Diagnostic Method Of Mycobacterium Tuberculosis Assignment

Strategies for Mycobacterium tuberculosis Detection, from Microscopy to Molecular Tests & Interferon-Gamma Release Assay (IGRA)

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Introduction Of Diagnostic Method Of Mycobacterium Tuberculosis Assignment

Tuberculosis (TB) primarily targets the lungs. But it can be seen that other organs of the body are also affected by this infection. Medical history and physical examination are the first steps that are performed in determining the symptoms of TB. The side effects of TB may include steady fever, hack, night sweats, low body weight, and weakness. Various diagnostic tests are performed if TB is suspected. A small quantity of purified protein derivative (PPD) is injected into the skin of the patient to examine the reaction after 48 to 72 hours. The positive confirms that the patient has been exposed to the bacteria. By examining a chest X-ray report, the cavity can be found in the lungs, which is used to diagnose TB. In order to investigate the presence of M. tuberculosis bacteria, mucus from the lungs is collected to make a culture is performed. The main accurate diagnostic test for diagnosing TB is this one. Blood tests can also identify the presence of antibodies to M. tuberculosis. Treatment of TB is performed by various methods of diagnosis. This process is done based on the set of some antibodies and it takes a huge time to produce a fruitful result. The patient’s clinical presentation and the community’s TB prevalence are all important aspects when selecting a diagnostic method. A combination of diagnostic techniques may be required to definitively diagnose TB. Early detection and treatment are necessary to save the patient from life-threatening danger. Otherwise, the condition of the patient will worsen over time.

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Detailed analysis of the methods

A combination of radiological, clinical, microbiological, and immunological tests is required to do the diagnosis process of tuberculosis (TB) (Acharya, et al. 2019). The most prevalent TB diagnostic techniques are listed below.

  • “Tuberculin skin test” (TST) - TST involves infusion of a filtered protein subsidiary (PPD) under the skin of the lower arm and the will be observed the response after 48 to 72 hours. A positive reaction indicates exposure to TB but does not necessarily indicate the activeness of TB (LJ, 2019).
  • “The interferon-gamma release assay” (IGRA)- IGRA is a blood test that searches for the release of interferon-gamma when TB antigens are present in the body. It is less affected by BCG vaccinations and more specific for TST.
  • Chest X-ray: Nodules, infiltrates, and other typical changes associated with TB in the lungs can be observed on a chest X-ray. But, it can not affirm a finding of TB.
  • Sputum smear microscopy: Sputum smear microscopy finds acid-fast bacilli (AFB) in a sample of sputum (Eloi, et al. 2019)). Although this test is simple to perform and relatively inexpensive, its sensitivity for TB detection is low.
  • Culture: The TB bacteria are cultured in the laboratory from a sample of tissue or sputum. It is the accurate process for diagnosing TB but requires half a month time to yield results.
  • Molecular tests - The genetic material of TB bacteria in sputum or tissue samples can be identified by conducting molecular tests like polymerase chain reaction (PCR). They are expensive, have given faster results, and are more sensitive than smear microscopy (Bruneska, et al. 2019).
  • Chest computed tomography (CT) scan: A CT scan can give a detailed picture of the lungs and can show small changes that might not show up on a chest X-ray.
  • Biopsy: In a biopsy, a sample of the affected area’s tissue is examined under a microscope for TB bacteria.

In conclusion, a combined set of radiological imaging, microbiological, clinical examination, and immunological tests is needed for the diagnostic process of TB. In spite of that culture is a good standard, molecular tests can give faster results (Kakhki, et al. 2019). It is necessary to do an early accurate diagnosis for prompt treatment For preventing the spreading of tuberculosis.

Comparison of the methods

The bacteria that causes TB is known as Mycobacterium tuberculosis. The common target of TB is the Lungs. But it can spread and affect other body parts. Each method used for the diagnosis of TB has its own advantages and disadvantages. Sputum samples are examined under a microscope for TB bacteria using this method. In spite of being a simple process to perform and relatively inexpensive, this method shows low sensitivity, mainly when the bacterial load is low. Culture includes developing TB microbes in the laboratory from a sample of tissue or sputum. Although this method is more sensitive, it takes a long time to get results. So, it can cause delays in treatment. It is expensive to process because it requires specialized equipment and trained workers (Li, et al. 2019). Amplification tests using nucleic acids (NAATs) detect hereditary material (DNA or RNA) of TB microorganisms in sputum tests. These tests give results within a few hours. However, they need specialized equipment and are more expensive than sputum smear microscopy. Abnormalities related to TB in the lungs, such as infiltrates or cavities, can be observed on a chest X-ray. A chest X-ray alone cannot detect the infection, but confirm a TB diagnosis. Assays for interferon-gamma release (IGRAs) are blood tests that search for immune responses which is specific to TB in the bloodstream. These tests are more useful to give positive results to persons who have been immunized with the Bacille Calmette-Guérin (BCG) vaccine or who have been already exposed to mycobacteria. On the other side, IGRAs need a blood sample and an expensive process (Luo, et al. 2019). Each TB diagnostic method has advantages and disadvantages. The availability of resources, The patient’s clinical presentation, and the community’s TB prevalence are all important aspects when selecting a diagnostic method. A combination of diagnostic techniques may be required to definitively diagnose TB. [Referred to Appendix 1]

Introduction of a new method

Tuberculosis (TB) is an infection caused by bacteria that can spread all over the body. TB is a serious issue in the world. Now it has become a primary concern in the medical field. Therefore incorporation of innovative strategies are required to handle this situation. The utilization of a blood test defined as the “interferon-gamma release assay” (IGRA) is a new method for diagnosing tuberculosis potentially. This test measures how much interferon-gamma, a protein is mixed with the blood because of the presence of TB microscopic organisms. The traditional skin test of TB, which gives false-positive results in persons who have received the TB vaccine or who have been exposed to other mycobacteria, is less specific than the IGRA (Amegroups.com, 2019).

There are many advantages of using IGRA to diagnose TB (Machado, et al. 2019). It is more convenient than other traditional approaches. It only requires a one-time clinical visit of the patient, whereas the skin test requires various numbers of clinical visits. Second, in comparison to the conventional approach based on bacteria culture, which takes huge time, it gives results more quickly. Third, the IGRA can be utilized in persons who have been vaccinated with the TB antibody, while the skin test is not helpful in this case. [Referred to Appendix 2]

Although, IGRA has shortcomings like any new diagnostic method. It is a very expensive process that cost more than a skin test. It is one of the limitations (Pedreira and Santiago, 2019). It is not as sensitive as the traditional method, especially in case of the persons whose immunity power is weak, which is another limitation of it. Eventually, the IGRA is used with other symptomatic techniques, to guarantee the exact finding of TB. For example, chest X-beams and sputum culture are also done while performing IGRA. In conclusion, using IGRA to diagnose TB has the potential to speed up and increase its accuracy. However, to ensure an accurate diagnosis, it should be used in conjunction with other diagnostic methods, particularly in patients with compromised immune systems.

diagnostic tools for TB

Figure 1: Various diagnostic tools for TB point-of-care testing.

(Source: Self-Created in MS Word)

Various types of disorders

There is various type of TB can be seen in a section of society. The most common cause of TB is aspiratory TB. However, there are other types of TB that can affect the health of the patient. Those are-

  • TB outside of the lungs: This is a type of condition of TB that occurs beyond the lungs, in different parts of the body. The body parts that are affected by this type of are reproductive organs, bones, joints, kidneys, or lymph nodes.
  • Miliary TB: This is a rare form of tuberculosis. When the bacteria spread throughout the body and cause small organ lesions, this type of TB takes place. It is also cause serious condition for the patient (Rasool, et al. 2019).
  • Dormant TB: When the person does not have the active condition of TB this type of TB occurs. In this situation, the microorganisms are torpid. No side effects can be seen in this case.
  • HIV-related TB: This is TB that HIV-positive individuals develop (Wang, et al. 2019). HIV-positive individuals are more likely to develop severe forms of TB and have a higher risk of developing it.

The part of the body that is affected, the severity of the disease, and other factors like whether the individual has a weakened immune system or has been exposed to drug-resistant TB will all play a role in determining the type of TB they have (Rizi, et al. 2019). Sometimes it can be seen that bacteria get resistant to the antibiotics that are used to treat TB


From the above discussion, it can be concluded that “The microscopic organisms that cause tuberculosis” (TB), Mycobacterium tuberculosis, can be identified using a few symptomatic methods. There are two broad categories that can be used to organize these methods: strategies with and without a research facility. This involves searching sputum or other body fluids with a microscope for “acid-fast bacilli” (AFB), which are typical of mycobacteria. This method lacks sensitivity despite its speed and simplicity. To decide the presence of the microorganisms, this includes developing it for quite a long time in a particular medium. Culture is the most reliable method for diagnosing tuberculosis, but it requires specialized tools and trained personnel. These molecular tests can be used to check for tuberculosis “DNA or RNA” in sputum or other samples. Each method used for the diagnosis of TB has its own advantages and disadvantages. Sputum samples are examined under a microscope for TB bacteria using this method. In spite of being a simple process to perform and relatively inexpensive, this method shows low sensitivity, mainly when the bacterial load is low. Culture includes developing TB microbes in the laboratory from a sample of tissue or sputum. Although this method is more sensitive, it takes a long time to get results. There are many advantages of using IGRA to diagnose TB. It is more convenient than other traditional approaches.

Reference list


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Acharya, B., Acharya, A., Gautam, S., Ghimire, S.P., Mishra, G., Parajuli, N. and Sapkota, B., 2020. Advances in diagnosis of Tuberculosis: an update into molecular diagnosis of Mycobacterium tuberculosis. Molecular biology reports, 47, pp.4065-4075.

Eloi, P., Nascimento, G.A., Córdula, C., Visani, V., Castelletti, H., Bezerra, G., Soares, L., Lima, B., Bruneska, D., Montenegro, L.M.L. and Schindler, H.C., 2020. Toward a point-of-care diagnostic for specific detection of Mycobacterium tuberculosis from sputum samples. Tuberculosis, 121, p.101919.

Kakhki, R.K., Neshani, A., Sankian, M., Ghazvini, K., Hooshyar, A. and Sayadi, M., 2019. The short-chain dehydrogenases/reductases (SDR) gene: a new specific target for rapid detection of Mycobacterium tuberculosis complex by modified comparative genomic analysis. Infection, Genetics and Evolution, 70, pp.158-164.

Li, X., Du, W., Wang, Y., Liu, Z., Li, K., Chen, H., Liu, R., Ma, L., Zhang, L., Dong, Y. and Che, N., 2020. Rapid diagnosis of tuberculosis meningitis by detecting Mycobacterium tuberculosis cell-free DNA in cerebrospinal fluid. American Journal of Clinical Pathology, 153(1), pp.126-130.

Luo, J., Luo, M., Li, J., Yu, J., Yang, H., Yi, X., Chen, Y. and Wei, H., 2019. Rapid direct drug susceptibility testing of Mycobacterium tuberculosis based on culture droplet digital polymerase chain reaction. The International Journal of Tuberculosis and Lung Disease, 23(2), pp.219-225.

Machado, D., Couto, I. and Viveiros, M., 2019. Advances in the molecular diagnosis of tuberculosis: from probes to genomes. Infection, Genetics and Evolution, 72, pp.93-112.

Pedreira, A.L.S. and Santiago, M.B., 2020. Association between Takayasu arteritis and latent or active Mycobacterium tuberculosis infection: a systematic review. Clinical rheumatology, 39(4), pp.1019-1026.

Rasool, G., Khan, A.M., Mohy-Ud-Din, R. and Riaz, M., 2019. Detection of Mycobacterium tuberculosis in AFB smear-negative sputum specimens through MTB culture and GeneXpert® MTB/RIF assay. International journal of immunopathology and pharmacology, 33, p.2058738419827174.

Rizi, K.S., Hatamluyi, B., Rezayi, M., Meshkat, Z., Sankian, M., Ghazvini, K., Farsiani, H. and Aryan, E., 2021. Response surface methodology optimized electrochemical DNA biosensor based on HAPNPTs/PPY/MWCNTs nanocomposite for detecting Mycobacterium tuberculosis. Talanta, 226, p.122099.


Wang, W.H., 2020. A novel, rapid (within hours) culture-free diagnostic method for detecting live Mycobacterium tuberculosis with high sensitivity. EBio Medicine, 60, p.103007. Accessed from: https://www.us.elsevierhealth.com/diagnostic-pathology-lymph-nodes-and-extranodal-lymphomas-9780323847582.html [Accessed on: 2-4-2023]


Amegroups.com, 2019, Primary extranodal B-cell lymphoma: current concepts and treatment strategies. Accessed from: https://cco.amegroups.com/article/view/5458/6753 [Accessed on: 2-4-2023]

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