Page 79 - JSOM Spring 2018

venipuncture of scheduled bloodwork for semiannual clinical Lead levels measured by the ICP-MS system and by the com-
diagnostic evaluations. Samples were divided and prepared for mercial system strongly correlated with lead levels across the
analysis using the commercial blood lead detection unit Lead- entire range of values (R = 87.7%; p < .0001), demonstrating
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Care II (Magellan Diagnostics, http://www.leadcare2.com/) the overall ability to leverage the commercially available hu-
®
and inductively coupled plasma mass spectrometry (ICP-MS). man-blood lead detector for use with canine samples. ICP-MS
detection capability was as low (0.31μg/dL), and the minimum
Commercial Test limit of detection of the commercial system, 3.3μg/dL, was re-
Blood samples were analyzed using the protocol provided by corded in multiple instances. Although the discrepancy between
the commercial test’s manufacturer. Briefly, the analyzer was the two methods at low lead levels may be substantial, the need
calibrated and quality-control tests were conducted using the for precision in detection of lead levels below 4.0μg/dL for rapid
provided materials and reagents. Whole canine blood (50μL) evaluation of canine lead toxicity is not crucial, considering the
was deposited into a treatment capillary tube and combined minimal consequence and lack of symptoms at these levels.
with the included reagent (250μL of 0.34 mol/L HCl). Sample
mixtures were transferred to the instrument sensor and results Multipurpose canines (left set) generally had higher blood lead
were read after a 3-minute analysis period. levels than did the military working dog group (right set). The
LeadCare II commercial testing system demonstrated similar
ICP-MS results to the ICP-MS (±18%) for lead levels above the Lead-
We mixed 2.0mL of whole canine blood with 1.0mL of 2% Care II system’s lower limit of detection (3.3μg/dL). ICP-MS,
nitric acid, and this mixture was digested for 24 hours. After inductively coupled plasma–mass spectrometry.
digestion, 2.0mL of water was added to yield a final volume
of 5.0mL and the sample was passed through a 0.22μm poly- Conclusion
ethersulfone filter to remove residual solids. Standards were es-
tablished using standard reference materials (IV-ICPMS-71A; These findings show that, like SOF Operators who spend ex-
Inorganic Ventures, https://www.inorganicventures.com), and tended periods in training areas or other scenarios with high
a 5ppb indium solution in 2% nitric acid was used as the in- environmental lead levels, SOF canines can have elevated
strumental internal standard during the analyses. Isotope Pb blood lead levels. None of the individual SOF canines tested
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was quantitatively monitored in a peak hopping mode with a had lead levels at which signs of lead toxicity have been previ-
total of 100 scans per point per isotope. The blank equivalent ously reported in animals. In addition, blood lead levels were
was measured at 0.24 ppb. determined to be subclinical; however, we were unable to cor-
relate the time or severity of exposure to environments having
Statistical Analysis high levels of lead with the measured blood lead levels of spe-
First, to evaluate the correlation of the two measurement cific canines. Because exposure to aerosolized lead particulate
platforms, the correlation coefficient was calculated, and a t occurs from ballistic primers, additional study is required to
test for correlations was performed to test the statistical sig- assess the absorption of aerosolized lead particulates by ca-
nificance of this correlation. For any values below the limit nines and the relationship of those exposure conditions to ab-
of detection, the halfway value of the limit of detection was sorption rates in humans.
inputted for further analysis.
To our knowledge, this was the first demonstration of the ac-
Second, to compare differences in the lead values between curacy of a commercially available human-blood lead level
MPC and MWD groups, a Kruskal–Wallis rank-sum test was test system used for canine blood level analysis. Although the
performed separately for each lead measurement platform. A accuracy and detection limits of the LeadCare II system dem-
value of p ≤ .05 was considered statistically significant. Al- onstrated a discrepancy versus ICP-MS at low levels of lead
though the p values were not directly corrected for multiple in blood samples, samples in which the lead level was greater
testing, all results would have the same conclusions with even than 4.0μg/dL did correlate well between the two methods.
a strict Bonferroni correction applied. All analyses were per- Based on the previously established minimum of 35μg/dL in
formed using Stata, version 12 (StataCorp, www.stata.org). animals showing clinical symptoms of lead toxicity, the lack of
correlation of the LeadCare II system at low levels is unlikely
to be a factor for veterinarians or animal technicians in diag-
Results
nosing canines.
Measured lead levels with both procedures are shown in Fig-
ure 1. As expected, lead levels were higher in blood samples Although the ICP-MS technique is recognized by the World
of the MPC group than in those of the MWD group. This Health Organization as a robust analytic tool for lead analysis
likely was due to SOF operational activities that resulted in in human blood, the LeadCare II system offers some ben-
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greater exposure to environmental lead. The maximum read- efits over ICP-MS, such as portability, assay duration (10–20
ing among the MPCs was 15.44μg/dL. The difference between minutes versus 24+ hours), and less sample draw requirement
the two groups was statistically significant for both measure- (50μL versus 2.0mL). In addition, the estimated cost per sam-
ment platforms (p < .0062 for the LeadCare II platform; p < ple was reduced from $30 for ICP-MS to $7.90 for the Lead-
.0093 for the ICP-MS). Samples from three of the MPCs ex- Care II system.
ceeded the previously defined threshold for lead toxicity in a
small animal population (i.e., 10μg/dL), but in none of the In this study, the LeadCare II system was accurate at levels
canines sampled did lead levels approach those at which clini- within range of those necessary to indicate lead toxicity. Given
cal symptoms have been reported (i.e., 35μg/dL). All MWD this accuracy, as well as the benefits of instrument portabil-
blood samples had minimal lead levels; these varied from ity, assay time, sample volume requirement, and cost per run,
0.31μg/dL to 1.1μg/dL, using ICP-MS. the potential for using this or another similarly performing,

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