Development and Validation of an Algorithm to Classify as Equivalent the Procedures in ICD-10-PCS That Differ only by Laterality

BACKGROUND: The switch from International Classification of Diseases, Ninth Revision, Clinical Modification to International Classification of Diseases, Tenth Revision, Procedure Coding System (ICD-10-PCS) for coding of inpatient procedures in the United States increased the number of procedural codes more than 19-fold, in large part due to the addition of laterality. We examined ICD-10-PCS codes for pairs of mirror-image procedures that are surgically equivalent. METHODS: We developed an algorithm in structured query language (SQL) to identify ICD-10-PCS codes differing only by laterality. We quantified the impact of laterality on the number of commonly performed major therapeutic procedures (ie, surgical diversity) using 2 quarters of discharge abstracts from Texas. RESULTS: Of the 75,789 ICD-10-PCS codes from federal fiscal year 2017, 16,839 (22.3%) pairs differed only by laterality (with each pair contributing 2 codes). With the combining of equivalent codes, diversity in the state of Texas decreased from 78.2 to 74.1 operative procedures (95% confidence interval, 5.1 to -3.1; P <.001). CONCLUSIONS: Our algorithm identifies ICD-10-PCS codes that differ only by laterality. However, laterality had a small effect on surgical diversity among major therapeutic procedures. Our SQL code and the lookup table will be useful for all US inpatient analyses of ICD-10-PCS surgical data, because combining procedures differing only by laterality will often be desired.