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The Journal of Applied Laboratory Medicine

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Research ArticleArticle

Performance of the 4Kscore Test in Plasma and Serum and Stability of the Component Analytes in Clinical Samples

Christina E. Higgins, Patricia Neybold, Marcella B. Holdridge, Catherine R. Barnes, Yan Dong, Michael Reeve, Vinita Mathur, James Weisberger, Vincent Linder
DOI: 10.1373/jalm.2017.024612 Published January 2018
Christina E. Higgins
OPKO Diagnostics, LLC, Woburn, MA;
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  • For correspondence: chiggins@opko.com
Patricia Neybold
BioReference Laboratories, Elmwood Park, NJ;
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Marcella B. Holdridge
OPKO Diagnostics, LLC, Woburn, MA;
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Catherine R. Barnes
OPKO Lab, Nashville, TN.
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Yan Dong
OPKO Diagnostics, LLC, Woburn, MA;
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Michael Reeve
OPKO Diagnostics, LLC, Woburn, MA;
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Vinita Mathur
OPKO Lab, Nashville, TN.
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James Weisberger
BioReference Laboratories, Elmwood Park, NJ;
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Vincent Linder
OPKO Diagnostics, LLC, Woburn, MA;
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Abstract

Background: The 4Kscore Test determines a personalized risk score for aggressive prostate cancer by combining the blood sample measurements of total prostate-specific antigen (tPSA), free PSA (fPSA), intact PSA (iPSA), and human kallikrein-related peptidase 2 (hK2) with patient clinical information to generate the patient risk's score; thus, accuracy and precision of the 4Kscore depend on the reliability of these measurements. Although tPSA and fPSA are measured on a Food and Drug Administration (FDA)-approved platform, the performance of the iPSA and hK2 assays in the clinical setting has not previously been reported.

Methods: Analytical performance was determined for the iPSA and hK2 assays in both serum and EDTA plasma, according to Clinical and Laboratory Standards Institute guidelines. Equivalence of the 4Kscore in both sample matrices was demonstrated in a 353-patient clinical cohort, and the stability of endogenous iPSA and hK2 for at least 3 days was demonstrated in a smaller subset.

Results: Intralaboratory and interlaboratory precision of the iPSA and hK2 assays in both matrices was comparable with that of FDA-approved tPSA and fPSA assays (<18% for iPSA; <8% for hK2). The picogram per milliliter sensitivity and wide dynamic range of the iPSA and hK2 assays allowed for accurate measurements in the target population. The 4Kscore generated in either matrix up to 3 days after collection is equivalent to that measured within 24 h of collection (Passing–Bablok slope 95% CI: plasma, 0.999–1.034; serum, 0.997–1.040).

Conclusions: The robust performance of component assays and reliable stability of the endogenous analytes in clinical samples proven here ensures an accurate 4Kscore Test result.

  • Received July 14, 2017.
  • Accepted November 27, 2017.
  • © 2017 American Association for Clinical Chemistry

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The Journal of Applied Laboratory Medicine: 2 (5)
Vol. 2, Issue 5
March 2018
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Performance of the 4Kscore Test in Plasma and Serum and Stability of the Component Analytes in Clinical Samples
Christina E. Higgins, Patricia Neybold, Marcella B. Holdridge, Catherine R. Barnes, Yan Dong, Michael Reeve, Vinita Mathur, James Weisberger, Vincent Linder
The Journal of Applied Laboratory Medicine Jan 2018, jalm.2017.024612; DOI: 10.1373/jalm.2017.024612
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Performance of the 4Kscore Test in Plasma and Serum and Stability of the Component Analytes in Clinical Samples
Christina E. Higgins, Patricia Neybold, Marcella B. Holdridge, Catherine R. Barnes, Yan Dong, Michael Reeve, Vinita Mathur, James Weisberger, Vincent Linder
The Journal of Applied Laboratory Medicine Jan 2018, jalm.2017.024612; DOI: 10.1373/jalm.2017.024612

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