Hi people, hope you guys enjoy your SIP. I’ve been posted to the same lab as Maya, Lloyd, Azeimah and Ivan so what we learned are the same. But I realized even those who are not in our lab, they learned similar things as us too.
For the first 2 weeks I’ve been posted to Immunology with Maya and the 3rd and 4th week we are posted to Biochemistry. For these two sections they are closely link as they used the same automated track that helps them to automatically load samples into their machine. As mentioned in Maya’s and Ivan’s blog, for Immunology section they have this machine called Centaur and for Biochemistry, their machine is called Bayer Advia 1650 Chemistry System. Since both of them had already posted on the machines, I guess I’ll post on the manual test that biochemistry section does then.
Basically, the manual test procedures are not difficult or as many steps as we thought. The types of manual test that biochemistry does in out lab are OGTT, G6PD Qualitative test, and Drug Analysis (Drug Screen Test). I’ll share a little about the Drug screen test since no one has really talked about it.
Drug analysis (Drug Screen Test)
Samples to collect: Urine
The Drug Screen Test is a fast and easy test to determine drug abuse. The company purchases these cassettes (test device) that can be used to test for different drugs such as Amphetamine (AMP), Barbiturates (BAR), Benzodiazepines (BZO), Cocaine (COC), Marijuana (THC), Methadone (MTD), Methamphetamine (MET), Methylenedioxymethamphetamine (MDMA), Opiate (OPI), Phencyclidine (PCP) and Tricyclic Antidepressants (TCA). Simply just drop 3 drops of urine to the cassette well and the results will be out in a few seconds.
Signs and symptoms of patient with drug abuse:
Eg. Benzodiazepines— this drug is usually prescribed for treatment foe anxiety and sleep disorder. When this drug is taken more frequently, it will cause dependence and stopping abruptly can bring about symptoms such as trouble sleeping, gastrointestinal upset, feeling unwell, loss of appetite, sweating, trembling, weakness, anxiety and changes in perception.
Principle: Competitive binding.
During testing, the urine migrates upwards through capillary action. The drug present in the urine competes against their respective drug conjugate for binding sites on their specific Ab. If the presence of drug in the urine is below the cut-off concentration, it will not saturate the binding sites of its specific Ab. The Ab will then react with the drug-protein conjugate and a visible coloured line will appear at the test region. If the drug present in the urine is above the cut off concentration, it will saturate all the binding sites of the Ab, thus the coloured line will not appear due to drug competition.
Interpretation of result:
Coloured line appears—negative
No coloured line appears—positive—drug abuse
Note: The assay only provides a preliminary analytical test result. A more specific alternate method should be used to confirm this analytical result. The preferred confirmatory test is Gas chromatography/mass spectrometry (GC/MS). However these test are not done in our lab so I’m not sure how is it done. The lab would usually report positive cases to which ever clinic or hospital that requested for the test. When this preliminary test shows positive result, clinical consideration and judgment from professional are needed in order to make sure that the patient is really having drug abuse.
Sharon
TG01
9 comments:
hi sharon,
i'd like to ask u some questions.
u mentioned about the cassettes for the drug screen test, so there are different cassettes to test for different drugs? inside these cassettes, it contains specific Ab to specific drugs? lastly, cut off concentration as in the conc. that does not cause adverse effects to our body? thanks!
Malerie
TG02
Hello..
For the drug screen test, it can only be performed on urine samples?
The cut off concentration is the maximum concentration of drug to be detected in a normal person? And What is the most common drug that is detected?
THAnks!
Shihui
0607135A
Hi Sharon,
How do u know or assure that the cassette is working properly and produce the correct result?
Hardina =)
Hi Sharon!
My lab also do this test, but we're merely looking only at 7 drugs. So which drug do you normally have positive cases? And what do they indicate?
Leslie
Hi sharon
I would like to ask what is the minumum cut off concentration that would result in a positive result.
And also, how long(hours) until the urine sample is deemed invalid to be tested for such drugs?
Thanks
Johan
TG01
Hi Sharon,
I have some questions to ask:
1)What is the mode of action of OPI, MDMA, THC and MTD?
2)Does the drug bind to its specific Ab via Ag-Ab reaction?
3)What negative impacts can drug abuse bring to the society?
Thankz!
Han Yang
TG01
To Malerie:
Yes there are different cassettes testing for different drug. Some test on all the listed drugs while the others only test out on a few kind of the listed drug. Each drug test in the test device contains monoclonal antibody-coupled particles and corresponding drug-protein conjugates. The cut-off concentration as in the amount not exceeding what the body will usually excrete. If it’s above the cut-off concentration, it shows that the patient it taking too much off that drug which may result in adverse reaction.
To Shihui:
Yup for this cassette it’s only for urine samples. And yes the cut-off concentration is the maximum amount that should be found in normal human urine. So far I’ve not encounter any positive cases before and the staffs told me it’s really rare to have positive result. The most frequent they told me is Opiate.
To Hardina:
Well the cassette has a control line region. If there’s coloured line at the control region, it shows that the cassette is working properly and giving reliable result. If the coloured line fails to appear at the control region, it can also be due to insufficient volume of urine so we will have to repeat the test using a new cassette. If problem persist, that lot/batch must be discontinued and they have to contact the supplier.
To Leslie:
Hmm, I haven encountered any positive cases so far. The staffs told mi that they seldom encounter positive cases too. They told me the most frequent ones is Opiate. If positive cases appears, it shows that the drug concentration in the urine specimen exceeds the cut-off value for that specific drug which indicates that the person is taking too much of that drug or drug abuse.
To Johan:
The cut-off concentration for AMP: 1000ng/mL, BAR: 300ng/mL, BZO: 300ng/mL, COC: 300ng/mL, THC: 50ng/mL, MTD: 300ng/mL, MET: 100ng/mL, MDMA: 500ng/mL, OPI 300: 300ng/mL, OPI 2000: 2000ng/mL, PCP: 25ng/mL, TCA: 1000ng/mL. The urine samples have to be stored at 2-8°C for up to 48hrs prior to testing, if it’s put at room temperature, it cannot be more than 24 hrs.
To Han Yang:
1)OPI: generally acts on opioid receptor found on the central nervous system to help pain relief. MDMA: its mode of action is thought to release neurotransmitter serotonin which can help in treatment of obesity as it can affect one’s appetite and one may sweat more. THC: it acts on cannabinoid receptors found in the brain to give an ecstatic effect. MTD: it helps to relieve long acting pain and it acts like heroin which is a semi-synthetic drug of OPI, it is also use for treatment of opiate dependence.
2)It’s competitive binding so yup it’s Ag-Ab reaction.
3)Well this question….. maybe it will bring up more crime cases as those people need more money to buy those drugs?
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