LDH 2 (Flipped pattern) is suggestive of myocardial infarction