Hi everybody. This week's my turn again to share what I've learnt with you'll.
Occult Blood Test(Blood in the stools)
Clinical Interpretation
Fecal occult blood test is performed as part of routine physical examination during examination of the rectum and it is a screening tool for colorectal cancer. Blood in the stools could indicate gastrointestinal diseases such as inflammatory bowel disease, gastric ulcers, etc.
Materials needed
-Test card(contains guaiac)
-Developing solution(contains hydrogen peroxide and denatured ethyl alsohol)
-Wooden applicator sticks
Test Principle
The test is based on the oxidation of guaiac by hydrogen peroxide to a blue compound. The heme portion of hemoglobin that is present in the stool will catalyse the oxidation of alpha-guaiaconic acid to form a blue colouration.
A small fecal sample is collected and a thin smear is applied on the test card using wooden applicatior sticks. The cover flap is closed and we have to wait for 2-3 mins for the stool to be absorbed into the test paper. The back of the test card is opened and a drop of the developer is added to the the guaiac paper directly over the smear and both positive and negative controls. Results are read after 1 minute and a blue colouration is indicative of occult blood. A brown colouration indicates negative results.
Patients should avoid red meat and NSAIDs as these substances can cause false positive results. Occult blood test must be done with screening endoscopy to detect colorectal cancer as a negative result for OB does not guarantee that a patient does not have colorectal cancer.
Enjoy reading!
Cheong Shu Hui
TG02
Saturday, September 29, 2007
Monday, September 24, 2007
Haematology-ESR ( Sasi's)
Hi! Sasi here! Its my turn to blog! So, here I go....
Recently I have been attached to the Haematology department.
In this blog, I would like to highligh one test I frequently was assigned to do besides ABO blood grouping and FBC (which has been previously elaborated by Lizzie). The test would be ESR.
ESR stands for Erythrocyte Sedimentation rate. The rate at which the red blood cells falls is measured and reported in mm/h. It is an easy, cheap, non specific test that has been used for years to help diagnose conditions associated with acute and chronice inflammation including infections, cancers and auto immune diseases. According to a senior at work, I learnt that ESR is said to be non specific because increases in the rate do not tell exactly where the inflammation is in the body or what is causing it. For this reason, ESR is typically used in conjunction with other tests like Full Blood Count, Anitinuclear antibody etc to aid in the diagnosing aspect. ESR is particularly useful in diagnosing two specific inflammatory diseases, Temporal arteritis and Polymyalia Rheumatica. A high ESR is one of the main test results use to support the diagnosis. ESR is also used to monitor disease activivity and response to therapy in both of these diseases.
In our haematology lab, once the EDTA bloody tubes arrive,they are run in the FBC analyzers first. After FBC is run, ESR is run. ESR is given the very next priority as it has to be ensured that the blood volume is sufficient for the test. (Hence, that is why ABO is done last). After preparing the worklist for the ESR test, I had to alliguot the blood into the small tubes provided by the ESR commercial kit, mix it well with the anticoagulant in the tubes and make sure the sample is homogenous. Long pipettes are provided in the kit. These pipettes are thrusted into the tubes and I have to make sure the blood level reaches the brim of the pipette. Once the tubes are fit into the automated readers, it would take approximately 40 mins for the readings to be out.
When an inflammatory process is present, the high proportion of fibronogen in the blood causes red blood cells to stick to each other. The red cells form stacks called 'rouleaux' which settle faster. The height of the remaining plasma is read.
Samples with results more than 50 have to be rerun.The reference range applies as follows:
(ESR 95% limits) (Adults)
Age (years) 20 55 90
Men 12 14 19
Women 18 21 23
A low ESR is seen with polycythemia which is the condition where a patient makes too many red blood cells or with extreme leokocytosis where the patient has too many white blood cells or with protein abnormalities. Some changes in red cell shape such as sickle cells in sickle cell anemia aso lowers the ESR.
That marks the end of my blog. Feel free to drop ya questions if any :) Take care!
Sasi
Tgo2
0503804g
Recently I have been attached to the Haematology department.
In this blog, I would like to highligh one test I frequently was assigned to do besides ABO blood grouping and FBC (which has been previously elaborated by Lizzie). The test would be ESR.
ESR stands for Erythrocyte Sedimentation rate. The rate at which the red blood cells falls is measured and reported in mm/h. It is an easy, cheap, non specific test that has been used for years to help diagnose conditions associated with acute and chronice inflammation including infections, cancers and auto immune diseases. According to a senior at work, I learnt that ESR is said to be non specific because increases in the rate do not tell exactly where the inflammation is in the body or what is causing it. For this reason, ESR is typically used in conjunction with other tests like Full Blood Count, Anitinuclear antibody etc to aid in the diagnosing aspect. ESR is particularly useful in diagnosing two specific inflammatory diseases, Temporal arteritis and Polymyalia Rheumatica. A high ESR is one of the main test results use to support the diagnosis. ESR is also used to monitor disease activivity and response to therapy in both of these diseases.
In our haematology lab, once the EDTA bloody tubes arrive,they are run in the FBC analyzers first. After FBC is run, ESR is run. ESR is given the very next priority as it has to be ensured that the blood volume is sufficient for the test. (Hence, that is why ABO is done last). After preparing the worklist for the ESR test, I had to alliguot the blood into the small tubes provided by the ESR commercial kit, mix it well with the anticoagulant in the tubes and make sure the sample is homogenous. Long pipettes are provided in the kit. These pipettes are thrusted into the tubes and I have to make sure the blood level reaches the brim of the pipette. Once the tubes are fit into the automated readers, it would take approximately 40 mins for the readings to be out.
When an inflammatory process is present, the high proportion of fibronogen in the blood causes red blood cells to stick to each other. The red cells form stacks called 'rouleaux' which settle faster. The height of the remaining plasma is read.
Samples with results more than 50 have to be rerun.The reference range applies as follows:
(ESR 95% limits) (Adults)
Age (years) 20 55 90
Men 12 14 19
Women 18 21 23
Children
Newborn: 0 to 2 mm/hr.
Neonatal to puberty: 3 to 13 mm/hr.
Newborn: 0-5 mm/hr.
Neonatal to puberty: 0-15 mm/hr.
A very high ESR may occur due to a marked increase in globulins, that can be due to a severe infection. The doctor would then order for other follow-up tests like cultures depending on the patient's symptoms.
A low ESR is seen with polycythemia which is the condition where a patient makes too many red blood cells or with extreme leokocytosis where the patient has too many white blood cells or with protein abnormalities. Some changes in red cell shape such as sickle cells in sickle cell anemia aso lowers the ESR.
That marks the end of my blog. Feel free to drop ya questions if any :) Take care!
Sasi
Tgo2
0503804g
Saturday, September 22, 2007
Answers to ur questions!!!
Dear all, thanks for reading my post and I can see that most of you are very curious about why the patient has to lie down on the left side and not the right side after consuming the tablet. Well, the answer is actually shown in the second picture which I have posted. If you have noticed, you will realise that the human stomach has a larger surface area on the left side or you can say that the stomach is tilted to the left. Therefore, when the patient lie on the left side after consumption of the tablet, it allows the tablet to be in contact with a larger surface area of the stomach, thus more H. pylori (if present in the patient) can act on the tablet effectively and results will be more accurate too.
The reason why the patient has to be seated after lying down is to allow the labelled carbon dioxide (produced as a result of the presence of H. pylori) to move up to the lungs for breathing out into the bag. (answered gail, shu hui and vino)
Is there anything in the bag and how the breath bag is sent to the lab? Will results be inaccurate if the breath bag is exposed to the surrounding air?
The breath bag is a sterile bag which contain no anticoagulant. There is no special procedure that must be followed during the sending of bag to the lab. Once patient breathes out into the bag, it must be capped immediately. Of course results will be inaccurate if the patient does not capped the bags properly, therefore the bags will be sealed in another big plastic bag when sent to the lab. As this test is usually conducted in the hospital, the breath bag will be sent immediately up to the lab for processing. The processing and sample handling part is less complicated. However, the med techs do act fast when they are processing the samples. For example, when they remove cap on the breath bag, they will quickly fit the mouth of the breath bag to the machine. In another words, they will try to lessen the exposure of the breath inside the bag to the surrounding air .The tedious part will have to be sample collection. (answered ci liang, martin and liu qian)
Why patient cannot chew the tablet?
Because chewing may reduce the actual amount of the tablet that goes into the stomach and results can be inaccurate. Patient's result may be negative when actually very little tablet is present in the stomach, more of it is remained on the patient's teeth. (answered Kangting)
Why not do a culture for the detection of the microorganism?
This is a good question. Yes, biopsy check during endoscopy with a rapid urease test, histological examination and microbial culture are much better and relaible choice for the detection of the microorganism. In fact, histological examination is the gold standard for the detection of H. pylori. But seriously thinking, all the above three methods are evasive. Let's say if a patient is under treatment and doctor want to see the effectiveness of the treatment, do you think the patient will like it if he has to do endoscopy every now and then. It will be uncomfortable to the patient. Therefore, with UBT, patient's treatment progress can be updated and he does not have to undergo any evasive procedure.
This is also the advantage of UBT. UBT is the gold standard for the determination of treatment process. (answered jia hao)
Additional info:
Disadvantage of UBT is that it is subjected to non-conformance by patient as there are many instructions that must be followed before taking the test.
They are:
Sally
The reason why the patient has to be seated after lying down is to allow the labelled carbon dioxide (produced as a result of the presence of H. pylori) to move up to the lungs for breathing out into the bag. (answered gail, shu hui and vino)
Is there anything in the bag and how the breath bag is sent to the lab? Will results be inaccurate if the breath bag is exposed to the surrounding air?
The breath bag is a sterile bag which contain no anticoagulant. There is no special procedure that must be followed during the sending of bag to the lab. Once patient breathes out into the bag, it must be capped immediately. Of course results will be inaccurate if the patient does not capped the bags properly, therefore the bags will be sealed in another big plastic bag when sent to the lab. As this test is usually conducted in the hospital, the breath bag will be sent immediately up to the lab for processing. The processing and sample handling part is less complicated. However, the med techs do act fast when they are processing the samples. For example, when they remove cap on the breath bag, they will quickly fit the mouth of the breath bag to the machine. In another words, they will try to lessen the exposure of the breath inside the bag to the surrounding air .The tedious part will have to be sample collection. (answered ci liang, martin and liu qian)
Why patient cannot chew the tablet?
Because chewing may reduce the actual amount of the tablet that goes into the stomach and results can be inaccurate. Patient's result may be negative when actually very little tablet is present in the stomach, more of it is remained on the patient's teeth. (answered Kangting)
Why not do a culture for the detection of the microorganism?
This is a good question. Yes, biopsy check during endoscopy with a rapid urease test, histological examination and microbial culture are much better and relaible choice for the detection of the microorganism. In fact, histological examination is the gold standard for the detection of H. pylori. But seriously thinking, all the above three methods are evasive. Let's say if a patient is under treatment and doctor want to see the effectiveness of the treatment, do you think the patient will like it if he has to do endoscopy every now and then. It will be uncomfortable to the patient. Therefore, with UBT, patient's treatment progress can be updated and he does not have to undergo any evasive procedure.
This is also the advantage of UBT. UBT is the gold standard for the determination of treatment process. (answered jia hao)
Additional info:
Disadvantage of UBT is that it is subjected to non-conformance by patient as there are many instructions that must be followed before taking the test.
They are:
- Fast for 8-9 hrs before test because food can interfere with results
- Stop taking Proton Pump Inhibitors (PPI) eg. omeprazole, lansoprazole one week before the test because they are acid-reducing medication which can cause the stomach condition to become less acidic. This is no good for the thriving of H. pylori. Helicobacter spp. are the only known microorganisms that can thrive in the highly acidic environment of the stomach.
- Stop taking antibiotics eg amoxicillin, tetracycline 4 weeks before test. This test measures active H. pylori infection. If antibiotics are suppressing the amount of H. pylori present in the stomach, results will not be accurate too.
Sally
Saturday, September 15, 2007
Biochemistry/ Immunology
Hello to all of you. For this week, I shall talk about a very special test called the Urea Breath Test (UBT). Firstly, we have to know that this is not a commonly requested test. It is unique in the sense that detection of an illness can be done using the patient's breath sample instead of common samples like blood or urine.
Purpose of UBT
To identify infections by Helicobacter pylori, a spiral bacterium implicated in gastritis, gastric ulcer, and peptic ulcer disease.
Helicobacter pylori is a helical shaped, gram-negative bacterium. It infects various area of stomach and duodenum. Its helical shape is thought to have evolved to penetrate and favour its motility in the mucus gel layer.
During the resting period after taking of the tablet, the bacterium (if present in the stomach) will metabolize the labelled urea and produce labelled carbon dioxide that can be detected in the breath. Detection of isotope-labelled CO2 in exhaled breath indicates that urea in the breath is split. This also means that urease (enzyme used by H. pylori to metabolize urea) is present in the stomach, hence the bacteria are present. Refer to top.
Interpretation of results
That's all.
Purpose of UBT
To identify infections by Helicobacter pylori, a spiral bacterium implicated in gastritis, gastric ulcer, and peptic ulcer disease.
Helicobacter pylori is a helical shaped, gram-negative bacterium. It infects various area of stomach and duodenum. Its helical shape is thought to have evolved to penetrate and favour its motility in the mucus gel layer.
Helicobacter pylori
Principle of UBT
Patient will swallow urea labelled with an uncommon isotope, either radioactive carbon-14 or non-radioactive carbon-13. For the two different forms of urea, different instrumentation is required; carbon-14 is normally measured by scintillation, whereas carbon-13 by isotope ratio mass spectrometry (IRMS). For carbon-13, a baseline sample is taken before taking the urea tablet and used to compare with the post urea sample. In this case, my lab uses the carbon-13 method and so 2 samples are collected from each patient.
UBIT-IR300 is an infrared spectral analyzer that measures the change in the carbon isotope (13CO2/12CO2) in carbon dioxide in breath air gas.
During the resting period after taking of the tablet, the bacterium (if present in the stomach) will metabolize the labelled urea and produce labelled carbon dioxide that can be detected in the breath. Detection of isotope-labelled CO2 in exhaled breath indicates that urea in the breath is split. This also means that urease (enzyme used by H. pylori to metabolize urea) is present in the stomach, hence the bacteria are present. Refer to top.
Procedure of test
- Patient has to breathe into the first sample bag (before taking the UBIT tablet). This bag will be labelled as 'Baseline'.
- Immediately (within 5 secs), swallow one UBIT tablet on an empty stomach with 100 ml of water. Do not chew, crush or dissolve the tablet.
- After taking the UBIT tablet, lie down on your left side for 5 min.
- Remain seated for a further 15 min.
- 20 min after taking the UBIT tablet, collect breath again using the 2nd sample bag which will be labelled as 'Sample'. The two sample bags will be analysed uisng the machine UBIT-IR300.
Interpretation of results
This is also the reason why a 'pre' and 'post' breath are collected from the patient so that the difference between the pre and post urea measurements can be compared to a cut-off value. Results below the value are assumed to be negative, those above is positive.
That's all.
Sally
0503315D
Sunday, September 9, 2007
Hematology
It’s my turn to blog again. This week I was attached to hematology. Our lab use ruby to do the full blood count and retic count and D10for beta-thalassemia. There is a test we never learned in the school before is D- dimmer. I want to share with you here.
D-DIMER
D-dimer is a blood test to diagnose thrombosis. A negative result can rules out thrombosis, a positive result can indicate thrombosis but can not rule out other potential etiologies. It is to exclude thromboembolic disease where the probability is low.
Principle
D-dimers are unique in that they are the breakdown products of a fibrin mesh that has been stabilized by Factor XIII. This is the final step in the generation of a thrombus. D-dimer assays rely on monoclonal antibodies to bind to this specific protein fragment.
Types of assays
l ELISA
l Latex turbidimetric assay (automated immunoassay)
l Enhanced microlatex
l Latex-enhanced photometric
Reference range
Values exceeding 250, 300 or 500 ng/ml (different for various kits) are considered positive.
Next I want to share some information about beta-thalassemia.
There are two forms of beta thalassemia. They are thalassemia minor and thalassemia major.
Thalassemia minor: The individual with thalassemia minor has only one copy of the beta thalassemia gene (together with one perfectly normal beta-chain gene). This situation can very closely with mild iron-deficiency anemia. However, persons with thalassemia minor have a normal blood iron level. No treatment is necessary for thalassemia minor.
Thalassemia major: The child born with thalassemia major has two genes for beta thalassemia and no normal beta-chain gene. This causes a striking deficiency in beta chain production and in the production of Hb A. Thalassemia major is, therefore, a serious disease.
At birth the baby with thalassemia major seems entirely normal. This is because the mosyt of the hemoglobin at birth is still fetal hemoglobin (Hb F). Hb F has two alpha chains (like Hb A) and two gamma chains (unlike Hb A). It has no beta chains so the baby is protected at birth from the effects of thalassemia major.
Ok that is all. Every thing in the lab looks really very easy as loading and unloading the sample from the machine. So I go and find some more information about the test. I hope it is helpful!!!
Enjoy reading^_^
D-DIMER
D-dimer is a blood test to diagnose thrombosis. A negative result can rules out thrombosis, a positive result can indicate thrombosis but can not rule out other potential etiologies. It is to exclude thromboembolic disease where the probability is low.
Principle
D-dimers are unique in that they are the breakdown products of a fibrin mesh that has been stabilized by Factor XIII. This is the final step in the generation of a thrombus. D-dimer assays rely on monoclonal antibodies to bind to this specific protein fragment.
Types of assays
l ELISA
l Latex turbidimetric assay (automated immunoassay)
l Enhanced microlatex
l Latex-enhanced photometric
Reference range
Values exceeding 250, 300 or 500 ng/ml (different for various kits) are considered positive.
Next I want to share some information about beta-thalassemia.
There are two forms of beta thalassemia. They are thalassemia minor and thalassemia major.
Thalassemia minor: The individual with thalassemia minor has only one copy of the beta thalassemia gene (together with one perfectly normal beta-chain gene). This situation can very closely with mild iron-deficiency anemia. However, persons with thalassemia minor have a normal blood iron level. No treatment is necessary for thalassemia minor.
Thalassemia major: The child born with thalassemia major has two genes for beta thalassemia and no normal beta-chain gene. This causes a striking deficiency in beta chain production and in the production of Hb A. Thalassemia major is, therefore, a serious disease.
At birth the baby with thalassemia major seems entirely normal. This is because the mosyt of the hemoglobin at birth is still fetal hemoglobin (Hb F). Hb F has two alpha chains (like Hb A) and two gamma chains (unlike Hb A). It has no beta chains so the baby is protected at birth from the effects of thalassemia major.
Ok that is all. Every thing in the lab looks really very easy as loading and unloading the sample from the machine. So I go and find some more information about the test. I hope it is helpful!!!
Enjoy reading^_^
Thursday, September 6, 2007
SIP
Helloo everyone! I'm here to answer Ms Chew's question for me..
Sigificance of Nitrite dipstick test in Urine FEME
The presence of nitrite in the urine indirectly indicates that there is nitrite-releasing bacteria present. This test depends on the conversion of nitrate to nitrite by nitrate reductase, an enzyme usually produced by gram-negative bacteria. A positive nitrite test is shown by a pink colouration in the nitrite test region on the test strip, indicating bacterial infection. Not all kinds of bacteria releases nitrite. However, if bacteriuria is significant but WBCs are absent when viewed microscopically, the bacteria formed may be due to contamination because of wrong collection or handling method. Hence, bacteria should not be reported.
That's all folks!
Cheong Shu Hui
TG02
Sigificance of Nitrite dipstick test in Urine FEME
The presence of nitrite in the urine indirectly indicates that there is nitrite-releasing bacteria present. This test depends on the conversion of nitrate to nitrite by nitrate reductase, an enzyme usually produced by gram-negative bacteria. A positive nitrite test is shown by a pink colouration in the nitrite test region on the test strip, indicating bacterial infection. Not all kinds of bacteria releases nitrite. However, if bacteriuria is significant but WBCs are absent when viewed microscopically, the bacteria formed may be due to contamination because of wrong collection or handling method. Hence, bacteria should not be reported.
That's all folks!
Cheong Shu Hui
TG02
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