California Ambulatory Surgery Diagnosis and External Cause Code Frequencies

Statewide counts for every diagnosis, procedure, and external cause of injury code reported on ambulatory surgery data in California. Diagnosis and external cause codes are reported using both ICD-9-CM and ICD-10-CM standards, with ICD-10 replacing ICD-9 as of October 1, 2015. Physician-owned clinics do not report to HCAI and are excluded from these frequencies.

Use Cases

• Analyze frequency distributions of specific diagnosis codes across the state's ambulatory surgery facilities.
• Track the adoption and reporting patterns of ICD-10-CM codes versus ICD-9-CM codes following the October 2015 transition.
• Study statewide patterns in external cause of injury codes to identify common morbidity sources in outpatient surgical settings.
• Compare procedure code frequencies to diagnosis code frequencies for population health analysis.

Strengths

• Covers statewide ambulatory surgery data for California, a large population base.
• Includes both ICD-9-CM and ICD-10-CM coding standards, capturing a major transition in medical classification.
• Specifically enumerates external cause of injury codes, a distinct analytical feature.

Limitations

• Excludes data from physician-owned ambulatory surgery clinics, creating a coverage gap.
• Row and column counts, sample size, and temporal range are unspecified, limiting assessment of scale.
• Data is provided in XLS and ZIP formats, which may require specific tools for parsing and lack a modern API.

Provenance

Source

State of California, via the Healthcare Associated Infections (HCAI) program.

Collection Method

Aggregated from mandatory reports submitted by non-physician-owned ambulatory surgery clinics.

Time Range

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Freshness

Last updated March 23, 2026, indicating recent maintenance.

Geography

State of California, USA.