Tuberculosis Program

Professional

Diagnosis

A complete medical evaluation for TB includes:

• Medical history
• Physical examination
• TB skin test
• Chest radiograph
• Bacteriologic or histologic exam: All biological specimens being tested for Mycobacterium tuberculosis must be sent to the Rhode Island Department of Health Laboratory for analysis.

Frequently Asked Questions for Laboratory Testing

How long does it take to get acid fast bacilli (AFB) smear results for specimens processed at the HEALTH Laboratory?

• All specimens undergo an AFB smear within one business day.
• Positive smear results are faxed and telephoned to the provider upon completion. Negative smear results are faxed only.

How long do cultures take to grow?

• It can take up to eight weeks for a culture of Mycobacteria to grow. Therefore, the lab must incubate the specimen for eight weeks and document no Mycobacterial growth in order to confirm a negative result. A provider would receive a faxed confirmation of a negative result.
• If Mycobacteria are found in a specimen, providers are notified via phone and fax.
• When a Mycobacterial species is identified, providers are notified via phone and fax.

Are drug susceptibility tests done on M. tuberculosis?

• All M. tuberculosis isolates are tested against isoniazid (INH), ethambutol, rifampin, pyrazinamide (PZA), and streptomycin.
• If the isolate is resistant to isoniazid and rifampin, it is tested against second line drugs such as kanamycin, cycloserine, PAS, ofloxacin, ciprofloxacin, amikacin, and ethionamide.
• Susceptibility testing takes from one to four weeks following identification.
• Providers are notified by fax of susceptibility results.

Related guidelines, laws, rules, and/or regulations:

Department of Health guidelines on specimen submission.

State law on laboratory cultures for tuberculosis