Comparative Accuracy of ICD-9 vs ICD-10 Codes for Acute Appendicitis

Abstract

BACKGROUND ICD codes are used to identify patients with appendicitis and to classify disease severity for reimbursement and research purposes. We sought to compare the accuracy of ICD-9 vs ICD-10 codes in classifying appendicitis as uncomplicated vs complicated (defined as perforated, necrotic, or abscess) compared with the clinical gold standard: surgeon characterization of the appendix in the operative report. STUDY DESIGN This is a retrospective review of operative reports and discharge ICD-9/10 codes for patients 18 years or older who underwent noninterval, nonincidental appendectomy from January 2012 to December 2019 at a tertiary referral center. Sensitivity, specificity, and positive predictive value were calculated for ICD-9/10 codes to classify appendicitis as complicated when compared with surgeon description. Chi-square testing was used to compare agreement between ICD-9/10 codes and surgeon description. RESULTS A total of 1,585 patients underwent appendectomy. ICD-9 codes had higher sensitivity than ICD-10 codes for complicated appendicitis (sensitivity 0.84 and 0.54, respectively) and a similar positive predictive value (0.77 and 0.76, respectively). Overall, 91% of ICD-9 codes agreed with surgical description of disease, but 84.4% of ICD-10 codes agreed with surgical description (p < 0.01). Among cases classified as complicated by the surgeon, 84% (79/94) had an accurate ICD-9 code for complicated disease, but only 53.8% (57/106) of cases had an accurate ICD-10 code (p < 0.01). CONCLUSIONS Compared with ICD-9 codes, ICD-10 codes were less accurate in characterizing severity of appendicitis. The ICD-10 coding schema does not provide an accurate representation of disease severity. Until this system is improved, significant caution is needed for people who rely on these data for billing, quality improvement, and research purposes.

Racial, Ethnic, and Socioeconomic Disparities in Glaucoma Onset and Severity in a Diverse Nationwide Cohort in the United States

“…We also found that 57% of participants did not have any glaucoma severity staging specified, highlighting a large gap in the utilization of ICD coding for documenting and monitoring glaucoma disease severity. Given the inconsistency of results in prior literature regarding the use and accuracy of diagnosis codes, 12–15 our data suggest the underutilization of ICD codes with specified severity staging is present on a national scale, which poses a challenge when analyzing patterns of disease progression and identifying disparities among patients. When used correctly, diagnosis coding provides the opportunity to conduct population health surveillance regarding diagnosis and treatment patterns 35,36 .…”

“…However, there has been inconsistent use and accuracy of International Classification of Disease (ICD) coding in prior studies. [12][13][14][15] Thus, even this measure requires validation in a new dataset, such as the All of Us database.…”

“…As surgery rates may vary by surgeon, diagnosis coding offers another option for monitoring disease progression. However, there has been inconsistent use and accuracy of International Classification of Disease (ICD) coding in prior studies 12–15 . Thus, even this measure requires validation in a new dataset, such as the All of Us database.…”

Validity of the coding for appendicitis, appendectomy, and diagnostic laparoscopy in the Danish National Patient Registry

“…Decrease in PPV for appendicitis when the histopathology report versus the operative report was used was also seen in an American validation study of ICD-10 codes. 15 The choice of either of these two gold standards can be advocated for. The histopathology report is an excellent and rather objective gold standard if the actual and final diagnosis of the patient is sought.…”

Diabetes as a Risk Factor for Perforated Appendicitis: A National Analysis

“…A recent study showed that the classification of perforated and non-perforated appendicitis in ICD-9 has a higher sensitivity and more accurately agrees with the surgical description of disease compared to ICD-10. 20 We opted to use the most recent years of data that are classified using ICD-9 to ensure clinical accuracy of disease severity for acute appendicitis as much as possible.…”