The Spitting Image of a Heart Attack

   When treating a cardiac emergency, have you ever considered the value of your patient's spit?

   While this may seem odd, research indicates many heart attack biomarkers found in blood can also be detected in patients' saliva. Identifying these biomarkers in saliva may help rapidly identify non-ST segment elevation myocardial infarctions (NSTEMIs). By collecting saliva--much easier to obtain than blood--from suspect patients in the field, prehospital caregivers may be able to further speed the early identification of AMIs and contribute to better outcomes. Personnel with minimal training can easily perform the required point-of-care saliva test in a prehospital setting.

   John McDevitt, PhD, a chemist at Rice University, developed the groundbreaking "lab on a chip" technology that makes this possible, and it is currently manufactured commercially by LabNow, Inc., a biotechnology firm in Austin, TX. The chip's analyzer has a footprint about the size of a shoebox, and is light enough for wall mounting. The analysis card uses a 1-cm square stainless steel chip with dozens of wells containing tiny detection beads. If the applied sample contains the characteristic proteins of the disease of interest--in this case the proteins indicative of AMI, although the technology is applicable to many disease processes--the detection beads emit a fluorescent color. The analyzer will then "read" the chip and indicate the probability the patient is experiencing an AMI. The first product using this technology is currently being deployed in Africa, targeting HIV immune function.

   University of Kentucky researchers have identified higher concentrations of 32 salivary proteins in victims suffering heart attacks. Of these 32 proteins, four (myeloperoxidase, C-reactive protein, matrix metalloproteinase 9, interleukin 1B) were identified as a salivary protein "fingerprint." When combined with EKG results, this biomarker fingerprint was found to be comparable to standard blood serum using current testing methods.

IN THE FIELD

   Researchers at the University of Texas Health Science Center at San Antonio seek to answer the question of how feasibly this test can be performed in the busy EMS environment.

   Field testing is ongoing by paramedics with the San Antonio Fire Department. Twenty-six paramedics voluntarily participated in three hours of training to prepare for the trial. This instruction covered institutional review board compliance, participant recruitment and consent, study protocol and collection techniques. This phase of field testing involves recruiting patients experiencing symptoms suspicious of AMI and acute coronary syndrome.

   With these patients, medics use swabs to collect small saliva samples, about 0.1 ml. Each saliva sample is applied to the credit card-size lab-on-a-chip card and inserted into the analyzer. In less than 15 minutes, the instrument indicates the probability of AMI. If the EMS crew obtains the sample early in the patient encounter, they should have results by arrival at the emergency department.

   To date, researchers in the San Antonio EMS study have analyzed the saliva of 42 patients, about a third of their recruiting goal. The study will continue for another year. Preliminary results are promising and indicate the technology is a strong candidate for a larger multisite study in the pre-hospital setting.

   The noninvasive nature of the test ideally suits it to be performed by either advanced or basic EMTs with or without access to 12-lead interpretation and/or telemetry. This diagnostic tool may also be valuable to rule in patients who have NSTEMIs.

   This program has been enthusiastically supported by the San Antonio Fire Department and its Office of the Medical Director. This research is supported by the National Institute of Dental and Craniofacial Research at the National Institutes of Health.

   David A. Wampler, PhD, LP, is a paramedic researcher and civilian training officer in the San Antonio Fire Department's Office of the Medical Director.

   Geoffrey Smith, BS, NREMT-P, is a civilian training officer for the San Antonio Fire Department. He was involved in the initial development of the salivary diagnostic study.

   Jeremy McElroy, EMT-P, is a paramedic with the San Antonio Fire Department.

   Spencer W. Redding, DDS, MEd, is professor and chair of the Department of Comprehensive Dentistry at the University of Texas Health Science Center at San Antonio. His research is focused on salivary diagnosis of systemic disease.

   Craig Manifold, DO, is medical director for the San Antonio Fire Department and San Antonio AirLIFE, as well as commander of the 149th Medical Group, Texas Air National Guard.