Liver Function Tests and their Interpretation

1 Indian Journal of Pediatrics, Volume 74 July, 2007663 Correspondence and Reprint requests : Prof. Thapa, Professorand Head Division of Pediatric Gastroenterology, Hepatology andNutrition, Post Graduate Institute of Medical Education andResearch, Chandigarh 160012[Received August 10, 2006; Accepted August 11, 2006]Symposium : Newer Diagnostic TestsLiver Function Tests and their Thapa and Anuj WaliaDivision of Pediatric Gastroenterology, Hepatology and Nutrition, Post Graduate Institute of Medical Educationand Research, ChandigarhABSTRACTL iver Function Tests (LFT) are a helpful screening tool, which are an effective modality to detect hepatic dysfunction.

2 Since theliver performs a variety of functions so no single test is sufficient to provide complete estimate of Function of Liver . Often cliniciansare faced with reports that do not tally with the clinical condition of the patient and they face difficulty in interpreting the attempt is being made to study and understand the LFT and simplify their Interpretation with algorithms. [Indian J Pediatr2007; 74 (7) : 663-671] E-mail: words : LFT; Alkaline phosphatase; Albumin; Prothrombin time; Aminotransferases (ALT & AST) Liver has to perform different kinds of biochemical,synthetic and excretory functions, so no singlebiochemical test can detect the global functions of laboratories usually employ a battery of Tests forinitial detection and management of Liver diseases andthese Tests are frequently termed Liver Function Tests ,although they are of little value in assessing the liverfunction per se.

3 In spite of receiving a lot of criticism forthis terminology, the phrase Liver Function Tests is firmlyentrenched in the medical lexicon. It might be argued that Liver injury Tests would be a more appropriateterminology. Moreover, the clinical history and physicalexamination play important role to interpret thefunctions. The role of specific disease markers,radiological imaging and Liver biopsy can not ,2 USESThe various uses of Liver Function Tests include:Screening : They are a non-invasive yet sensitivescreening modality for Liver of disease : They are helpful to recognize thepattern of Liver disease.

4 Like being helpful indifferentiating between acute viral hepatitis and variouscholestatic disorders and chronic Liver disease. (CLD).Assess severity : They are helpful to assess the severityand predict the outcome of certain diseases like primarybiliary up : They are helpful in the follow up of certainliver diseases and also helpful in evaluating response totherapy like autoimmune sensitivity: The LFT may be normal in certain liverdiseases like cirrhosis, non cirrhotic portal fibrosis,congenital hepatic fibrosis, specificity : They lack specificity and are not specificfor any particular disease.

5 Serum albumin may bedecreased in chronic disease and also in nephroticsyndrome. Aminotransferases may be raised in cardiacdiseases and hepatic for serum bile acids the LFT are not specific forliver diseases and all the parameters may be elevated forpathological processes outside the ,3 Thus, we see that LFT have certain advantages as wellas limitations at the same time. Thus, it is important toview them keeping the clinical profile of the patient OF Liver Function TESTSA. Tests of the Liver s capacity to transport organicanions and to metabolize drugs- Serum bilirubin, urinebilirubin, urobilinogen Tests that detect injury to hepatocytes (serum enzymetests) Aminotransferases, alkaline phosphatase, and A.

6 Walia664 Indian Journal of Pediatrics, Volume 74 July, 2007glutamyl transpeptidase, 5 nucleotidase, leucineaminopeptidase Tests of the Liver s biosynthetic capacity- Serumproteins, albumin, prealbumin, serum ceruloplasmin,procollagen III peptide, a 1 antitrypsin, a feto protein,prothrombin time clinical significance of LFT is given in Table 1A. Tests of the Liver s capacity to transport organicanions and to metabolize drugs1. SERUM BILIRUBINB ilirubin is an endogenous anion derived fromhemoglobin degradation from the RBC. The classificationof bilirubin into direct and indirect bilirubin are based onthe original van der Bergh method of measuringbilirubin.

7 Bilirubin is altered by exposure to light soserum and plasma samples must be kept in dark beforemeasurements are made. When the Liver Function testsare abnormal and the serum bilirubin levels more than17 mol/L suggest underlying Liver of bilirubini. Total bilirubin: This is measured as the amount, whichreacts in 30 minutes after addition of alcohol. Normalrange is mg/dl (2-15 mol/L). It is slightly higherby 3-4 mol/L in males as compared to females. It is thisfactor, which helps to diagnose Gilbert syndrome inmales Direct Bilirubin : This is the water-soluble is measured by the reaction with diazotizedsulfanilic acid in 1 minute and this gives estimation ofconjugated bilirubin.

8 Normal range ( mol/L)iii. Indirect bilirubin: This fraction is calculated by thedifference of the total and direct bilirubin and is ameasure of unconjugated fraction of ,5 The diazo method of bilirubin estimation is not veryaccurate especially in detecting low levels of bilirubin over estimates bilirubin esters at lowbilirubin levels and under estimates them at highconcentration. Thus slight elevation of unconjugatedbilirubin not detected, which is of value in detectingconditions like Gilbert newer highly accurate method of estimationinvolves alkaline methanolysis of bilirubin followed bychloroform extraction of bilirubin methyl esters and laterseparation of these esters by chromatography andTABLE 1.

9 Clinical Significance of Liver Function Tests in ChildrenNormalBasis ofAssociated liverExtrahepaticabnormality disease sourcesBilirubin 0-1mg/dlDecreased hepaticMild elevations: Liver diseases,Hemolysis, ineffectiveclearancephysiological jaundice, inheritederythropoiesis, hematoma,hyperbilirubinemiasmyoglobinemi aModerate elevations: EHBA, IHBA, drugs,viral hepatitis, inherited hyperbilirubinemiasAminotransferases ALTL eakage fromMarked elevations: Hepatitis, autoimmune,ALT specific for hepatocytic10-55 U/Ldamaged tissuestoxic, neonatal hepatitis, ischaemicnecrosis.

10 AST for skeletal,AST 10-40 U/LAST/ALT >2 in CLDcardiac, muscle, kidney, <1 acute hepatitis/ injuryAlkaline phosphataseOverproduction andMild elevations: Liver diseaseBone diseases, placenta,45-115 U/Lleakage in bloodModerate elevations: EHBA, IHBA,intestine, tumourinfiltrating disorders, granulomatoushepatitis glutamyl transpeptidaseOverproduction andSame as alkaline phosphatase,Kidney, spleen,pancreas,0-30 U/Lleakage in bloodRaised in EHBA, PFIC heart, lung, brain5- nucleotidaseOverproduction andSame as alkaline phosphataseSpecific for liver0-11 U/mlleakage in bloodProthrombin timeDecreased syntheticAcute/chronic Liver disease- nonVit K deficiency secondary10-14seccapacityresponsive to Vit Kto MAS, PEM.