Apples to Apples
Were you ever one of those techs that questioned the utility
of parallel testing? Ok, I admit it, me
too! I used to think that lot-to-lot verification, also referred to as
crossover studies or parallel testing, was a nuisance, but that is because I
didn’t fully understand it. Therefore, I get it when customers call me with
questions about this process. In fact, lot-to-lot verification is one of the
hot topics of the CQA line.
Simply put, parallel testing helps ensure the integrity of
the new lot before it is used. Parallel testing helps us assess: 1) the integrity
of the lot (kit, controls and reagents) and 2) lot performance or, in other
words, ensures that the recovered expected results are accurate. It is
essential to assess the integrity of the new lot before being used and to
ensure that there were no changes during shipment. This is particularly
important if there is any chance supplies were subjected to drastic climate
changes in transit.
While qualitative tests just need to have positive and negative
reactivity verified, quantitative assays need to be verified over a range of
values. Generally, five values are considered adequate when verifying a new lot
number.* Be sure to check the package insert and your accrediting agency’s
recommendations for specific requirements. Essentially, parallel testing, in
addition to being a regulatory or compliance requirement, is an exercise in
good laboratory practices. Here are a few tips when doing lot to lot
1. Check the lot
inventory to ensure expiration date of reagents, storage conditions and that
inventory levels are adequate to perform the crossover studies.
2. Assign the
lot to lot verification to a specific staff member or communicate to all
testing staff assigned to the bench, so as not to miss any runs. It is
recommended the verification is done over the span of a few days vs. all in one
3. Check your
accreditation agency standards and manufacturer’s instructions to determine the
number of data points or values needed.
procedure manual/package insert instructions to perform the verification.
qualitative tests, the laboratory must ensure positive and negative reactivity.
quantitative test, if the new lot results are within the manufacturer’s
specifications or the criteria established by the lab director, then the
verification was successful.
7. Make sure to
analyze the data and note any calculations needed. Remember, documentation is
laboratory director or designated person must review and evaluate the
verification and determine if it was acceptable or not.
9. If the
verification is not acceptable, be sure to perform a root cause analysis and
implement a corrective action plan.
Have you ever had a situation where the current lot runs out
before the new lot gets verified? How did you handle that?
*COLA Laboratory Accreditation Manual, April 2014