Infectious disease billing depends on accurate CPT code selection across office visits, laboratory testing, and IV infusion services. The Centers for Medicare and Medicaid Services (CMS), a federal agency that administers Medicare Part B reimbursement, updates physician fee schedule rates annually through the Physician Fee Schedule Final Rule. Practices billing infectious disease services must match each CPT code to a documented diagnosis, appropriate modifier, and supporting medical record or risk audit-triggered claim denials. MMBS maintains a 98.2% clean claim rate across all infectious disease clients by combining coder specialization with real-time eligibility verification before each encounter.
Office Visit E/M Codes for Infectious Disease
Evaluation and Management (E/M) codes form the backbone of infectious disease billing. CPT 99214 covers a moderate-complexity office visit, typically used when the physician reviews an established patient with one or more chronic infections, orders labs, and adjusts antimicrobial therapy. CPT 99215 covers a high-complexity office visit and applies to patients with HIV (ICD-10 B20), sepsis workups, or multi-drug resistant organism management requiring extensive data review and high-risk decisions.
Medical Decision Making (MDM) or Total Time documentation must support the selected level. Under 2023 and forward E/M guidelines from the American Medical Association (AMA), CPT code guidelines published in CPT Professional Edition require either MDM or total time as the basis, not the traditional history and exam elements. Infectious disease physicians frequently manage patients on multiple antimicrobials or antiretrovirals, which supports a higher MDM level.
Consultation Codes and Transfer-of-Care Distinction
CPT 99243 (office consultation, moderate complexity) and CPT 99244 (office consultation, high complexity) remain billable to commercial payers but are not reimbursed by Medicare or Medicaid under CMS policy effective since 2010. For Medicare patients, infectious disease physicians who accept a consult request must bill using the appropriate E/M office visit code (99213-99215) based on the complexity of the encounter. The distinction between a consultation and transfer of care affects billing code selection: a consultation requires a formal request, a report back to the requesting provider, and no assumption of ongoing management.
Laboratory and Diagnostic Testing Codes
Infectious disease practices frequently order or perform point-of-care or send-out laboratory tests. CPT 87491 (Chlamydia trachomatis, NAAT, any source) and CPT 87798 (infectious agent detection, not otherwise specified, NAAT) are two commonly billed laboratory codes. When the practice does not perform the test in-house, billing the lab code is appropriate only if the physician performed the technical component or ordered a test performed under the practice’s Clinical Laboratory Improvement Amendments (CLIA) certificate.
IV Infusion Billing for Infectious Disease
CPT 96365 covers the first hour of intravenous infusion, therapeutic or prophylactic, and is the primary infusion code for antibiotic or antifungal administration in the office or infusion suite setting. Each additional hour bills under CPT 96366. Concurrent infusions (two drugs running simultaneously) bill under CPT 96367 for the secondary drug, not an additional 96365. Infusion coding errors are among the top denial triggers in infectious disease practices: billing 96365 twice for the same drug instead of 96366 for additional time is a common mistake that triggers CO-4 (inconsistent with modifier) or CO-97 (bundling) denials.