Medical Coding Systems
Ok, what we’re going to try to tackle here is the variety of medical coding system and databases that one might encounter as they are working in health care.
I’ll answer some broad questions about the purposes of these types of systems in general, then I’ll go into the individual coding systems and what they’re used for.
What are they for?
When a clinician provides care for a patient, they take notes, which is useful for that provider and any other future providers who may treat the patient. In an effort to be consistent and scalable, especially with an eye to how medical services will be billed and paid for, medical coding systems were invented. These medical coding systems will take things like diagnoses, procedures, medicines, etc., and turn them into alphanumeric codes.
Who uses them and how does it work?
Providers might use them directly, but there is also a specialized role, the medical coder, who can review treatment notes and turn them into medical codes for submission on claims.
Often, the claims will go to a clearinghouse, which checks for errors and makes it available to payers.
Then, payers will see the codes on a claim, compare them against what is covered and will pay out to providers at the contracted rates based on the codes.
This process is often automated and happens millions of times per day.
Coding Systems
Here we will describe a few of the most-used medical coding systems. There is a link to more information about each in the acronym. Then, I spell out what the acronym stands for. In parenthesis is a quick description of what the codes document. Finally, in normal text I give a longer description.
ICD - International Classification of Diseases (Diagnoses)
These are diagnostic codes, meaning codes for a condition or symptom (eg. back pain, diabetes, or psoriasis).
The current version ICD-10 has 68,000 diagnostic codes.
The first three characters of the code indicate the category
The next three indicate clinical details, and the final character is an extension used for some kind of sequence.
All claims require a ICD code, but it is usually not used for actual reimbursements.
CPT - Current Procedural Terminology (out-patient procedures)
This coding system incorporates outpatient procedures (things that you do to treat a patient that don’t require an overnight stay).
There are about 10,000 CPT codes, describing medical, surgical and diagnostic procedures. They’re divided into large categories ‘Evaluation and Management’, ‘Anesthesiology’, ‘Surgery’, ‘Radiology’, ‘Pathology’, and ‘Laboratory’.
CPT codes are developed, maintained and licensed by the American Medical Association (AMA)
DRG - Diagnosis Related Group (in-patient diagnoses & procedures)
These are codes for diagnoses & procedures that occur in an in-patient setting (things that one would do to treat a patients when they have to stay overnight at least one night).
The DRG codes determine the reimbursement payers make to the provider or hospital regardless of how much the care of the patient actually cost.
The system attempts to group patients by resource consumption, severity of illness and length of stay.
NDC - National Drug Codes (Drugs)
Numeric codes used to identify drugs universally. Encoded in a 10-11 digit code are the labeler (manufacturer, repackager or distributor), product code (including strength, dosage, form and drug formulation), and package code (the package size and type).
NDCs are used for both over-the-counter and prescription drugs
HCPCS - Healthcare Common Procedure Coding System (outpatient procedures with more procedures included)
A set of procedure codes created by Medicare. CPTs are included in the HCPCS system but there are also additional procedure codes not covered by the CPT system.
Other helpful systems
SNOWMED -
An international clinical terminology system used in more than 80 countries. This includes concepts for diagnoses, drugs and procedures and can be mapped to the other coding systems described above.
Anecdotally, the descriptions are often easier to use and understand than those in the other coding systems, so it can be useful to have a SNOWMED mapping as well as all the other systems described.
FDB - First Data Bank (drug data base & API)
This isn’t really a coding system, but I learned about it as I was ramping up on coding systems so I thought I’d throw it in here. First Data Bank (FDB) is a drug database that is kept up-to-date and searchable that can be useful to integrate to provide drug information to providers
Resources
https://www.cms.gov/Medicare/Coding/ICD10
https://www.nlm.nih.gov/pubs/techbull/so17/brief/so17_umls_snomed_ct_update.html
https://www.cms.gov/Medicare/Fraud-and-Abuse/PhysicianSelfReferral
First Databank - https://www.fdbhealth.com/