Analytical validation of soluble fms-like tyrosine and placental growth factor assays on B·R·A·H·M·S KRYPTOR Compact Plus automated immunoassay platform

Pregnancy Hypertens. 2018 Jan;11:66-70. doi: 10.1016/j.preghy.2017.12.009. Epub 2018 Jan 2.


Background: Preeclampsia is one of the leading hypertensive disorders of pregnancy. Angiogenic biomarkers such as anti-angiogenic factor soluble fms-like tyrosine kinase 1 (sFlt1) and pro-angiogenic factor placental growth factor (PlGF) are involved in the pathophysiology of preeclampsia.

Objective: The aim of this study is to validate the analytical performance of sFlt1 and PlGF on the B·R·A·H·M·S KRYPTOR Compact Plus (ThermoFisher Scientific).

Study design: We examined K2-EDTA plasma samples from 50 patients on B·R·A·H·M·S KRYPTOR Compact Plus, an automated immunoassay platform. QC materials were used to assess intra- and inter-precision of the assay. Lower limit of quantitation and interference studies were determined using pooled patient plasma.

Results: The sFlt1 and PlGF assays demonstrated an analytical measuring range of 90-69,000 pg/mL and 11-7000 pg/mL, respectively (r2 > 0.99). Lower limit of quantitation (20% CV) was interpolated to be 35 pg/mL for sFlt1 and 10 pg/mL for PlGF. Total precision for both assay displayed CVs of <10%. Interference studies showed that both assays were not significantly affected by hemolysis up to an H-index of 1100 for sFlt1 and 300 for PlGF; L- and I-index of 800 and 80 respectively for both assays. The Passing-Bablok regression analysis for sFlt1/PlGF yielded an equation of y = 1.05x + 0.02, and the Bland Altman analysis showed an average bias of 0.84.

Conclusion: Plasma levels of sFlt1 and PlGF measured on the B·R·A·H·M·S KRYPTOR Compact Plus platform demonstrate excellent analytical performance and are acceptable as clinical grade assays.

Keywords: Analytical validation; PlGF; Preeclampsia; sFlt1.

Publication types

  • Validation Study

MeSH terms

  • Automation, Laboratory
  • Biomarkers / blood
  • Equipment Design
  • Female
  • Humans
  • Immunoassay / instrumentation
  • Immunoassay / methods*
  • Limit of Detection
  • Placenta Growth Factor / blood*
  • Pre-Eclampsia / blood*
  • Pre-Eclampsia / diagnosis
  • Predictive Value of Tests
  • Pregnancy
  • Reproducibility of Results
  • Vascular Endothelial Growth Factor Receptor-1 / blood*


  • Biomarkers
  • PGF protein, human
  • Placenta Growth Factor
  • FLT1 protein, human
  • Vascular Endothelial Growth Factor Receptor-1