Medical Coding Fundamentals

What is Medical Coding?

Medical coding is the transformation of healthcare diagnoses, procedures, medical services, and equipment into universal medical alphanumeric codes. These codes are used for billing, insurance claims, data analysis, and healthcare statistics.

Core Code Systems

ICD-10-CM:
  Purpose: Diagnosis coding (WHY)
  Used by: All healthcare settings
  Example: J18.9 = Pneumonia, unspecified
  Structure: 3-7 alphanumeric characters

CPT (AMA):
  Purpose: Outpatient procedure coding (WHAT)
  Used by: Physician offices, outpatient, ASC
  Example: 99213 = Office visit, established patient, low complexity
  Structure: 5-digit numeric

ICD-10-PCS:
  Purpose: Inpatient procedure coding (WHAT)
  Used by: Hospital inpatient ONLY
  Example: 0LT20ZZ = Resection of right shoulder tendon
  Structure: Always 7 alphanumeric characters

HCPCS Level II:
  Purpose: Supplies, DME, drugs, ambulance
  Used by: All settings
  Example: A4570 = Splint
  Structure: Letter + 4 digits

Medical Terminology Essentials

PREFIXES:
  Brady- (slow)    Tachy- (fast)    Hyper- (above)   Hypo- (below)
  Poly- (many)     Mono- (one)      Pre- (before)    Post- (after)
  Intra- (within)  Inter- (between) Sub- (under)     Supra- (above)

SUFFIXES:
  -itis (inflammation)    -ectomy (surgical removal)
  -plasty (surgical repair) -oscopy (visual examination)
  -otomy (incision)       -ostomy (new opening)
  -algia (pain)           -pathy (disease)
  -ology (study of)       -gram (record/picture)

ROOT WORDS:
  Cardio (heart)    Pulmon (lung)     Hepat (liver)
  Nephro (kidney)   Neuro (nerve)     Osteo (bone)
  Gastro (stomach)  Derm (skin)       Hem (blood)

The Revenue Cycle

PATIENT ENCOUNTER FLOW:
  1. Patient scheduling and registration
  2. Insurance verification and pre-authorization
  3. Clinical encounter (physician documents)
  4. Medical coder assigns codes (ICD-10-CM + CPT/PCS)
  5. Medical biller submits claim (CMS-1500 or UB-04)
  6. Payer adjudication (approve/deny/request more info)
  7. Payment posting and denial management
  8. Patient billing for balance after insurance

CLAIM FORMS:
  CMS-1500: professional claims (physicians, outpatient)
  UB-04 (CMS-1450): institutional claims (hospitals, SNFs)

PAYERS:
  Medicare: federal, age 65+ or disability (Parts A, B, C, D)
  Medicaid: state/federal, low income
  Commercial: private insurance (BCBS, Aetna, United, Cigna)
  TRICARE: military members and families
  Workers Comp: work-related injuries

Study Resources

•AAPC free resources (aapc.com/education) — free coding basics

•AHIMA student resources — textbooks and study guides

•CMS website (cms.gov) — free official coding guidelines

•Khan Academy Health — free medical terminology and anatomy