TyG Index

Determines insulin resistance and can also identify individuals at risk for NAFLD.

In the text below the calculator there is more information about the index variables and its interpretation.


The triglyceride and glucose index was originally proposed as a marker of insulin resistance (study by Guerrero-Romero et al.).

In 2017, Zhang et al. compared the predictive value of ALT (alanine aminotransferase laboratory determination) to that of TyG in identifying patients at risk for non-alcoholic fatty liver disease.


The following table summarizes the two cut-off points identified, for insulin resistance and NAFLD positive diagnosis likelihood: 

Condition Cut-off value Values below cut-off Values above cut-off
Insulin resistance 4.68 Insulin resistance unlikely Suggestive of insulin resistance
Nonalcoholic fatty liver disease 8.5 NAFLD diagnosis is unlikely High likelihood of NAFLD

Triglycerides:*
Glucose:*
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TyG index explained

The triglyceride and glucose index is a screening method for insulin resistance that is very simple to use and only requires two laboratory determinations: serum triglycerides and serum glucose.

According to the study by Guerrero-Romero et al. insulin resistance cut off is placed at the TyG index value of 4.68 (96.5% sensitivity and 85% specificity).

Subjects with an index of 4.68 or greater are likely to suffer from insulin resistance.

The TyG equation is:

TyG = ln (Triglycerides in mg/dL x Glucose in mg/dL / 2)

Also note that in the Guerrero-Romero et al. study, lipid-lowering drugs and insulin were exclusionary for patients (oral hypoglycemic agents were allowed).

Ultrasound is the first-line tool to detect liver steatosis but it may not be fully available or may require extra costs. It also has the limitation of detecting steatosis if present in more than 20-30% of hepatocytes. Therefore, prediction tools that are less costly and non-invasive are being sought.

The TyG is considered a screening tool for large-scale studies. The reason is its accuracy and easiness to be calculated with data obtained from medical records.

In the comparative study by Fedchuk et al. on the performance and limitations of steatosis biormarkers in patients with NAFLD, TyG is one of the example tools for steatosis, with an AUROC of 0.90. The gold standard for steatosis diagnosis is in this case liver biopsy.

According to Fedchuk et al. at TyG values above 8.38, there was a positive predictive value (PPV) of 99% for predicting steatosis equal to or greater than 5%.

A recent cross sectional study by Zhang et al. aimed to determine whether TyG has any predictive value for NAFLD. To do that it compared the predictive value of TyG with that of determinations of ALT (alanine aminotransferase) in a cohort of 10,761 patients where non-alcoholic fatty liver disease was diagnosed via ultrasonography.

The association between a screening method using triglycerides and glucose should not come as a surprise as NAFLD is considered the liver manifestation of metabolic syndrome, while triglyceride and serum glucose are key components of this process.

Alanine aminotransferase is the liver enzyme most reflective of liver fat content and is often included as variable with high prediction value in hepatic steatosis biomarkers.

ALT is also considered as a non-traditional cardiometabolic risk factor, meaning that it can be associated with type 2 diabetes, metabolic syndrome and risk of cardiovascular disease.

The study has found that the prevalence of NAFLD was significantly increased along the increasing levels of TyG and ALT but that TyG performed better than ALT in discriminating NAFLD.

According to the ROC analysis, the optimal cut-off point of TyG for NAFLD was 8.5. The AUROC was 0.782 (95% CI 0.773–0.790). TyG of 8.5 and above identified cases with NAFLD with 72.2% sensitivity and 70.5% specificity.

 

Hepatic steatosis predictors

There are several other screening tools for non-alcoholic fatty liver disease, including:

Fatty Liver Index (FLI);

Hepatic Steatosis Index (HSI);

ALD/NAFLD Index (ANI);

Non-Alcoholic Fatty Liver Disease - Liver Fat Score (NAFLD-LFS).

 

Original source

Zhang S, Du T et al. The triglyceride and glucose index (TyG) is an effective biomarker to identify nonalcoholic fatty liver disease. Lipids Health Dis. 2017; 16: 15.

Other references

1. Simental-Mendía LE, Rodríguez-Morán M, Guerrero-Romero F. The product of fasting glucose and triglycerides as surrogate for identifying insulin resistance in apparently healthy subjects. Metab Syndr Relat Disord. 2008; 6(4):299-304.

2. Fedchuk L, Nascimbeni F, Pais R, Charlotte F, Housset C, Ratziu V; LIDO Study Group. Performance and limitations of steatosis biomarkers in patients with nonalcoholic fatty liver disease. Aliment Pharmacol Ther. 2014; 40(10):1209-22.

3. Guerrero-Romero F, Simental-Mendia LE, Gonzalez-Ortiz M, et al. The product of triglycerides and glucose, a simple measure of insulin sensitivity. Comparison with the euglycemichyperinsulinemic clamp. J Clin Endocrinol Metab 2010; 95: 3347–51.


Article reviewed by Dr. Antonio Olveira


App Version: 1.0.1

Coded By: MDApp

Specialty: Hepatology

System: Digestive

Type: Index

No. Of Variables: 2

Year Of Study: 2008

Abbreviation: TyG

Article By: Denise Nedea

Published On: September 11, 2017 · 09:29 AM

Last Checked: September 11, 2017

Next Review: September 11, 2018