COMPONENTS & CONCENTRATION OF WORKING SOLUTION

 SPECIMEN COLLECTION & PRESERVATION

Blood should be collected in a clean dry container. Although serum is preferred, plasma with heparin or EDTA can be used. Samples with any visible haemolysis are not acceptable since erythrocytes contain approximately ten times the normal activity of GOT (AST) found in serum. GOT (AST) activity in serum/plasma is stable for 1 week at 2 - 8 Degree C and Expected range varies from population to population. It is therefore recommended that each laboratory should establish its own normal range.

PROCEDURE

• Reaction type : UV - Kinetic
• Reaction direction: Decreasing
• Wavelength : 340 nm.
• Flowce temperature: 37 degree C
• Zero setting with: Distilled water
• Delay time : 60 seconds
• No. of readings: 4
• Interval 30 seconds
• Blank absorbance limit : 0.900 Abs.
• Sample volume 0.05 ml (50 uI)
• D Working solution volume (4 R1 : 1 R2) 1.0 ml (1000I) D  Factor 3339
• Linearity : 800 IU/1

MANUAL ASSAY PROCEDURE

Prewarm at 37 Degree C the required amount of working solution before use. Perform the assay as given below:

Mix and aspirate. After the initial delay of 60 seconds, record the absorbance of the test at an interval of 30 seconds for the next 90 seconds at 340 nm. Determine the mean change in absorbance per minute and calculate test results.

Calculation:

Activity of GOT (AST) in lU/1 A Abs J min. x 3339

Conversion factors :

Following factors can be used for conversion of IU/1 from one temperature to another:

Temperature Conversion

• From 37 Degree C to 30 Degree C : 0.67
• From 37 Degree C to 25 Degree C : 0.49

EXPECTED VALUES

PROCEDURE LIMITATIONS

If the GOT (AST) activity exceeds 800 IU/1, dilute the specimen with normal saline and repeat the assay. The result obtained should then be multiplied with the dilution factor to obtain correct GOT (AST) activity.

The working solution is considered unsatisfactory and should not be used if the absorbance is less than 0.900 at 340 nm. against distilled water.

QUALITY CONTROL

To ensure adequate quality control, it is recommended that each batch should include normal and an abnormal commercial reference control serum. It should be realised that the use of quality control material checks both instrument and reagent functions together. Factors which might affect the performance of this test include proper instrument function, temperature control, cleanliness of glassware and accuracy of pipetting.