False positive results in diagnostic immunohistochemistry are related to horseradish peroxidase conjugates in commercially available assays

Publication date: Available online 26 September 2016
Source:Annals of Diagnostic Pathology
Author(s): Gerard Nuovo
False positive results in diagnostic immunopathology can lead to unnecessary treatments. The purpose of this study was to do a side-by-side comparison of ten different antibodies commonly used in the clinical laboratory altering only the horseradish peroxidase (HRP) conjugate. The automated Leica BOND-MAX platform was used to study serial sections from 203 tissues including controls compared in a blinded fashion using the HRP conjugates from Leica (Refine HRP), Ventana Medical Systems (Ultraview HRP), and Enzo Life Sciences (Polyview HRP). False positive results, defined as signal from cases known to not contain the target, were noted in 23/171 cases (13%) with the Leica HRP, 62/171 cases (36%) with the Ventana HRP, and no cases with the Enzo HRP. Each data set was performed simultaneously allocating one tray for each of the three different HRP conjugates. HER2/neu analysis from triple negative breast cancers were scored as positive by immunohistochemistry in 6/25 cases (24%) using either the Refine or Ultraview HRP and in 0/25 cases with the Enzo conjugate. It is concluded that false positive results in a wide spectrum of diagnostic immunopathology tests can occur in from 13 to 36% of cases with two commonly used commercial assays based on the HRP conjugate.



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