73-P

Abstract

Aim The Cylex ImmuKnow (ICF) is a biologic assay that has a great deal of inherent variability. Our lab performs both internal (IPT) and external (EPT) proficiency testing to show assay proficiency. This abstract demonstrates our use of data from PT to improve performance of the assay. Methods Duplicate specimens were collected from 5 subjects each time. Aging studies were tested on the draw day and 24 hours later. IPT was performed by multiple techs in our own lab on these samples. For the EPT, the duplicate specimens were shipped to the external lab. The other lab also drew 5 duplicate samples and shipped them to us for testing. Both labs tested the 10 samples at 24 hours. Results were evaluated qualitatively (QL) and quantitatively (QN). Results Assay results were reproducible in a quantitative and a qualitative manner (QN results within +/−10% of the QL cutoff were considered a QL match) but there was a significant amount of variability. Shipped samples from either lab had an avg deviation of −20 (avg %CV 18.6% & SD 111). 60% of shipped samples showed a negative shift between the sending and receiving lab. 24 hour old unshipped samples showed an avg deviation of −19.5, (avg %CV 15.5 & SD 77). 54% of all unshipped samples showed a negative shift of result relative to the fresh sample. Using the results of IPT, we were able to reduce variability among technologists by insuring careful adherence to the procedure. Improvement was measured by looking at assay variability among techs on the same sample. From a baseline of 15.5% avg %CV and 67.3 avg SD from 2006 – 2008, we reduced our test variation by 33% to 10.3% avg CV and 42.3 avg SD. Conclusions The best ICF results are obtained by serial monitoring of a patient in a single lab. Testing fresh samples gives more reproducible results than shipped/aged samples. When it is necessary to use shipped or 24 hour old samples, it should be noted in the test report. We used our PT data to reduce the variation of ICF assay results.