Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1397 page)

   Collection of sputum induced by inhalation of nebulized hypertonic saline or BAL specimens improve detection of pulmonary TB.

   Twenty-four–hour sputum collections should not be submitted.

   First-morning gastric aspirates may be collected for patients unable to produce sputum, like small children and the frail elderly.

   Up to five, first-morning urine specimens should be submitted for patients with suspected renal TB.

   Lysis–centrifugation, biphasic, and automated mycobacterial culture techniques are optimal for blood and bone marrow specimens submitted for detection of systemic mycobacterial disease.

   Specimens should be transported to the laboratory as soon as possible in sterile containers with tight-fitting lids.

   If same-day AFB stain results are needed, the specimen should arrive in the laboratory early enough in the day to allow enough time for specimen processing (decontamination and concentration) and smear interpretation.

   Specimens for mycobacterial culture should not be collected using swabs.

   Use

   Patients with tuberculosis, and specimens collected from them, are a significant risk for health care–acquired infection. Appropriate safety precautions must be followed through all aspects of TB diagnosis.

   AFB smears should be performed on all specimens submitted for mycobacterial culture. See
ACID-FAST BACILLUS (AFB) SMEAR
.

   Large-volume liquid specimens should be concentrated, usually by centrifugation, and specimens likely to be contaminated by endogenous flora should be decontaminated and concentrated prior to medium inoculation.

   Specimens are inoculated into liquid (e.g., Middlebrook 7H9) media and at least one type of solid media. Special media may be required for fastidious mycobacterial pathogens, like
M
.
haemophilum
, or special incubation temperature for agents causing superficial infection, like
M
.
marinum
.