Lactate dehydrogenase isoenzyme assay is an analysis that uses electrophoresis to separate and measure the five different LDH isoenzymes (LDH-1 to LDH-5) in serum. Each isoenzyme (form) is concentrated in specific tissues. The relative pattern of each isoenzyme (profile) reveals the source of the overall elevated enzyme, providing more specialized diagnostic information than measuring total LDH alone.