Exhibit 4:

Largest denial shares by narrow service type

Medicare Coverage Rules			Medicare Advantage Insurer Coverage Rules
Specific Service Type	Denied Spending Share	Denied Services Share	Specific Service Type	Denied Spending Share	Denied Services Share
Chemistry studies	29.0%	56.9%	Chemotherapy	13.6%	1.8%
Vascular procedures, other	5.5%	2.4%	Chemistry studies	11.2%	19.3%
Drug administration	4.1%	0.7%	Drug administration	9.4%	10.5%
Microbiology studies	3.7%	8.4%	Supplies	6.9%	5.4%
Self-injected drug administration	3.1%	0.1%	Microbiology studies	6.3%	11.1%
Vascular access procedures	2.6%	1.3%	Percutaneous coronary intervention	3.3%	0.2%
Rehabilitation or Physical Therapy	2.3%	2.2%	Miscellaneous administrative codes	2.9%	0.4%
Supplies	2.3%	1.1%	Knee arthroscopy	2.7%	2.2%
Chemotherapy	2.1%	0.1%	Neurologic procedures, other	2.6%	0.1%
Skin lesion biopsy/excision	1.9%	0.9%	Major vascular procedures	2.5%	10.1%
Neurologic procedures, other	1.9%	0.5%	Vascular access procedures	2.3%	3.5%
Anesthesia	1.8%	0.5%	Ultrasound	2.1%	0.5%
Echocardiography	1.6%	0.6%	Nasal/sinus endoscopy	2.0%	0.9%
Pacemaker or defibrillator procedure	1.6%	0.0%	Eye Procedures - Other	2.0%	1.1%
Peripheral nerve procedures	1.5%	0.0%	EEG	2.0%	0.1%
Total	65.1%	75.6%	Total	71.6%	67.2%

Source: Authors’ calculations, 2014–2019 Aetna Medicare Advantage claim

Notes: The shares of denied services and denied spending are presented for the 15 specific service categories accounting for the greatest shares of denied spending. The denominator for each share is the total number of services or total spending that was denied within each category of coverage rules (Medicare or Medicare Advantage).