Medical Coding
Coding translates documentation into standardized codes for claims and statistics. Candidates should know the structure and purpose of ICD-10-CM (diagnoses), CPT (procedures and services), and HCPCS Level II (supplies, drugs, equipment). Understand code selection principles: code to the highest level of documented specificity, sequence the primary diagnosis first, and never code from a suspected or rule-out condition in the outpatient setting. Know modifiers (e.g., -25 for a significant, separately identifiable E/M service; -59 for distinct procedural service) and the concept of medical necessity linking diagnosis to procedure.
Traps to watch
- Coding "rule out" or "probable" diagnoses on outpatient claims - not permitted.
- Upcoding (billing a higher level than documented) or unbundling (billing components separately that are included in a code).
- Using a modifier to bypass a payer edit rather than to reflect accurate documentation.
- Ignoring laterality, encounter type (initial vs. subsequent), or combination codes.
- Assuming CPT and ICD-10 have a one-to-one relationship - they do not.
Rule of thumb
If it is not documented, it cannot be coded. The note must support the code at the level billed; the coder's job is to translate, not to infer.
Worked example
A note states "likely bronchitis, pending chest X-ray." Outpatient coding rule: do not assign a bronchitis code for a suspected condition. Code the documented signs/symptoms (e.g., cough) instead. Once the diagnosis is confirmed and documented, the definitive code may be used for that encounter.