Kristien Dorst - Lagerwerf (Presenter)
Erasmus University Medical Center
Authorship: K.Y. Dorst, Y.B. De Rijke
Depts Clinical Chemistry/Internal Medicine, Erasmus University Medical Center, 3000 CB Rotterdam, the Netherlands
| Short Abstract In our steroid profile (kit Perkin Elmer, LC-MS/MS Waters) we were confronted with a failure of our QC for testosterone in home-made QC samples, while the performance of commercial, stripped serum QC samples is good. We ruled out various errors in the pre-treatment of the samples. After contacting the MS vendor, several parts of the MS were cleaned and/or replaced. The problem couldn’t be solved by the vendor so far. This case is illustrating that commercial QC samples are not useful in detecting sensitivity related problems. |
Long Abstract
1. Problem
In our steroid profile we measure 9 hormones, including testosterone. In each serie of patient samples we measure three levels of commercial QC samples (spiked stripped serum) and two levels of home-made, pooled patients serum samples.
The concentration range of the highest commercial control is between 12.9 and 15.5nM.
The concentration range of the highest home-made control is between 13.2 and 16.8 nM, but shifts to a range of 10.0 (-3.1 SD) and 25.8 nM (+6.7 SD), in case of QC error.
2. Method Information
• Perkin Elmer CHSTM MSMS Steroids Kit for calibration and QC samples (both in charcoal stripped serum) and Internal Standard Mix
• 100 µL Serum is deproteinized with 200 µL Acetonitrile which contains deuterated Internal Standards. Supernatant is dried under nitrogen and resuspended in initial gradient.
• Acquity UPLC coupled with Waters Xevo-TQS
• Mobile Phase A: 1.25mM Ammonium Acetate in H2O
• Mobile Phase B: 1.25mM Ammonium Acetate in MeOH
• 10 min gradient LC program, 0.25 mL/min flow rate
• 100x1.0 mm, 1.8 µm HSS T3 column, 80°C
• Injection volume 40 µL
3. Troubleshooting Steps
First we checked the other 8 compounds, but they all showed acceptable deviations, thereby excluding pipetting errors. We ran several sets of samples yielding unacceptable results for testosterone in the home-made QC samples only.
After contacting the MS vendor several cleaning procedures were executed, which did not have the desired effect. Both stepwave and collision cell had to be replaced to resolve sensitivity problems and receive normalized QC results. Unfortunately, current results show that either cleaning of the ion source and quads or replacing of the stepwave and collision cell still yields aberrant results for home-made QC samples.
4. Outcome
At this moment the problem hasn’t been solved . This case is illustrating that commercial QC samples are not useful in detecting sensitivity related problems, due to matrix difference between stripped serum and patient samples.
References & Acknowledgements:
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| Salary | no | |
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| Expenses | no |
IP Royalty: no
| Planning to mention or discuss specific products or technology of the company(ies) listed above: | yes |