The $19.7 Billion Problem That Starts With a Documentation Gap
The American Hospital Association calculated that hospitals spent $19.7 billion in 2022 dealing with insurance denials — not on care, not on staffing, not on technology, but on the administrative work of fighting payer decisions after the fact. Medical necessity is consistently the top denial reason across Medicare, Medicaid, and commercial payers. And yet most hospitals still treat it as a revenue cycle problem to be managed downstream, rather than a clinical documentation problem to be solved upstream.
That framing mismatch is expensive.
Facilities that hold denial rates below 3% are not simply better at appealing. They have built a process that intercepts documentation gaps before claims leave the system. That is a fundamentally different operational posture, and it starts with understanding what payers are actually checking when they make a medical necessity determination.
What Payers Are Looking For
Commercial payers and Medicare Advantage plans do not evaluate medical necessity based on the treating physician's clinical judgment alone. They run submitted documentation against a structured criteria set, and the two systems that dominate the industry are InterQual, now owned by Change Healthcare under Optum, and MCG Health, formerly published as Milliman Care Guidelines. Most major commercial payers use one of these two frameworks, then layer their own coverage policies on top.
The practical consequence of that structure is significant. A physician can document a legitimate clinical picture that justifies admission, and a payer can still deny the claim because the documentation doesn't map to the specific severity indicators in their criteria set. The care was appropriate. The documentation simply didn't speak the payer's language.
Knowing which criteria set governs each of your major payer contracts is the starting point for any serious medical necessity review process. Without that knowledge, your clinical reviewers are essentially guessing at what the payer wants to see. With it, they can check documentation against the actual thresholds before the claim is submitted.
Since 2020, both CMS and commercial payers have tightened medical necessity criteria noticeably, particularly around inpatient admission thresholds, observation status determinations, and elective procedure authorization. Recovery Audit Contractor activity has also increased, with RAC auditors specifically targeting inpatient admissions for one and two midnight stays. The criteria have moved. Documentation practices at many facilities have not kept pace.
The Three Documentation Gaps That Drive Most Denials
Admission Criteria Not Documented
The most common gap is also the most straightforward to fix. A physician documents a diagnosis — pneumonia, sepsis, CHF exacerbation — but does not document the specific clinical indicators that establish severity at the inpatient threshold. Under InterQual, for example, an inpatient admission for community-acquired pneumonia requires documentation of specific vital sign abnormalities, oxygen requirements, or laboratory findings that place the patient above the observation-level criteria. A note that says "admitted for pneumonia management" tells a coder what happened. It does not tell a payer reviewer why the patient required the level of care billed.
The fix requires physicians to document not just the condition, but the clinical picture that makes lower-level care inadequate.
Continued Stay Criteria Missing
Inpatient denials frequently occur not on the day of admission but on day two or three, when the payer's concurrent review team looks at whether the patient still meets criteria for inpatient status. If the progress notes during that period don't document why the patient continues to require inpatient-level services rather than discharge to a lower-acuity setting, the continued stay is vulnerable.
This is where concurrent review during the patient's stay becomes critical. A clinical reviewer checking daily documentation against the payer's continued-stay criteria can identify gaps while the physician is still available to address them, rather than after the patient is discharged and the claim is denied 45 days later.
Procedure Documentation That Doesn't Match the Authorization
For elective procedures, the denial scenario looks different. Pre-authorization was obtained, the procedure was performed, and the claim is still denied. The reason: the documentation submitted with the claim does not align with what was described in the authorization request. This happens when procedure coding or clinical documentation shifts between the pre-authorization stage and the actual encounter, and nobody reconciles the two before billing.
Spine surgery cases and cardiology procedures are particularly prone to this pattern. An authorization granted for a specific CPT code can become a denial if the operative report supports a different procedure than what was authorized, even a related one. A pre-submission coding quality audit that checks claim codes against authorization records before submission catches these mismatches at a point when they can still be corrected.
How a Medical Necessity Review Process Actually Works
A functioning pre-submission review process has three components operating at different points in the patient encounter.
Pre-Submission Review
For elective admissions and scheduled procedures, a clinical reviewer checks the available documentation against the applicable criteria set before the claim is submitted. This is not a coding review and not a utilization management function in the traditional sense. It is a targeted check: does this documentation, as written, meet the threshold this payer will apply? If not, the physician query process is triggered before the claim leaves the system.
This is the core function of a medical necessity review service applied proactively rather than as a denial response tool.
Concurrent Review for Inpatient Stays
For inpatient admissions, pre-submission review alone is not enough because the documentation builds throughout the stay. Concurrent review assigns a clinical reviewer to check daily progress notes against the payer's continued-stay criteria while the patient is still in the facility. When gaps appear, a query goes to the treating physician the same day, not after discharge.
The window for this kind of intervention is short. Once a patient is discharged and the medical record is finalized, retroactive documentation changes are limited in what they can address. Concurrent review captures the gap while something can still be done about it.
Pairing concurrent review with discharge summary review closes the loop at the end of the stay, ensuring that the final documentation accurately reflects the clinical course and supports the level of care billed.
The Physician Query Process
Neither pre-submission nor concurrent review works without a reliable mechanism for getting documentation clarified by the attending physician. The query process has to be fast enough to fit a clinical workflow, specific enough to be useful, and compliant with AHIMA and ACDIS guidelines governing what queries can appropriately ask.
An effective CDI program support structure handles this by having clinical documentation improvement specialists who understand both the clinical and coding dimensions of the gap. A query that says "please clarify the severity of the patient's respiratory failure" is unlikely to produce useful documentation. A query that explains specifically what clinical indicator is needed to support the documented acuity level is far more productive, and more defensible in an audit.
Build Versus Outsource: The Real Cost Calculation
Setting up an internal medical necessity review function requires a specific combination of skills that is genuinely difficult to hire for. Clinical reviewers need a nursing or clinical background, familiarity with InterQual or MCG criteria sets, coding knowledge sufficient to connect documentation to claim codes, and working familiarity with payer-specific coverage policies that change on their own schedules.
A single experienced clinical documentation specialist with utilization review background commands a salary in the $75,000 to $95,000 range in most US markets, before benefits and overhead. A team capable of covering high-volume inpatient admissions across multiple service lines and multiple payer criteria sets requires several of these individuals, plus supervisory oversight and continuing education to track payer policy changes.
For many facilities, the math does not favor building the function internally. That is particularly true in three situations: facilities with significant volume from payers that use complex or frequently updated criteria sets, hospitals with high observation case volumes where the inpatient versus observation determination is contested regularly, and smaller or critical access hospitals that do not have an existing utilization review department to build from.
Outsourcing to a team with dedicated clinical reviewers, existing payer criteria expertise, and the infrastructure to handle query workflows allows these facilities to get the function operating without the 90-plus day hiring and onboarding cycle. It also provides coverage continuity during vacations, turnover, and census surges that would create gaps in an internal team.
Larger systems with existing UR staff can still benefit from external review on specific payer segments or high-risk service lines where internal expertise is thin. A hybrid model, where the internal team handles routine cases and external reviewers cover complex or contested payer criteria, often produces better denial rates than either approach alone.
What Proactive Review Actually Changes
The facilities that have shifted from reactive denial management to pre-submission review consistently report the same outcomes: lower initial denial rates, shorter accounts receivable cycles on contested claims, and reduced write-offs. The appeals process does not disappear, but it handles a smaller volume of claims, and the cases that do go to appeal tend to have stronger supporting documentation because the review process already identified and addressed the weak points.
There is also a compounding effect over time. When physicians receive consistent feedback through the query process about what documentation is missing and why it matters, their baseline documentation improves. That reduces the query volume required in subsequent months, which reduces the cost of running the review function. The investment pays down over time in a way that reactive denial management does not.
The AHA's $19.7 billion figure reflects a system where most hospitals are funding appeals rather than prevention. The gap between facilities with 2% denial rates and those carrying 8% or 10% is not primarily a technology gap or a payer relations gap. It is a documentation review gap, and it is closable.
If your organization is ready to move from managing denials to preventing them, our medical necessity review service is a direct place to start.