Nonalcoholic fatty liver disease (NAFLD) in the Veterans Administration population: development and validation of an algorithm for NAFLD using automated data

Abstract

Background In practice, non-alcoholic fatty liver (NAFLD) is diagnosed based on elevated liver enzymes and confirmatory liver biopsy or abdominal imaging. Neither method is feasible in identifying individuals with NAFLD in a large-scale healthcare system. Aim To develop and validate an algorithm to identify patients with NAFLD using automated data. Methods Using the Veterans Administration Corporate Data Warehouse, we identified patients who had persistent ALT elevation (≥2 values ≥40IU/ml ≥6 months apart) and did not have evidence of hepatitis B, hepatitis C, or excessive alcohol use. We conducted a structured chart review of 450 patients classified as NAFLD and 150 patients who were classified as non-NAFLD by the database algorithm, and subsequently refined the database algorithm. Results The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) for the initial database definition of NAFLD were 78.4% (95%CI=70.0-86.8%), 74.5% (95%CI=68.1-80.9%), 64.1% (95%CI: 56.4-71.7%), and 85.6% (95%Ci: 79.4-91.8%), respectively. Reclassifying patients as having NAFLD if they had 2 elevated ALTs that were at-least 6 months apart but within 2 years of each other, increased the specificity and PPV of the algorithm to 92.4% (95%CI=88.8 - 96.0%) and 80.8% (95%CI=72.5 - 89.0%), respectively. However, the sensitivity and NPV decreased to 55.0% (95%CI=46.1 - 63.9%) and 78.0% (95%CI=72.1 - 83.8%), respectively. Conclusions Predictive algorithms using automated data can be used to identify patients with NAFLD, determine prevalence of NAFLD at the system-wide level, and may help select a target population for future clinical studies in veterans with NAFLD.

Trends in the Burden of Nonalcoholic Fatty Liver Disease in a United States Cohort of Veterans

“…Most clinicians rely on these readily available noninvasive test criteria—such as elevated blood levels of ALT in the absence of other liver diseases to detect NAFLD and our previous work provided support for the validity of our algorithm. 11 We recognize that NAFLD can exist in the absence of elevated ALT 6 and that we may have missed individuals who have some evidence of hepatic steatosis yet have never developed abnormal liver biochemistries. Of note, most of the available literature on the prevalence of elevated ALT in NAFLD stems from cross-sectional studies (where ALT tests were performed at one point in time) in which it was unknown if patients classified as having normal ALT based on these single assessments maintain normal biochemistries throughout their clinical course.…”

“…We defined NAFLD based on our previously validated algorithm. 11 Specifically, patients were classified as having NAFLD if they had at had two or more elevated ALT values (≥40 IU/ml) more than 6 months apart, with no evidence of positive serologic testing for HBV (HBV surface antigen) or HCV (HCV RNA), and no alcohol related ICD-9 codes or positive AUDIT-C scores within one year of the elevated ALT. This definition had good sensitivity and specificity for identifying NAFLD compared to clinical, biochemical and radiological data abstracted from the electronic medical record review of 600 VA patients (sensitivity=78.4%, negative predictive value= 85.6%).…”

“…This definition had good sensitivity and specificity for identifying NAFLD compared to clinical, biochemical and radiological data abstracted from the electronic medical record review of 600 VA patients (sensitivity=78.4%, negative predictive value= 85.6%). 11 We used the date of first elevated ALT as the index date for NAFLD diagnosis. For all patients in this cohort, we extended follow-up through December 31, 2013 to allow sufficient time for ascertainment of persistence in ALT elevation (see below), and we examined data from January 1, 2001 to December 31, 2002 to exclude patients with prevalent or pre-existing ALT elevations from incidence calculations.…”

Development and Validation of an Algorithm to Identify Nonalcoholic Fatty Liver Disease in the Electronic Medical Record

“…[15] Husain et al have developed an algorithm for the identification of NAFLD associated with elevated ALT in the VA System. [16] This algorithm serves as a valuable tool for the study of NAFLD within the VA system. This study is limited, however, by its development in a predominantly male population and its strict requirement for inclusion of individuals with multiple elevated ALTs over time.…”

Delta hepatitis within the Veterans Affairs medical system in the United States: Prevalence, risk factors, and outcomes

“…diagnosis codes) from all outpatient and inpatient encounters from the Veterans Health Administration, which serves 8.76 million US veterans each year at over 1,700 sites. The CDW is a relational database that has been utilized extensively for epidemiology studies in chronic viral hepatitis studies 6–8 . In a cohort of HBsAg-positive individuals, the following demographic and laboratory data were extracted: age, gender, race/ethnicity, presence and results of anti-HDV antibody (HDVAb), HDV RNA, HBeAg, HBeAb, HBV DNA titers, HBcIgM, HIV antibody (HIVAb), Hepatitis C antibody (HCVAb), alanine aminotransferase (ALT), total bilirubin, and international normalized ratio (INR).…”