Specimen Reception and Immunology

Hi all,

Sorry for the late posting.
I have just finished Specimen Reception department in my lab and now currently at Immunology.

At the specimen reception department, it is basically about SOPs and following strictly to SOPs. As we have major clients apart from normal clinics, we have to know our clients well because the specimens received from each client are processed differently. So basically, I spent a long time just learning the procedures because we are expected to work like the other staff there.

It is also essential to know the different types of tubes and their functions because we have to inform the doctors and reject the specimen if wrong specimen types are sent for testing. (It has happened quite frequently)

Long Plain tubes:

Known as serum separator tubes when gel is added to the tube. It contains a clot activator (I don't know the exact ingredient) pre-coated in the tube. When spun down the red cells are at the bottom and the gel in the middle with the serum at the top. It is important to note that different type of gels from different materials may cause inaccuracies. For those without the gel, it only has the clot activator. Long plain tubes are usually used for serum analysis such as VDRL testing.

Heparin tubes:

Usually available as sodium, litium or ammonium salt pre-coated in the tube, it is used for trace elements screening in industrial toxicology for patients working in heavily polluting industries. It is also recommended that for potassium analysis, heparin tubes are to be used. When using the long plain, potassium would be released from the platets giving an increased in serum potassium. EDTA tubes comes with potassium salts and would cause falsely high potassium results.

Fluoride/oxalate tubes:

Oxalate will cause osmotic redistribution between the the plasma and erythrocytes, diluting the plasma as a result (water moves from erythrocytes to the plasma ). This would decrease hematocrit levels, disrupt the morphology and cell membranes of erythrocytes. When the samples arrive in our lab, "water condensation" may be observed inside the tube because of the osmotic redistribution. Therefore, fluoride/oxalate tubes are only used for ABO and antibody screening in our lab. Oxalate will also bind to calcium in the blood, causing a falsely low blood calcium level.

Citrate tubes:
Usually for coagulation studies because it preserves the coagulation factors. Citrate also causes osomotic redistribution and decreases the concentration of many analytes (like fluoride/oxalate tubes). However in our lab, citrate tubes are most commonly sent along with a EDTA for full blood count or as a follow up of an EDTA specimen usually due to possible/observed platelet clumping in certain patients (cause unknown) when the specimen is sent in EDTA.


Immunology

During my term in Immunology, the common tests run in the department are:

1. Dengue (most common but low sample volume compared to HIV and it is the only manual test.)

Run by the Centaur machine

2. HIV (most common)
3. Tumor markers ( Ca 199, Ca 125 etc)
4. Ferritin
5. Vitamin B 12 and folate acid
6. Hormones such as cortisol and testosterone

Principles of Dengue is the same as Sally's post.
Principles of HIV is the same as Lizzie's post a number of weeks ago.

As promised, I managed to find out about the alternative system to HIV testing with a much shorter testing time. As it is newly tried out in the Serology department, I don't know much about it yet. It is the Roche Modulla from Roche diagnostics.


Ca 15-3

Ca 15-3 is usually for testing of metastatic breast cancer. When a women is diagnosed with breast cancer, usually, her specimen has the presence of cancer-related antigens especially Ca 15-3. Note that for all tumor marker tests conducted, an abnormal result does not mean that ther patient has cancer. There are also conditions where abnormalities are observed in normal healthy patients. Therefore, a confirmatory test is necessary to detect cancer in patients.
Ca 15-3 can be used to monitor response to treatment of disease. In patient with known metastasis, a reduction may mean a good sign of positive response to treatment while an increase may mean the disease progressing to the next stage.

Principle of the test:
2 step sandwhich ELIZA using direct chemilluminescent.

The system will perform:

1. Dispense sample into cuvette

2. Dispense conjugate reagent and solid phase and incubate at 37 deg celcius.
The conjugate is made of monoclonal mouse antibody 115D8 labelled with fluorescein, which is specific for CA 15-3 antigens. The solid phase is made of monoclonal mouse capture antibody coupled to paramagnetic (refer to PIPC 2 notes for definition of paramagnetic) particles.

3. After incubation, the complex (conjugate and solid phase) is washed to remove unbound antibodies.

4. The complex is resuspended using the wash solution and Lite reagent is dispensed. The Lite reagent consists of monoclonal mouse antibody, DF3, specific for CA 15-3 labeled with acridinium ester.

5. Cuvette is washed to remove unbound Lite reagent.

6. Acid and base reagent is dispensed to initiate the chemiluminescent reaction.

High amount of CA 15-3 in patient's sample = high amount of relative light units (RLU) detected. This means that with an increase in CA 15-3, the intensity of chemiluminescence increases.



Once again, I appologise for posting so late.

With regards,
Yeng Ting
TG02