Specimen Requirements

Because of irregular release of AFB from subepithelial foci of tuberculosis, the recovery of acid-fast bacteria from specimens may vary from day to day.  For this reason, a minimum of three first morning specimens should be collected from patients suspected of having either pulmonary or renal tuberculosis.  All Specimen must be properly labeled with the type of specimen, the date of collection and the patient's first and last name.

Sputum:  Collect three to five early morning samples from deep in the lungs.  Saliva, nasopharyngeal secretions, or other extraneous materials are refused.  Between 5-10ml of sputum is collected in a sterile, wide-mouthed container with a leak-proof screw cap lid.  Up to 40ml of bronchial washings may be submitted.

Urine:  Urine collected surgically or by suprapubic aspiration may be assumed to be sterile and processed as for other body fluids.  For routine AFB studies, a series of entire early morning voiding (clean catch) is recommended for three consecutive days.  The early morning voiding is collected in a sterile container large enough to hold the entire voiding.  Catheterized urine specimens are not recommended unless it is not possible to get a voided specimen.  Catheterized specimens, when necessary, are collected by clamping off the tubing and all urine is collected from the tubing for three hours.  Twenty-four hour specimens are not satisfactory because urine may be toxic to acid fast organisms, the specimen is not as concentrated as a first morning voided specimen, and is more likely to be contaminated.

Body fluids and tissue:  Specimens of CSF and other body fluids, pus, joint fluid, tissues, and autopsy material are collected by the physician when mycobacterial infection is suspected.  These specimens may be refrigerated but should be set up as soon as possible.  Up to 50ml of fluid may be submitted.

Wound, laryngeal swabs, etc.: Swabs are not recommended for AFB culture because the amount of material is limited and the hydrophobicity of the organisms inhibits transfer onto solid or broth media.

Blood:  10ml of blood is drawn into Isolator 10 or transport tube containing SPS or heparin.  Only one specimen is needed, but a volume of at least 5ml is required.  Mix the tube immediately to prevent clots.  The specimen should be kept at room temperature before shipping.

Bone Marrow:  The specimen is placed into a tube containing SPS (transport tube or Isolator 1.5) during the procedure.  Smears are made during the procedure or from the specimen tube.  The specimen should be kept at room temperature before shipping.

Gastric contents:  Gastric contents may be submitted for culture if the patient is unable to raise a sufficient amount of sputum (e.g., esp. comatose patients, or young children).  A series of specimens is collected over three consecutive days.  Specimens are collected early in the morning from fasting patients, at least 8 hours after eating or drug therapy.  The specimen must be neutralized within 4 hours of collection to neutral pH with 100mg of sodium carbonate (included in the collection kit from the state health laboratory). 

Feces:  Stool for AFB should be submitted only on patients with confirmed or suspected immunocompromised status.  Submit one gram (pea-sized portion) of stool in a clean, sealed container.  Note:  Freezing specimens will decrease yield of acid-fast organisms and should be avoided.