Specimen Collection and Transport Instructions
Tuberculosis Testing Timelines and Turnaround Times
|Test Type||Test Schedule||Turnaround Time (TAT)||Comments|
|AFB Culture and Smear||Monday through Friday within normal operating hours*||Smear reports are available the same day as specimen receipt||Culture reports and other reflex tests will be finalized between six and eight weeks after sample delivery to the laboratory|
|GeneXpert MTB/RIF||Monday through Friday within normal operating hours*||Results available within twenty-four hours**||Run on all respiratory samples that are a first time + smear per the regulations set by the TB Controller|
|Quantiferon Gold Plus||Thursday||3-5 days depending on date received||N/A|
*The laboratory processes samples on federally recognized holidays for hospitals within Santa Barbara County. Turnaround times remain unaffected for inpatient samples received on holidays.
** Special testing accommodations can be made with prior approval in mitigating circumstances.
Tuberculosis (TB or MTB) is one of the world's deadliest diseases plaguing one fourth of the human population. In 2016, 10.4 million people around the world were infected with TB, which lead to an estimated 1.7 million TB-related deaths worldwide. In addition, TB is a leading cause of death for those who are infected with HIV (Tuberculosis, 2018).
In California alone, there were 2,062 reported cases, which placed our state in the top three regions of the country with a case rate higher that the national average (2016 national average was 2.9 cases and California has 5.3 cases per 100,000 individuals)1
From 2008-2017, Santa Barbara County reported an average of 22.5 TB cases, with the highest number of cases occurring in 2008. Although there has been a 70% decrease of reported TB cases, the Public Health Laboratory continues to test over 3,000 samples per year.
1Tuberculosis (TB). (2018, March 22). Retrieved from https://www.cdc.gov/tb/statistics/default.htm
The GeneXpert MTB/RIF identifies DNA sequences specific for Mycobacterium tuberculosis and recognizes strains of TB that are resistant to rifampicin (RIF) via polymerase chain reaction (PCR).
Molecular beacons are fluorescent probes that are used to rapidly review the bacteria's genome in a real time format that identifies clinically significant rifampicin resistant inducing mutations in the RNA polymerase beta (rpoB) gene. The Santa Barbara County Public Health Laboratory in the only facility in Santa Barbara County that offers an assay for the rapid detection of MTB and RIF resistance. Once the sample is processed, results can be made available in as little as ninety minutes.
Food and Drug Administration (FDA) Approvals
The GeneXpert MTB/RIF assay has been approved for the diagnosis of pulmonary and extrapulmonary TB in adults and children. For samples that deviate from the FDA's approved testing criteria, the Public Health Laboratory will qualify the results with the following statement:
Disclaimer: The GeneXpert MTB/RIF was used to analyze a sample that has not been approved by the Food and Drug Administration (FDA). This result should not be used independently to diagnose or treat pulmonary and/or extrapulmonary tuberculosis.
**Pyrosequencing is only orderable by the TB Controller and is a test that is not performed by the Santa Barbara Public Health Laboratory**
Pyrosequencing is a laboratory method used to detect extensively drug-resistant (XDR) tuberculosis. PSQ assays aim to detect mutations associated with resistance to drugs which include isoniazid, rifampin, and the quinolones (e.g., ofloxacin, levofloxacin, or moxifloxacin). Compared to culture-based drug susceptibility testing (DST), which typically takes at least four weeks or longer to produce a viable result, pyrosequencing can be completed in as little as six hours.
**Genotyping is only orderable by the TB Controller and is a test that is not performed by the Santa Barbara Public Health Laboratory**
TB genotyping is a laboratory-based technique used to analyze the genetic material of Mycobacterium tuberculosis by generating a "genetic map" or genome.
Genotyping of Mycobacterium tuberculosis isolates has been made available to all TB control programs in the United States and the data may be used to confirm a suspected outbreak, identify false culture positive TB suspects, identify a previously unsuspected outbreak, evaluate the effectiveness of contact investigations, and gain insight into TB infection patterns and populations most vulnerable to recent transmission.