The Limits of Detection: A New Horizon Beckons

First responders – whether law-enforcement personnel, firefighters, or EMS (emergency medical services) technicians – need real-time, easy-to-operate biological-agent detection technology, designed with detection limits below what is considered an infectious dose. Such detection capabilities are currently available for solid and liquid samples, but not yet for the analysis of airborne samples.

First responders also need clear guidance – immediately – at the scene of a potential release, for several reasons: (a): to protect the public through isolation and quarantine; (b) to recommend further medical care to any persons who might have been exposed to the biological agent(s); (c) to make a decontamination decision; and/or (d) to protect and collect potential evidence.

Current technology leaves much to be desired, unfortunately, in terms of most individual system’s sensitivity, accuracy, reliability, and ease of use. Some experts have suggested that the American people could serve as hundreds of millions of human “detectors” per se – but that suggestion certainly does not measure up to the modern standards of care either in medicine or in public health matters in general.

A complex and expensive ad hoc bio-surveillance system has emerged in the United States that includes hundreds of air samplers and clinical laboratories as well as epidemiological monitoring on a large scale. Airborne biological-agent detection programs – such as BioWatch – have generally been handicapped by a 24-36 hour time delay between the initiation of detection efforts and the receipt of definitive results. The BioWatch program currently relies on an extended cycle – approximately 24 hours – of air sampling, followed by laboratory analysis of the samples collected. The combination of delayed results and comparatively high cost makes this approach less thaneal. However, this system provides earlier detection than previously was available by relying solely on epidemiological surveillance.

Quantum Improvements in Sight; Also Additional Hurdles 
 The next generation of the BioWatch program – Generation 3.0 – is currently testing and deploying highly accurate, autonomous biological-agent detectors that have the ability to monitor more than 20 agents, continuously, for 30 days at a time, and without human intervention required. These newer detectors also have the capability to collect samples, carry out the analyses needed, and quickly relay the results developed to decision-making authorities – all within the space of only a few hours. The numerous benefits provided by this technological development promise to revolutionize first-responder biological-agent detection for years to come.

The primary technologies used to detect biological agents fall into two categories – those that are antibody-based; and those that are DNA-based. Antibody-based detection devices, which use shape recognition of a specific region of the target as their primary indicator, canentify a relatively broad spectrum of biological agents.  These devices have not been reliable in the past, but the improved current technology can be extremely accurate and, depending on the type of antibody used, acceptably precise for most operational purposes.

It is important to recognize, though, that antibodies can be relatively non-specific, a characteristic that can lead to many false positives. On the other hand, when the antibodies used are specific to a single disease-causing organism, they can be extremely accurate. The hand-held assays that responders have become familiar with are examples of antibody-based technology capable of detecting bacteria, viruses, and toxins. Their primary advantage is speed – less than 15 minutes for accurateentification in most if not all cases, for example. However, there also is a primary disadvantage – namely, a lack of sensitivity, because they are not able to detect biological agents below the infectious dose postulated.

DNA-based detection devices recognize biological agents by analyzing their genetic material (deoxyribonucleic acid, or DNA). These devices first amplify, or copy, a specific region of the target agent’s genetic material and use the information provided to detect the presence of the amplified DNA. The amplification process, which copies the genetic material through use of an enzyme known as polymerase, is commonly known as a polymerase chain reaction (PCR).

Sensitivity and Speed – Or the Lack Thereof
 Theoretically, PCR technology has the ability to detect a single biological agent – if and when the genetic material is intact. The primary advantage of a PCR analysis is sensitivity; its primary disadvantage is speed or, more accurately, the lack of speed – assays typically take an hour or more, which in most life-or-death situations is unacceptable.

Neither of these improved biological-agent detection technologies currently has the ability to detect viable organisms. For that reason, culturing the organism in a laboratory is still the gold standard for biological agententification. Nonetheless, BioWatch Gen 3.0 technology – because it automates biological agent detection – represents a major step forward in developing rapid, sensitive, and accurate new bio-detection capabilities for the nation’s first responders. Other advances in the biotechnology arena – e.g., in the field of micro-fluidics – promise to miniaturize and further automate biological-agent detection in the future. (Micro-fluidics is the multi-disciplinary science dedicated to the manipulation of liquids on a miniature scale.)

Theoretically, all biochemical reactions – e.g., air sampling, biological sample preparation, DNA amplification, antibody-antigen recognition, andentification – can be automated and analyzed on a computer chip-sized device. Eventually, therefore, first responders may carry highly accurate and automated pager-sized devices capable ofentifying biological agents in ambient air in as little as 15 minutes – using two or more complementary technologies such as antibody- and DNA-based detection.

Nonetheless, there is still a long way to go. Given the additional technological hurdles that still must be overcome, real-time airborne bio-detection at the first-responder level – i.e., using devices capable of detecting bacteria, viruses, and toxins at levels below the “probably harmful” threshold  – is in all probability still a generation away.