NAFLD Fibrosis Score Calculator

How does this NAFLD fibrosis score calculator work?

This is a health tool that assesses the level of fibrosis, scarring of the liver, consistent with the existence of nonalcoholic fatty liver disease (NAFLD). There are several liver conditions that are defined under this term which includes steatosis which is or not accompanied by various degrees of inflammation and cannot be appointed to alcohol consumption.

The score increases in importance as NAFLD affects almost 30% of population in developed countries and the common consequence, liver fibrosis, is consistent with the progression to end stage liver disease.

The variables used in the NAFLD fibrosis score calculator are interpreted as follows:

■ Age in years – this calculator is addressed to adults, there is a particular pediatric version available online. There is also a researched increased prevalence of the condition with age.

■ BMI measured in kg/m² – the body mass index is used in order to give a certain degree of information in regards to the patient’s weight status.

■ IGF/ Diabetes – refers to the existence of impaired fasting glucose.

■ Platelets x10⁹/L – platelet levels are an accurate predictor in nonalcoholic fatty liver disease and the decreased peripheral count is associated with liver fibrosis.

■ AST – the aspartate aminotransferase test measures the level of this enzyme in the blood. This is released when liver or heart tissue is damaged.

■ ALT – the alanine aminotransferase test, similar to AST, this enzyme is released in case of damage. This was previously known as serum glutamic pyruvic transaminase (SGPT).

■ Albumin measured in g/dL – the liver produced protein with normal serum levels between 3.4 – 5.4 g/dL or 34 – 54 if measured in g/L.

These variables strengthen the idea that NAFLD is associated with risk factors such as type 2 diabetes mellitus, obesity, dyslipidemia and metabolic syndrome.

Conditions with emerging association to this condition are hypothyroidism, hypopituitarism, hypogonadism, polycystic ovary syndrome and even sleep apnea.

The male gender is also a risk factor for NAFLD although not included in this fatty liver scoring system.

The formula used to compute the degree of fibrosis is:

NAFLD Score = -1.675 + 0.037 × age (years) + 0.094 × BMI (kg/m2) + 1.13 × IFG/diabetes (yes = 1, no = 0)

+ 0.99 × AST/ALT ratio – 0.013 × platelet (×10⁹/L) – 0.66 × albumin (g/dL).

Since the NAFLD fibrosis score panel relies on readily available clinical data, the score is easy to apply and can reflect in a matter of minutes, the possible level of liver fibrosis.

NAFLD score interpretation

Once the above formula is calculated the resultant score is interpreted after the following:

■ <-1.455: indicates the absence of significant fibrosis (F0-F2 fibrosis);

■ ≤-1.455 to ≤0.675: an indeterminate score;

■ >0.675: indicates the presence of significant fibrosis (F3-F4 fibrosis).

The next recommendation is that of elastography or liver biopsy in specific high risk cases while low risk patients are to be monitored at periodic intervals.

However, one of the benefits of the score is that in cases where the score is highly obvious, unnecessary costs and complications of detection biopsy can be avoided.

The original score has been validated in subsequent clinical testing and is supported by three main authorities in the field:

■ The American Association for the Study of Liver Diseases (AASLD);

■ The American College of Gastroenterology (ACG);

■ The American Gastroenterological Association (AGA).

Hepatic fibrosis stages

Certain hepatic inflammations are caused by a chronic and sustained attack on the liver which in turn leads to the creation of scarring in the form of fibrosis. This process tries to replace the damaged cells but the replacement cell unfortunately does not maintain the functionality the previous cell had when healthy.

The extent of hepatic fibrosis is quantified in stages:

■ Normal liver is placed at stage F0 and F1;

■ Light fibrosis makes stage F2;

■ Severe fibrosis begins from stage F3;

■ Stage F4 already defines cirrhosis with extended scar tissue.

Fibrosis in the first stages is reversible under pharmacological treatment with hepatic function resuming in the affected areas.

Second to fibrosis there are complications caused by portal hypertension which leads to the creation of oesophageal varicose veins, ascites consisting in abdominal liquid effusion, icterus or jaundice and hepatic encephalopathy due to the impairment in the hepatic toxic breakdown function.

References

1) Angulo P, Hui JM, Marchesini G, Bugianesi E, George J, Farrell GC, Enders F, Saksena S, Burt AD, Bida JP, Lindor K, Sanderson SO, Lenzi M, Adams LA, Kench J, Therneau TM, Day CP. (2007) The NAFLD fibrosis score: a noninvasive system that identifies liver fibrosis in patients with NAFLD. Hepatology; 45(4):846-54.

2) Angulo P, Bugianesi E, Bjornsson ES, et al. (2013) Simple noninvasive systems predict long-term outcomes of patients with nonalcoholic fatty liver disease. Gastroenterology; 145:782-789.

3) Chalasani N, Younossi Z, Lavine JE, et al. (2012) The diagnosis and management of non-alcoholic fatty liver disease: practice guideline by the American Association for the Study of Liver Diseases, American College of Gastroenterology, and the American Gastroenterological Association. Hepatology; 55:2005-2023.

4) Dowman JK, Tomlinson JW, Newsome PN. (2011) Systematic review: the diagnosis and staging of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis. Aliment Pharmacol Ther; 33(5): 525–540.