Quantitative Assessment of Immunohistochemistry Laboratory Performance by Measuring Analytic Response Curves and
Seshi R Sompuram, Kodela Vani, Anika K Schaedle
1From Medical Discovery Partners LLC, Boston, Massachusetts (Drs Sompuram, Balasubramanian, and Bogen and Mses Vani and Schaedle); and the Department of Pathology and Laboratory Medicine, Tufts Medical Center, Boston, Massachusetts (Dr Bogen).
Insights
Quantitative assessment of immunohistochemistry (IHC) sensitivity using analytic response curves revealed significant inter-vendor variability. This objective method improves diagnostic accuracy and identifies outlier laboratories for better standardization.
Area of Science:
- Biomedical diagnostics
- Pathology
- Laboratory medicine
Background:
- Interlaboratory variability in diagnostic immunohistochemistry (IHC) testing is a persistent challenge.
- Current methods for assessing immunostain sensitivity lack quantitative and objective measures, hindering standardization.
Purpose of the Study:
- To quantitatively and objectively assess the sensitivity of human epidermal growth factor receptor type 2 (HER2), estrogen receptor (ER), and progesterone receptor (PR) IHC stains.
- To introduce analytic response curves and limits of detection as novel parameters for evaluating IHC sensitivity in a proficiency testing format.
Main Methods:
- Thirty-nine diagnostic IHC laboratories participated in a proficiency testing study.
- Laboratories stained slides with HER2, ER, and PR targets using IHControls at five different concentrations.
- Quantitative assessment of analytic response curves and limits of detection was performed.
Main Results:
- Commercial immunostains showed reproducible analytic response curves within laboratories using consistent automation and reagents.
- Significant differences, up to 100-fold, in analytic sensitivity were observed between different commercial vendors.
- Quantitative assessment via analytic response curves proved superior to subjective limit of detection interpretation for proficiency testing.
Conclusions:
- Quantitative measurement of analytic response curves is a powerful and objective tool for assessing IHC laboratory performance.
- This method effectively identifies outlier laboratories and evaluates immunostain performance across defined analyte concentrations.
- Analytic response curves offer a superior approach to interlaboratory standardization in diagnostic IHC.
Context:
- Numerous studies highlight interlaboratory performance variability in diagnostic immunohistochemistry (IHC) testing. Despite substantial improvements over the years, the inability to quantitatively and objectively assess immunostain sensitivity complicates interlaboratory standardization.
Objective:
- To quantitatively and objectively assess the sensitivity of the immunohistochemical stains for human epidermal growth factor receptor type 2 (HER2), estrogen receptor (ER), and progesterone receptor (PR) across IHC laboratories in a proficiency testing format. We measure sensitivity with parameters that are new to the field of diagnostic IHC: analytic response curves and limits of detection.
Design:
- Thirty-nine diagnostic IHC laboratories stained a set of 3 slides, one each for HER2, ER, and PR. Each slide incorporated a positive tissue section and IHControls at 5 different concentrations. The IHControls comprise cell-sized clear microbeads coated with defined concentrations of analyte (HER2, ER, and/or PR). The laboratories identified the limits of detection and then mailed the slides for quantitative assessment.
Results:
- Each commercial immunostain demonstrated a characteristic analytic response curve, reflecting strong reproducibility among IHC laboratories using the same automation and reagents prepared per current Good Manufacturing Practices. However, when comparing different commercial vendors (using different reagents), the data reveal up to 100-fold differences in analytic sensitivity. For proficiency testing purposes, quantitative assessment using analytic response curves was superior to subjective interpretation of limits of detection.
Conclusions:
- Assessment of IHC laboratory performance by quantitative measurement of analytic response curves is a powerful, objective tool for identifying outlier IHC laboratories. It uniquely evaluates immunostain performance across a range of defined analyte concentrations.
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