Cervical Intraepithelial Neoplasia Grade 3 and Adenocarcinoma in situ: Comparison of ICD-9 Codes and Pathology Results - Kaiser Permanente, United States, 2000-2005

Background: Cervical intraepithelial neoplasia, grade 3+ and Adenocarcinoma in situ (CIN3+) incidence will be an important measure of HPV vaccine impact. Integrated healthcare delivery systems, such as Kaiser Permanente, could be used to monitor CIN3+ trends; however, limited evaluations of data from healthcare delivery systems for CIN3+ surveillance exist. Methods: We compared CIN3+ diagnoses by ICD-9 code with CIN3+ diagnoses by pathology results among 121,211 females aged 11-30 years who were continuously enrolled from 2000-2005 in either Kaiser Permanente Northern California or Kaiser Permanente Northwest. We calculated sensitivity and positive predictive value of diagnosis by ICD-9 codes using pathology CIN3+ diagnosis as the gold standard. Results: There were 1,090 women with at least one CIN3+ diagnosis by ICD-9 code 233.1 and 1,200 women with at least one CIN3+ diagnosis by pathology results. The sensitivity of the ICD-9 code for detecting a woman with at least one pathology diagnosis for CIN3+ was 62% (740/1200); positive predictive value was 68% (740/1090). Among women with at least one CIN3+ diagnosis by ICD-9 code, 679 (62%) had more than one visit with this code; whereas, among women with at least one CIN3+ diagnosis by pathology, 466 (39%) had more than one CIN3+ pathology result. Conclusions: ICD-9 codes may underestimate the number of women with at least one CIN3+ diagnosis. Pathology results, when available, may provide better estimates of true disease burden.