VALIDATION ELEMENTS EXPLAINED
As has now become obvious, Quasar places great emphasis on the entire process of getting your laboratory up and running. It is not solely a matter of installing the LC-MS/MS equipment and running a validation protocol.
By this time your method should have been developed, installed, and fine-tuned on your LC-MS/MS. Your technician will have gone through training and certification. (Quasar’s training course is PACE certified.) Your refrigeration, air supplies, electrical build-out, etc. have been accomplished and the experiments necessary to prove out your laboratory’s competence can begin… the validation.
There are two major components to validation: One, can you find the compounds / analytes that you are looking for, if they are known to exist? Two, can you replicate the results? There is a series of runs that will need to be conducted that will help to answer these questions. Below is the list of validation runs that will occur along with a brief description of what they entail.
Validation run used to establish the best fit regression model for each analyte.
Accuracy & Precision
Validation run used to assess inter and intra batch consistencies and reliability with the accuracy of QC’s. The practical application is simply to ensure that your instrument is seeing consistent results and known QC values are exactly where they should be.
Validation run that assesses how much carryover (if any) is seen between sample to sample. This is done by injecting a blank sample after a 10X. The practical application of this is to ensure that there are not false positives with patient samples; however, it is still good practice to re-prep and rerun any patient samples that follow a positive (if they are positive).
LOD / LOQ
Validation run that ensures that the instrument is capable of detecting even further than the known limit of quantification (lowest curve point – 50% cutoff). This basically proves that detection levels can be reached as low as they have been reported to be.
Validation run that assesses whether typical over-the-counter compounds will have any interference with the drugs of interest in the panel. This is showing that things like ibuprofen, acetaminophen, etc. are not going to interfere.
Validation run that ensure that other matrices within urine (due to water, diet, pH, etc.) are not going to give an interference or false positive with any patient samples. This is done by assessing multiple lots of known blank human urine.
Processed Sample Stability (Autosampler Stability)
Validation run that assesses a processed batch on the autosampler 72-96 hours after it has already been prepared. The practical application of this is to ensure that should the instrument stop working on a Friday evening or over the weekend, the batch can be resubmitted for analysis on the next business day.
Stored Sample Stability (Unprocessed Stability)
Validation run that assesses how long the compounds can still be detected within a known, acceptable range. The practical application of this is very important and quite simple: to determine how long patient samples can sit in the refrigerator prior to analyzing them upon receipt. Typically, a goal is 7-10 days for this.
Validation run that proves and ensures that the glucuronidase enzyme that is used during sample prep is indeed doing its job. (That is, to cleave the gluconide molecule so that analysis for the parent compound can be run.)
This step ensures that the results provided by the instrument that has been validated corresponds with another validation system (off-site, from another laboratory) of similar capacity. Consistent results ensure that patient samples are processed in a manner in which reliable data will be produced.