Plethysmography — NCD 165 | CMS Coverage Update

TL;DR: The Centers for Medicare & Medicaid Services modified NCD 165, the National Coverage Determination governing Medicare plethysmography coverage, effective March 7, 2026. Here's what billing teams need to know.

This policy update touches every internal medicine, vascular surgery, and podiatric practice that bills Medicare for peripheral vascular diagnostic testing. The CMS plethysmography coverage policy under NCD 165 draws a hard line between covered procedures and experimental ones — and that line determines whether your claims get paid or denied. No specific CPT or HCPCS codes are listed in the policy document itself, but the clinical categories map to several codes your billing team should already have in your charge master.

Quick-Reference Table

CMS Plethysmography Coverage Criteria and Medical Necessity Requirements 2026

NCD 165 is the National Coverage Determination that defines whether Medicare will reimburse plethysmography procedures. The Centers for Medicare & Medicaid Services divides plethysmographic methods into two categories: covered (Category I) and experimental (Category II). If your team is billing a Category II method, expect a claim denial.

The coverage policy is based on medical necessity tied to specific clinical presentations. Medicare covers plethysmography when it's used for diagnostic, preoperative, or postoperative evaluation of peripheral artery disease. It's also covered for preoperative podiatric evaluation of diabetic patients, or patients with intermittent claudication or other signs of peripheral vascular disease that bear on their candidacy for foot surgery.

That last point matters for podiatry practices. If you're billing plethysmography in a podiatric context, the medical necessity documentation needs to show one of those specific indications. "Peripheral vascular disease" alone isn't enough — you need to connect it to surgical candidacy or the clinical decision at hand.

The policy also addresses care setting. Venous occlusive pneumoplethysmography is covered in a hospital vascular laboratory setting. The policy explicitly states it's unsuitable for routine use in a physician's office. If your office-based practice is billing this method, that's a problem you need to fix before March 7, 2026.

For prior authorization: NCD 165 does not list a prior authorization requirement for covered plethysmography procedures. That said, your Medicare Administrative Contractor may have a local coverage determination that adds prior auth requirements at the regional level. Check with your MAC before assuming none applies.

CMS Plethysmography Exclusions and Non-Covered Indications

This is where the real claim denial risk lives. CMS identifies four specific methods as experimental under Category II. These are not covered — period. Billing them under any clinical scenario will result in denial based on §1862(a)(1) of the Social Security Act, which is the standard non-covered service provision.

Here are the four experimental methods, and why CMS won't pay for them:

Inductance Plethysmography — CMS says this method doesn't produce reproducible results. That's a hard bar to clear for coverage, and they're not covering it until the evidence changes.

Capacitance Plethysmography — Same finding. Not reproducible, not covered.

Mechanical Oscillometry — CMS calls this non-standardized, with poor sensitivity. They also note it's not superior to a simple peripheral blood pressure measurement — which Medicare already covers separately.

Photoelectric Plethysmography — Limited to detecting pulse presence only. That's not a diagnostic workup for peripheral vascular disease. CMS won't pay for it in that context.

If any of these methods appear in your procedure mix, pull those claims and review them now. If you're not sure how your current plethysmography billing maps to these categories, that's the conversation to have with your billing consultant before the effective date.

Coverage Indications at a Glance

CMS Plethysmography Billing Guidelines and Action Items 2026

The effective date of March 7, 2026 is your hard deadline. Here's what to do before then.

If your practice has a high volume of plethysmography billing or you serve a mix of vascular and podiatric patients, loop in your compliance officer before March 7, 2026. The Category I vs. Category II distinction is clean in the policy, but mapping it to your actual charge capture requires someone who knows your specific procedure mix.

CPT, HCPCS, and ICD-10 Codes for Plethysmography Under NCD 165

A Note on Codes

NCD 165 does not list specific CPT or HCPCS codes in the policy document. This is not uncommon for older NCDs — the clinical categories are defined by method, not by code. Your plethysmography billing will use CPT codes that correspond to the clinical methods described in the policy (segmental plethysmography, impedance plethysmography, strain gauge plethysmography, etc.), but the NCD itself doesn't enumerate them.

This creates a real risk. Without an explicit code list in the NCD, your billing team needs to confirm which CPT codes your MAC maps to each covered method. Different MACs handle this differently, and a code your team assumes is covered may not be recognized as such in your region.

Do not assume a CPT code is covered under NCD 165 just because the method sounds similar to a Category I description. Confirm the mapping with your MAC or your billing consultant. For Doppler (ultrasonic blood flow measurement), refer to §50-7. For oculoplethysmography, refer to NCD 20.17.

What to Do Without a Code List

Pull your claim data for the past 12 months. Filter for any plethysmography-related CPT codes your team has billed. Then map each one to either Category I or Category II using the method descriptions in NCD 165. If any codes land in Category II territory — or if you can't confirm which category they belong to — that's your audit priority before the March 7, 2026 effective date.