ICD-10 Transition Influences Trends in Perforated Appendix Admission Rate

This study sought to evaluate the influence of International Classification of Diseases, Tenth Revision (ICD-10) transition on Perforated Appendix Admission Rate (PAAR), which is a commonly used indicator representing access to care developed by Agency for Healthcare Research and Quality (AHRQ).

In this interrupted time series study of Pediatric Health Information System database from 2013 to 2018, we employed three study phases (pre-implementation, washout, and initial implementation) to evaluate the influence of ICD-10 transition on trends in PAAR. ICD-10 diagnosis codes suggested by AHRQ's specifications were used to identify perforated and simple appendicitis, and PAAR was estimated accordingly. Generalized linear mixed models were used to examine the association of ICD-10 initial implementation and being documented as perforated appendicitis on encounter level.

We identified a total of 94,810 encounters diagnosed with appendicitis, and almost all patients' characteristics were similar over the three study phases, except for PAAR. The pre-implementation PAAR in October 2013 was 33.1%, and the immediate influence of ICD-10 transition on PAAR was 3.2% (P = 0.002), with a 0.38% per quarter increase over time (P = 0.02). After adjusting for age, gender, race/ethnicity, payer, and year, the likelihood of being documented as having perforated appendicitis in 2016 was 1.5 times higher than the estimated likelihood before the implementation (adjusted Odds Ratio: 1.51; 95% Confidence Interval: 1.40-1.63; P < 0.001).

The 2015-2018 ICD-10 transition may be erroneously associated with an increasing trend of PAAR. Care should be taken when interpreting the metric during this period.