Tuberculosis other diagnostic studies: Difference between revisions

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==Overview==
==Overview==


Other diagnostic studies that could be performed in a patient with tuberculosis are the Adenosine Deaminase Test and Nucleic Acid Amplification Test(NAAT).
Apart from [[X-rays]], [[Computed tomography|CT scans]], [[MRI]], [[diagnostic studies]] that can be done in patients with [[tuberculosis]]  are the Xpert MTB/RIF test, Adenosine Deaminase Test, and [[Nucleic Acid Amplification Test]] ([[Nucleic acid test|NAAT]]).


<br />
==Other Diagnostic Studies==
==Other Diagnostic Studies==
====Xpert MTB/RIF Test====
*The [[Xpert MTB/RIF]] test is a [[molecular]] [[test]] that is used to detect the [[DNA]] of the tubercule bacillus complex (MTBC) and also the [[genetic mutations]] related to [[Drug resistance|resistance]] to [[rifampin]] in unprocessed [[sputum]] and concentrated [[sputum]] [[sediments]] <ref> {{cite web |url=http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6241a1.htm | title=Availability of an Assay for Detecting Mycobacterium tuberculosis, Including Rifampin-Resistant Strains, and Considerations for Its Use — the United States, 2013}}</ref>
*[[World Health Organization]] ([[World Health Organization|WHO]]) recommends the Xpert MTB/RIF test for the initial diagnosis of [[multi-drug resistance TB]] ([[Multi-drug-resistant tuberculosis|MDR]]-TB) or [[Human Immunodeficiency Virus (HIV)|HIV]] co-infection.<ref name="WHO XPERT"> {{cite web| url=http://who.int/tb/features_archive/factsheet_xpert.pdf| title=WHO Tuberculosis Diagnosis Xpert MTB/RIF Test 2013}} </ref>
*The advantages of this rapid Tuberculosis test are the following:<ref name="WHO XPERT"> {{cite web| url=http://who.int/tb/features_archive/factsheet_xpert.pdf| title=WHO Tuberculosis Diagnosis Xpert MTB/RIF Test 2013}} </ref>
:*Detects [[M. tuberculosis]] and [[rifampicin]] drug resistance simultaneously.
:*Results are available in less than 2 hours so the patient can be treated the same day of the test.
:*The [[bio-safety]] requirements and training are minimal.
:*It can be stored in non-conventional laboratories.
====Adenosine Deaminase====
====Adenosine Deaminase====
It is an additional test in case of suspecting [[Tuberculosis|TB]] in a patient.<ref name="pmid24319523">{{cite journal| author=Farazi A, Moharamkhani A, Sofian M| title=Validity of serum adenosine deaminase in diagnosis of tuberculosis. | journal=Pan Afr Med J | year= 2013 | volume= 15 | issue=  | pages= 133 | pmid=24319523 | doi=10.11604/pamj.2013.15.133.2100 | pmc=PMC3852508 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24319523  }} </ref>


It is usually an auxillary test if tuberculosis is suspected in the patient.<ref name="pmid24319523">{{cite journal| author=Farazi A, Moharamkhani A, Sofian M| title=Validity of serum adenosine deaminase in diagnosis of tuberculosis. | journal=Pan Afr Med J | year= 2013 | volume= 15 | issue=  | pages= 133 | pmid=24319523 | doi=10.11604/pamj.2013.15.133.2100 | pmc=PMC3852508 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24319523  }} </ref> ADA is used for diagnosing Tuberculosis in endemic tuberculosis where TB diagnostic procedures are expensive. ADA isoenzymes are more accurate. For both pleural TB and TB meningitis , ADA has a high degree of sensitivity.
*[[ADA]] is used for [[Tuberculosis|TB]] [[diagnosis]] in endemic regions where [[Tuberculosis|TB]] diagnostic tools are not affordable.
*[[Isoenzymes]] are more accurate.  
*ADA has a high degree of [[Sensitivity (tests)|sensitivity]] for [[Tuberculous meningitis|TB meningitis]] and [[Pleural disease|pleural]] [[Tuberculosis|TB]] .


====Nucleic Acid Amplification Tests (NAAT) <small><small><small> Adapted from CDC <ref name="CDC NAAT"> {{Cite web| url=http://www.cdc.gov/tb/publications/guidelines/amplification_tests/reccomendations.htm| title= CDC Report of an Expert Consultation on the Uses of Nucleic Acid Amplification Tests for the Diagnosis of Tuberculosis}}</ref></small></small></small>====
====Nucleic Acid Amplification Tests (NAAT) <small><small><small> Adapted from CDC <ref name="CDC NAAT"> {{Cite web| url=http://www.cdc.gov/tb/publications/guidelines/amplification_tests/reccomendations.htm| title= CDC Report of an Expert Consultation on the Uses of Nucleic Acid Amplification Tests for the Diagnosis of Tuberculosis}}</ref></small></small></small>====
*This is a heterogeneous group of tests that use [[polymerase chain reaction]] (PCR) to detect mycobacterial nucleic acid.
*These test vary in which nucleic acid sequence they detect and vary in their accuracy.
*The two most common commercially available tests are the amplified [[mycobacterium tuberculosis]] direct test (MTD, Gen-Probe) and Amplicor (Roche Diagnostics).
*The CDC recommends that NAA testing should be performed on a respiratory specimen from each patient with signs and symptoms of active pulmonary TB disease for whom a diagnosis of TB is being considered (i.e., TB suspect), but has not been established.
*NAA testing does not replace the need for AFB smear and culture. All current guidelines and recommendations for culture-based testing should remain in effect, especially recommended turn around times for culture and DST.
*A single positive NAA test result can support the diagnosis of TB in a patient for whom there is a reasonable index of suspicion. This result should trigger reporting to public health officials, initiation of treatment if not already started, and intensified efforts to obtain an isolate for drug susceptibility testing.
*In a patient with little suspicion of having active TB, a single positive NAA test result should be viewed with suspicion (i.e., a possible false-positive result) and interpreted in the same way as a single culture-positive result, i.e., by correlating the results with other diagnostic findings.
*A single negative NAA test result should never be used as a definitive test to exclude TB, especially in suspects with a moderate to high clinical suspicion of TB. Rather, the negative NAA test result should be used as additional information to aid in making clinical decisions to expedite a work-up for an alternative diagnosis or to prevent unnecessary use of TB treatment in suspects with a low clinical suspicion.      .
*The [[FDA]]-approved NAA tests for TB have slightly less sensitivity than culture-isolation methods, and the 15% to 20% of U.S. TB cases that are reported with negative culture results may also have negative NAA test results.  Thus, a negative NAA test result does not exclude the diagnosis of TB.
*Further research is needed before specific recommendations can be made on the use of NAA testing in the diagnosis of TB in children who cannot produce [[sputum]] and in the diagnosis of extrapulmonary TB, although there is much anecdotal evidence of the utility of such testing in individual cases.


====Xpert MTB/RIF Test====
*[[NAAT]] is a group of tests that use [[polymerase chain reaction (PCR)]] to detect a [[Mycobacterium|mycobacterial]] macromolecule.
* The Xpert MTB/RIF test is a molecular test that detects M. tuberculosis and determines rifampin drug resistance. <ref> {{cite web |url=http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6241a1.htm | title=Availability of an Assay for Detecting Mycobacterium tuberculosis, Including Rifampin-Resistant Strains, and Considerations for Its Use — United States, 2013}}</ref>
*These tests are variable regarding the accuracy and which [[macromolecule]] sequence they can detect.
*The two most widely available tests are the amplified tubercle bacillus direct test (MTD, Gen-Probe) and Amplicor (Roche Diagnostics).
*The [[Centers for Disease Control and Prevention|CDC]] recommends that [[NAA testing]] should be performed on a respiratory specimen from each patient with signs and symptoms of active pulmonary TB disease for whom a diagnosis of [[Tuberculosis|TB]] is suspected, but has not been confirmed.
*[[NAA testing]] cannot replace the value for [[AFB stain|AFB]] [[Smear test|smear]] and [[Culture medium|culture]].
*A single positive [[Nucleic acid test|NAA]] test result can support the [[diagnosis]] of [[Tuberculosis|TB]] during a patient for whom there's an inexpensive index of suspicion. This result should trigger reporting to public health officials, initiation of treatment if not already started, and vigorous efforts to get an isolate for [[drug susceptibility testing]].
*In a patient with little suspicion of getting active TB, one positive [[Nucleic acid test|NAA]] test result should be viewed with suspicion (i.e., a possible [[False-positive test result|false-positive]] result) and interpreted within the same way as one [[culture-positive]] result, i.e., by correlating the results with other diagnostic findings.
*A single negative [[NAAT|NAA]] test result should never be used as a specific test to exclude [[Tuberculosis|TB]], especially in suspects with a moderate to high clinical suspicion of [[Tuberculosis|TB]]. However, the negative [[NAAT]] result may be used as additional information to help with making clinical decisions to establish a [[work-up]] for an alternate [[diagnosis]] or to prevent unnecessary use of [[Tuberculosis|TB]] [[medication]] in suspected [[cases]].
*The [[FDA-approved]] [[NAAT]] tests for [[Tuberculosis|TB]] have slightly less [[Sensitivity (tests)|sensitivity]] than [[culture-isolation methods]], and therefore the 15% -20% of U.S. [[Tuberculosis|TB]] cases that are reported with negative culture results can also have negative [[NAAT|NAA]] test results. Thus, a negative [[Nucleic acid test|NAA]] test result doesn't exclude the [[diagnosis]] of [[Tuberculosis|TB]].
*Further research is required before specific recommendations are often made on the utilization of [[NAAT]] testing within the [[diagnosis]] of [[Tuberculosis|TB]] in children who cannot produce [[sputum]] and within the [[diagnosis]] of [[extrapulmonary]] [[Tuberculosis|TB]], although there's much scientific evidence of the utility of such testing in individual cases.


==References==
==References==
{{Reflist|2}}
{{Reflist|2}}
{{WH}}
{{WS}}


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Latest revision as of 01:46, 27 March 2021

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mashal Awais, M.D.[2]; Alejandro Lemor, M.D. [3]

Overview

Apart from X-rays, CT scans, MRI, diagnostic studies that can be done in patients with tuberculosis are the Xpert MTB/RIF test, Adenosine Deaminase Test, and Nucleic Acid Amplification Test (NAAT).


Other Diagnostic Studies

Xpert MTB/RIF Test

  • Detects M. tuberculosis and rifampicin drug resistance simultaneously.
  • Results are available in less than 2 hours so the patient can be treated the same day of the test.
  • The bio-safety requirements and training are minimal.
  • It can be stored in non-conventional laboratories.

Adenosine Deaminase

It is an additional test in case of suspecting TB in a patient.[3]

Nucleic Acid Amplification Tests (NAAT) Adapted from CDC [4]

  • NAAT is a group of tests that use polymerase chain reaction (PCR) to detect a mycobacterial macromolecule.
  • These tests are variable regarding the accuracy and which macromolecule sequence they can detect.
  • The two most widely available tests are the amplified tubercle bacillus direct test (MTD, Gen-Probe) and Amplicor (Roche Diagnostics).
  • The CDC recommends that NAA testing should be performed on a respiratory specimen from each patient with signs and symptoms of active pulmonary TB disease for whom a diagnosis of TB is suspected, but has not been confirmed.
  • NAA testing cannot replace the value for AFB smear and culture.
  • A single positive NAA test result can support the diagnosis of TB during a patient for whom there's an inexpensive index of suspicion. This result should trigger reporting to public health officials, initiation of treatment if not already started, and vigorous efforts to get an isolate for drug susceptibility testing.
  • In a patient with little suspicion of getting active TB, one positive NAA test result should be viewed with suspicion (i.e., a possible false-positive result) and interpreted within the same way as one culture-positive result, i.e., by correlating the results with other diagnostic findings.
  • A single negative NAA test result should never be used as a specific test to exclude TB, especially in suspects with a moderate to high clinical suspicion of TB. However, the negative NAAT result may be used as additional information to help with making clinical decisions to establish a work-up for an alternate diagnosis or to prevent unnecessary use of TB medication in suspected cases.
  • The FDA-approved NAAT tests for TB have slightly less sensitivity than culture-isolation methods, and therefore the 15% -20% of U.S. TB cases that are reported with negative culture results can also have negative NAA test results. Thus, a negative NAA test result doesn't exclude the diagnosis of TB.
  • Further research is required before specific recommendations are often made on the utilization of NAAT testing within the diagnosis of TB in children who cannot produce sputum and within the diagnosis of extrapulmonary TB, although there's much scientific evidence of the utility of such testing in individual cases.

References

  1. ↑ "Availability of an Assay for Detecting Mycobacterium tuberculosis, Including Rifampin-Resistant Strains, and Considerations for Its Use — the United States, 2013".
  2. ↑ 2.0 2.1 "WHO Tuberculosis Diagnosis Xpert MTB/RIF Test 2013" (PDF).
  3. ↑ Farazi A, Moharamkhani A, Sofian M (2013). "Validity of serum adenosine deaminase in diagnosis of tuberculosis". Pan Afr Med J. 15: 133. doi:10.11604/pamj.2013.15.133.2100. PMC 3852508. PMID 24319523.
  4. ↑ "CDC Report of an Expert Consultation on the Uses of Nucleic Acid Amplification Tests for the Diagnosis of Tuberculosis".

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