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 comparisons:
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 day.
3. Check your accreditation agency standards and manufacturer’s instructions to determine the number of data points or values needed.
4. Follow procedure manual/package insert instructions to perform the verification
5. For qualitative tests, the laboratory must ensure positive and negative reactivity
6. For 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 key!
8. The 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