Infectious disease billing presents distinct workflow challenges because practices manage a wide range of service types in a single visit: office-based E/M encounters, in-office IV infusions, specimen collection, point-of-care testing, and referrals for imaging or hospitalist consults. Each service type carries its own coding rules, documentation requirements, and payer-specific coverage criteria. A clean claim rate of 28-32 AR days, compared to the industry average of 45-55 days, requires that every step from patient registration through payment posting is executed without gaps. The six-step workflow below reflects the actual process MMBS uses for infectious disease clients.
Step 1: Patient Registration and Insurance Verification
Accurate patient registration is the foundation of infectious disease billing. Front-desk staff verify demographics, insurance coverage, and any existing prior authorization requirements before the appointment. Infectious disease payers including UnitedHealthcare, Anthem Blue Cross Blue Shield, Aetna, and Cigna may require prior authorization for long-course IV antibiotics, antifungals, or antiretrovirals administered in the office. Checking eligibility through a clearinghouse or payer portal catches plan changes, deductible status, and coverage exclusions before the physician sees the patient. Eligibility failures are a leading cause of CO-22 (patient responsibility) and CO-29 (timely filing) denials in this specialty.
Step 2: Encounter Documentation and E/M Level Selection
The physician or advanced practice provider completes the encounter note in the EHR (Electronic Health Record), documenting the presenting problem, clinical data reviewed (labs, cultures, imaging), assessment, and plan. For infectious disease encounters, medical necessity documentation must connect the diagnosis to each ordered service. For example, a visit for Candida esophagitis (ICD-10 B37.0) must document dysphagia, failed empiric therapy, or immunocompromised status to justify the encounter complexity level. The coder reviews the note and selects the appropriate E/M code based on MDM or total documented provider time.
Step 3: Procedure and Infusion Code Assignment
When the patient receives an in-office IV infusion, the clinical staff document start and stop times for each drug administered. CPT 96365 applies to the first infusion hour; CPT 96366 covers each additional hour. Documentation must state the drug name, dose, route, and duration. J-codes (HCPCS Level II drug codes published by CMS) identify the specific drug and quantity for billing. For example, ceftriaxone 1g IV bills under HCPCS J0696, while vancomycin 500mg IV bills under J3370. Missing drug quantity documentation or mismatched J-codes trigger CO-16 (missing information) and CO-4 (modifier inconsistency) denials.
Step 4: Diagnosis Coding and Medical Necessity Linkage
ICD-10-CM codes published annually by the Centers for Disease Control and Prevention (CDC) and maintained by CMS must support medical necessity for every procedure billed. In infectious disease, the primary diagnosis code links the presenting condition to the ordered services. Sepsis (A41.9), pneumonia (J18.9), HIV disease (B20), and Clostridium difficile infection (A04.72) each carry specific coding rules. Sepsis coding follows official ICD-10-CM guidelines: the principal diagnosis is the systemic condition (A41.9), with the causative organism coded additionally (e.g., A41.51 for Methicillin-resistant Staphylococcus aureus). Incorrect principal diagnosis sequencing is a common root cause of CO-16 denials in inpatient infectious disease billing.
Step 5: Claim Submission and Clearinghouse Scrubbing
Claims are submitted electronically through a HIPAA-compliant clearinghouse such as Availity or Change Healthcare. The clearinghouse applies edit rules that check code combinations, modifier validity, and payer-specific billing requirements before the claim reaches the payer. Common scrubbing catches for infectious disease include: billing 96365 and 96366 without documented start/stop times, submitting consultation codes (99241-99245) to Medicare without substituting E/M codes, and missing NPI (National Provider Identifier) linkage between the ordering and performing provider on lab codes. Fixing claims before submission reduces days in AR and avoids full resubmission cycles.
Step 6: Payment Posting, Denial Management, and Appeals
ERA (Electronic Remittance Advice) files from the payer post payment details to the practice management system. CARC (Claim Adjustment Reason Code) and RARC (Remittance Advice Remark Code) codes on the ERA identify the reason for any adjustment or denial. The billing team categorizes denials by type: medical necessity, coding error, authorization, or timely filing. Infectious disease CO-97 (bundling) denials on infusion codes require an unbundling review: confirming the drugs were administered separately, not concurrently, and that documentation supports each line. MMBS appeals infectious disease denials at an 85% first-pass resolution rate by submitting clinical notes and specialty-specific coverage criteria letters to payers.