Medical Coding Mock Exams Interview Questions
Common Interview Q&A
Q: How do you code an uncertain diagnosis in inpatient vs outpatient settings?
A: There is an important distinction. In the inpatient setting, ICD-10-CM guidelines allow coding of conditions documented as "probable," "suspected," "likely," "questionable," or "rule out" as if confirmed — as long as the condition was evaluated and treated during the admission. In the outpatient or physician office setting, you must code the sign or symptom that prompted the visit rather than the uncertain diagnosis. For example, if an ED note says "rule out appendicitis," inpatient coders would code appendicitis; outpatient coders would code abdominal pain.
Q: What is the difference between a principal diagnosis and a primary diagnosis?
A: Principal diagnosis is an inpatient term — it is the condition established after study to be chiefly responsible for occasioning the hospital admission. It may not be the admitting diagnosis; after workup, the principal diagnosis reflects what was actually treated. Primary diagnosis is an outpatient term — the condition chiefly responsible for the visit, sequenced first on the claim. The distinction matters because inpatient and outpatient coding guidelines differ significantly.
Q: What would you do if a physician documents "COPD exacerbation" but also documents "bronchitis" as a separate entry?
A: COPD with acute exacerbation (J44.1) is a combination code that represents COPD in exacerbation. Acute bronchitis with COPD also has its own code (J44.0). I would review the full documentation to determine: Is the exacerbation due to bronchitis or another cause? If bronchitis is clearly the cause of the exacerbation, J44.0 is appropriate. If the documentation is ambiguous, I would initiate a compliant query to the physician asking which condition best represents the patient's presentation. I would not assume one or the other without sufficient documentation.
Q: What is a clean claim rate and why does it matter?
A: A clean claim rate is the percentage of claims submitted that are paid on the first submission without any correction, additional information request, or resubmission needed. A high clean claim rate (target 95%+) means less administrative burden, faster cash flow, lower cost to collect, and fewer denials to appeal. A low rate indicates upstream problems: coding errors, missing authorizations, eligibility issues, or incorrect patient information. Monitoring clean claim rate by payer, coder, and procedure helps identify and fix systemic issues.
Q: How do you stay current with coding changes?
A: ICD-10-CM updates take effect October 1 each year; CPT updates take effect January 1. I stay current by: reviewing CMS annual code updates when released, reading AHA Coding Clinic (ICD-10-CM) and CPT Assistant (CPT) for official guidance, attending AAPC or AHIMA webinars, participating in local chapter meetings, following OIG Work Plan for audit focus areas, and monitoring CMS transmittals for policy changes that affect billing.
Quick Skills Assessment
Q: What resources do you use to stay current with coding changes?
A: ICD-10-CM updates effective October 1 each year; CPT updates effective January 1. I monitor CMS transmittals for Medicare policy changes, read AHA Coding Clinic for ICD-10-CM guidance, CPT Assistant for CPT interpretation, and follow AAPC/AHIMA newsletters. I also review the OIG Work Plan annually to understand audit focus areas and attend webinars for continuing education units required to maintain certification.
Q: Describe a time you found a coding error. What did you do?
A: In a strong answer, describe discovering an upcoded E&M, a bundled procedure billed separately, or a diagnosis not supported by documentation. Explain: you verified the issue against guidelines, documented your finding, reported through proper channels (supervisor, compliance department), and helped identify whether it was systemic or isolated. Demonstrate that you understand the difference between error correction and whistleblowing, and that you follow proper escalation procedures.