Sample stability:
-
3 days at 15-25 o C
-
7 days at 2-8 o C
- >7 days at -70 o C
Units: U/L
Reference range: 0 - 45
Pregnancy:
ALT falls by about 30% from pre-pregnant values. In patients with normal ALT values before pregnancy the upper reference limit in pregnancy will be 32 U/L.ALT is more specific for liver cell damage than AST.
Uncertainty of Measurement: 10% at levels under 25 U/L
4% at levels over 150 U/L
Common causes of raised plasma aminotransferases ALT and AST include
-
viral hepatitis
-
alcohol related hepatitis
-
non-alcoholic fatty liver disease (steatohepatitis)
-
toxic or ischaemic hepatitis.
Less common causes include
-
hemochromatosis
-
autoimmune hepatitis
-
Wilson's disease
-
alpha-1 antitrypsin deficiency.
Patients with cholestatic liver disease, cirrhosis or hepatic carcinoma can have normal or mildly raised aminotransferase activity. Acute biliary obstruction occasionally can cause an early, transient and significant rise in aminotransferase level.
ALT is more liver-specific than AST. ALT is usually increased more than AST in most hepatic conditions. However, AST/ALT >1 can occur in chronic hepatitis, cirrhosis, haemolysis and classically AST is <300U/L with AST/ALT >2 in alcoholic hepatitis.
AST or ALT >3000U/L are rare in viral hepatitis but common in both toxin ingestion (especially acetaminophen) and ischaemia hepatic injury.
When raised aminotransferase is apparently unexplained, several "non-hepatic" conditions may be considered :
-
Coeliac disease
-
adrenal glucocorticoid deficiency e.g. Addison's disease
-
muscular dystrophies (check CK)
-
macro-ALT or macro-AST (these are complexes with immunoglobulins, leading to slow clearance of the enzyme; contact laboratory to arrange evaluation)
-
thyroid dysfunction (hyper or hypo)
-
sleep apnoea-related disorder (can be associated with or independent of obesity/metabolic syndrome)
Note: The drugs sulfasalazine and sulfapyridine cause negative interference in the assay; patients on these drugs may have falsely low results . Additionally, iron infusions (such as ferric carboxymaltose ) interfere with testing and may give falsely low results or make AST & ALT unmeasurable . This effect appears to resolve rapidly (around 24hrs).
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427