Dear editor,

We read with great interest the paper by Johansson et al. who evaluated, in a cross-sectional study, the clinical and laboratory characteristics of 124 patients before and at 1 year after Roux-en-Y gastric bypass (RYGBP). Among their findings, the authors reported a decrease in both gamma-glutamyltransferase (GGT) and serum alanine aminotransferase (ALT) after surgery (p = 0.011 and p = 0.006, respectively). Hence, they concluded that this result could be attributed to the amelioration of the non-alcoholic fatty liver disease (NAFLD) of these patients [1].

NAFLD, comprising hepatic steatosis, non-alcoholic steatohepatitis (NASH), and progressive liver fibrosis, is considered the most common liver disease in obese subjects [2]. It is well-known that serum enzyme tests are sensitive markers of liver injury but cannot be expected to differentiate one form of hepatitis from another. The main causes of hepatitis are hepatitis C virus and hepatitis B virus infections, NASH, excessive alcohol intake (> 2 units/day), autoimmune hepatitis, primary biliary cholangitis, sclerosing cholangitis, Wilson’s disease, alpha1-antitrypsin deficiency, and haemochromatosis [3]. Although NAFLD/NASH has an increasing role in the context of liver diseases [4], the other etiologies remain a relevant challenge for clinicians.

In their work, Johansson et al. considered several laboratory variables but they did not report the search for the abovementioned causes of hepatitis. Since this data could influence the future management of these patients, it represents a crucial step in the diagnostic workup.