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Guide to the Application of Genotyping to Tuberculosis Prevention and Control										Related Pages
										**Tuberculosis Genotyping Case Studies: How TB Programs Have Used Genotyping**
**Algorithm to Detect False-Positive Cultures**
Genotyping can help identify instances of incorrect TB diagnoses that are based on false-positive cultures. Incorrect diagnoses can result from laboratory cross-contamination of cultures, mislabeling of patient specimens, collection errors, and reporting errors. Such errors occur in an estimated 1%–3% of all reported cases of TB, and as many as 300 persons per year in the United States may be started erroneously on anti-tuberculosis treatment. Universal genotyping permits TB programs to establish simple algorithms to flag suspected errors.
The California Department of Health Services, in collaboration with San Francisco General Hospital, Santa Clara Valley Medical Center, and Solano County Public Health Laboratory, evaluated this type of algorithm to find methods to decrease the occurrence of laboratory cross-contamination (Jasmer 2002).
During the study period from January 1998 through June 1999, cultures for 296 patients were positive for *M. tuberculosis*, and cultures for ten patients met one or more of the criteria for possible false-positive cultures. A review by a panel of experts determined that TB was misdiagnosed for six patients (representing 2% of all patients with cultures positive for *M. tuberculosis*) because of laboratory cross-contamination. In four of the six cases, contamination probably occurred when reagents were dispensed from a common flask. This practice was discontinued on the basis of the findings of this study. (See Chapter 6, *Applying Genotyping Results to Tuberculosis Control Practices*, for more information on investigating false-positive cultures.)
							
					
						Page last reviewed:  September 1, 2012					Content source: 	Division of Tuberculosis Elimination, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention homeGuide to the Application of Genotyping to Tuberculosis Prevention and Control
Acknowledgments
Introduction to Tuberculosis Genotypingplus icon
Introduction to this Guide
Overview of Tuberculosis Genotyping
Overview of the CDC Tuberculosis Genotyping Program
TB Program Eligibility and Application Procedures
Tuberculosis Genotyping Case Studiesplus icon
Investigation of a Genotyping Cluster in a Low-Incidence State
Apparent Genotyping Cluster among Recent Immigrants from the Philippines
False-Positive Culture Investigation
Algorithm to Detect False-Positive Cultures
A Misdiagnosis that was Identified with Genotyping
Genotyping Used to Improve Contact and Cluster Investigations
Identification of Nontraditional Transmission Settings
Investigation of a Multistate Tuberculosis Outbreak
Homeless Shelter Outbreak Investigation
Using Genotyping to Evaluate the Impact of a Screening Program
CDC Tuberculosis Genotyping Laboratory Proceduresplus icon
Science behind Tuberculosis Genotyping
Description of Genotyping Methods
Submission of Isolates
Genotyping Results, Designation of Clusters, and Reporting
Suspected False-Positive Cultures
IS*6110*-based RFLP Analysis
Combining Genotyping and Epidemiologic Data to Improve Our Understanding of TB Transmissionplus icon
Definitions
Reading the Genotyping Laboratory Report
Comparing Genotyping and Epidemiologic Results from Two TB Patients
Comparing Genotyping and Epidemiologic Results from Three or More TB Patients
Clustering as a Surrogate Measure of Recent Transmission
Developing a Tuberculosis Genotyping Programplus icon
Developing a Written Plan
Initial Decisions
Establishing Procedures for:plus icon
Submitting Isolates
Receiving and Acting on Genotyping Results
Requesting RFLP Analysis
Submitting Additional Isolates from the Same Patient
Comparing Genotyping Results between Jurisdictions
False-Positive Cultures
Database Management and Quality Control
Special Issues
Applying Genotyping Results to Tuberculosis Control Practicesplus icon
Evaluating Matching Genotypes
Evaluating Nonmatching Genotypes
Suspected False-Positive Culture Investigations
Expanded Contact Investigations
Outbreak Investigations
Cluster Investigations
Monitoring Trends
Appendicesplus icon
Appendix A: Glossary and Abbreviations
Appendix B: References and Useful Resourcesplus icon
References Cited in the Guide
NTGSN Special Issue References
Information on Packaging and Shipping Infectious Substances
Core Steps of an Outbreak Investigation
Consultants Available to Offer Guidance To receive email updates about this page, enter your email address: Email Address			What's this?				Submit


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