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Suspicious Powder Episodes and the ED
By Richard J. Hamilton, MD, FAAEM, ABMT
One weekday morning a few months ago, seven people inside a hotel in downtown Philadelphia were quarantined. Why? A suspicious powder was found in one of the rooms. Fire department personnel, police, and anti-terrorism personnel responded to the 911 call for assistance from the hotel management. An initial on-scene test produced a positive result for anthrax. Traffic was stopped and hotel business came to a halt. Subsequent laboratory testing, plus questioning of the individual who had occupied the hotel room where the powder was found, revealed that it was simply baking soda, used as a substitute for toothpaste. The entire episode lasted more than three hours. No one presented to the emergency department (ED) for medical care in this case, but they have in prior cases—and often with the powdery substance with them. The response of emergency medicine physicians and staff varies from the common sense to the irrational, as individuals struggle to come to grips with dilemmas that protocol and procedure have yet to clarify.
The next time you are in the ED and have a quiet moment, review your hazardous material protocols. Imagine a scenario where, by terror attack, terror hoax, or public fear, an asymptomatic individual (or individuals) brings to you a suspicious powder or substance. Is there a rational approach to handling this situation? Do you understand what emergency personnel mean when they tell you that a "SMART ticket" test was negative or positive? What patients should be tested and by what means? Is decontamination required for everyone? Excellent resources exist, both on-line and in text form, which help to demystify the process behind the response to a potential hazardous material.1-3
Field testing generally consists of immunoassay tests. Three basic types of tests serve to detect and measure the binding of antigens highly specific to biological agents: disposable matrix devices (tickets or kits), biosensors that use reagent labels to indirectly assess binding, and biosensors that directly measure substances.1
Examples of ticket or kit technologies include the hand-held immunochromatographic assays (HHAs), BioThreat Alert (BTA) test strips (Tetracore, Gaithersburg, MD), and the sensitive membrane antigen rapid test (SMART) system. HHAs are similar to urine dipsticks. They provide a qualitative result based on color change, but an experienced observer can detect the strength of the reaction and make quantitative presumptions. Like other dipstick technologies, the quality of the tests improves when an automatic reader replaces the naked eye. BTA test strips use a different approach—lateral flow immunochromatography. This technique provides fewer false positives in environmentally collected samples. Like other lateral flow tests, there is a control reaction as well as variable reaction, and it can be read manually or by a powered reader. This is not unlike the urine pregnancy tests used by most hospitals.
Anthrax and ricin assays are available, and other assays are in development. The ticket system frequently discussed in the media is the SMART ticket. The SMART ticket works by tagging certain antigens with antibodies; positive tests are signified by forming a red dot that is detected by an automated system.1
The Centers for Disease Control and Prevention (CDC) does not completely support the use of these hand-held assays. In the case of anthrax, the tests require a minimum of 10,000-100,000 spores to generate a positive result, and they perform best when there are 1 million spores present. Inhalational anthrax requires an inoculation of 8000-50,000 spores. Thus, false negatives and false reassurance from these tests may be of grave concern. However, emergency services personnel often are asked to evaluate large bulk powders. Knowing that 10,000 spores of anthrax takes up a space about the size of a grain of salt, one would assume that sufficient material ought to be present to trigger a true positive. Therefore, even though these tests are not particularly robust, they do have a role in providing the "all clear" for innumerable suspicious-powder calls when there is a great quantity of material present. The CDC currently is studying these tests, and guidance should be forthcoming.2,3
CDC and the Laboratory Response Network
The CDC and the Laboratory Response Network (LRN) laboratory in your area will employ a two-step process when a sample is submitted. The first generally is an examination of the material for biological weapon characteristics as well as Gram staining. In addition, a polymerase chain reaction (PCR) assay may be employed. Most ED physicians are familiar with PCR assays for chlamydia or gonoccocal infections. In a PCR assay, any sample that contains even a small amount of the target DNA or RNA of bacterial or viral origin can be used. The specimen is collected and placed in a reagent container that liberates the DNA from the cells. Through a specialized protein denaturing and polymerase manufacturing process, the quantity of DNA is amplified. Finally, using a DNA probe, the amplified genetic material is labeled and can be read by an automated device.2
The CDC has funded the purchase of platforms for real-time polymerase chain reaction (PCR) assays for the LRN. Currently, the CDC still uses a combination of PCR, culture, and typing methods to identify biological weapons. These assays are being developed for field use, to eliminate transport time and speed identification of suspicious powders. PCRs are not considered final confirmatory evidence, but are highly sensitive and specific across a range of source specimens.2
The Greater New York Hospital Association has published some excellent advice for suspicious powders and substances. (See Table.) Common sense must prevail at all times; it should be remembered that anthrax is transmitted only by direct skin contact or direct inhalation of aerosolized anthrax spores. These recommendations are not intended for confirmed anthrax contamination.
In anticipation of the next time you are asked to evaluate a patient exposed to a suspicious powder, know which field test your local emergency medical service personnel may be employing, and understand its limitations. Expect field tickets or kits to err on the false-positive side. False negatives are concerning, but theoretically less likely if sufficient material is present and tested. PCR assays available through the CDC and LRN can require hours to report, but are highly sensitive and specific.
Dr. Hamilton, Associate Professor of Emergency Medicine, Residency Program Director, Department of Emergency Medicine, Drexel University College of Medicine, Philadelphia, PA, is on the Editorial Board of Emergency Medicine Alert.
1. National Institute of Justice. An introduction to biological agent detection equipment for emergency first responders. NIJ Guide 101-00, December 2001. (Accessed at www.ojp.usdoj.gov/nij.)
2. Centers for Disease Control and Prevention Website on Emergency Preparedness and Response. (Accessed at www.bt.cdc.gov/index.asp.)
3. Zajtchuk R, et al. Textbook of Military Medicine: Medical Aspects of Chemical and Biological Warfare. Sidell FR, et al, eds. Office of The Surgeon General, Department of the Army, Washington, DC; TMM Publications: 1997.