Medical Claims Auditing Checklist for Infectious Disease Practices

Introduction

Infectious disease claims rarely look like a standard office visit. Between OPAT orders, infusion start and stop times, drug wastage, and payer-specific authorization rules, there are a dozen places a claim can go wrong before it ever reaches a payer.

According to MGMA's 2024 poll, 60% of medical group leaders reported more denials in early 2024 than the same period a year earlier, with coding updates, modifier errors, and authorization disputes topping the list of causes.

For an infectious disease practice, those same pressure points show up constantly: a lapsed authorization mid-course of therapy, a site-of-care mismatch, or drug units that don't match what was actually administered.

This checklist walks physicians, group leaders, administrators, and billing teams through a full claims audit, from clinical documentation to payment posting. You'll prepare the audit, choose a method and sample, compare claims against source records and payer rules, classify what you find, and assign fixes.

Key Takeaways

• Audit the full claim lifecycle from identity and eligibility through coding, remittance, and follow-up
• Sample paid, denied, rejected, underpaid, high-value, and OPAT or infusion claims
• Check findings against current coding guidance, payer policy, and the correct service year
• Separate one-off mistakes from recurring workflow problems; assign an owner and re-audit date

What You Need to Check Medical Claims in an Infectious Disease Practice

A real audit needs the full claim lifecycle, not a billing report or a stack of clearinghouse rejections. Pulling just the denial file tells you what the payer flagged. It misses everything your own team got wrong before submission, and everything the payer underpaid without comment.

Audit Scope and Source Documents

Start by defining:

• The review period, payer mix, and locations involved
• Which providers and service lines to include (office, inpatient, observation, telehealth, OPAT, infusion)
• Claim types: new patient, established, consult, drug administration, E/M

Then gather:

• Encounter notes, orders, and infusion or lab records
• Charge tickets, superbills, and authorizations
• Eligibility records, claim forms, and clearinghouse reports
• Remittance advice, payment-posting entries, denial letters, and appeal documentation

Check each claim against current, dated guidance, not whatever reference binder is sitting on the shelf:

• Current-year CPT and ICD-10-CM codes and guidelines
• HCPCS Level II updates (these are quarterly, so a new J-code may not be in last quarter's list)
• NCCI procedure-to-procedure edits and Medically Unlikely Edit limits
• Medicare, Medicaid, and the specific commercial payer's own policy
• The actual payer contract terms, not a general fee schedule assumption

Claim-Level Checklist

For every claim, confirm:

• Patient identifiers, date of service, rendering and billing provider details, place of service, and coordination-of-benefits data
• Diagnoses match the clinical record: confirmed versus suspected conditions, with organism and resistance details only where documented
• Procedures reflect what was actually performed, with defensible sequencing
• Modifiers, units, time, and frequency match the note (verify current modifier rules rather than assuming last year's)
• Drug and supply details tie to administration records

For OPAT, infusion, and other recurring services, also check:

• Order validity, plus start and stop dates
• Administration documentation (volumes, rates, timestamps)
• Site-of-service information and clinical-billing coordination

Medicare's home infusion benefit requires a signed plan of care before submission. Compare signature dates against billing dates, per CMS's home infusion FAQ.

Finally, confirm authorization, referral, eligibility, medical necessity, and timely-filing requirements were met before submission, and that supporting records are retained.

Methods to Audit Medical Claims in an Infectious Disease Practice

No single method catches everything. Most practices combine three approaches, weighted by claim volume, payer mix, staffing, and what prior audits turned up.

Pre-Submission Claim Review

Catch errors before the claim ever leaves the building, while documentation and correction are still easy.

What you need:

• Claim scrubber or billing-system report
• Documentation checklist
• Authorization and eligibility records
• Current payer edits
• Reviewer worksheet

Steps:

1. Select high-risk or frequently denied claim types (drug administration and OPAT claims are good candidates)
2. Compare each line against the encounter note, order, authorization, and charge record
3. Verify provider, patient, diagnosis, procedure, modifier, unit, and place-of-service fields against current requirements
4. Document the defect, correct it, identify the root cause, and keep an audit trail of who changed what

Pre-submission review prevents denials and rework. Review too many claims this way, though, and you slow down submission. It also won't catch payment-posting or underpayment problems that only surface after the payer responds.

Retrospective Sample Audit

This looks backward across the full claim path, testing whether billed services, documentation, coding, and internal controls actually line up.

What you need:

• Stratified sample report
• Complete medical records
• Claim images and remittance advice
• Denial codes and payer policies
• Scoring sheet

Steps:

1. Build a sample with paid, denied, rejected, appealed, underpaid, high-value, and representative infectious disease claims, and document how you picked them
2. Trace each claim from registration and eligibility through coding, submission, adjudication, payment posting, and follow-up
3. Tally findings, separate one-off errors from patterns, assign corrective actions, and schedule a repeat sample to confirm the fix worked

Retrospective audits give you the broadest view of compliance exposure and revenue leakage. The catch: once filing or appeal windows have closed, some findings can be documented but not corrected.

Payment, Denial, and Underpayment Audit

This method checks whether the payer paid, and your team posted, according to the actual contract.

What you need:

• Remittance advice and deposit records
• Contract terms and fee schedules
• Adjustment codes
• Denial and appeal logs
• A/R aging reports

Steps:

1. Reconcile billed, allowed, paid, adjusted, and patient-responsibility amounts against the contract for each selected claim
2. Trace denials and partial payments to their reason codes, authorization status, documentation, and any appeal activity
3. Identify recurring payer, coding, or posting issues, and quantify the dollar impact using your own claims data

A drug claim paid below the contracted rate doesn't trigger a rejection or an alert. It just sits there underpaid unless someone compares the remittance to the contract line by line.

This audit catches missed payments and systemic payer issues, but it depends on accurate, current contract data. Not every variance is a billing error; some are legitimate contractual adjustments.

How to Interpret the Results

A finding only matters if you classify it correctly. Lumping everything into "denied" or "error" tells you nothing about what to fix next.

Supported or acceptable: The record backs the billed service, coding matches current guidance, authorization is present, and payment agrees with payer terms. Document the evidence and move on.

Correctable process issue: Minor, fixable problems such as inconsistent eligibility documentation, incorrect routing, or an isolated data-entry slip. Correct the claim where allowed, coach the team member, and watch for recurrence.

Material coding or documentation finding: Unsupported diagnoses, undocumented services, wrong units or modifiers, missing authorization, or inaccurate provider data. These need escalation, correction, and review by a qualified coding or compliance professional, including repayment or appeal analysis where applicable.

Financial or payer variance: Compare the remittance against contract terms and payer policy before calling it a short payment. Underpayment, incorrect adjustments, duplicate payments, and posting errors each need separate investigation.

Turn every material finding into an action register entry with:

• Claim or batch reference
• Issue category and financial or operational impact
• Responsible owner and deadline
• Corrective action and escalation path
• Re-audit date

Common Errors and Best Practices in Medical Claims Auditing

Most audit failures trace back to a handful of recurring habits:

• Auditing only paid claims and ignoring denials and rejections
• Pulling an unrepresentative sample (all easy claims, none of the complex ones)
• Reviewing codes in isolation, without the full clinical note
• Relying on outdated payer guidance or last year's policy
• Overlooking authorization status entirely
• Never reconciling remittance data against the contract

Be Precise With Infectious Disease Documentation

Don't code clinical facts that aren't documented. A reviewer should:

• Distinguish a confirmed diagnosis from a suspected one
• Verify organism and resistance details only when the record supports them
• Resist rounding up complexity from clinical judgment rather than the note itself

Protect the Audit Itself

• Limit record access to people who need it
• Use secure systems for claim images and remittance data
• Separate coaching from discipline for isolated errors
• Document reviewer qualifications, such as CPC, CPB, RHIT, or CCS credentials
• Escalate suspected fraud, abuse, privacy, or repayment issues through your practice's approved process

Build a repeat cycle:

• Train staff on what the audit found
• Update checklists and system edits
• Monitor denial and A/R trends
• Track payer policy changes
• Re-audit a comparable sample after remediation

OIG's 2023 guidance recommends at least an annual risk assessment, with more frequent reviews when payer rules change, systems migrate, new providers join, or denials spike.

If your team needs a plain-English way to apply its own claims and payment data to OPAT and infusion economics, GrowInfectiousDisease is a free resource hub built around that exact problem. It's not a substitute for coding, legal, or compliance advice, but it helps connect the mechanics.

Conclusion

Reliable claims auditing follows the whole path: patient and payer information, documentation, coding, authorization, submission, adjudication, payment posting, and follow-up. Skip a step, and you'll miss the errors hiding there.

Use current authoritative sources and your own claim, denial, payment, and contract data. Generic benchmarks and last year's assumptions won't catch what's actually happening in your practice.

Next steps:

1. Choose an audit period and define a representative sample
2. Assign a reviewer with the right access and qualifications
3. Document findings, owners, and deadlines
4. Schedule a re-audit to confirm the corrections held

Frequently Asked Questions

How much do medical billers charge?

Pricing varies by scope, claim volume, specialty complexity, staffing model, and whether the arrangement is hourly, fixed-fee, subscription-based, or tied to collections. Ask for a defined scope and confirm exactly what's included before comparing quotes.

How often should an infectious disease practice audit its medical claims?

Use a risk-based schedule rather than a fixed calendar. Audit more often after payer changes, system migrations, new provider onboarding, a denial spike, or any known control failure.

How many claims should be included in a medical claims audit?

Sample size depends on claim volume, audit purpose, and risk tolerance. Document your selection method and include paid, denied, rejected, complex, and representative claims rather than picking the easiest ones.

What are common claim-audit problems in infectious disease practices?

Documentation-to-code mismatches, eligibility or authorization gaps, incorrect place of service or modifiers, inconsistent recurring-service billing, missing supporting records, and payment-posting or underpayment issues all show up repeatedly.

Should a practice audit denied claims separately from paid claims?

Yes. Paid claims test accuracy and payment integrity, while denied or rejected claims reveal preventable workflow, coding, authorization, and payer-policy problems before they recur.

When should a practice obtain outside coding or compliance assistance?

Bring in outside help when findings involve repeated unsupported billing, possible repayment, suspected fraud or abuse, complex payer disputes, privacy concerns, or questions needing qualified coding, legal, or compliance expertise.