Week 13 is over! Like finally...

Its the end of week 13 in case some of you aren't aware that our SIP has already been more than halfway through. Most of us cant wait for the 20 week attachment programme to be over, which is considered long for most courses. School life is seriously much better than working life, and all of us are seriously deprived for holidays to start once again.

So I am now currently based in the Paragon branch of my company. Yes, no more being based in the main office but at Orchard Road. What I am dealing now in Paragon clinics is doing on Immunology.

Like I mentioned in my previous post, automated machines are being utilized greatly, so I am gonna talk about automated machines, since manual work (what we learnt in practical labs) are no longer in use at all. The most common equipment used in Immunology would be

ADVIA Centuar

(Some of you would also be using this in your company)

There are many tests done for ADVIA Centuar, such as for Prostate Specific Antigen (PSA) - Tumour marker for prostate cancer or prostatic hypertrophy, prostatistis or even CA 125 (Cancer Antigen 125) - Glycoprotein produced by ovarian cancers. May signify cancers of gastrointestinal tract, breast etc. However, I shall concentrate on the test for HBsAg:

• HBsAg (Hep B surface Antigen) - When a person is exposed to Hep B viral infection, the HBsAg will appear after three weeks. The antigen remains in the blood for 4 to 5 months, before dissapearing. In some cases, HBsAg will persist for long periods, thus people in this group suffers from chronic Hep B. However, some cases happen whereby there is no recovery at all, and these people are so-called carriers of Hep B. Carriers of Hep B have a high chance of getting liver cancer.

The detection of antibody to hep B signfies and determine immune status to HBV or disease progression in individuals infected with HBV. An increase in anti-HBs levels, together with loss of detectable circulating hep B surface antigen denotes convalscence in hep B.

PRINCIPLES:

The principle inolves a sandwich immunoassay using direct, chemiluminometric technology. HBsAg are covalently coupled to magnetic latex particles in the solid phase. In the Lite reagent, the HBsAg is labelled with acridinium ester. Non magnetic latex particles are added from the ancillary wall. The sample is incubated with lite reagent, solid phase, and ancillary reagent. Ag-ab complex will form if anti-HBs is present in the sample.

Reagents stored in the internal system

Steps - The system performs:

• dispensing 100uL of sample into a cuvette
• dispensing 50uL of Ancillary reagent and incubation for 2.75 mins at 37 degrees
• dispensing 100uL of solid phase, 50uL of Lite reagent, incubation of mixture for 6.75 mins at 37 degrees
• separating solid phase from mixture and aspirates the unbound reagent
• washes cuvette and dispensing 300uL each of acid reagent & base reagent to initiate the chemiluminscent reaction

Results are then released by index values numbering system.

Any index value of less than 1.0 means negative for HBsAg.

Greater than 1 signifies positive for HBsAg. It is recommended to repeat the test to double-confirm. Confirmatory tests include ADVIA HBsAg confirmatory assay or additional HBV marker assays.

Careful quality control procedures include calibration done often & proper barcoding of samples.

Lloyd Lam 0607775D