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Patient Review Highlights
Diagnosis of tuberculosis is based on a combination of clinical features, smear examination of sputum where available, tuberculin skin testing or Mantoux test, chest X-ray and Histopathologic / cytologic examination as appropriate. Common clinical features are weight loss, persistent fever and /or cough of more than 2 weeks duration and history of close contact with another Tuberculosis patient.
Mantoux test also known as Tuberculin skin test is used for the detection of infection by Mycobacterium Tuberculosis bacteria. The test consists of slowly injecting a liquid intradermally (superficially within the layers of the skin) on the forearm, leading to formation of a raised vesicle which should be easily visible to the naked eye. This liquid, used in India, is Tuberculin PPD RT 23 strain. Tuberculin is a glycerol extract of the Tuberculosis bacteria. This is one of the two WHO accepted standard tuberculins, apart from PPD-S. In India, where the prevalence of tuberculosis is high, the recommended dose of this liquid is 0.1 ml of 1 TU (TU stands for tuberculin units) .1 TU is the strength of the liquid mentioned on the vial. This liquid is usually administered by a very tiny syringe, usually of 26 gauge. (Needle diameter).
Please click on the link to watch a video demonstrating how this procedure is performed.
Test principle : The individual who has been infected with Tubercle bacilli responds with a hypersensitivity reaction at the test site in the form of induration. Induration is the palpable raised hardening of the skin, while erythema refers to redness of skin. Only induration is clinically significant and measured after 48 to 72hours following injection. Diameter of the Induration is measured by a scale in millimetres perpendicular to the long axis of the forearm.
Interpretation of the tuberculin test
- Size of induration 15 mm and above : - signifies infection with tubercle bacilli
- Size of induration 10-14 mm : - could be due to infection with tubercle bacilli, BCG induced sensitivity, or due to cross reaction with other environmental mycobacteria.
It is more likely to be attributable to infection with tubercle bacilli in case of history of contact with smear positive case of pulmonary TB, clinically confirmed TB OR X-ray consistent with active TB.
- Size of induration 5 -9 mm: usually non tuberculous in nature generally
- Size of induration <5 mm : indicates absence of any type of mycobacterial infection.
Precautions during this procedure :
- If a raised vesicle does not appear it means that the liquid has been injected too deeply, and the test should be repeated on the other arm. If the same arm is used the injection site should be should be separated at least 5 cm from the first injection site.
- Occasional patients may experience severe allergic reaction to the tuberculin PPD
- Larger the size of the induration, higher the probability of presence of infection with tubercle bacilli.
- Almost all reactions with induration more than 15 mm maybe considered attributable to infection with tubercle bacilli.
- Formation of necrosis (ulcer) at the test site, indicates high degree of tuberculin sensitivity and suggests presence of infection with tubercle bacteria.
- Tuberculin reaction may be suppressed (falsely low) in presence of immunosuppressive states. Like HIV, malnutrition, patient on steroid therapy etc.
- Mantoux test is generally not recommended for infants less than 12 weeks old. If the test turns out to be positive, then it is significant, but if the test is negative, then the test needs to be repeated again.
- The tuberculin test detects only the presence or absence of tuberculosis infection. The presence of infection is not synonymous with disease. It simply means, that even if you have tuberculosis infection in your body, as detected by positive Mantoux test, it does not mean you have active Tuberculosis in your body and require anti tuberculosis drugs in all cases. The clinician will correlate your mantoux test result with other tests ( as mentioned at the top of the blog) to give you a final picture.
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FNAC or FNA stands for fine needle aspiration cytology. This is a simple OPD procedure generally done by pathologists . In this a patient would have a visible swelling or lump. The pathologist will insert a needle in the swelling ,move the needle back and forth, and aspirate ( suck) cells present within the lump. Slides are prepared from these cells aspirated. They then study the cells on a microscope and give a report.
Time required for procedure : few minutes only
Done by : pathologists
Fasting required : not necessary
Any complications of the procedure : usually mild pain for a few minutes, rarely and depending on site of
lump, may experience transient shock, hematoma etc
Report availability : usually by next day .Please check with the doctor performing the procedure.
Special comments :
1. If the swelling is not visible, say it is within the body and detected on scans, then the procedure is done by a Radiologist who localizes the swelling and the pathologist inserts the needle under guidance.
2. Always discuss the report with the pathologist who has done the procedure. Please do not make your own impressions from the report. They may be vastly different from what the pathologist is trying to convey
3. Usually FNAC is diagnostic of parasitic infections .In cases of suspected cancer, report usually says that atypical ( not good looking cells ) present. This needs to be further worked up by biopsy for definite categorization of swelling.
4. Tiny swellings ( usually less than 0.5 cm in diameter ), indiscreet swellings, or swellings that usually cannot be fixed between two fingers generally , should not undergo FNAC procedure - as chances of aspirating cells are pretty low in such cases. So the report would be misleading in most such cases.
I am 15 years old boy. My full body pains a lot. And I asked the doctor to advise something. He said to walk daily. I am doing that but it don't works. I am scared that I am suffering from diabetes because my father is suffering. But doctor negotiate for that. Please suggest something!
In the current season, dengue is not the only cause of decrease in platelet counts. Other causes like malaria, other viral infections, Vitamin B12 and folate defiiency etc can also cause reduction in platelet counts. That said, dengue patients may also clinically present without any decrease in platelet counts.
It is well-known that thrombocytopenia ( reduction in platelet counts) is one of the critical parameters in patient management. Therefore, it is very important that laboratories assess platelet counts with utmost accuracy. The normal range of platelet count in a healthy adult individual is 150000 - 400000/μL. Babies and children have different reference ranges.compared to adults Therefore please check on the lab report for normal age wize reference range. A count of 1.5 lacs would be considered as normal in adults but would qualify as decreased count in a child.
Platelets can be counted either on automated machines( automated method) or on manual blood smear by pathologist.(manual method).
Generally hospitals and laboratories measure platelet counts on automated hematology analyzers- as .these are simple to use and give fast results.However, they suffer from a very big disadvantage. This disadvantage is based on the principle on which these machines work.The machines are programmed in such a manner that any blood particle falling within a predermined size range is counted as platelet and above this range is counted as red cell(RBC – which contains hemoglobin and is responsible for red colour of blood).Although this concept works well in majority of cases, but machine readings are seldom reliable , especially when platelet counts are below 30,000/ cmm. Giant platelets will be counted as RBCs and the machine will give a factitiously low reading of platelets. - Again , if the sample has not been properly mixed at the time of collection, platelets will stick and form clumps. Again the size of these clumps will be more than that of individual platelets and machine will count these as RBCs , thus give a falsely low platelet count. Also, if the sample is collected in a periphery and takes a lot of time to reach the main lab , by this time the platelets would have swelled up due to presence of additives in the blood tube, and not be counted in platelets.but as RBCs instead. (due to size factor)
So what is the solution, ?
All such cases, where platelets are reported low on analyzers, must be screened on peripheral smear by pathologist. Only on looking at the peripheral smear , will the pathologist be able to confirm whether the platelet counts are actually low or not.
Summary : The analyzer is reliable in majority of cases . However, for all cases with low platelets, manual screening by a pathologist is must for confirmation and to avoid unnecessary panic and unrequired platelet transfusions.