Search by CPT code Lookup. Aetna. Accessed October 18, 2020. https://www.aetna.com/health-care-professionals/precertification/precertification-lists.html 32. 42 CFR § 422.113 (b) (2); 2020. 33. Baicker K, Chernew ME, Robbins JA. The spillover effects of Medicare managed ...