Detecting cyanide exposure based on thiocyanate measurement
Inventors
Reed, David A. • Emmett, George C.
Assignees
US Department of Homeland Security
Publication Number
US-11589808-B2
Publication Date
2023-02-28
Expiration Date
2041-04-30
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Abstract
In an example, a method of detecting cyanide exposure of an individual comprises measuring a thiocyanate level of the individual, and comparing the measured thiocyanate level to a preset thiocyanate threshold to determine whether the measured thiocyanate level is above the preset thiocyanate threshold indicating a level of cyanide poisoning requiring immediate medical assessment.
Core Innovation
The invention provides a rapid, on-scene method for detecting cyanide exposure in an individual by measuring a thiocyanate level and comparing it to a preset thiocyanate threshold. Thiocyanate is a direct metabolite produced when the body detoxifies cyanide, and its elevated level in saliva or other bodily fluids indicates that the detoxification mechanisms have been overwhelmed, suggesting acute cyanide poisoning requiring medical assessment or treatment. The method can further involve measuring methemoglobin and carboxyhemoglobin levels to improve diagnostic confidence and assess exposure to carbon monoxide in combination with cyanide.
The problem addressed is the difficulty of timely and reliable cyanide exposure detection among fire smoke victims or individuals exposed to cyanide. Cyanide poisoning is a significant cause of mortality associated with smoke inhalation but is hard to measure quickly and accurately. Existing detection methods are either not widely available, not affordable, or too slow to guide the critical early administration of antidotes. The current reliance on clinical signs and symptoms is problematic because cyanide intoxication symptoms overlap with those of carbon monoxide poisoning.
This invention provides a practical and affordable approach using saliva samples combined with colorimetric chemical indicators, such as iron nitrate, to rapidly assess thiocyanate levels, supported optionally by pulse oximetry measurements of methemoglobin and carboxyhemoglobin levels. The preset thresholds for thiocyanate and other measured factors are derived from comparative studies of exposed and unexposed individuals and health monitoring outcomes, enabling better medical screening, decision-making, and timely treatment. This method can be deployed at emergency scenes to help save lives by facilitating rapid identification of cyanide poisoning.
Claims Coverage
The patent contains multiple independent claims focusing on methods to detect cyanide exposure by measuring thiocyanate levels and comparing them to defined thresholds, with optional additional measurements for methemoglobin and carboxyhemoglobin to refine medical assessment decisions.
Defining preset thiocyanate threshold based on monitored exposure outcomes
Determining a preset thiocyanate threshold by measuring thiocyanate levels before and after cyanide exposure in a plurality of test individuals, monitoring them for health effects, identifying harmed individuals requiring treatment, and comparing these levels to set a threshold indicative of harmful exposure.
Measuring thiocyanate levels to detect cyanide poisoning
Measuring thiocyanate (SCN−) levels catalyzed by enzyme rhodanese in an individual and comparing against the predetermined threshold to determine acute cyanide poisoning requiring medical treatment.
Use of biological fluids and chemical indicators for measurement
Measuring thiocyanate in biological fluids, particularly saliva collected via swabs or strips, contacted with a chemical colorimetric indicator such as iron nitrate, enabling a rapid, on-site detection.
Sequential diagnostic decision process involving methemoglobin and carboxyhemoglobin
If thiocyanate level is below a primary threshold, performing further assessments by measuring methemoglobin and carboxyhemoglobin levels with comparisons to respective lower preset thiocyanate thresholds and preset thresholds for methemoglobin and carboxyhemoglobin to recommend medical assessment.
Multiple time-point measurements after exposure
Measuring thiocyanate and optionally methemoglobin levels multiple times at different time intervals after exposure to assess changes in biomarker levels relative to the preset thresholds.
The claims collectively cover a comprehensive method for detecting cyanide exposure by quantifying thiocyanate levels with predetermined thresholds established through population studies, optionally combined with methemoglobin and carboxyhemoglobin measurements, using biological fluids and simple chemical indicators, enabling rapid diagnosis and timely medical intervention.
Stated Advantages
Provides a fast, affordable, and widely deployable on-scene test for presumptive identification of dangerous cyanide exposure.
Enables timely administration of life-saving antidotes based on objective biomarker measurements rather than relying solely on clinical symptoms.
Improves reliability of cyanide poisoning detection by combining thiocyanate measurement with methemoglobin and carboxyhemoglobin level assessments.
Allows differentiation of cyanide exposure severity through threshold-based interpretation of biomarker concentrations.
Utilizes stable and high-concentration markers such as salivary thiocyanate for easier and more precise measurement.
Documented Applications
On-site screening of firefighters exposed to fire smoke for cyanide poisoning.
Rapid detection and assessment of cyanide exposure in victims of building fires and hazardous materials incidents.
Field testing and medical monitoring of individuals potentially exposed to cyanide to guide medical treatment decisions.
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