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Analysis of a novel field dilutionmethod for testing samples that exceedthe analytic range of point-of-careblood lead analyzersAntonio James Neria, Joannie Royb, Jeffery Jarrettc, Yi Panc,Carrie Dooyemaa, Kathleen Caldwellc, Nasir Tsafe Umar-Tsafed,Ruth Olubiyoe & Mary Jean Brownf

a US Centers for Disease Control Prevention, Atlanta, GA, USAb Médecins Sans Frontières OCA, Amsterdam, the Netherlandsc US Centers for Disease Control and Prevention, Inorganic andRadiation Analytical Toxicology Branch, Atlanta, GA, USAd Blood Lead/Inorganic Metals Laboratory, Gusau, Nigeriae Médecins Sans Frontières OCA, Nigeria, Gusau, Nigeriaf US Centers for Disease Control and Prevention, Healthy Homesand Lead Poisoning Prevention, Atlanta, GA, USAPublished online: 25 Nov 2013.

To cite this article: Antonio James Neri, Joannie Roy, Jeffery Jarrett, Yi Pan, Carrie Dooyema,Kathleen Caldwell, Nasir Tsafe Umar-Tsafe, Ruth Olubiyo & Mary Jean Brown , International Journalof Environmental Health Research (2013): Analysis of a novel field dilution method for testingsamples that exceed the analytic range of point-of-care blood lead analyzers, International Journalof Environmental Health Research, DOI: 10.1080/09603123.2013.857390

To link to this article: http://dx.doi.org/10.1080/09603123.2013.857390

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Analysis of a novel field dilution method for testing samples thatexceed the analytic range of point-of-care blood lead analyzers

Antonio James Neria*, Joannie Royb, Jeffery Jarrettc, Yi Panc, Carrie Dooyemaa,Kathleen Caldwellc, Nasir Tsafe Umar-Tsafed, Ruth Olubiyoe and Mary Jean Brownf

aUS Centers for Disease Control Prevention, Atlanta, GA, USA; bMédecins Sans Frontières OCA,Amsterdam, the Netherlands; cUS Centers for Disease Control and Prevention, Inorganic andRadiation Analytical Toxicology Branch, Atlanta, GA, USA; dBlood Lead/Inorganic MetalsLaboratory, Gusau, Nigeria; eMédecins Sans Frontières OCA, Nigeria, Gusau, Nigeria;fUS Centers for Disease Control and Prevention, Healthy Homes and Lead Poisoning Prevention,Atlanta, GA, USA

(Received 4 March 2013; final version received 14 August 2013)

Investigators developed and evaluated a dilution method for the LeadCare II analyzer(LCII) for blood lead levels > 65 μg/dL, the analyzer’s maximum reporting value.Venous blood samples from lead-poisoned children were initially analyzed in the fieldusing the dilution method. Split samples were analyzed at the US Centers for DiseaseControl and Prevention (CDC) laboratory using both the dilution method andinductively coupled plasma-mass spectrometry (ICP-MS). The concordance correlationcoefficient of CDC LCII vs. ICP-MS values (N = 211) was 0.976 (95 % confidenceinterval (CI) 0.970–0.981); of Field LCII vs. ICP-MS (N = 68) was 0.910 (95 % CI0.861–0.942), and CDC LCII vs. Field LCII (N = 53) was 0.721 (95 % CI0.565–0.827). Sixty percent of CDC and 54 % of Field LCII values were within ±10 %of the ICP-MS value. Results from the dilution method approximated ICP-MS valuesand were useful for field-based decision-making. Specific recommendations foradditional evaluation are provided.

Keywords: laboratory; lead poisoning; dilution methods

Introduction

An expanding body of literature has demonstrated that lead negatively impacts humanhealth (Laraque et al. 1990; Centers for Disease Control and Prevention [CDC] 1994,2002; Advisory Committee on Childhood Lead Poisoning Prevention 2007). The devel-oping organs of children are particularly vulnerable to lead poisoning. Low levels oflead poisoning cause long-term brain damage and behavior problems while higher levelscause kidney damage, neurological impairment with encephalopathy, and possibly death(Dart et al. 2004; Henretig 2006; CDC 2007). Screening in the USA is often done usingpoint-of-care blood lead testing instrumentation (CDC 2002; Stanton et al. 2006).Currently, the only commercially available point-of-care blood lead testing analyzer inthe USA is the LeadCare II analyzer (LCII), manufactured by Magellan Biosciences(Shannon & Rifai 1997). This analyzer is approved by the US Food and Drug Adminis-tration (FDA) for blood lead analysis for the range 3.3–65 μg lead/dL of blood. TheFDA has determined the LCII to be “substantially equivalent” to graphite furnace

*Corresponding author. Email: aneri@cdc.gov

© 2013 Taylor & Francis

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atomic absorption spectrometry results, yet simple enough to be waived from standardClinical Laboratory Improvement Amendment (CLIA) requirements for proficiency test-ing (FDA 2005; Shannon & Rifai 1997). Development of the LCII was a milestone inadvancing point-of-care measurement for blood lead. The LCII has markedly decreasedthe time from diagnosis to treatment and has allowed for lead-poisoning investigationsto proceed quickly in low-resource settings.

Childhood lead poisoning occurs globally and is often found to be much more severein low-resource countries compared to the USA. A recent investigation in Nigeria revealedover 100 child fatalities related to lead poisoning (Dooyema et al. 2011; Lo et al. 2012).There are also reports of lead-related fatalities from Senegal (Haefliger et al. 2009), wherethe World Health Organization (WHO) confirmed at least 18 children died from leadpoisoning. Additionally, there are many reports of extremely elevated blood lead levelsfrom other countries (Nduka et al. 2008; Orisakwe and Nduka 2009; Shi et al. 2009;Brown et al. 2010; Niu 2010; Norman et al. 2010; Ramos et al. 2010; Rowley 2010). Inmost of these reports, the average BLLs reported were > 65 μg/dL, levels considered to belife-threatening to children (CDC 2002).

In March 2010, Médecins Sans Frontières (MSF) reported to local health authoritiesan unusually high number of children under five years of age dying in mining commu-nities in Northern Nigeria. In May 2010, the government of Nigeria requested assistancefrom the US Centers for Disease Control and Prevention (CDC) to join the effort inidentifying and addressing lead poisoning in Northern Nigeria. Investigations revealedthat children were being exposed to high levels of finely ground lead-contaminated dustresulting from artisanal gold mining processes. Teams used LCII at the point-of-care toconfirm the diagnosis of lead poisoning, triage children for life-saving chelation treat-ment, and monitor the efficacy of treatment (CDC 2010; Dooyema et al. 2011; VonLindern et al. 2011). Eighty-five percent of 204 venous blood samples taken from chil-dren in the field exceeded the upper reportable limits of the LCII (> 65 μg/dL) (CDC2010, Dooyema et al. 2011). Prioritization of medical needs required immediate deter-mination of BLL rather than waiting for inductively coupled plasma-mass spectrometry(ICP-MS) results. This led investigators in the field to collaborate with the CDC labora-tory and LCII manufacturer to evaluate methods to modify the LCII method with anadditional dilution step to extend the reporting range. Initially, blood was diluted withsaline prior to LCII analysis. However, the results of this method consistently overesti-mated ICP-MS values by twofold or greater and the concordance correlation coefficient(CCC) was poor (0.423, 95 % confidence interval (CI) 0.202–0.603, N = 29). A dilutionstep that used whole blood with lead levels verified to be < 3.3 μg/dL demonstratedmarkedly improved agreement with ICP-MS results, deserving further attention. Thisarticle compares the agreement of the values resulting from a blood dilution methodused in the field and laboratory on LCII to ICP-MS values using blood from lead-poisonedchildren with extremely high BLLs.

Methods

Patients and samples

This study analyzed venous blood samples taken between 14 July 2010 and 24 September2012 from 227 children aged < 5 years admitted for chelation therapy to the MSF ward.Consent for treatment was obtained from childrens’ parents. Eligible sample values werefrom those known to have undergone the LCII dilution method either in the field or theCDC laboratory.

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Blood for analysis at CDC was drawn directly from the patient into a separate tubeand sent to the CDC Inorganic Analytical Toxicology Laboratory in Atlanta, Georgia,USA. Samples were shipped to CDC in batches using ambient-temperature shipping,the only method readily available.

Analytical methods

The CDC laboratory first analyzed samples with ICP-MS (Jones et al. 2009) using amodification of a method of Nixon et al. (1999) for analyses of metals in biologicalmatrices. If sufficient blood remained, samples were then analyzed on LCII. Sampleswhose LCII results were > 65 μg/dL (reported as “HI” on the LCII) were prepared andanalyzed using the blood dilution method as described below. To ensure quality controland ensure precision of the ICP-MS method, the CDC laboratory undertook repeatedICP-MS analyses of quality control materials during the time of sample processing.Precision (2 SD) of quality control analyses was 7 % at 10 μg/dL, 9 % at 100 μg/dL,and 4 % at 400 μg/dL.

The goal of the dilution method was to dilute the sample to within the operating rangeof the LCII (3.3–65 μg/dL) without changing the matrix of the blood and reagent-mixtureagainst which the analyzer is calibrated. The method presented here required the diluentbe a human blood sample verified to have a BLL < 3.3 μg/dL (reported on the analyzer as“LOW”) using standard LCII analytic methods on a machine calibrated using the test kitmaterials (ESA Biosciences Inc 2007). This will be referred to as “low blood” in the sub-sequent steps. “Low blood” specimens obtained at each site were typically fresh (drawnwithin previous 24 hours), but were sometimes reused up to seven days, being stored at2–8 °C when not in use. The “low blood” reagent-mixture to be used was prepared foranalysis in an LCII reagent vial per the standard LCII protocol: 50 μL of the “low blood”specimen was transferred from the mixed (ideally with a vortex) tube of blood obtainedfrom the patient verified to have a BLL < 3.3 μg/dL to an unused LCII reagent vial usingan LCII capillary tube and plunger. This was followed by thorough mixing to create a“low blood” reagent-mixture with a total volume of 300 μL (250 μL of reagent and 50 μLof “low blood”). A “high blood” reagent-mixture was then prepared by using a capillarytube and plunger to transfer 50 μL of blood from the tube of the specimen previouslydetermined by LCII analysis to have a BLL > 65 μg/dL (reported as “HI” on the LCII) intoa separate, unused, LCII reagent vial. Next, 50 μL of the “high blood” reagent-mixturewas transferred to the vial containing 300 μL of “low blood” reagent-mixture using anunused LCII capillary tube and plunger, mixing well after the transfer. One drop of thisfinal mixture was then analyzed on the LCII. Note that the LCII is calibrated to giveresults given a 1 + 5 dilution of blood upon adding 50 μL of blood to a 250 μL reagentcontainer (50 μL in 300 μL of total solution = sixfold dilution). By adding an alreadydiluted 50–300 μL to create a total volume of 350 μL, there was an additional 1 + 6dilution (50 μL in 350 μL of total solution = sevenfold dilution). Hence, to obtain themeasured blood lead concentration in the “HI” sample, investigators simply multiplied theLCII result by 7.

Statistical analysis

Field and CDC LCII dilution values were independently compared to ICP-MS values aswell as each other if available. For the Field LCII values, only those known to haveresulted from the dilution procedure described above were considered in this analysis.

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Agreement was determined using three approaches. First, the CCC, a commonagreement coefficient used in medical device validation studies which takes into accountthe uncertainties of both methods, was applied to compare the data from either the Fieldor Laboratory LCII dilution values to the ICP-MS results, as well as to each other (Lin1989; Lin 2008). CCC results can range from 0 to 1.0, with 0 indicating no agreementand 1.0 indicating perfect agreement. A CCC result of ≥0.7 was used to indicate goodagreement. Next, to help healthcare providers in the field interpret a LCII value fromthe dilution method in relation to the ICP-MS value, investigators determined the per-cent of the LCII dilution values that were within ±10 % of the ICP-MS values. Finally,values were evaluated as to their positive or negative bias in comparison to ICP-MS val-ues using the mean bias observed in all samples as well as the mean bias in quartilesbased upon ICP-MS values, similar to that used by Taylor et al. (2001). This informa-tion was used to depict the differences between the Field and CDC LCII dilution valuesin comparison to ICP-MS results (Field/CDC LCII dilution value – ICP-MS) withboundaries of ±1.96 standard deviations to indicate the range of variability in 95 % ofthe samples. Information was entered in Microsoft Excel 2010 (Microsoft Corp.,Redmond, WA) and analyzed in SAS version 9.3 (SAS Institute Inc. Carey, NC) (SASInstitute 2002–2010).

Results

A total of 227 samples were analyzed by the CDC laboratory using ICP-MS. Sixteensamples could not be further analyzed using the dilution method at CDC due to lack ofsufficient sample volume and 158 samples from the field had no information regardingeither the result or the dilution method used. This resulted in a total of 69 Field LCIIdilution values that could be verified as having been done using the method reportedabove; the reported Field LCII values range was 56.5–262.5 μg/dL. There were 211CDC LCII dilution values (range 56.0–362.0 μg/dL). Field and CDC LCII values werecompared to ICP-MS values (geometric mean 86.9, range 52.4–694.0 μg/dL). Therewere 53 Field LCII values for comparison to CDC LCII values.

Method comparison

The CCC of CDC LCII vs. ICP-MS values was 0.976 (95 % confidence interval (CI)0.970–0.981); of Field LCII vs. ICP-MS was 0.910 (95 % CI 0.861–0.942); and ofCDC LCII vs. Field LCII was 0.721 (95 % CI 0.565–0.827) (Table 1).

The ICP-MS quartiles were ≤66.6, 66.7–77.5, 77.6–94.7 and > 94.7 μg/dL. Overall,60 % of CDC LCII laboratory values were within ±10 % of the ICP-MS value; as were54 % of Field LCII values (Figures 1–4). There were no statistically significantdifferences between quartiles in regard to the percent within ±10 % of the ICP-MS valuefrom either laboratory (Table 2).

CDC LCII values overestimated ICP-MS values by an average of 7.8 μg/dL (8 % ofthe average ICP-MS value), with 95 % of values falling between −7.9 and + 23.5 μg/

Table 1. CCC results comparing each site vs. ICP-MS as well as to each other.

Comparison n CCC 95% CI

CDC LCII vs. ICP-MS 211 0.976 (0.970, 0.981)Field LCII vs. ICP-MS 68 0.910 (0.861, 0.942)CDC LCII vs. Field LCII 53 0.721 (0.565, 0.827)

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Figure 1. Field LCII vs. ICP-MS values with ±10 % error bounds from ICP-MS results*.Triangle: Field LCII vs. ICP-MS values. Dashed lines: ±10 % of ICP-MS value.Note: *One point is excluded from this chart for the sake of clarity. It had an ICP-MS result of 286µg/dL with a Field LCII result of 262.5 µg/dL. This value was within ±10 % of the ICP-MS values.

Figure 2. Difference between Field LCII and ICP-MS value as measured against ICP-MS*:Triangle: Field LCII-ICP-MS value. Dashed lines: 95 % Level of agreement (−14.6, +25.7).Dot-dash line: Average difference Field LCII – ICP-MS (+5.5).Note: *One point is excluded from this chart as it appeared to be a reporting error. This point hadan ICP-MS result of 694 µg/dL with a bias of −234.1.

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Figure 3. CDC LCII vs. ICP-MS values with ±10 % error bounds from ICP-MS results. Trian-gle: CDC LCII vs. ICP-MS values. Dashed lines: ±10 % of ICP-MS value.

Figure 4. Difference between CDC LCII and ICP-MS value as measured against ICP-MS.Triangle: Field LCII-ICP-MS value. Dashed lines: 95 % Level of agreement (−7.9, +23.5).Dot-dash line: Average difference Field LCII – ICP-MS (+7.8).

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dL. Field LCII values overestimated ICP-MS values by an average of 5.5 μg/dL (7 % ofthe average ICP-MS value), with 95 % of values falling between −14.6 and 25.7 μg/dL.One outlying Field LCII value skewed the quartile and overall bias for the Field LCIIvalues; this measured value was 459.0 μg/dL and ICP-MS value was 694.0. This valuewas excluded from analysis or figures as it was not possible under the dilution proce-dure (i.e. at most the measured value could have been 65 μg/dL × 7 = 455 μg/dL).

Discussion

As a number of factors – including time from sampling to analysis, field analysis andshipping conditions, field staff training, and quality control – affected the findings, theyare reported here to provide a better context prior to discussing results.

Factors affecting results

The long times between blood being drawn and being analyzed by LCII at CDC (approx-imately 2–3 weeks) as well as the high ambient temperatures for analysis and shipping inthe field were certainly outside of manufacturer-recommended conditions for analysis ofblood on LCIIs in either laboratory. The LCIIs used in this investigation have anoperational temperature range 12.2–36.1 °C and relative humidity range 12–80 % (ESABiosciences Inc 2007). The investigation area bordered the Sahara desert and local radioreports indicated daily temperatures well above 38 °C. The closest town with easilyaccessible temperature records (Kano, Nigeria), approximately 200 miles away from theMSF field station, reported an average daily high of 37.2 °C and a monthly record highof 43.9 °C with average relative humidity ranging between 33 and 81 % for May–June

Table 2. Number and percent of CDC and Field LCII dilution procedure values within ±10 % ofthe ICP-MS value by ICP-MS quartile.

ICP-MS groups(μg/dL) (n dilutionsamples)

Average CDC LCII dilutionbias (μg/dL) (% differencevs. mean ICP-MS value)

Range ofvalues (μg/dL)

Number of valueswithin ±10% ofICP-MS value (%)

CDC LCII≤ 66.6 (n = 55) 5.9 (10 %) −5.2–21.4 31 (56 %)a

66.7–77.5 (n = 52) 5.1 (7 %) −8.9–15.7 35 (67 %)77.6–94.7 (n = 51) 8.0 (9 %) −6.6–23.2 25 (49 %)> 94.7 (n = 53) 12.3 (7 %) −12.0–44.0 36 (68 %)

All CDC LCII samples(n = 211)

7.8 (8 %) −12.0–44.0 127 (60 %)

Field LCII≤ 66.6 (n = 11) 8.3 (13 %) −7.0–27.7 4 (36 %)a

66.7–77.5 (n = 24) 7.0 (10 %) −8.3–21.3 12 (50 %)77.6–94.7 (n = 26) 4.7 (5 %) −15.5–36.0 15 (58 %)> 94.7 (n = 7) 9.5 (9 %) −23.5–13.1 6 (86 %)b

All Field LCII samples(n = 68)

5.5 (7 %) −23.5–36.0 37 (54 %)b

aΧ2 for equal proportions among categories (p = 0.9994 for CDC LCII and p = 0.9932 for Field LCII).bOne Field LCII dilution result was outside of the analytic range of LCII, even when using the dilutionmethod, and was excluded. This field value was 459.9 μg/dL and ICP-MS value was 694.0 μg/dL. If this valueis included in the analysis, results for > 94.7 (n = 8) are dilution −29.9 (18%), range (−234.1–13.1), 6 within±10% (75%). For overall results, n = 69, 2.1 bias (2 %), range (−234.1–36.0), 37 within ±10% (54%).

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(BBC 2010). These conditions were not often amenable to the proper functioning of theLCIIs in the field. When daily indoor temperatures in the field laboratory exceeded theLCII temperature parameters, the LCIIs would simply turnoff. This required analyses tobe undertaken in the cooler mornings and late afternoons. Electricity was initiallyunavailable, thus neither indoor air conditioning (which provided both temperature anddust control) nor external power for the LCIIs was available; the analyzers were operatedusing batteries. Manufacturer instructions included in the LCII indicate that unrefriger-ated samples should be analyzed “within 24 hours stored at 10.0 –32.2 °C.” Given theconditions noted above, these requirements could not always be met in the field and,despite the best efforts at using a timely cold-chain technique, could not be met duringtransit of samples to the CDC laboratory.

As can be expected with any novel method developed and implemented in the field,the development, implementation, and refining of laboratory procedures, includingquality assurance, occurred over time. Unfortunately, the operational constraints inherentin the start-up of any large medical intervention did not allow for investigators tocompletely control which blood draw equipment was used and not all equipment waspre-screened for lead. Investigators estimate that approximately 70 % of the samplestaken used blood draw and storage materials pre-screened for lead. Also as a conse-quence of a new operation, proper sampling, liquid transfer, storage, and transportationprocedures for blood were reviewed and put in place over time. Having health careworkers with limited experience operating in a low-resource setting implement a novelmethod in the field laboratory may have introduced some operator errors. In addition,the small sample volumes used and the temperatures encountered in the field could havecaused some evaporation of blood samples, leading to false high readings on the FieldLCII due to concentrated blood. Lastly, while practical on a short-term basis, a methodrelying on a constant supply of blood from donors with BLLs below 3.3 μg/dL wouldlikely be difficult to sustain over longer time periods in highly lead-contaminatedsettings.

Yet, despite these extremes of time, temperature, and quality assurance in the fieldthere appeared to be remarkable correlation and moderately good approximation ofblood lead levels when using this dilution method. CCC analyses for both laboratoriesin relation to the ICP-MS as well as to each other were good and the agreementanalyses also indicated concordance within a range that would be helpful to makeclinical decisions.

Clinically, both the Field and CDC LCII dilution values consistently overestimatedBLLs determined by ICP-MS but not so much as to be misleading for diagnosis ortreatment. Finding that 95 % of the differences for CDC LCII values vs. ICP-MS were−11.2–26.6 μg/dL and that 60 % of these samples were within ±10 % of the ICP-MSvalue was promising considering an average BLL of 86.9 μg/dL, given the observedprecision of the ICP-MS method quality control analyses. Data with this amount ofdifference from laboratory-based methods would still be considered helpful to at leastinitiate and monitor life-saving chelation therapy under appropriate protocols untilvalues came within a range that could be measured using standard LCII procedures.Additionally, 95 % of the differences for Field LCII values vs. ICP-MS values were−14.6–25.7 μg/dL and approximately half (54 %) of Field LCII values were within±10 % of the ICP-MS value, this added assurance as to the clinical applicability ofthe values resulting from this method. Finally, as there were no significant differencesbetween ICP-MS quartiles for either laboratory it indicated to investigators that thisbias was not related to the concentration of lead in the blood analyzed.

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While these results are promising, there was still considerable variability and biasin the findings presented; a variety of factors likely contributed to these findings.Despite the best of efforts, ambient lead levels in the field laboratory may have beenhigher than those in the CDC laboratory. Small volumes used in combination withhigher temperatures in the field likely caused evaporation and concentration of thesample in the LCII, which may have resulted in a reported concentration greater thanthe actual concentration. Use of a laboratory pipettes with disposable tips instead ofthe capillary tubes and plungers that come with the LCII test kits would provide morereproducible liquid transfer during the dilution method steps. However, these supplieswere not available at the point-of-care, so use of LCII test kit supplies was requiredin the field (and maintained at CDC to mirror the procedures being used in the field).Finally, prolonged shipping times and high temperatures may also have affected theblood prior to it being analyzed on the LCII at CDC laboratories.

CDC and MSF strongly recommend all laboratories adhere to a rigorous qualityassurance program. This program should include internal quality control procedures,using materials provided by the manufacturer that are evaluated for lead content and rig-orous standard operating procedures. The LCII, when operated in its normal manner,should not need external quality control with a reference laboratory. In Nigeria, the LCIIwas being used outside of the manufacturer’s instructions and operating environment.For this reason, MSF developed a pragmatic quality control protocol with referencelaboratories that included repeat analysis of every 10th BLL > 65 μg/dL by a separatetechnician, over-sampling of blood specimens requiring the dilution method for thereference laboratories and, the use of small, frequent batches of samples for validationto allow the program to make data-driven decisions quickly. The low statistical powerof such a protocol can be overcome by retrospective quartile analysis of samplescollected over time (Klarkowski and Orozco 2010). As of October 2012, 55 samplesthat required the use of the dilution method had been analyzed by two separatetechnicians in the field laboratory. The CCC between values from the two technicianswas 0.976 (95 % CI 0.965–0.984), indicating good agreement. These results indicatethat a reliable field-based blood lead testing program utilizing the dilution procedure isachievable.

Conclusion

These results indicate that, while additional work is needed to evaluate this procedureand why results overestimated the ICP-MS values, it appears that this novel dilutionmethod can be used to both inform clinical decisions regarding baseline BLLs andmonitor the effectiveness of therapy when BLLs are > 65 μg/dL in the field. Futureevaluations of this method should focus on a rigorous evaluation of field implementa-tion in comparison to a reference laboratory so as to produce more accurate results forclinical decision-making in the field. Specifically, the issues that need to be addressedare (i) improving field reporting of BLLs to central laboratories (including test kitlot numbers, analytic method, technician identifier, and patient-tracking information);(ii) evaluation of the accuracy and precision of the LCII dilution method in the fieldwith a reference instrument utilizing a more planned approach; (iii) protocols for screen-ing all the blood sampling materials as well as for their storage in lead-contaminatedenvironments; (iv) a process evaluation of the procedure to determine the most efficientmeans of implementing it; and (v) undertaking a search for a diluent that does not relyupon low-BLL human blood, as this resource in such settings is limited.

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AbbreviationsBLL Blood lead levelCDC Centers for Disease Control and PreventionCLIA Clinical Laboratory Improvement AmendmentsICP-MS Inductively Coupled Plasma-Mass SpectrometryLCII LeadCare II analyzerMSF Médecins Sans FrontièresWHO World Health Organization

AcknowledgmentsThe authors wish to acknowledge the Nigerian Government, United States Agency forInternational Development, United Nations, WHO, and Terragraphics Environmental EngineeringInc. for their partnership in responding to this environmental disaster. The findings and conclu-sions in this report are those of the authors and do not necessarily represent the views of theCDC.

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