Every year the US Center for Disease Control (CDC) conducts the National Ambulatory Medical Care Survey (NAMCS), a national patient chart review with outpatient physicians. This annual survey collects details for over 32,000 patient visits from 3,000 doctors in 15 major specialties.


For each visit, the physician enters the patient’s demographics, complaints, history, the physician’s diagnoses, and medications provided, prescribed or continued.

NAMCS is a weighted multilevel sample projectible to all US outpatient visits. So it’s not limited to just commercially insured or Medicare patients. It has an amazingly high invite-to-complete ratio with zero honoraria, so is a credible sample minimizing selection bias.

One unique feature of NAMCS is it includes the patient’s reason(s) for the visit. Given a complaint, such as a fever or sore throat, how often is that diagnosed as one condition versus another? Try answering that in any other commercial or public data source.

Some interesting questions one can answer:

  • What diagnoses are typical for a fever in a child age 1-10?
  • What does a typical lupus patient look like?
  • What diagnoses do patients taking methotrexate have?


Keep in mind this is a sample of visits not patients, so patients who visit more often are more likely to appear in this sample.

It is not a longitudinal study matching individuals across multiple visits.

NAMCS does not match each current medication to a specific current diagnosis, so we can tell what medications diabetes patients take, but not which medications they take for diabetes.

Lastly, NAMCS sample size is small relative to commercial surveys like NDTI and TreatmentAnswers (formerly PDDA), and releases lag by 3-4 years vs 3-4 months, which limits its utility for rarer conditions and recent market events.

Explore it

Explore the NAMCS 2009 data in Protobi. This page shows a few interesting fields for all 32,281 patient records in the 2009 NAMCS survey.

Read more about the NAMCS survey and methodology on the CDC website .

Contact us at info@protobi.com for more information.