Liver function tests (LFTs) can reveal important information about underlying liver conditions or other systemic diseases. This document provides guidance on interpreting abnormal LFT results in primary care settings. It recommends a tiered testing approach based on the pattern of abnormal LFT findings and risk factors. First tier tests include full blood count, glucose, lipids, iron studies, and hepatitis/alcohol screens. Second tier tests may involve ultrasound, autoantibody screens, or other tests depending on clues from history, examination, and first tier results. The goal is to identify potential causes and determine if follow up testing or referral is needed.

1. Haematology Hepatology
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Liver function tests (LFTs)
Summary: interpreting abnormal LFTs in primary care
Summary: tiered testing recommendations for stable patients with elevated aminotransferase
levels (ALT or AST)
Test Abnormality Interpretation or potential cause
First tier
Full blood count (FBC) Macrocytosis Possibly due to excessive alcohol intake, particularly if
GGT also raised
Thrombocytopenia Portal hypertension (possible hypersplenism) which
may also be associated with ultrasound findings of
enlarged spleen, portal vein and ascites or varices.
Also common in chronic liver disease.
HbA or fasting glucose Elevated (e.g. HbA > 41 mmol/mol
or fasting glucose > 5.5 mmol/L)
Indicates glucose intolerance conditions, e.g. type 2
diabetes and pre-diabetes; MAFLD is common in these
patient groups
Lipid profile Abnormal Contributor to fatty liver diseases, i.e. alcohol-related
liver disease or MAFLD
Iron studies,
inc. ferritin and TSAT
Elevated Possible haemochromatosis. Check hereditary
haemochromatosis (HFE) genotype if repeat testing
remains high in fasting and otherwise well patients
Hepatitis screening
(HBsAg and anti-HCVAb)
Positive Suggests hepatitis B or C infection. HCV requires
confirmation of infection by either detection of HCV
RNA or HCV Antigen
AUDIT-C screening Positive
(score ≥ 3 in female or ≥ 4 in male)
Suggests potential alcohol misuse; full AUDIT tool
assessment should then be undertaken
Second tier
Abdominal/ liver
ultrasound
Echogenic liver, mass or dilated ducts Can be used to detect fatty liver, malignancy or gall
stones/obstruction
Testing for other causes
of viral hepatitis, e.g.
Hepatitis A, Epstein Barr
virus, Cytomegalovirus
Positive Suggests infection with corresponding virus; hepatitis
A testing may be a first-tier investigation if the patient
reports travel to a country where infection is prevalent
or contact with local outbreak or MSM
Autoantibodies and
Immunoglobulins
Antimitochondrial antibody (AMA) positive,
increased IgM in combination with cholestatic
LFTs
Diagnostic of primary biliary cirrhosis
Anti-smooth muscle antibody (SMA)/ anti-liver
kidney microsomal (LKM)/anti-liver soluble
antigen (SLA)/anti-nuclear antibody (ANA)
positive, particularly with elevated IgG
Probable autoimmune hepatitis
Coeliac serology screen Positive Suggestive of coeliac disease-related liver damage
Other tests dictated by clinical context or family history of liver disease, such as:
Checking alpha-1 antitrypsin levels in people with a family history of deficiency
Serum/urine copper and caeruloplasmin testing in patients with a family history of Wilson’s disease
If these tests have been performed for other clinical reasons and an abnormality is found, then subsequent LFT testing is usually warranted
A fasting sample may improve the accuracy of results if there is uncertainty about an abnormal result
In patients where ultrasound does not identify any underlying cause and the diagnosis remains uncertain, consider referring for further assessment with
FibroScan, if needed (see: “FibroScan is an emerging alternative tool to liver biopsy”). Liver ultrasound is first tier investigation if cholestasis is suspected.
It is strongly recommended to review the original resource at your convenience for full details of recommendations and evidence.
See full article here: Liver function tests in primary care
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PatientwithanabnormalLFT
finding(s)
Patientatriskofliverdisease
Referralforacutehepatology
assessment/urgentultrasoundatliver
unitorgastroenterologydepartment
(oremergencydepartment)
Evaluatehistoryforcluesaboutthepotentialcause(ifnotalreadyconfirmed):
•Co-morbidities,e.g.obesity,type2diabetes, RiskfactorsforhepatitisBandCinfection
dyslipidaemia,pregnancy •Familyhistoryofliverdisease
•Medicinehistoryandsupplementuse •Hepatotoxicchemical/substanceexposure
Alcoolmisuse(e.g.usingAUDIT-Ctool) •Symptoms+physicalexaminationfindings Red
flags
Suspectedsyntheticliverfailure
Valbumin+plateletsand†prothrombin
time/INR(especiallyifjaundiceispresent)
Suspectedmalignancye.g.weightlossand
markedcholestasis(seebelow)
Ifmodifiable
causeisnot
apparentorLFT
changeismore
significant
Ifitisaborderlineabnormalityandthepatientisasymptomatic,address
anypotentialmodifiablecause(s),suchas:
•Changedose/substitute/discontinuemedicine(ifpossible)
•Reduce/avoidalcoholconsumption(ifapplicableorconcerning)
Suspectedacutehepatitis/injurydueto
severeLFTincrease/symptoms
sthereacommonclinical
patternpresent?
Hepatocellularinjury
†ALTand/or
†AST
(comparedwithALP)
With/without†bilirubin
MarkedALTorASTincreasesindicateacute
ormoresevereinjury
Cholestasis/cholestaticinjury
TALP(often>4xULN)
†GGT
(comparedwithALT/AST)
With/without†bilirubin
No
Isthereanisolatedincrease
inbilirubinlevels?ie.
normalALT/ASTandALP/GGT
No
Isthereanotherisolated
abnormality?
†ALT
†AST
†ALP
†GGT
•TestINRifnotalreadyavailabletoassessforsyntheticliverfailure(seeredflagsabove)
~Serumalbumin
•Othercausesincludecachexia,catabolicstatessuchassepsisorcancer,nephroticsyndromeandprotein-losingenteropathy
•Totalproteincomprisesbothalbuminandglobulins;isolatedsignificantchangesinpatientswithnormalalbuminmaysuggestanimmune.
T/VTotalprotein
relatedcause(e.g.activeinfectionorautoimmunedisease),malignancy
IftheabnormalLFTfinding(s)persistsorworsens RepeatLFTwithin3monthstosee
ifalterationpersistsandtoinform
subsequentaction(s)required
Potentialliver-relatedcause
Acute:acuteviralhepatitis,acute
ischaemicinjury,medicine-induced
injury,acuteautoimmunehepatitis
Chronic:HepatitisBandC,alcohol-
related,MAFLD,chronicautoimmune
hepatitis,orraregeneticcauses,e.g.
haemochromatosis,Wilsondisease
Yes OConsidertheAST:ALTratio
.<1=possibleMAFLD(nocirrhosis),chronichepatitisBorC,
acuteinjury
=≥2=possiblealcohol-ormedicine-injury,cirrhosisormalignancy
•≥5=possibleextra-hepaticcauseifALTlowornormal
Applyatieredapproachtosubsequentlabinvestigationsaccordingto
mostlikelycauses+riskfactors(seethetieredtestingsummarysection
below
Acute:choledocholithiasis(gall
stones),acutecholangitis,medicine-
inducedinjurytobileducts
Chronic:primarybiliarycholangitis,
primarysclerosingcholangitis,
autoimmunecholangiopathy,bile
ductstricture,malignancy
Possibleextra-hepaticcauses:coeliacdisease,heartfailure,MI,skeletal
muscleinjury,thyroiddisorders,malnutrition,excessiveexercise
Yes Requestultrasoundifsuspectedliver-relatedcause
Considerautoantibody/immunoglobulintestingifimagingis
negative
Possibleextra-hepaticcauses:bonedisordersormetastases,
vitaminDdeficiency,pregnancy-related,thyroiddisorders
Manageaccordingtounderlyingcause+consider
needforreferral
Potentialliver-relatedcause
Benignhereditaryliverdisordersuchas
Gilbert'ssyndrome(prevalence5-8%)
N.B.bilirubincanincreaseinadditionto
otherLFTmarkersinmostliverdiseases
Yes
•Requestfractionatedconjugated/directbilirubintestand
haemolyticscreen(thesearesometimescombined)
Ifhaemolysisnegativeandconjugatedbilirubinis<20%of
totalbilirubinthenGilbert'ssyndromeislikely
•Requestultrasoundifconjugatedbilirubin>50%total
Ifconjugatedbilirubin≥20%oftotal:canoccurwitheither
acutehepatocellularorcholestaticinjury,vanishingbileduct
syndrome,totalparenteralnutrition,Rotorsyndrome
Yes •Reinforcegeneralliverhealthadvice
•Considerneedforotherinvestigation(s)based
onspecificLFTchange(below)andanyrelevant
patientriskfactors
RepeatLFTwithin3monthstosee
ifalterationpersistsandtoinform
subsequentaction(s)required
•Potentialhepatocellularinjuryorextra-hepaticcauses(asabove)
•IsolatedASTincreasesmayalsoindicateaextra-hepaticcauseifALTnormal,e.g.cardiacorskeletalmuscularinjury
•Fractionatedisoenzymetestingmaybeusefultodetermineorigin(e.g.liverorbone)ifisolatedincreasepersists>6months;however,this
testisnotreadilyavailableincommunitylabsandisgenerallyonlyrequestedaftersecondarycareassessment
•Rarelyindicativeofsignificantliverdiseaseifraisedinisolation;potentiallycausedbyexcessalcoolintakeormedicineuse
Abbreviations:ALP,alkalinephosphatase;ALI,Alanineaminotransterase;ASI,aspartateaminotransterase;GGI,y-glutamyl-transterase;INK,internationalnormalisedratio;LtI,livertunctiontest,MI,myocardialintarction
MAFID.metabolic-associatedtattvliverdiseast
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