Guide to the Application of Genotyping to Tuberculosis Prevention
Developing a Tuberculosis Genotyping Program
Continuity Between Past Genotyping Activity and New Genotyping
Many programs have IS6110-based RFLP results on a large
number of isolates. It will not be possible for the new genotyping
laboratories to perform spoligotyping and MIRU analysis on a large
number of previously collected isolates. But if the TB program has
on-going outbreaks that have been documented by genotyping and you
believe there may be additional cases in the future, a single isolate
from each outbreak may be submitted for genotyping. A reasonable
definition of an outbreak is a cluster of at least four patients
who have matching genotypes that includes at least one patient who
received a TB diagnosis within the last 3 years. A notation that
these isolates came from previous outbreak cases should be made
in the “Comments” field of the TB Genotyping Isolate Submission
Evaluation of the Usefulness of Genotyping
The TB program should collect data that allow an evaluation of
the impact of the genotyping program on their TB control practice.
Consider the following as helpful items to track:
- Unsuspected outbreaks identified through genotyping.
- False-positive cultures identified through genotyping.
- Epidemiologic links between two TB cases that were identified
during contact investigations and later confirmed or refuted by
subsequent cluster investigations.
- New epidemiologic links that were identified during cluster
investigations but not discovered during previous contact investigations.
These data can be used to evaluate the impact of the genotyping
activity. It should be noted that the value of genotyping for detecting
unsuspected transmission increases over time. The minimum time needed
for establishing a background of genotypes for an area is 2–3 years.
DTBE - Genotyping -