Instruction Manual

22
Attachment 1 – Protocol for Monitoring of Specimen Pooling Testing Strategies
Monitoring plan for use of pooling
Laboratories should evaluate the appropriateness of the pooling and pool size using the FDA recommended monitoring
procedure described below. Laboratories may also consider the sensitivity of pooled testing based on the assay’s
Limit of Detection.
Ongoing assessment of positivity rate during application of the initial selected n-sample pooling strategy:
a. If historical data on testing individual samples from the laboratory is available:
• The percent positivity rate, P
pools
, should be updated daily using a moving average of the data
from pooled samples from the previous 7-10* days. If P
pools
is less than 85% of P
individual
(P
pools
< 0.85 · P
individual
), then it is recommended that the pool size be adjusted to maximize
pooling efficiency, according to the criteria in Table 1 below.
• It is recommended that n
maxefficiency
, using P
pools
and Table 1 be re-assessed periodically while
sample pooling is implemented by the laboratory to ensure maximum pooling efficiency
b. If historical data on testing individual samples from the laboratory is unavailable:
• After initiating the pooling strategy, calculate the initial pooling positivity rate (P
pools-initial
) for
the first 7-10* days using a moving average of the data from n pool testing results.
• If P
pools-initial
is greater than 25%, then Dorfman pooling of patient specimens is not efficient
and should cease.
• Following the first 7-10* day period of sample pooling, calculate the pooling positivity rate
(P
pools-x
) for the next 7-10* day period based on n pool testing results.
• If P
pools-x
is less than 90% of P
pool-initial
(P
pools-x
< 0.90 · P
pools-initial
), it is recommended that the
pool size be adjusted to maximize pooling efficiency, according to the criteria in Table 1.
• It is recommended that n
maxefficiency
, using P
pools-x
and Table 14 be re-assessed periodically while
sample pooling is implemented by the laboratory to ensure maximum pooling efficiency.
* It is recommended that P
individual
be calculated from the previous 7-10 days, while P
pools
and P
pools-x
are
calculated from data collected during a 7-10 day time frame. However, when determining if 7-10 days is
appropriate, take into consideration the laboratory testing volume and percent positivity, among other
factors. Note that if the number of individual or pooled positive results collected during a given time frame
is less than 10, P
individual
, P
pools
and P
pools-x
may not be representative of the percent positivity in the testing
population and the laboratory may want to consider extending the testing time period to increase the
chance of capturing positives.