We determined the PPVs of three ICD-9-CM-based coding algorithms to identify clinically confirmed ESLD (Table 1). Our focus was on PPV because if this parameter is sufficiently high, we and other researchers will have confidence that the algorithm identified ESLD with minimal misclassification. Algorithm 1 required a diagnosis of a hepatic decompensation event plus a chronic liver disease diagnosis. Algorithm 2 required a diagnosis of a hepatic decompensation event plus a cirrhosis diagnosis. Algorithm 3 required a diagnosis of a hepatic decompensation event, chronic liver disease, and cirrhosis. The rationale for these algorithms was based on observations that some patients with ESLD may only be coded for a chronic liver disease and not cirrhosis, or vice versa. The large sample size of algorithm 3 permitted determination of a variety of PPVs using different cut-off points for the minimum number of hepatic decompensation codes. Finally, to estimate the likelihood of missing ESLD events with the specified algorithms, we evaluated for the presence of ESLD in a sample of patients who did not meet the algorithms but who had non-specific diagnoses that typically accompany ESLD (e.g. coagulopathy, jaundice, hyponatremia, and portal hypertension).
All data were analyzed using State 12.0 (Stata Corp, College Station, TX, USA).