Work through the ten groups in order, because diagnosis conventions and E/M foundations support the later procedure and drug-billing applications. Each concept pairs a rule with a resolved example and a common error, so read the explanation, predict the example outcome, and check yourself against the mistake note. Code alongside your current ICD-10-CM, CPT, and HCPCS Level II books, since the credential exam assumes fluency with them. This guide teaches subject matter drawn from the references below; it is not an official syllabus and does not replace official references or hands-on experience.
ICD-10-CM Conventions and Structure
1. Index-Then-Tabular Workflow
Always locate the main term in the Alphabetic Index first, follow every see and see also cross-reference, then verify the code in the Tabular List before assigning it. Reading Tabular instructional notes, footnotes, and inclusion terms prevents errors the Index alone cannot reveal.
Example: A note documents a marrow abnormality; the coder finds the index entry, follows a see reference, and confirms the final code in the Tabular List, catching an excludes note that changes selection.
Mistake to avoid: Assigning a code straight from the Alphabetic Index without verifying Tabular instructions and required characters.
Reference: AAPC CHONC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
2. Placeholder Character X
The placeholder X fills empty character positions in codes that require a seventh character but have fewer than six characters, such as adverse effect codes in categories T36-T50. Without the X in each empty position, the code is invalid for reporting purposes.
Example: An adverse effect code with four characters and a required seventh character needs two X placeholders inserted before the seventh character to become a valid, billable code.
Mistake to avoid: Omitting X placeholders, producing an invalid code that claims reject.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
3. Seventh-Character Requirement
Certain categories require a seventh character for every code within them, and it must always occupy the seventh position. Fracture coding illustrates the depth needed: location, laterality and displacement, and episode of care must all be documented or the code cannot be selected accurately.
Example: A wrist fracture note lacks laterality, so the coder cannot build the required sixth and seventh characters and must query the provider rather than guess.
Mistake to avoid: Appending the seventh character in the wrong position or defaulting to an unspecified episode without documentation.
Reference: AAPC CHONC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
4. NEC Versus NOS
NEC means the documentation specifies a condition for which no dedicated code exists, directing you to an other specified code. NOS means documentation is insufficient for anything more specific, matching an unspecified code. Choosing between them depends on whether the provider actually named the condition.
Example: A documented rare lymphoproliferative disorder with no exact code takes the other specified entry; vague anemia without detail takes the unspecified code instead.
Mistake to avoid: Using an unspecified code when the note actually names a specific condition, or vice versa.
Reference: AAPC CHONC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
5. Excludes1 Versus Excludes2
An Excludes1 note means the two conditions cannot be coded together because they are mutually exclusive, such as congenital versus acquired forms. An Excludes2 note means the excluded condition is not part of the code but may coexist, so both codes may be reported when documented.
Example: A patient with a documented unrelated condition listed under an Excludes1 note may still have both codes reported because the exception applies when the conditions are clearly unrelated.
Mistake to avoid: Treating every Excludes note as a prohibition and dropping a legitimately coexisting Excludes2 condition.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
6. The With Linkage Presumption
When with or in links two conditions in a title, index entry, or instructional note, the classification presumes a causal relationship even without explicit provider linkage, unless documentation clearly states they are unrelated. Outside these linked terms, provider documentation must connect the conditions before coding them together.
Example: An index entry joining a malignancy with a documented manifestation lets the coder report both as related despite no explicit linkage sentence in the note.
Mistake to avoid: Assuming relatedness for unlinked conditions the classification never connects with these terms.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
Oncology and Hematology Diagnosis Coding
7. Navigating the Table of Neoplasms
The Table of Neoplasms organizes entries by anatomic site with columns for primary, secondary, in situ, benign, and uncertain behavior. Match the documented histology and behavior to the correct column, and when behavior is not yet pathologically established, follow the index direction for neoplasm of uncertain behavior.
Example: A skin lesion documented only as a neoplasm pending pathology maps to the uncertain behavior column rather than a malignant primary code.
Mistake to avoid: Selecting a malignant column entry before pathology confirms behavior.
Reference: AAPC CHONC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
8. Secondary Neuroendocrine Tumor Codes
Codes exist for secondary neuroendocrine tumors so metastatic spread of hormone-producing tumors to distant sites can be tracked separately from primary sites. These tumors differ biologically from adenocarcinomas and may cause clinically significant hormone release, which supports reporting both the secondary site and any functional activity.
Example: A patient with a metastatic hormone-secreting tumor to bone receives the secondary neuroendocrine code plus a code for the hormone excess manifestation.
Mistake to avoid: Reporting metastatic neuroendocrine spread with generic secondary malignancy codes that miss tumor type.
Reference: AAPC CHONC study guide sample
9. Merkel Cell Carcinoma Classification
Merkel cell carcinoma is a rare, aggressive neuroendocrine skin tumor, most common on the head and neck of sun-exposed older patients, with its own distinct code family separate from basal and squamous cell carcinoma codes. Its separate classification reflects a worse prognosis and the need for independent tracking.
Example: A head lesion confirmed as Merkel cell carcinoma is coded to the dedicated Merkel cell family, not the codes for common skin carcinomas.
Mistake to avoid: Lumping Merkel cell carcinoma into ordinary skin cancer codes, understating its severity.
Reference: AAPC CHONC study guide sample
10. Tumor Lysis Syndrome Reporting
Tumor lysis syndrome, coded E88.3, comprises metabolic complications from dying cancer cells after therapy, seen most with leukemia and lymphoma treatment. Report the syndrome code, a code for the complication present, and an external cause code identifying the antineoplastic drug when applicable, since steroids or spontaneous onset occasionally cause it.
Example: A leukemia patient develops the syndrome after chemotherapy; the coder reports E88.3, the metabolic complication, and the drug-related external cause code.
Mistake to avoid: Reporting only the electrolyte abnormality and omitting the syndrome or causal drug code.
Reference: AAPC CHONC study guide sample
11. Chemotherapy-Induced Anemia
A dedicated code exists for anemia caused by antineoplastic chemotherapy, distinguishing it from drug-induced aplastic anemia and unspecified anemia that were previously paired with adverse effect codes. Because chemotherapy suppresses marrow and red cell production, confirm the documented causal relationship before selecting the specific code over broader alternatives.
Example: A note documenting anemia from chemotherapy supports the chemotherapy-induced anemia code rather than unspecified anemia with an adverse effect code.
Mistake to avoid: Defaulting to unspecified anemia when documentation clearly ties it to antineoplastic therapy.
Reference: AAPC CHONC study guide sample
12. ALPS and Lymphoproliferative Conditions
Autoimmune lymphoproliferative syndrome is a rare genetic defect causing lymphocyte proliferation, with enlarged spleen, liver, and nodes, possible anemia, thrombocytopenia, and neutropenia, and a lifelong elevated lymphoma risk. Code the documented manifestations and any treatment such as splenectomy, keeping the lymphoma surveillance in mind for future encounters.
Example: A child with documented ALPS and splenomegaly receives the ALPS code plus the manifestation code for the enlarged spleen.
Mistake to avoid: Coding only individual cytopenias and missing the underlying syndrome diagnosis.
Reference: AAPC CHONC study guide sample
Outpatient Diagnosis Selection Rules
13. First-Listed Diagnosis Logic
In outpatient coding, the first-listed diagnosis describes the most significant reason for the visit, generally reflecting the chief complaint. Relevant coexisting diseases, related history, and family history conditions are secondary. Each date of service must stand alone, supported by documentation linked to that particular claim.
Example: A patient presents for chemotherapy side effect management; the side effect reason is listed first, with the underlying malignancy as a secondary code.
Mistake to avoid: Sequencing the historical malignancy first when today's reason is a treatment complication.
Reference: AAPC CHONC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
14. Symptoms Before Confirmed Diagnosis
When no definitive diagnosis is established by the end of an outpatient encounter, report signs and symptoms instead of an unconfirmed diagnosis. Reporting cancer before clinical confirmation can damage the patient's future insurability, so code the documented lump, symptom, or finding until pathology establishes the diagnosis.
Example: A breast lump without pathologic confirmation is coded as the lump, not breast cancer, protecting the record from an unsupported malignancy.
Mistake to avoid: Coding a suspected malignancy as confirmed based on the plan to biopsy.
Reference: AAPC CHONC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
15. Chronic Condition Reporting Threshold
Report a chronic condition only when it is treated at the encounter or becomes an active factor in the patient's care. Conditions that no longer exist or do not pertain to the visit are not reported, and the assigned code must identify the current reason for medical management.
Example: A cancer patient whose stable thyroid disease is untouched at a chemotherapy visit has the thyroid condition omitted from that claim.
Mistake to avoid: Carrying every historical chronic diagnosis onto each claim regardless of encounter relevance.
Reference: AAPC CHONC study guide sample; CDC ICD-10-CM Official Guidelines, FY 2027
16. Code All Coexisting Conditions
For outpatient encounters, code all documented conditions that coexist at the time and require or affect patient care. The rule does not require the condition to be newly managed; it must simply be documented and clinically relevant to the services rendered at that visit.
Example: A lymphoma patient with documented chemotherapy-induced anemia has both coded because the anemia affects today's drug administration decisions.
Mistake to avoid: Coding only the malignancy and dropping comorbidities that influenced the encounter.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
17. Laterality From Other Clinicians
Diagnosis code assignment generally rests on the patient's own provider's documentation, but laterality is an exception: another clinician's record may establish the affected side. If documentation conflicts about the side, query the provider rather than defaulting to an unspecified side code.
Example: The oncologist documents a mass without a side, but the infusion nurse's note specifies the left arm, which supports left-sided coding.
Mistake to avoid: Routinely using unspecified side codes when other record documentation or a query could establish laterality.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
18. Confirmed-Only HIV Exception
Only confirmed HIV cases are coded, an exception to the inpatient rule permitting uncertain diagnoses documented at discharge. Confirmation does not require serology in the record; the provider's diagnostic statement that the patient is HIV positive or has an HIV-related illness suffices.
Example: A note stating the patient is HIV positive supports the HIV disease code even without lab results attached to the claim.
Mistake to avoid: Coding HIV from a screening exposure or pending test rather than a provider's confirmed statement.
Reference: CDC ICD-10-CM Official Guidelines, FY 2027
E/M Leveling Foundations
19. The 2021 and 2023 Guideline Shift
In 2021 the AMA rewrote office and outpatient E/M code descriptors and added codebook guidelines, and in 2023 extended those rules to other E/M categories, retiring the 1995 and 1997 documentation guidelines. Current leveling rests on the revised framework rather than old bullet and element counting.
Example: A 2026 note is leveled under current guidelines using MDM or time, not by counting 1997 exam bullets that no longer apply.
Mistake to avoid: Auditing modern notes against retired 1995 or 1997 documentation grids.
Reference: AAPC CHONC study guide sample
20. Leveling by MDM or Total Time
The level of an E/M service may be supported by either the level of medical decision making or the total time spent on the date of the encounter, chosen case by case. Whichever element is used, documentation must still support the medical necessity of the visit.
Example: A brief-appearing note with high-complexity decisions is leveled by MDM, while a time-documented coordination-heavy visit is leveled by total time.
Mistake to avoid: Averaging or mixing the two methods within one encounter to inflate the level.
Reference: AAPC CHONC study guide sample
21. Code 99211 Sits Outside MDM
Code 99211 describes services that typically do not require the provider's presence, so the MDM concept does not apply to it. It remains a valid choice for clinical staff performing minimal evaluation under established orders, distinct from provider-performed visits leveled through MDM or time.
Example: A nurse administers a scheduled injection per standing orders and documents minimal evaluation; the encounter fits 99211 rather than a higher level.
Mistake to avoid: Attempting to assign an MDM level to 99211 or using it for provider decision-making visits.
Reference: AAPC CHONC study guide sample
22. Core Documentation Principles
Three verification principles anchor E/M documentation: it must be legible to someone other than the documenting provider and staff; the date, patient name, and provider name must be easily demonstrated; and the note must support the nature of the visit and medical necessity of services rendered.
Example: An illegible scanned note fails the first principle, so the coder cannot verify the service and must obtain a readable record before billing.
Mistake to avoid: Billing from notes that omit the servicing provider or fail to establish medical necessity.
Reference: AAPC CHONC study guide sample
23. History and Exam No Longer Level the Code
Under current guidelines, a medically appropriate history and physical examination, when performed, is included in the service but is not used to determine the code level. History and exam should still be documented, yet leveling hinges entirely on MDM or total time.
Example: An exhaustive exam documented alongside low-complexity decisions still levels low, because the exam no longer raises the code.
Mistake to avoid: Upcoding because a comprehensive exam was recorded despite straightforward decision making.
Reference: AAPC CHONC study guide sample
24. MDM-to-Code Correlation
Four MDM levels map directly to code pairs: straightforward to 99202 or 99212, low to 99203 or 99213, moderate to 99204 or 99214, and high to 99205 or 99215. New versus established patient status selects the column, while the MDM level selects the row.
Example: Moderate MDM for an established oncology patient selects 99214; the same MDM for a new patient selects 99204.
Mistake to avoid: Choosing the new patient code for a patient seen within the established period.
Reference: AAPC CHONC study guide sample
Medical Decision Making Components
25. Problems Must Be Addressed
A problem counts toward the number and complexity of problems addressed only if it is addressed within that encounter. Reading the entire note, not just the chief complaint, reveals which conditions were genuinely assessed or managed and which were merely mentioned.
Example: A note listing five problems but assessing only two counts two problems, because the others were not addressed at the visit.
Mistake to avoid: Counting every problem listed in the history toward MDM without evidence of assessment.
Reference: AAPC CHONC study guide sample
26. Data Reviewed and Analyzed
The second MDM element measures the amount and complexity of data reviewed and analyzed, such as reviewing outside records, ordering tests, and discussing results with other clinicians. The CPT definitions in the codebook govern what qualifies at each level, so apply them precisely.
Example: A provider reviews an outside pathology slide and orders flow cytometry, which counts toward the data element for leveling the visit.
Mistake to avoid: Counting routine vitals or standard office data as complex data review.
Reference: AAPC CHONC study guide sample
27. Risk Requires Addressed Comorbidities
Risk of complications and morbidity rises with comorbidities or underlying diseases, but only when the documentation shows the provider addressed them or they contributed to case severity. Simply listing a chronic illness in the history does not elevate the risk element.
Example: Diabetes discussed as complicating chemotherapy decisions raises risk; diabetes merely listed in the past medical history does not.
Mistake to avoid: Upcoding risk based on chronic diseases that appear only as history entries.
Reference: AAPC CHONC study guide sample
28. Managed-By-Another-Provider Rule
When a physician documents that another provider manages a condition, that condition does not count toward leveling unless additional documentation shows assessment or care coordination beyond the bare statement of outside management. The distinction separates awareness from active management.
Example: A note stating cardiology manages the patient's arrhythmia excludes it from MDM, but a documented medication review with the cardiologist includes it.
Mistake to avoid: Counting every externally managed condition toward problem complexity without documented coordination.
Reference: AAPC CHONC study guide sample
29. Symptom Clustering Around a Diagnosis
Per CPT, symptoms may cluster around a specific diagnosis, and each symptom is not necessarily a unique condition. When one underlying diagnosis explains multiple presenting symptoms, they count as one addressed problem rather than several, preventing artificial inflation of the problems element.
Example: Fatigue, pallor, and dizziness all attributed to documented anemia count as one problem, not three, for leveling.
Mistake to avoid: Counting each clustered symptom separately to push the problem element to a higher level.
Reference: AAPC CHONC study guide sample
30. Diagnosis Does Not Equal Risk
The final diagnosis alone does not determine complexity or risk, because extensive evaluation may be needed to conclude that symptoms do not represent a highly morbid condition. Conversely, multiple lower-severity problems may aggregate into higher risk through their interaction.
Example: Ruling out a serious marrow disorder with extensive workup supports moderate MDM even though the final diagnosis is benign.
Mistake to avoid: Leveling strictly from the diagnosis list and ignoring the workup and aggregate risk.
Reference: AAPC CHONC study guide sample
Physician Billing Scenarios
31. Same-Date Return Visit
When a patient returns to the office on the same date of service, evaluate whether a distinct, separately identifiable service occurred. A return for the same problem generally folds into one E/M level for the day, while a new, unrelated problem may support separate reporting under applicable rules.
Example: A patient returns hours later with a new reaction; the coder verifies whether documentation supports a separate service or one combined level.
Mistake to avoid: Automatically billing two office visits for same-day returns without distinct-service documentation.
Reference: AAPC CHONC study guide sample
32. Incident-To Services
Incident-to billing lets services furnished by clinical staff be reported under a physician when strict requirements are met, including the physician's prior involvement in the care plan and presence in the office suite. The CHONC exam treats incident-to guidelines as a core competency for oncology practices.
Example: A nurse administers a chemotherapy premedication under an established plan with the physician on site, meeting incident-to conditions for physician billing.
Mistake to avoid: Billing staff services under the physician when the physician is absent or never established the plan.
Reference: AAPC CHONC study guide sample
33. Split and Shared Visits
A split or shared visit occurs when a physician and another qualified health professional each personally perform part of the same E/M encounter. Determine who performed the substantive portion and apply the applicable documentation and billing rules rather than defaulting to one contributor.
Example: An oncologist and a nurse practitioner each document portions of one visit; the coder identifies the substantive contributor before selecting the billing provider.
Mistake to avoid: Reporting the visit twice, once for each contributor, instead of as one split service.
Reference: AAPC CHONC study guide sample
34. Bundled Access and Support Services
When performed to facilitate an injection or an infusion service, use of local anesthesia, starting the IV, access to an indwelling IV, subcutaneous catheter or port, the flush at the conclusion of the infusion, and standard supplies are all included in that service. The physician claim therefore carries the administration code and the drug itself, not separate line items for vascular access, flushing, or routine supplies.
Example: A chemotherapy patient with an implanted port has the port accessed so the infusion can run; because the access facilitated the reported chemotherapy administration, the claim carries only the administration code and the drug, with no separate port-access line.
Mistake to avoid: Appending separate codes for port access, IV starts, or concluding flushes that merely facilitated a reported injection or infusion service.
Reference: AAPC CHONC study guide sample
35. Standby Services
Standby services involve a physician remaining available, ready to perform or intervene, rather than directly performing the service. Distinguish standby from ordinary waiting and from direct attendance, and require documentation of the physician's time and availability before considering any reportable service.
Example: An oncologist stays immediately available during a risky infusion without performing it; the coder evaluates whether documented standby time meets reporting criteria.
Mistake to avoid: Confusing physician presence during a routine infusion with a separately reportable standby service.
Reference: AAPC CHONC study guide sample
36. Advance Beneficiary Notice Use
An Advance Beneficiary Notice informs a Medicare patient, before a potentially non-covered service, that Medicare may deny payment and that the patient accepts financial responsibility. Proper ABN use protects the practice when medical necessity is uncertain, and the CHONC exam lists it among tested competencies.
Example: Before a screening the payer may deny, staff obtain a signed ABN so the patient, not the practice, bears the cost if denied.
Mistake to avoid: Delivering an ABN after the service or failing to obtain the patient's signature.
Reference: AAPC CHONC study guide sample
Surgical and Procedural CPT Coding
37. Aspiration Versus Biopsy
Bone marrow has a fluid portion and a solid portion. Aspiration withdraws the fluid through a needle; biopsy withdraws the solid core. Each has its own diagnostic code, and both are performed at the posterior iliac crest or sternum to diagnose and monitor blood and marrow diseases.
Example: A note describing withdrawal of a marrow core specimen supports the biopsy code, not the aspiration code, because solid tissue was obtained.
Mistake to avoid: Interchanging the aspiration and biopsy codes based on needle type rather than specimen obtained.
Reference: AAPC CHONC study guide sample
38. Combined Same-Site Marrow Procedures
When aspiration and biopsy are performed at the same site through the same skin incision during one surgical encounter, report the single combination code 38222. The combination code replaces both individual codes because one access served both specimen types.
Example: One incision at the iliac crest yields both fluid and core; the coder reports only 38222 for the combined service.
Mistake to avoid: Reporting 38220 and 38221 separately when a single incision and site served both.
Reference: AAPC CHONC study guide sample
39. Separate-Site Marrow Procedures
When aspiration and biopsy occur at separate sites or through separate incisions, report both services: the biopsy code and the aspiration code with modifier 59 appended to show a distinct service. Modifier 59 communicates that the second procedure was independent, not a repeat.
Example: Bilateral iliac crest sampling through two incisions supports both codes, with the distinct-procedure modifier on the aspiration.
Mistake to avoid: Appending modifier 59 routinely without documentation of truly separate sites or incisions.
Reference: AAPC CHONC study guide sample
40. Zero-Day Global and Modifier 25
Bone marrow procedures are minor with zero global days, so no separate E/M is implied by the procedure itself. When a significant, separately identifiable E/M occurs the same day, append modifier 25 to the E/M code to report both services.
Example: A new patient evaluation of cytopenias precedes a marrow biopsy; modifier 25 on the E/M allows both the visit and procedure to pay.
Mistake to avoid: Billing the E/M without modifier 25, causing the visit to bundle into the zero-day procedure.
Reference: AAPC CHONC study guide sample
41. Procedure Sequencing by RVU
When multiple procedures are performed, CPT codes are sequenced with the most complex or labor-intensive procedure first, meaning the highest relative value unit codes lead the claim. Correct sequencing reflects the primary work performed and follows CPT conventions rather than chronological order.
Example: A marrow biopsy followed by a venipuncture sequences the biopsy first because it carries the greater work value.
Mistake to avoid: Sequencing procedure codes by the order documented in the note instead of by relative value.
Reference: AAPC CHONC study guide sample
42. Unlisted and Category III Codes
When no specific CPT code describes a procedure, select the appropriate unlisted procedure code and be prepared to explain the service. Category III codes, optional temporary tracking codes for emerging technology, are also tested; choose them when the service matches their descriptor rather than forcing a similar Category I code.
Example: A novel marrow-sampling technique with no specific code is reported with the unlisted code plus supporting documentation, not a look-alike code.
Mistake to avoid: Mapping an unlisted service to the closest paid code to avoid payer review.
Reference: AAPC CHONC study guide sample
Hydration, Injection, and Infusion Coding
43. Initial Service by Primary Reason
For physician coding, select the initial administration code for the primary reason for the encounter, not the order in which drugs were given. A premedication given before chemotherapy is the sequential service; the chemotherapy itself is the initial service.
Example: An antihistamine precedes IV chemotherapy; the chemotherapy administration is coded initial and the antihistamine sequential, despite administration order.
Mistake to avoid: Coding the first drug administered as the initial service regardless of encounter purpose.
Reference: AAPC CHONC study guide sample
44. Facility Reporting Hierarchy
Facilities report administration services by a hierarchy that supersedes CPT parenthetical instructions: chemotherapy first, then therapeutic, prophylactic, and diagnostic services, then hydration. Across routes, infusions outrank pushes, which outrank injections.
Example: A facility encounter with chemotherapy, a therapeutic infusion, and hydration reports chemotherapy as initial, with the others sequenced by hierarchy.
Mistake to avoid: Applying physician-style primary-reason selection to facility claims instead of the fixed hierarchy.
Reference: AAPC CHONC study guide sample
45. Defining an IV Push
CPT defines an intravenous or intra-arterial push as either an injection with the administering professional continuously present to administer and observe the patient, or an infusion of fifteen minutes or less. The definition determines whether push codes apply instead of infusion codes.
Example: A medication infused over ten minutes qualifies as a push, so the push code replaces the infusion code family.
Mistake to avoid: Coding a short infusion as an infusion because an IV line was used rather than timing it.
Reference: AAPC CHONC study guide sample
46. Hydration Time Thresholds
Hydration services of thirty minutes or less are not reported. The initial hydration code covers thirty-one minutes to one hour, and hydration given concurrently with another infusion service is not separately coded, though the substance itself may be reported with the appropriate HCPCS code.
Example: Fifteen minutes of saline flush before chemotherapy is not reported as hydration; the drug supply code alone is billed.
Mistake to avoid: Reporting the initial hydration code for runs of thirty minutes or less.
Reference: AAPC CHONC study guide sample
47. Add-On Hour Rules
Add-on codes for each additional hour require more than thirty minutes beyond the full-hour increment. Time between the thirty-one minute threshold and the next full hour is captured only when the interval exceeds thirty minutes past the completed hour.
Example: A ninety-minute infusion reports the initial hour code plus the add-on, but a seventy-five-minute run reports only the initial hour.
Mistake to avoid: Reporting an add-on hour for any time beyond sixty minutes, including short intervals.
Reference: AAPC CHONC study guide sample
48. Incidental Hydration With Drugs
When fluids are used to administer drugs, the fluid administration is incidental hydration and is not separately reported, nor is the saline supply billed. Hydration codes apply only to pre-packaged fluids and electrolytes infused for hydration itself.
Example: Saline carrying an IV medication is not billed as hydration; only the drug and its administration code are reported.
Mistake to avoid: Billing hydration alongside every infusion that uses a saline carrier.
Reference: AAPC CHONC study guide sample
Drug Reporting and Medicare Policy
49. Calculating HCPCS Drug Units
HCPCS Level II J codes describe drugs with unit values such as up to a stated milligram amount per unit. Calculate units by dividing the dose administered by the unit quantity, and report the drug separately from the administration code.
Example: A 300 mg IV steroid with a J code unit of up to 100 mg reports three units alongside the infusion administration codes.
Mistake to avoid: Reporting one unit regardless of dose, or billing the drug without the calculated units.
Reference: AAPC CHONC study guide sample
50. Chemotherapy Codes Include Drug Preparation
Chemotherapy and other highly complex drug or biologic administration codes form a separate family from the therapeutic, prophylactic, and diagnostic administration codes because these agents carry a higher incidence of severe adverse reactions, and the chemotherapy codes include both the administration and the preparation of the drugs. Supportive drugs that are not chemotherapy agents or highly complex biologics, such as antiemetics given at the same encounter, are administered under the therapeutic code family, and no separate preparation service is reported for the antineoplastic itself.
Example: A nurse reconstitutes an antineoplastic agent in the office and administers it, while the patient also receives an IV antiemetic; the claim reports the chemotherapy administration code with no separate mixing or preparation line, and the antiemetic administration is reported from the therapeutic infusion family because it is not an antineoplastic or highly complex biologic agent.
Mistake to avoid: Billing a separate preparation or handling charge on top of the chemotherapy administration code, or reporting supportive-care drugs under the chemotherapy administration codes.
Reference: AAPC CHONC study guide sample
51. ESA Modifiers EA Versus EC
For erythropoiesis-stimulating agents billed to Medicare under J0881, the EA modifier signals the ESA treats anemia due to anti-cancer chemotherapy, while EC signals anemia from other causes. The modifier must match the documented anemia etiology on the claim.
Example: An ESA given for anemia caused by lymphoma chemotherapy carries EA; the same drug for kidney-disease anemia carries EC instead.
Mistake to avoid: Appending EC to every ESA claim regardless of the documented anemia cause.
Reference: AAPC CHONC study guide sample
52. Dual Diagnosis Requirement
Under the ESA policy, certain diagnosis codes require a dual diagnosis, pairing an etiology code with the anemia code on the same claim. Group 2 codes, the cancer-related list, all require the dual diagnosis, and selected Group 1 codes marked with an asterisk do as well.
Example: A claim for an ESA in a chemotherapy patient pairs the malignancy code with the anemia code to satisfy the dual diagnosis rule.
Mistake to avoid: Submitting the malignancy code alone for an ESA claim that requires the paired anemia diagnosis.
Reference: AAPC CHONC study guide sample
53. Physician Versus Facility Administration
Administration codes for chemotherapy, infusions, injections, and hydration are not reported by the physician when the services are performed in a facility setting; the facility reports them under its own rules. Physician reporting applies in the office or other non-facility settings.
Example: Hospital staff run a chemotherapy infusion; the physician does not bill the administration code, which belongs to the facility.
Mistake to avoid: Physician billing of administration codes for infusions run by facility staff.
Reference: AAPC CHONC study guide sample
54. Payer Policy Versus CPT on Exams
On the CHONC exam, individual payer rules are not considered unless the case states the patient has Medicare coverage and supplies the policy. Absent that, follow CPT coding guidelines, which keeps answers grounded in universal conventions rather than local payer edits.
Example: A case note omitting payer details is coded purely by CPT guidelines; a note citing Medicare and an LCD is coded by that policy.
Mistake to avoid: Applying remembered payer policies to exam cases that never establish Medicare coverage.
Reference: AAPC CHONC study guide sample
HIPAA Privacy in Oncology Practice
55. Covered Entities and PHI Scope
The Privacy Rule covers health plans, clearinghouses, and providers who transmit health information electronically in standard transactions. Protected health information is individually identifiable health information in any form, electronic, paper, or oral, relating to health, care, or payment and identifying the individual.
Example: An oncology practice emailing standard claims is a covered entity, so its verbal chemotherapy discussions are protected just like its records.
Mistake to avoid: Assuming oral communications or paper notes fall outside protected health information.
Reference: HHS Summary of the HIPAA Privacy Rule
56. Minimum Necessary Standard
Covered entities must make reasonable efforts to use, disclose, and request only the minimum protected health information needed for the purpose, and may not send whole records unless specifically justified. The standard does not apply to treatment disclosures, disclosures to the individual, or authorized uses.
Example: A payer request for one diagnosis is answered with that code, not the entire chart, because payment disclosures must be limited.
Mistake to avoid: Releasing the complete record routinely when a narrow disclosure would serve the purpose.
Reference: HHS Summary of the HIPAA Privacy Rule
57. Treatment, Payment, and Operations
A covered entity may use and disclose protected health information without authorization for its own treatment, payment, and health care operations, and may share it for other providers' treatment, other entities' payment, and qualifying operations when both entities have a relationship with the patient.
Example: An oncologist consults a radiologist about a shared patient under treatment permissions without any signed authorization.
Mistake to avoid: Demanding authorizations for ordinary treatment coordination that the Rule already permits.
Reference: HHS Summary of the HIPAA Privacy Rule
58. Business Associate Agreements
A business associate is a non-workforce person or organization performing functions for a covered entity involving protected health information, such as claims processing or billing. A written agreement must impose safeguards, and the entity cannot authorize any use or disclosure the Rule itself would prohibit.
Example: An outside billing company handling the oncology practice's claims signs a business associate agreement before receiving any patient data.
Mistake to avoid: Sharing patient data with a billing vendor before a compliant agreement is executed.
Reference: HHS Summary of the HIPAA Privacy Rule
59. De-Identification Versus Limited Data Set
De-identified information, created by removing specified identifiers or by statistical determination, carries no use restrictions. A limited data set removes fewer direct identifiers and may be used only for research, public health, or operations, and only under a data use agreement.
Example: A registry receives a limited data set with dates retained under a signed data use agreement, not a fully de-identified extract.
Mistake to avoid: Treating a limited data set as freely releasable without a data use agreement.
Reference: HHS Summary of the HIPAA Privacy Rule
60. Research and Clinical Trial Disclosures
Research uses of protected health information require either the individual's written authorization, an IRB or Privacy Board waiver, preparatory-to-research representations, or decedent-research representations. Clinical trial services are a tested CHONC competency, and conditioning trial-related treatment on authorization is permitted in defined circumstances.
Example: A practice enrolling a patient in an oncology trial obtains the required authorization before using the record for research purposes.
Mistake to avoid: Releasing records to trial sponsors as treatment when the use is actually research requiring authorization or waiver.
Reference: AAPC CHONC study guide sample; HHS Summary of the HIPAA Privacy Rule
References and further reading
Source links checked on Oct 2, 2026.