Department: Clinical Biochemistry Laboratory

During the fourth week of my attachment, I was stationed at the DxI station where I observed and learnt about the Beckman DxI-600 and its day to day maintenance.

Every morning, the technician-in-charge of DxI would be responsible for its daily maintenance such as

Backing up the system and data – By doing so, the data (Eg. The type of test run on which specific specimen and its results) accumulated in the previous day would be saved into floppy disks and could be used for further reference.)

Checking Inventory – This is important as it ensures that all reagents required by the DxI to perform all its tests are topped up and sufficient to last the entire day.

Recording Test count – This simply requires the technician to record the total number of tests performed by the DxI the day before.

Shaking the solid waste container – The waste container is where DxI deposit solid waste such as pipette tips. Usually, the waste would accumulate at one side of the box (as the tips are dropped from the same spot) and shaking the box would balance out the level of the contents.

Running a daily special clean – This daily special clean is commercially prepared by the DxI manufacturer. The special clean solution is transferred to a reaction vessel (plastic holding cups) by a dropper and the reaction vessel is then placed on a specific rack that carries the solution into the DxI once the task is assigned for the rack to run. This daily special clean is used for cleaning probes in the DxI. Probes are in fact mechanical arms that the machine used to pipette and transfer specimens and reagents within the DxI. Although it is constantly washed by the machine, running a special clean very morning would ensure removal of possible specimen/reagent traces from the probe itself and its pipes.

Other than its daily maintenance, I have also researched on the one of the common tests carried out by the DxI – Insulin.

Brief overview of Insulin:
Insulin is a hormone secreted by the pancreas that facilitates the uptake of glucose from the blood and storing it as glycogen in the liver and muscle. Glycogen (fuel storage) would be broken down to glucose when energy is required by the body later on.

When insulin level is low or absent, glucose is not taken up from the blood and stored the liver or muscle cells. The glycogen storage would eventually deplete as the body utilizes energy, this would then results in the body utilizing body fats as energy source. At the same time, glucose in the blood remains high as insulin fails to function. This condition is known as diabetes mellitus.

Test Principle:
DxI is able to test the levels of insulin in patient’s serum by using the ultrasensitive insulin assay which is an immunoenzymatic sandwich assay.

1. A sample is added to a reaction vessel with monoclonal anti-insulin antibody and anti- insulin alkaline phosphatase conjugate.

2. Insulin in the patient’s serum will bind to the anti-insulin antibody on solid phase, while the conjugate reacts with different antigenic sites on the insulin molecule.

3. Unbound materials are washed away.

4. The chemiluminescent substrate LumiPhos 530 is added to the reaction vessel and light generated when this substrate react with the conjugate is measured with luminometer.

Additional notes:
Patient’s serum are used for insulin testing and as red blood cell contains insulin-degrading enzymes, badly hemolyzed samples are not suitable as insulin levels may be suppressed, causing pre-analytical variations and inaccurate results.

Tan Zhao Rong
Tg01