The recent epidemic of lab testing errors has been concentrated mainly among a handful of tests called breast biomarkers, widely used by pathologists to break down the molecular characteristics of a cancer so treatments can be tailored to attack it.
Results of the tests open the gateway for many women to lifesaving treatments.
All are part of a broader family of cutting-edge tests called immunohistochemistry (IHC). They are a relatively new breed of subjective tests, requiring doctors to observe the intensity of cellular staining patterns and make judgment calls based on what they see.
Because the tests are new and subjective and accuracy hinges on how much experience pathologists have with them, they have yet to be fully regulated in Canada and the United States. And with more than 40 sensitive steps, a small error at any stage can compromise the specimen and the pathologist's ability to accurately interpret the final result.
Currently, the breast biomarker tests are the only IHC tests routinely used to guide treatment decisions. One of them detects whether cancer cells have too much of a protein called Her-II, making patients eligible for the popular drug Herceptin. Two other tests, done in tandem, check tumour cells for the presence of receptors for the hormones estrogen and progesterone, which feed tumours if not blocked with hormone treatments.
Anatomical pathologists predict that over the next 10 years, several more IHC tests will become critical for treating other types of cancer, including colon and lung. That prospect has intensified the need for robust regulations to ensure cross-country consistency in test results, including a cohesive external quality-control program to enable inter-lab comparisons.
