Test
275 - Mycobacteria DNA by PCR with AFB Culture &
Stain
Method
Polymerase
Chain Reaction (PCR)-Qualitative
Acid Fast Bacilli Culture
Specimen
Requirements
10.0
ml (5.0 ml) Sputum, Ambient or Refrigerated; 1.0 ml (0.5
ml)12B BACTEC, a growth index of >50 is sufficient,
or a small colony from a slant (e.g., Lowenstein-Jensen)
liquid culture; 3.0 ml (1.0 ml) Bronchial Washing, Transtracheal
Aspirates, Bronchoalveolar Lavage, or Bronchial Brushings,
Ambient or Refrigerated; 1.0 ml (0.5 ml) AFB Smear Positive
Specimen, decontaminated concentrate for culture, Ambient
or Refrigerated; 20.0 ml (10.0 ml) Urine, Ambient or Refrigerated;
Fresh Tissue, Refrigerated or Frozen; Stool sample.
Collection
& Transport
Collect
a minimum of 3 early morning sputum or urine samples in
successive 24 hour period, collect in sterile, leak proof
container; ship all respiratory, urine and stool specimens
on cold pack; ship CSF and/or tissue refrigerated or frozen
in Styrofoam cooler; send all specimens to Genetic Assays
within 24 hours of collection.
Causes
for Rejection
Insufficient
volume; stored or shipped at incorrect temperature; swab
specimens are not acceptable; heparin is a known inhibitor
of PCR.
Specimen
Stability
Specimens
are stable at 2-8ºC up to 72 hours after collection
Reference
Range
Not
Detected
Types
of Results
Not
Detected - no mycobacterial species detected. Detected - one or any combination of the mycobacterial
species in the test group was detected. The presence of
a non target species cannot be ruled out. Genus Positive (Positive for a non target species)
- a mycobacterial species that is not in the test group
was detected, (i.e., not M. tuberculosis complex, M. avium
nor M. intracellulare species.
TAT
PCR
24-48 hours , Culture Prelim 21 days, Culture Final 42
days
Relevant
patient information is as follows: · Detection of M. tuberculosis almost
always suggests a disease state, however, detection
of other mycobacteria may not be indicative of disease. · PCR does not differentiate between dead
and live mycobacteria, therefore, a sputum sample from
a patient being treated with antituberculosis drugs
can remain positive for several weeks after initiation
of effective treatment. · False positive PCR results have been
reported in patients with carcinoma. This may be caused
by the release of mycobacterial DNA from tissue destruction. · It has been shown that residual DNA
from dead mycobacterial cells can contaminate sterile
bronchoscopes.
