Table 1.

Methods to Identify Hepatic Encephalopathy Using Administrative Data.

Tool	Description	Study	Database	Relevant Result	Validated Method for Identifying HE or Cirrhosis	Limitations	Benefits
International Classification of Diseases, 9th Revision (ICD-9)	International standard for defining and reporting diseases 9th revision was used in the United States from 1979 to 2015 ICD-9 code for HE is 572.2	V. Lo Re et al. (2011)	Veterans Affairs	Nine of 295 patients with an ICD-9 code or laboratory value indicating liver dysfunction had an ICD-9 code for HE; the PPV of this code was 0.11 and estimated NPV of 0.99	HE	ICD-9 is not being coded in the United States after 2015, so available data ranges are limited; Variable accuracy in coding	International; Currently best validated; Specific code for HE
		Goldberg et al. (2012)	Local registry (two tertiary care centers)	Presence of one inpatient or outpatient ICD-9 code for cirrhosis, chronic liver disease, and a hepatic decompensation (of which HE was one), the PPV of 0.85 for confirmed cirrhosis	Cirrhosis
		Kanwal et al. (2012)	Veterans Affairs	After identifying cirrhosis patients with ICD-9 codes and laboratory data, at least one ICD-9 code for HE had PPV of 0.86 and NPV of 0.87 for confirmed HE	HE
		Nehra et al. (2013)	Local registry (single hospital system)	ICD-9 code for HE had PPV 0.92 and NPV 0.36 for identifying confirmed cirrhosis; did not report if it identified HE	Cirrhosis
		Lapointe-Shaw et al. (2018)	Two Canadian hospitals	Having a single hospital diagnostic code for cirrhosis, including 572.2, was specific for cirrhosis (0.91–0.96 depending on subcohort), but not as sensitive (0.57–0.77); however, the authors did not specify in how many cases 572.2 was used vs. other codes	Cirrhosis
International Classification of Diseases, 10th Revision (ICD-10)	United States began using ICD-10 in 2015 Many countries began using this system earlier No specific code for HE, instead many use K72.90	Thygesen et al. (2011)	Danish National Registry of Patients	The PPV of one inpatient or outpatient ICD-10 code for moderate/severe liver disease, which included K72.90, correctly identifying cirrhosis was 1.00; however, the authors did not specify in how many cases K72.90 was used vs. other codes	Cirrhosis	Only available in the United States 2015 and thereafter	International; Required to use data after 2015 in the United States; Readily available in most databases
		Mapakshi et al. (2018)	Veterans Affairs	Unable to validate the use of ICD-10 codes for HE because there were no HE events during the study period	Neither
		Tapper et al. (2020)	Development cohort: single academic center Validation cohort: Veterans Affairs	In a validation cohort of veterans with HCV, ICD-10 code K72.90 identified development of HE with PPV 0.90 and NPV 0.93	HE
		Lapointe-Shaw et al. (2018)	Two Canadian hospitals	Having a single hospital diagnostic code for cirrhosis, including K72.90, was specific for cirrhosis (0.91–0.96 depending on subcohort), but not as sensitive (0.57–0.77); however, the authors did not specify in how many cases K72.90 was used vs. other codes	Cirrhosis
Prescription Data	Record of a medication prescription	Tapper et al. (2020)	Development cohort: single center Validation cohort: Veterans Affairs	In a validation cohort of veterans with HCV, lactulose prescription had PPV of 0.73 and NPV of 0.99 for HE diagnosis, while lactulose or rifaximin prescription had a PPV of 0.71 and NPV of 0.99	HE	Not available in every database	Lactulose therapy for overt HE is nearly uniform
Combination	ICD-9 + prescription data	Kaplan et al. (2015)	Veterans Affairs	An algorithm based on the ICD-9 code for HE and prescription fills for lactulose or rifaximin had weighted kappa agreement of 0.51 with the CTP-subscore for HE	HE	Not available in every database	Using multiple modalities in one algorithm can enhance predictive value

ICD, International Classification of Diseases; PPV, positive predictive value; NPV, negative predictive value; CTP, Child-Turcotte-Pugh.