By Don Finley
San Antonio Express-News
SAN ANTONIO — For those unlucky enough to suffer crushing chest pain over the next year or so, don’t be surprised if the paramedic who answers the call asks for a little spit.
San Antonio Emergency Medical Services — and local heart attack patients — are taking a lead role in a federally funded research effort to develop an on-the-spot, highly accurate test for diagnosing heart attacks using saliva and a so-called “lab on a chip.”
If paramedics and the doctors supervising them can be certain a heart attack is occurring, precious minutes might be saved — and heart damage minimized — by beginning treatment in the ambulance, particularly in rural areas far from the nearest hospital.
At the very least, it might allow the patient to skip an hour’s worth of tests in the emergency room and go straight to the cath lab.
“Right now, when someone has a heart attack — or if it’s thought they’re having a heart attack — they have an EKG done” by paramedics, said Dr. Spencer Redding, chairman of dental diagnostic science at the University of Texas Health Science Center. “Those are accurate in about 65 percent of patients. But the other 30-35 percent that have still had a heart attack, they’re not going to have had any EKG changes.”
Doctors hope the saliva test, used together with an EKG, might boost that accuracy to about 95 percent, Redding said.
The lab on a chip was developed by chemists and engineers at the University of Texas at Austin. The prototype of the card, which is a little bigger and thicker than a credit card, slides into an analyzer about the size of a kitchen bread-making machine. The chip contains a biosensor that can be programmed to recognize antibodies and proteins that point to specific diseases.
To identify these heart attack biomarkers, the health science center is working with the University of Kentucky, which collected saliva from hospitalized patients within 24 hours of their heart attacks.
Now, the San Antonio paramedics are taking mouth swabs for saliva within minutes of suspected heart attacks, to see if the types and amounts of those biomarkers are the same — and if the differences can provide more information about the type of heart attack and when it occurred. The results should help the Austin engineers program the chip.
The first saliva collected here was from a patient who called EMS about a month ago, said Geoffrey Smith, an instructor at the health science center who trains paramedics and is heading up the EMS part of the study.
“We arrived on scene and we found a lady who was in mild distress, sweating,” Smith said. “So while the medics were doing their initial assessment and doing their vital signs, once there was a little break, I explained to her what I was doing and asked if I could do this. She said absolutely.”
Right now, Smith is one of two people collecting saliva — about eight samples collected so far. But a dozen EMS paramedics have been selected to participate and will go through training soon, Smith said.
Researchers hope to obtain between 100 and 120 samples over the next year. Some of them will be from patients who aren’t having a heart attack, to serve as a comparison group.
The health science center’s institutional review board, which oversees the ethics of research studies, allowed an exception to the usual rule about getting written consent from subjects. Because time is of the essence in heart attacks, and because there’s little risk involved in collecting saliva, patients can give spoken consent at the scene and sign a written consent form later, Redding said.
Smith said cardiologists must eventually sign off on the technology before they’ll permit any shortcuts to treatment. Clot-busting drugs, for example, also raise the risk of bleeding strokes, so doctors want to make sure they’re given to the right patients.
“They are busy doctors. They want to trust us paramedics, but we don’t have the training of cardiologists. And it’s not just the trust issue. If we can definitively say someone had a heart attack six hours ago versus three hours ago, it’s going to have lots of different benefits.”
The health science center researchers are also looking for markers in saliva for HIV and hepatitis B and C to use in the chips.