Collect
Indicate specimen source: BAL, CSF, Sputum, Sputum (induced), Tissue (specify), Processed Specimen (specify) or Other Body Fluid (specify).
Indicate if patient is a Cystic Fibrosis patient (will require different decontamination), or if sample is environmental (contact laboratory before collection), or veterinary (animal type).
Specimen Preparation
Sputum: >5 mL of unprocessed (raw) sputum. Collect the first early morning expectoration in a sterile 50 mL polypropylene centrifuge tube capable of withstanding 3,000 x g (i.e, Falcon, Greiner, etc).
Processed Sputum: As much processed sputum as possible (450µL needed for test). This is an acceptable specimen type for MTB2.
Body Fluids or Cerebrospinal Fluid (CSF): As much body fluid as possible is aseptically collected by aspiration or during a surgical procedure. CSF should be maximum volume obtained, ideally at least 2 mL.
Gastric Aspirates: Must be neutralized (pH 7) with sodium carbonate if transport time exceeds four hours from collection. Transfer 5-10 mL to a sterile container.
Tissue: =10 g or as much as possible with a biopsy. Transfer to a sterile container (without formalin or preservatives).
Ship the specimen on the day of collection via airmail or by overnight courier.
Urine, Stool, and Blood are not tested with NAAT.
Patient Prep
Patients who are suspected of having pulmonary TB based on clinical evaluation and who have received no antituberculosis therapy, <7 days of such therapy, or have not received such therapy in the last 12 months may be evaluated with NAAT.
Sputum: Three sputum specimens at 8-24 hour intervals and at least one first-morning specimen.Have patient rinse mouth with water before collecting sputum to minimize contaminating specimen with food particles, mouthwash, or oral drugs, which may inhibit the growth of mycobacteria.
Induced sputum: Use sterile hypertonic saline. Avoid sputum contamination with nebulizer reservoir water which may contain saprophytic mycobacteria from tap water. Specify Sputum (Induced) on requisition form, since it may resemble saliva which is not an acceptable specimen.
Bronchoalveolar lavage (BAL): Avoid contaminating bronchoscope with tap water.
Cerebrospinal Fluid (CSF): Use maximum volume attainable, ideally at least 2 mL.
Gastric lavage: Aspiration of swallowed sputum from the stomach by gastric lavage may be necessary for infants, young children, and the obtunded. Fasting, early-morning specimens are recommended in order to obtain sputum swallowed during sleep. Samples of 5 to 10 mLl, adjusted to neutral pH, should be collected on 3 consecutive days.
Unacceptable Conditions
Swabs are not recommended for the isolation of mycobacteria, since they provide limited material. They are acceptable only if a specimen cannot be collected by other means. Negative results obtained from swab specimens are unreliable.
Gastric aspirates that have not been neutralized are not acceptable.
Frozen sputum is not acceptable.
Urine, Stool and Blood are not tested with NAAT.
NAAT cannot performed on grossly bloody specimen.
Specimen that leaked in transit is not acceptable.
Storage Transport Temp
If specimen cannot be mailed on the day of collection, keep the specimen refrigerated until the day of shipment.
Specimen can be shipped at room temperature or cold,using a cool-pack.
Notes
- AFB2 replaces test codes 2a (specimen is known to be NTM), effective February 1, 2013.
- Nucleic Acid Amplifiation Test (NAAT; AFB2) is performed on the first specimen or by request for subsequent specimens. The Centers for Disease Control and Prevention (CDC) recommends that NAAT should be performed on at least one respiratory specimen from each patient with signs and symptoms of pulmonary TB for whom a diagnosis of TB is being considered but has not yet been established, and for whom the test result would alter case management or TB control activities.
- If AFB smear and NAAT are positive, MTB1 (direct 10-drug agar proporation antimicrobial susceptibility testing (AST) and MTB4 (molecular MDR-TB screen) will be performed. In Fall 2012, the Association of State and Territorial Health Officials (ASTHO) recognized the use of a universal laboratory screening test for multidrug-resistant tuberculosis (MDR-TB). Reflex testing is beneficial, as it allows the most rapid detection of a MDR-TB patient.