Thursday, 6 September 2007


hello everyone! how was yr week? weenkend le.. relax.. i have been dreaming of works everynight... stress.

i'm going to blog abt CODA open microplate technique. This machine is used for ANA( anti-nuclear antibodies) screening test and Anti-ds DNA. i think someone blog this before but not using CODA. let see whether it will be the same. Normally, the doctor will only order ANA screening if he suspect the patient suffer from auto-immune diseases. ANA screening is not 100% accurate.


Refer to:

CODA is an interagated immunoassay analyzer intented for the automation of microplate based assays for in vitro diagnostic use. The system is open, such that a variety of microplatedbased (8wells X 12 strips) enzyme immunoassays (ELAs) can be programmed and run on the instrument. The sample and reagent pipettes, incubator, washer, reader and robotics are housed in the compact bench top unit.

System overview:

-->pipette all standards, calibrators. control, and samples

--> pipette reagents

-->shake & wash the microplate

-->incubate the plate @ ambient temperature or in a heated incubator

--> Read the optical density of the microtiter plate

--> Calculate the curve fitting and patient results

--> Print the run report, including interpretion of results

Principles of this test is the almost the same as normal immunoassay (Ab-Ag binding plus substrate). The principles for both ANA screening & ANti-ds DNA test is different, but both tests use the ELAs technique.

ANA screening test:

it is used to screen for the presence of antinuclear antibodies in the human serum as an aid in the diagnosis of certain systemic rheumatic diseases. This assay collectively detects, in one well, total ANAs against double stranded DNA (dsDNA, nDNA) histones, SS-A/Ro, SS-B/La, Sm, immunofluorescent (IFA) Hep-2 ANAs.


To screen for the presence of dsDNA antibodies in human serum as an aid in the diagnosis of systemic lupus erythematosus (SLE).

Workflow before the test begin:

1) Allow wash buffers, reagents and samples to warm up to room temperature

2) Install wash buffers onto Coda, Refill pipette wash

3) Switch on Coda and Computor

4) Prime wash bottles 1 & 2

5) Perform chamber adjust (-1000)


1. Apply 100ul diluted samples and controls to wells:

  • controls-apply 100ul of diluted controls (1:40) to assigned wells. add 100ul of sample diluent as a blank control.

  • patient sample- apply 100ul of diluted patient serum (1:40) to assigned wells

  • apply 100ul sample diluent to blank control well

2. Shake plate gently, then incubate for 30mins @ r.t.p

3. incubated samples are discarded to the waste bottle.

4. Gently fill 5X with 100ul of wash solution and discard. Remove all liquid before proceeding

5.adding 100ul conjugate to all wells. Discard excess liquid.

6. Incubate wells @ r.t.p for 30mins

7. Discard conjugate by flicking

8. Wash wells again 5X

9. add 100ul of substrate to each well. Discard excess transferred substrate after use

10. incubate @r.t.p for 30 mins

11. Stop color development by adding 100ul stop solution to each well.

12. REad the results with ELAs reader @ 450nm.


ANA screening: <1.0>

Positive Control: appear dark yellow

If the result is Negative, it will appear light yellow or colorless

Anti-ds DNA:



The Lab Freaks said...

hey elaine! (:

urm i wana ask is there any special characteristics or differences between the immunoassay test used at architect and coba? Or like why for this Anti-ds DNA test can be only tested with the Coba machine?


MedBankers said...


normally architect is used for testing of antigen or tumor marker. It is unable to do ANA screening because the process required a very long time to process (abt 1hr3omins), including incubation, washing, pipetting. ANA screening uses microplate technology. Architect unable to do tt.


Star team said...

If ANA screnning is not 100%accurate, why do this test? Can't we perform other test to detect abti-nuclear antibodies?


Anonymous said...


I've done the very same test on my first 3 weeks of attachment (tat's quite some time back). But my lab alternates between 2 machines. Mainly the test is done with the Evolis and sometimes, the Coda. But the methods, principles and procedures are the same with the exception that the Evolis can perform different tests simultaneously =)

So here's my 2 questions:

1. What is the confirmatory test that your lab performs in case of a positive reading?

2. What are the parameters that your lab defined so that the test can be valid? Like for example, the OD for the sample diluent must be less than 0.200 when zeroed against air. My lab has 4 main criteria....I just wonder if it is the same....

Have a nice day,
Yeng Ting

MedBankers said...

hey yeng ting,

if the Screening turned out to be positive, normally we will send to NUH or SGH.

The parameters:

cutoff control: OD 0.085-0.500
Positive Control: ANA #2.5-7.5
Negative Control: ANA #<1.0
Sample diluent: OD < 0.200

cheers, elaine

Star team said...

hello elaine,

which type of sample is collected? is anti-coagulant used? what other disease, other than SLE, can this machine help in its diagnosis?

thanks a lot!

phuiyuen, tg02

MedBankers said...


we uses serum to perform the test.

Other auto-immune diseases:
1)Rheumatoid arthritis (RA)
-->It is a form of arthritis that causes pain, swelling, stiffness and loss of function in your joints

2) Myositis
-->It is inflammation of muscle tissue, especially the muscles that control movement of the body. There are several types of myositis, such as one that also causes a rash (dermatomyositis) and one that occurs throughout the body (polymyositis).

3) Scleroderma
-->It is an uncommon disease in which parts of the skin, joints, and blood vessels break down and are replaced by fibrous tissue. Organ damage may also occur, which can lead to lung, kidney, or heart failure and other life-threatening conditions.

4) Sjögren's syndrome
--> It is a disease in which the immune system attacks the body's moisture-producing glands. This disease may cause the tear and saliva glands to become scarred and damaged, and can cause exceptional dryness in the eyes and mouth.

Hope it reply you.


MedBankers said...

hey eugene,

i'm sorry so late then reply u.

ANA screening is not 100% accurate, just like any other screening tests. It can detect anti-bodies but not specific 1.