immunohistochemistry calibrators, IHC calibrators

The first and only true calibrator for IHC testing

Studies show that up to 30 percent of clinical IHC test results are either erroneous or of borderline quality (1).


Why is the error rate so high for IHC, especially when compared to the less than one percent error rates of other diagnostic fields? Quite simply, the data show that the most important causes are the absence of traceable units of measure, international standards, calibrators traceable to standards, and quantitative monitoring of controls in clinical IHC (1).


Calibrators (with units of measure traceable to an international standard) are mandatory in every clinical laboratory discipline but until now such standards have been absent from IHC testing.


In order to address this critical need for improved test accuracy and reproducibility in clinical IHC, Boston Cell Standards developed and validated the first protein biomarker calibrators. This development has the potential to significantly reduce the error rate for the IHC testing industry.


(1) SA Bogen. A Root Cause Analysis Into The High Error Rate In Clinical Immunohistochemistry. App. Immunohistochem. Mol. Morphol. 2019. In press.

immunohistochemistry calibrators, IHC calibrators

The magnitude of the problem

External proficiency testing (PT) programs (i.e. NordiQC, UK NEQAS, CIQC) have demonstrated a general truth that year after year, there are about one-third of laboratory participants that achieve “optimal” results, while one-third are “good,” and one-third fail (2).


These inaccuracies in IHC testing have a profound societal impact.  A 2015 economic impact study analyzing HER-2 test inaccuracies concluded that misclassification and non-optimal treatment of approximately 12,025 US patients result in a total economic societal loss of nearly $1 billion (3).


Apart from HER-2 tests, there are also over 100 additional IHC tests that are routinely used for diagnosis that are subject to the same problem, and many more are in development, especially in the area of oncology.



(2) EE Torlakovic, et.al.Getting controls under control: the time is now for immunohistochemistry. J. Clin. Pathol.201568(11):879-882.

(3) LP Garrison Jr., et.al. The lifetime economic burden of inaccurate HER2 testing: estimating the costs of false-positive and false-negative HER2 test results in US patients with early-stage breast cancer. Value in Health2015 18(4):541-546.

immunohistochemistry calibrators, IHC calibrators
Lab 1
immunohistochemistry calibrators, IHC calibrators
Lab 2

Why a calibrator is important

Calibrators measure stain intensity and translate it to a concentration of the protein biomarker in question.  This is illustrated in the adjacent figure labeled “Lab 1”, showing three hypothetical tumor cells with different cell membrane stain intensities (brown color), scored 0, 1+, and 3+.  Without calibrators, there is no way to connect the stain intensity (0 – 3+) to the actual number of protein biomarker molecules.  Only with a calibration curve (“standard curve”) can the two be connected. With a calibration curve, we learn the actual concentration range that is being measured.


The problem is that another clinical IHC laboratory (“Lab 2”) may have a completely different calibration curve. This is shown in the adjacent figure labeled “Lab 2”.  Even though this second lab measures stain intensity in the same way, possibly even with image quantification software, the results don’t correlate with the first lab. Different results are measured on the same patients.  For example, a tumor cell expressing 50,000 molecules per cell will be strongly positive in lab 1 and unstained in lab 2.  The only way to ensure inter-laboratory consistency is to account for the differences in calibration.  That is the function of calibrators.

immunohistochemistry calibrators, IHC calibrators

Getting to the root cause

There are many potential causal factors for the high analytic error rates, including problems with reagents, instrument failures, personnel training, etc. These are important, but they are not the root causeThe underlying root cause is that problems are not promptly detected and corrected. This is the central difference between clinical IHC and other clinical laboratory disciplines (1).


In every other laboratory medicine discipline, this problem is addressed by using reference standards and calibrators. Reference standards and calibrators normalize the many variables in a laboratory test by creating a standard unit of measure regardless of the assay details.


For example, in clinical chemistry, there are more than 100 reference standards covering a broad range of blood analytes. In clinical IHC, however, there are none.


Creating IHC reference standards and calibrators with traceable units of measure has historically been a difficult technical challenge to solve. With the creation of IHCalibrators, we have solved the problem, creating an effective method to standardize Clinical IHC testing and ultimately improve patient outcomes.


(1) SA Bogen. A Root Cause Analysis Into The High Error Rate In Clinical Immunohistochemistry. App. Immunohistochem. Mol. Morphol. 2019. In press.