Medical Coding Interview Q&A
Q: What is the difference between ICD-10-CM and CPT?
ICD-10-CM: diagnoses — why the patient was seen, what condition they have. CPT (Current Procedural Terminology): procedures — what was done (surgery, office visit, lab test). Both are needed for a complete claim.
Q: What is a CPC certification?
Certified Professional Coder, issued by AAPC. It's the industry-standard entry credential for outpatient/physician-office coding, and it's open-book (CPT/ICD-10-CM/HCPCS manuals allowed).
Needs verification against current AAPC guidelines: the exact question count, time limit, and required passing score. AAPC has revised the exam format over time, so a specific number stated here without a current source check should not be treated as reliable.
Q: What is the 7th character in ICD-10-CM fracture codes?
A = initial encounter, D = subsequent encounter, S = sequela. The 7th character must always be assigned when the code requires one — it affects both clinical tracking and reimbursement.
Q: What is the sequencing rule for principal diagnosis?
The principal diagnosis is the condition established, after study, to be chiefly responsible for the admission. In outpatient settings, code to the highest degree of certainty known at the time of the encounter (a sign/symptom if a definitive diagnosis hasn't been confirmed). In inpatient settings, "probable"/"suspected"/"likely" diagnoses can be coded as if confirmed — a genuinely different rule from outpatient coding, not a minor variation.
Q: What are E/M codes and how are they selected?
Evaluation and Management codes cover physician/qualified-provider visits — for example, office/outpatient visits and inpatient visits each have their own code ranges. Selection is based on either medical decision-making (MDM) complexity — the number and complexity of problems addressed, the amount and complexity of data reviewed, and the risk of complications — or total time spent on the date of the encounter. The 2021 AMA revision to office/outpatient E/M simplified this to time-or-MDM, moving away from the older three-key-component model.
Needs verification against current CMS/AMA guidelines: the exact current code ranges and any settings not yet covered by the 2021-style revision. E/M code ranges and rules are refined periodically, so treat any specific number here as a starting point to confirm, not a final answer.
Q: What is Modifier 25 and when is it used?
Modifier 25 indicates a significant, separately identifiable E/M service by the same physician on the same day as a procedure. It applies when a patient comes in for a procedure but also receives a separate, medically necessary E/M service during that same visit. Without Modifier 25, the payer will typically bundle the E/M into the procedure's payment.
Q: What is HIPAA's role in medical coding?
HIPAA mandates standardized code sets for electronic transactions — ICD-10-CM/PCS for diagnoses and procedures, CPT/HCPCS for services and supplies — and all covered entities must use them. HIPAA also governs PHI (Protected Health Information): coders handle PHI and must follow minimum-necessary-access, security, and breach-notification requirements.
Q: What is the difference between ICD-10-CM and ICD-10-PCS?
ICD-10-CM covers diagnoses and is used across all settings — inpatient, outpatient, and physician office. ICD-10-PCS covers procedures and is used only in inpatient hospital (facility) billing; outpatient and physician procedure coding uses CPT instead. Structurally, PCS codes are 7-character alphanumeric; CM codes are 3-7 character alphanumeric.