Lab Matters Spring 2023 | Page 9

By Blake R . Elam , MS , CT supervisor , Nevada State Public Health Laboratory

FROM THE BENCH

On the afternoon of June 10 , 2022 , the Chemical Threat ( CT ) Department of the Nevada State Public Health Laboratory ( NSPHL ) received a request to analyze specimens from patients suspected of suffering from acute Thallium toxicity . The patients , who reside in Las Vegas , had consumed sweets from India , and their symptoms included hair loss and peripheral nerve pain . After these samples were sent to Quest Diagnostics for analysis and were found by that laboratory to be positive for Thallium , the finding sparked a discussion that would lead to a collaborative effort between NSPHL , the Southern Nevada Health District , the Agency for Toxic Substances and Disease Registry , the Las Vegas Metropolitan Police Department All-Hazard Regional Multi-Agency Operations and Response Unit and the University of Nevada ’ s Keck Museum . This team effort sought to identify the source of Thallium contamination . Factors of consideration included :

• Sample collection ( location , type , technique )

• Chain of custody procedures

• Laboratory analysis of environmental swabs , food samples , teas , soil , plant material and pool water via inductively coupled mass spectrometry ( ICP-MS ).

The aim of NSPHL ’ s CT group was to quantitatively analyze these samples to ensure the absence of environmental Thallium contamination and to elucidate the sources of patient poisoning .

Laboratory Testing

The NSPHL CT group prepared and analyzed 89 samples for Thallium testing . The matrices of these specimen were varied , and each sample type represented challenges that were overcome using variations of a nitric acid digestion and evaporation preparation method . These prepared samples were then subject to quantitative analysis via ICP-MS using a modified version of the Laboratory Response Network for Chemical Threats ( LRN-C ) Toxic Element Method . Control

“ Barfi ” imported sweets chemically tested for Thallium via ICP-MS . Photo : NSPHL

environmental swabs and of various minerals were procured from the Keck Museum . Control food samples were purchased at a local grocery store . All the prepared samples were analyzed in comparison to a prepared calibration curve and QCs on the Perkin Elmer Nexion 350D ICP-MS .

NSPHL also received four patient sample requisitions for Thallium analysis . The sealed package contained two urine samples and two blood samples . The urine samples were prepared and analyzed for Thallium content using the LRN-C standard toxic elements procedure . Since Thallium is cleared from blood very rapidly , the CT group designed a quantitative ICP-MS method that was successful in determining the amount of Thallium contained within the blood samples .

Result Interpretation and Reporting

Of all the food and environment samples received from the Southern Nevada Health District that were collected from inside and outside of the patient family home , only one contained clinically significant amounts of Thallium . The food product known as “ Barfi ” which had been consumed by multiple members of the household were contaminated with amounts of Thallium ranging from 10 – 100 µ g . The same Barfi samples were tested via X-ray fluorescence spectroscopy by a participating lab yielded negative analytical results for Thallium . To rule out any possible false positives and obtain a clearer understanding of the complexity of the Barfi matrix , the chemical terrorism group tested the top metallic frosted layer , the bottom unfrosted layer and vertical cross sections of multiple Barfi sweets . Interlaboratory verification of these results were executed by the Commonwealth of Virginia Department of General Services Division of Consolidated Laboratory Services in Richmond who performed a blind study of our samples via ICP-MS .

Final reports of all the testing were delivered to the Southern Nevada Health District and the Las Vegas Metropolitan Police Department . This case demonstrates that multi-agency cooperation and chemical testing by ICP-MS is crucial in the ascertainment of complex poisoning scenarios . g