We were excited to speak with Clare Thornton, Lead Immunohistochemistry Technologist at Dahl-Chase Diagnostic Services in Bangor, ME. Clare spoke with us about how she became a specialist in immunohistochemistry (IHC), her responsibilities, and some recent developments in the field.
How did you get started in histology?
It was by accident. Certain things are meant to be in life! I graduated in college with a bachelor’s degree in biology from the University of Maine in Orono, but I didn’t take the histology course there. Afterward, I worked for Eastern Maine Medical Center in a number of areas. Dahl-Chase advertised for someone to work in cytology prep. I had no idea what histology was until I was hired at Dahl-Chase as a lab assistant almost 15 years ago. Within a year I was starting to learn IHC, which is a very fast track. I was doing IHC before I was even a certified histotech. I can do almost anything in histology now.
What are your responsibilities? What does a lead immunohistochemistry technologist do?
I cut almost all of my own patient IHC slides, so I cut every day. Then I perform the stain.
We also precut many of our positive quality control (QC) slides, and sometimes we can go through a lot! Cutting positive QC slides and patient tissue takes up about 30 to 40 percent of my day. After automated staining, slides need to be dehydrated, coverslipped, and viewed under the scope. The IHC techs look at all of the slides before they are handed out to the pathologists, to ensure the protocol worked properly, the staining is appropriate, and the tissue adhered well to the slide. We would rather make the decision to repeat a slide ourselves and get a jump on it as opposed to handing it out to the pathologist and wait for them to request a repeat. I also spend some time most days looking for new positive control tissue, making positive control tissue blocks, and testing those blocks to make sure they work as expected.
I am responsible for quality control and validation of the antibody. I have to understand what cells we want to stain, how it should look, and how to reduce noise and increase signal. When we get a new antibody or a new clone, it’s up to me to optimize and validate that antibody. We need to compare every new lot of antibody with the previous lot. This is necessary because all antibodies can have slight shifts in concentration. Certain antibodies have levels of expression from weak to strong. If an antibody concentration shifts enough, you can lose your weak expressing proteins, which could lead to false negatives.
Sometimes the pathologist will come to us and say “it’s not staining a specific cell, can you fix it?”
One administrative task is that I have to establish new procedures. I also fill in throughout the lab, performing general histology as needed.
What skills do you need to be an IHC specialist?
You have to be detail oriented and be able to multitask. Multitasking is especially important in a clinical lab. We push out 2,000 IHC slides in a month, and I’m the only one in IHC full time, so it’s very busy.
The pathologist orders the IHC after they examine an H&E. It’s important to get the IHC slides back to the pathologist extremely quickly because the clinician could be calling the pathologist looking for a result at any time. We look to give same-day turnaround if it’s ordered by 2:30. After that we will have it out by the next morning.
You need to have a good understanding of biochemistry to understand what is happening on a molecular level. It’s not necessary, especially if the process is automated, but it’s important to know what is happening.
People sometimes pair IHC with molecular pathology. What does molecular pathology involve?
The molecular lab does PCR, FISH, and they are starting next gen sequencing.
Our lab handles some of the nuances for molecular. For example, do they want a charged slide or not charged slide? PCR should not be done on a charged slide because they want the tissue to come off.
What are your biggest concerns in IHC? What are your biggest challenges?
The biggest concerns are quality, safety, then cost.
A big challenge is keeping costs down. When the Centers for Medicare and Medicaid Services (CMS) cuts our reimbursement rates, our vendors aren’t necessarily cutting their prices. This makes a big difference in where we purchase an antibody.
What are recent developments in IHC technologies? Is there anything that you are preparing for that wasn’t on your radar a few years ago?
Immunotherapy drugs and companion diagnostics are interesting because they require specific approval on a new level. We bought a specific Dako stainer just staining for PD-L1 expression for treatment with Keytruda®. Dako was the only company to get FDA approval for their stainer with their antibody.
Some companies are getting patents on certain antibodies, which means you have to use a specific antibody with a specific protocol. That can be difficult for small labs.
When molecular technologies were popping up people thought IHC was going to go away, but I don’t see that happening. There is a lot of talk about multiplexing. We do a lot of stains with 2-3 antibodies, but multiplexing involves around 20 antibodies on one piece of tissue. Biopsies are getting smaller and smaller (sometimes 30-40 cells) to make them less invasive and reduce chance of infection, but we have to do an amazing amount of steps with this tissue. If it’s a lung biopsy where we have to determine what it is, there are a handful of molecular tests, meaning I’m bringing in 20 slides to the molecular lab. Overall, we are going to have to do more stains with less tissue.
Thank you for speaking with us, Clare!
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