Inborn errors of metabolism due to deficiencies in each of the 5 complexes (OXPHOS disease) account for as many as 1/5000 live births. Mutations in both nuclear and mt genes can cause OXPHOS diseases. Of these, Complex I and Complex IV deficiency are the most common while Complex III deficiencies are rare.

Diverse classes of drugs have been shown to inhibit OXPHOS. The ability to monitor the amount and activities of the 5 OXPHOS complexes is paramount in diagnosing and characterizing diseases presenting with energy deficit. These assays need to be a key part of drug development and drug toxicity studies.