Infectious Disease Billing & Coding Guide
Inpatient consult vs subsequent care, antimicrobial stewardship, OPAT home infusion coding.
Common Infectious Disease CPT Codes
Ranked by claim frequency, with current MPFS work RVUs and global periods.
| Code | Description | Work RVU | Total RVU | Global |
|---|---|---|---|---|
| 99221 | 1st hosp ip/obs sf/low 40 | 1.63 | 2.23 | XXX |
| 99222 | 1st hosp ip/obs moderate 55 | 2.60 | 3.50 | XXX |
| 99223 | 1st hosp ip/obs high 75 | 3.50 | 4.68 | XXX |
| 99231 | Sbsq hosp ip/obs sf/low 25 | 1.00 | 1.32 | XXX |
| 99232 | Sbsq hosp ip/obs moderate 35 | 1.59 | 2.11 | XXX |
| 99233 | Sbsq hosp ip/obs high 50 | 2.40 | 3.20 | XXX |
| 99213 | Office o/p est low 20 min | 1.30 | 2.85 | XXX |
| 99214 | Office o/p est mod 30 min | 1.92 | 4.06 | XXX |
| 99215 | Office o/p est hi 40 min | 2.80 | 5.76 | XXX |
| 99252 | Ip/obs consltj new/est sf 35 | 1.50 | 2.10 | XXX |
| 99253 | Ip/obs cnsltj new/est low 45 | 2.00 | 2.96 | XXX |
| 99254 | Ip/obs cnsltj new/est mod 60 | 2.72 | 4.12 | XXX |
| 99255 | Ip/obs consltj new/est hi 80 | 3.86 | 5.53 | XXX |
| 86592 | Syphilis test non-trep qual | 0.00 | 0.00 | XXX |
| 86593 | Syphilis test non-trep quant | 0.00 | 0.00 | XXX |
| 86701 | Hiv-1antibody | 0.00 | 0.00 | XXX |
| 86702 | Hiv-2 antibody | 0.00 | 0.00 | XXX |
| 86703 | Hiv-1/hiv-2 1 result antbdy | 0.00 | 0.00 | XXX |
What Infectious Disease practices are leaving on the table
High-value services that consistently get under-billed across the specialty. Each one is rooted in current 2026 fee schedule and policy updates.
99215 office visits under-billed; many ID practices code stable patients as 99213-99214 when chart supports high complexity. Patient with multiple comorbidities, polypharmacy review, and treatment plan adjustment = 99215 (2.8 RVU). Average 4-5 cases/month at undercoded level = $200-300/month revenue gap. Audit your charts for MDM supporting higher levels.
Modifier 25 not appended to labs when separate E/M performed: when patient comes for 99214 visit AND gets same-day syphilis serology recheck, many billers drop the 99214 charge assuming lab bundles it. Chart review shows visit occurred, merits modifier 25. Conservative estimate: 2-3 visits/month × $150 = $300-450/month lost. Train staff to bill visit + lab separately when both documented.
Inpatient consults (99252-99255) not captured when ID physician consulted by hospital on admission: hospitalist or surgeon pages ID for sepsis/infection workup, but claim shows only 99231 (subsequent visit). Consult codes (99252-99255) are higher RVU (1.5-3.86 vs. 1.0-2.4). First consult on day of admission = 99253-99254, not 99231. Estimated 5-10 missed consults/month = $500-800/month.
CPT 99291 (critical care, first hour, 4.5 RVU) not billed for ICU sepsis/endocarditis management: many ID physicians document ICU care but code routine 99233 (2.4 RVU). If patient is critically ill (organ failure, ventilator, continuous monitoring), 99291 applies. Requires time spent >30 min and high complexity. One 99291 vs. 99233 = ~$400 per case. If 2-3 cases/month missed, $800-1200 revenue loss.
Code pairs that auto-bundle to CO-97
From the National Correct Coding Initiative for Infectious Disease. The rationale tells you when a modifier legitimately bypasses the edit and when it cannot.
HIV-1 antibody (86701) and combined HIV-1/HIV-2 single result antibody (86703) bundle. Only one is reportable per encounter unless testing different specimens on same date. Modifier 59 is not appropriate here. Document separate specimen types or clinical rationale if both medically necessary on same date.
Syphilis non-treponemal qualitative (86592) and quantitative (86593) both test RPR/VDRL. Quantitative includes qualitative result, so 86593 alone is correct. Billing both triggers NCCI pair denial. Only claim 86593 if titer tracking is needed.
Office E/M levels 99213 and 99214 cannot both be billed same date by same provider. Choose ONE based on documented complexity, time, and MDM. Modifier 25 does not bypass E/M level stacking rules. Common RAC error finding.
Inpatient/observation consult (99252-99255) and initial hospital visit (99221-99223) do not bundle if different physicians. If same physician admits patient after consultation on same date, use initial visit code only. Document who performed each service.
Modifier Guidance for Infectious Disease
When each modifier legitimately applies in this specialty, with denial-pattern context and audit-defense documentation.
Modifier 25 applies when a separate, identifiable E/M service is performed on the same date as a lab or other service. Example: ID physician performs 99214 office visit for HIV medication management AND orders 86701 HIV-1 antibody recheck on same date. Document the E/M separately from the lab order in the chart. Without modifier 25, payer bundles the lab into the E/M.
Use only when two normally bundled codes are truly distinct and separately identifiable. In ID, this is rare given the lab-only and E/M-only nature of most codes. Example: if somehow two syphilis tests on different body site specimens were coded (hypothetical), 59 might apply. Requires detailed chart note explaining clinical necessity and distinction. Most denials on 59 in ID involve lab pairs where bundling rules actually apply.
Professional component modifier used when lab is interpreted by ID physician but performed at external lab. Attach to lab code (e.g., 86701-26) when billing interpretation only. Requires written report in chart and clear separation from TC (technical). Uncommon in primary care ID but relevant for academic or large group labs.
Medicare requirement when billing beyond frequency limits or medical policy thresholds. Example: if HIV-1 testing (86701) is medically necessary more than standard frequency per LCD, append KX to override denial. Chart must document specific clinical reason (e.g., acute illness, medication change, compliance check). Without KX and supporting docs, expect CARC 50 (not covered when billed).
Documentation requirements
What needs to live in the encounter note for these codes to survive a payer audit.
- Date, time, and duration of E/M service; document whether visit was straightforward (99213), moderate (99214), or high complexity (99215) based on MDM and ROS to defend level selection.
- Chief complaint tied to infectious disease diagnosis (e.g., 'Patient here for HIV viral load monitoring' or 'Syphilis follow-up after treatment') to justify medical necessity of labs ordered.
- Justification for each lab ordered (why 86701 vs 86703, why repeat 86593 instead of 86592) with clinical note stating indication and impact on treatment plan.
- If multiple E/M or consult codes billed same date, document separately WHO performed each service and WHEN (time stamps reduce ambiguity for bundling reviews).
- For modifier 26 claims, include written lab interpretation report in chart separate from ordering provider's note to prove professional component was performed and billed independently.
- Medication reconciliation or treatment plan update tied to lab results within 3 days of service, proving labs directly informed clinical decision-making (RAC auditors check if labs are medically necessary and acted upon).
OIG and audit triggers in Infectious Disease
Patterns that show up in OIG Work Plans, RAC audits, and CERT improper payment reviews. Build internal compliance checks around these.
RAC audit target: E/M level inflation (99214 billed when 99213 supported by chart). OIG Work Plan includes E/M coding accuracy for all specialties. Defend by printing note with documented time, ROS breadth, and MDM complexity that justifies selected level. Missing time documentation is primary denial driver.
Lab stacking denial: billing 86592 AND 86593 on same date or 86701 AND 86703 without separate specimen documentation. NCCI bundling automated; override requires modifier 59 with detailed chart rationale. Most ID practices cannot justify 59 here, so expect denial. Always claim quantitative (86593) if ordered, not both.
Consult-to-admission sequence error: same provider bills 99252 and 99221 same date. No bundling rule prevents this technically, but payer medical policy often disallows dual payment. Chart must clearly show consult performed, then separate later admission decision. If consult led to admission, code initial visit (99221) only, not both.
Frequency violation without KX modifier: Medicare LCD may limit HIV testing frequency to 1-2 times yearly for stable patients. Billing third test without KX modifier and clinical justification (acute illness, medication change, viral load >200) triggers CARC 50 denial. Requires ABN and pre-certification in many cases.
Payer-specific billing notes
Where the major payers diverge from generic Medicare rules in Infectious Disease.
ME Medicare +
LCD for HIV serology (86701-86703) requires medical necessity for repeat testing; stable patients typically limited to annual screening per CMS national policy. CMS bundled codes 86592 and 86593 under NCCI; do not report both. For initial patient workup, all three syphilis tests (86592, 86593, treponemal) are covered separately. No change to bundling expected in 2026 per CMS transmittals through 2025. Prior authorization not required but requires ABN if test frequency exceeds policy.
UN UnitedHealthcare +
Optum medical policy delegates syphilis and HIV testing to local medical review boards; expect variation by region. UnitedHealthcare bundles initial E/M with labs within same date unless modifier 25 appended with distinct documentation (separate time, separate condition). Preauthorization required for repeat testing beyond 12 months in stable asymptomatic patients. No specific 2026 changes announced; follow existing medical policy matrix on UnitedHealthcare provider portal.
AN Anthem +
Anthem bundles syphilis non-treponemal testing; if both 86592 and 86593 billed, expect auto-denial of 86592 as included in 86593. Anthem's ICR (Interqual Clinical Review) for IP consults requires 99252 minimum complexity for consult payment; cannot bill observation/consult codes below 99252 level. eClaims may route through Anthem's AIM (Automation and Implementation Management) tool; check prior auth requirements by state/product.
CI Cigna +
Cigna medical policy requires specific ICD-10 diagnosis code for each lab test (e.g., Z11.3 for HIV screening vs. B20 for known HIV); lack of specific diagnosis = denial under CARC 151. Cigna does not require prior auth for routine HIV/syphilis testing but may deny based on frequency limits if no clinical documentation of acute infection. eviCore is not delegated for ID labs; use Cigna's online portal for determinations.
Standard Infectious Disease coding workflow
Step 1: Verify provider type and setting (office vs. hospital vs. consult) to select correct E/M code family (99213-99215 office, 99221-99223 initial hosp, 99252-99255 consult). Step 2: Assign E/M level based on documented time, complexity, and medical decision-making per CMS guidelines; do not stack multiple E/M codes same date/provider. Step 3: List all labs ordered with clinical indication in note (do not bill 86592 if 86593 ordered; do not bill both 86701 and 86703 unless separate specimens documented). Step 4: Append modifier 25 only if separate, identifiable E/M service is distinct from lab service in timing, complexity, or documentation. Step 5: Review NCCI pairs and payer bundling rules before submission; flag KX when frequency limits are exceeded with supporting clinical note.
Get the full PayerReady toolkit
Credentialing + billing/coding tools built for Infectious Disease, free access with enrollment.
Start free →Run this code through our claim audit tool
Check NCCI bundling, MUE limits, and modifier logic before submission.
Try the auditor →Verified against CMS 2026 code set, current NCCI Quarterly Updates, and the X12 Claim Adjustment Reason Code reference. Last updated April 15, 2026. See data sources and methodology.
Did this page help?
Quick signal so we know what to improve.
If you want a code reference page that doesn't exist yet, email coding@payerready.com.
Tell us what's missing or wrong: coding@payerready.com. We respond within 5 business days.
Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
Powered by 11K CPT · 98K ICD-10 · 860K MPFS rates · 4.5M NCCI edits · 9.5M NPIs. Our data methodology · About our coding team