Specimen Collection

Sample stability:

• 4 days at 20-25 ^o C
• 7 days at 4-8 ^o C
• 3 months -20 ^o C

4.5 mL PST Blood (Preferred)

0.5 mL Paediatric Micro-PST Blood (Preferred)

5 mL Heparin Blood

4 mL Plain Serum

3.5 mL SST Blood

0.5 mL Paediatric Microsample Blood

0.5 mL Paediatric Micro-heparin Blood
Reference Intervals

Units : U/L

Reference interval

Adult:	0 - 45
Child:
<2 yr	0 - 80
2-10 yrs	0 - 60
>10 yrs	0 - 45
Pregnancy:	0 - 30

Uncertainty of Measurement: 8%

Turnaround Time: Within 3 hours
Assay Method

Principle: Colorimetric

Reagents: Roche AST kit

Analyser: Cobas c702

Diagnostic Use and Interpretation

In parenchymal liver diseases, the magnitude of AST rise in general is less than or at most equal to that of ALT (alanine transaminase) rise. Exceptions to this include hypoxic hepatopathy (or ischaemic hepatitis), alcoholic hepatitis and chronic hepatitis/cirrhosis where the AST / ALT ratio can be more than one.

AST is less specific than ALT for parenchymal liver conditions. Although AST can be raised in conditions like skeletal myopathies, myocardial cell injury or intravascular haemolysis, it is not specific enough for use in their diagnosis or monitoring. Other much better biomarkers like creatine kinase, high sensitive troponin T and haptoglobin/plasma Hb are easily available and should be used instead.

For the above reasons, AST test has been removed from routine "Liver function profile". However, AST test is still be available 24 hourly on specific, hand written requests.

Reference:

Xu Q et al. Limiting the testing of AST - a diagnostically nonspecific enzyme. Am J Clin Pathol 2015; 144:423-426

Specimen haemolysis can cause false elevations.

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).

Contact Information

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

Last updated at 15:26:00 06/01/2025