M. tuberculosis complex DNA Detection

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General Information

Lab Name
M. tuberculosis complex DNA Detection
Lab Code
Epic Ordering
M. tuberculosis complex DNA Detection

Detection of Mycobacterium tuberculosis complex DNA.

Although an acid fast smear (AF smear) can provide an important clue to the nature of the causative agent for a patient's disease, a positive result does not necessarily indicate the presence of Mycobcaterium tuberculosis complex (MTBC). The presence of AF Bacillis (AFBs) in clinical specimens can be simply due to the growth of common water contaminants such as M. chelonae and M. fortuitum. On the other hand, a negative smear result also does not rule out the presence of M. tuberculosis complex at low pathogen load. Recent developments in PCR based amplification and detection of organism specific DNA offers an alternative that can be more specific and sensitive than a smear test.

For an accurate detection of the presence of MTBC in clinical specimens, the UWMC Molecular Diagnosis Section utilizes a nested PCR protocol that targets heat shock protein 65 gene (hsp65). Utilization of species-specific fluorescent probes on a real-time PCR platform facilitates rapid and highly sensitive detection of M. tuberculosis complex-specific DNA in clinical specimens.

In many specimens acid fast bacilli can be seen microscopy of tissue sections but are very difficult to grow due to their fastidious nature, or are not viable as a result of antimicrobial therapy. Some specimens may never reveal the presence of a pathogen because of low abundance and/or lack of viability. The use of PCR to detect this DNA extracted directly from clinical specimens facilitates the identification of these pathogens.

For more information on this test, to download a requisition form, and for a list of acceptable and unacceptable specimens, please refer to: Molecular Diagnosis Microbiology Section Website

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DNA extraction, nucleic acid purification, polymerase chain reaction (PCR), sequencing

Reference Range
See individual components

Ordering & Collection

Specimen Type
Tissue (Fresh frozen or paraffin-embedded), Fluid (see Acceptable Specimens for details)

Acceptable specimens are listed below. Please see this page for complete specimen collection and handling instructions.

When possible, a mycobacterial culture is recommended regardless of the molecular test result to aid in clinical diagnosis.

Specimens should be collected into a DNA free container labeled with at least two identifiers.

Acceptable Specimens

  • Fresh frozen tissue
  • Fresh frozen fluid: any body fluid is acceptable if it is not listed under Unacceptable Specimens. See common examples below.
  • Formalin Fixed Paraffin-embedded tissues (FFPE, PET): blocks, scrolls, and unstained slides are acceptable
  • eSwabs and UTM (universal transport media)
  • Sodium polyanethol sulfonate (SPS, Wampole Isolator Tubes) acceptable with disclaimer

Common acceptable body fluid examples: cerebrospinal fluid, pleural fluid, pericardial fluid, urine, bronchial lavage, joint fluid, bone marrow, vitreous fluid, etc.

Additional Acceptable Specimens

  • Sputum

Unacceptable Specimens

  • Blood, serum, plasma, stool
  • No citrated or heparinized solutions
  • Tissues floating in formalin
  • Swab/fluid collected in tube containing agar
Handling Instructions

Fresh frozen tissue/fluid specimens should be submitted and maintained on dry ice.

Formalin Fixed Paraffin-embedded tissues (FFPE, PET) can be sent ambient or with ice packs during warmer summer months to prevent melting.

Optimal Quantity:

  • Fresh Tissue: 0.3-1.0 cm^3
  • Fluid: 0.2-1 mL
  • Formalin Fixed Paraffin-embedded Tissue (FFPE/PET): blocks are preferred and will be sent back to client upon completion of testing
  • Scrolls/unstained slides: cross-sectional area >1cm^2 send 10 sections of 10µm thickness, if <1cm^2 send 20 sections if available

Please note: We do not need a separate specimen aliquot for each test ordered. Only a single specimen aliquot or block of optimal quantity is necessary for performing multiple tests. If multiple aliquots or blocks of optimal quantity are sent, up to 2 will be pooled.

requested: See Optimal Quantity above
minimum: Diagnostic yield generally proportional to specimen size.



UWMC/HMC – store and send specimen refrigerated and freeze specimens at -20°C upon arrival in UW-ML Microbiology. If specimen storage and transport will exceed 8 hours, freeze at -20°C.

Freeze specimens at -20°C upon arrival

Outside Laboratories: Freeze specimens in sterile containers at -20°C. Transport all specimens on dry ice.


LIS Dept Code
Micro Molecular Diag (MMD)
Performing Location(s)
UW-MT Microbiology, Molecular Diagnostics

Clinical Lab, Room # NW177,
University of Washington Medical Center,
1959 NE Pacific street, Seattle, WA 98195

Fresh frozen tissues/fluids result in 2-3 business days after receipt of specimen. Formalin Fixed Paraffin-embedded tissues result in 3-4 business days after receipt of specimen.
Available STAT?

Billing & Coding

CPT codes
Interfaced Order Code