Accuracy-based proficiency testing for estradiol measurements.

OBJECTIVES: Accuracy of estradiol measurements is important but conventional proficiency testing (PT) cannot assess accuracy when possibly non-commutable samples are used and method peer-group means are the targets. Accuracy-based assessment of estradiol measurements is needed. DESIGN AND METHODS: Five serum samples were prepared from single donors, frozen, and distributed overnight to 76 New York State Department of Health (NYSDOH)-certified laboratories. Participants analyzed samples for estradiol. The biases of group means were assessed against the Centers for Disease Control and Prevention (CDC)-defined targets, evaluated using the Hormone Standardization Program (HoSt) E2 performance criterion of ±12.5 %. Each laboratory's performance was evaluated using total allowable error (acceptance limits) of target ±25 % or ±15 pg/mL (55 pmol/L) (whichever was greater, NYSDOH), target ±30 % (Clinical Laboratory Improvement Amendments [CLIA]), and target ±26 % (minimal limit based on biological variation [BV]). RESULTS: The biases (range) were 34 % (-17 % to 175 %), 40 % (-33 % to 386 %), 16 % (-45 % to 193 %), 5 % (-27 % to 117 %), and -4% (-31 % to 21 %), for samples at estradiol of 24.1, 28.4, 61.7, 94.1, and 127 pg/mL, or 89, 104, 227, 345, and 466 pmol/L, respectively. Large positive method/analytical systematic biases were revealed for 9 commonly used method/analytical systems in the United States at low estradiol concentrations. Of the 9 analytical systems, 0, 0, 3, 7 and 6 met the HoSt criterion for the samples with estradiol at the five respective concentrations. PT evaluation showed that 59 %, 69 % and 87 % of laboratories would receive a PT event passing (satisfactory) score when the CDC-defined target and a criterion of NYSDOH, CLIA or BV was used, respectively. However, >95 % laboratories would obtain PT passing score if method peer-group means were used as targets regardless of the criterion used. CONCLUSIONS: Improvement in accuracy of estradiol measurements is needed, particularly at low estradiol concentrations. Accuracy-based PT provides unambiguous information about the accuracy of methods/analytical systems.

Recommendations for Setting a Criterion and Assessing Commutability of Sample Materials Used in External Quality Assessment/Proficiency Testing Schemes.

It is important for external quality assessment materials (EQAMs) to be commutable with clinical samples; i.e., they should behave like clinical samples when measured using end-user clinical laboratory in vitro diagnostic medical devices (IVD-MDs). Using commutable EQAMs makes it possible to evaluate metrological traceability and/or equivalence of results between IVD-MDs. The criterion for assessing commutability of an EQAM between 2 IVD-MDs is that its result should be within the prediction interval limits based on the statistical distribution of the clinical sample results from the 2 IVD-MDs being compared. The width of the prediction interval is, among other things, dependent on the analytical performance characteristics of the IVD-MDs. A presupposition for using this criterion is that the differences in nonselectivity between the 2 IVD-MDs being compared are acceptable. An acceptable difference in nonselectivity should be small relative to the analytical performance specifications used in the external quality assessment scheme. The acceptable difference in nonselectivity is used to modify the prediction interval criterion for commutability assessment. The present report provides recommendations on how to establish a criterion for acceptable commutability for EQAMS, establish the difference in nonselectivity that can be accepted between IVD-MDs, and perform a commutability assessment. The report also contains examples for performing a commutability assessment of EQAMs.

Recommendations for Setting a Criterion for Assessing Commutability of Secondary Calibrator Certified Reference Materials.

A secondary higher-order calibrator is required to be commutable with clinical samples to be suitable for use in the calibration hierarchy of an end-user clinical laboratory in vitro diagnostic medical device (IVD-MD). Commutability is a property of a reference material that means results for a reference material and for clinical samples have the same numeric relationship, within specified limits, across the measurement procedures for which the reference material is intended to be used. Procedures for assessing commutability have been described in the literature. This report provides recommendations for establishing a quantitative criterion to assess the commutability of a certified reference material (CRM). The criterion is the maximum allowable noncommutability bias (MANCB) that allows a CRM to be used as a calibrator in a calibration hierarchy for an IVD-MD without exceeding the maximum allowable combined standard uncertainty for a clinical sample result (umaxCS). Consequently, the MANCB is derived as a fraction of the umaxCS for the measurand. The suitability of an MANCB for practical use in a commutability assessment is determined by estimating the number of measurements of clinical samples and CRMs required based on the precision performance and nonselectivity for the measurand of the measurement procedures in the assessment. Guidance is also provided for evaluating indeterminate commutability conclusions and how to report results of a commutability assessment.

Biomonitoring of exposure to Great Lakes contaminants among licensed anglers and Burmese refugees in Western New York: Toxic metals and persistent organic pollutants, 2010-2015.

Between 2010 and 2015, the New York State Department of Health (NYSDOH) conducted a biomonitoring program to gather exposure data on Great Lakes contaminants among licensed anglers and Burmese refugees living in western New York who ate locally caught fish. Four hundred and nine adult licensed anglers and 206 adult Burmese refugees participated in this program. Participants provided blood and urine samples and completed a detailed questionnaire. Herein, we present blood metal levels (cadmium, lead, and total mercury) and serum persistent organic pollutant concentrations [polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), dichlorodiphenyldichloroethylene (DDE), and trans-nonachlor]. Multiple linear regression was applied to investigate the associations between analyte concentrations and indicators of fish consumption (locally caught fish meals, store-bought fish meals, and consuming fish/shellfish in the past week). Licensed anglers consumed a median of 16 locally caught fish meals and 22 store-bought fish meals while Burmese refugees consumed a median of 106 locally caught fish meals and 104 store-bought fish/shellfish meals in the past year. Compared to the general U.S. adult population, licensed anglers had higher blood lead and mercury levels; and Burmese refuges had higher blood cadmium, lead, and mercury, and higher serum DDE levels. Eating more locally caught fish was associated with higher blood lead, blood mercury, and serum ∑PCBs concentrations among licensed anglers. Licensed anglers and Burmese refugees who reported fish/shellfish consumption in the past week had elevated blood mercury levels compared with those who reported no consumption. Among licensed anglers, eating more store-bought fish meals was also associated with higher blood mercury levels. As part of the program, NYSDOH staff provided fish advisory outreach and education to all participants on ways to reduce their exposures, make healthier choices of fish to eat, and waters to fish from. Overall, our findings on exposure levels and fish consumption provide information to support the development and implementation of exposure reduction public health actions.

IFCC Working Group Recommendations for Correction of Bias Caused by Noncommutability of a Certified Reference Material Used in the Calibration Hierarchy of an End-User Measurement Procedure.

Establishing metrological traceability to an assigned value of a matrix-based certified reference material (CRM) that has been validated to be commutable among available end-user measurement procedures (MPs) is central to producing equivalent results for the measurand in clinical samples (CSs) irrespective of the clinical laboratory MPs used. When a CRM is not commutable with CSs, the bias due to noncommutability will be propagated to the CS results causing incorrect metrological traceability to the CRM and nonequivalent CS results among different MPs. In a commutability assessment, a conclusion that a CRM is commutable or noncommutable for use with a specific MP is made when the difference in bias between the CRM and CSs meets or does not meet a criterion for that specific MP when compared to other MPs. A conclusion regarding commutability or noncommutability requires that the magnitude of the difference in bias observed in the commutability assessment remains unchanged over time. This conclusion requires the CRM to be stable and no substantive changes in the MPs. These conditions should be periodically reverified. If an available CRM is determined to be noncommutable for a specific MP, that CRM can be used in the calibration hierarchy for that MP when an appropriately validated MP-specific correction for the noncommutability bias is included. We describe with examples how a MP-specific correction and its uncertainty can be developed and applied in a calibration hierarchy to achieve metrological traceability of results for CSs to the CRM's assigned value.

Biomonitoring of populations in Western New York at risk for exposure to Great Lakes contaminants.

The New York State Department of Health conducted the Healthy Fishing Communities Program in collaboration with the Agency for Toxic Substances and Disease Registry to assess human exposure to contaminants common to Lake Ontario, Lake Erie and surrounding rivers and waterways among populations in western New York State who eat locally caught fish. The program enrolled licensed anglers and Burmese refugees and immigrants, living near four designated Great Lakes Areas of Concern: Buffalo River, Niagara River, Eighteenmile Creek, and the Rochester Embayment. These target populations were sampled and enrolled independently into the program between February and October of 2013. A core set of contaminants were measured in blood and urine of 409 licensed anglers and 206 Burmese refugees and immigrants which included lead, cadmium, mercury, PCBs, PBDEs, organochlorine pesticides (hexachlorobenzene, mirex, DDT, DDE, and chlordane and its metabolites oxychlordane and trans-Nonachlor), and PFOS and PFOA. Biomonitoring results showed that both groups had higher geometric means for blood lead, total blood mercury, and serum PFOS compared to the 2013-2014 NHANES reference levels. The Burmese refugee group also showed higher geometric means for creatinine-adjusted urine mercury and lipid-adjusted serum DDE compared to national levels. Licensed angler participants reported eating a median of 16 locally caught fish meals in the past year. Burmese participants consumed local fish throughout the year, and most frequently in the summer (median 39 fish meals or 3 times a week). The study results provide valuable information on populations at high risk of exposure to contaminants in the Great Lakes Basin of western New York. The results provide the foundation for developing and implementing public health actions to reduce potential exposures to Great Lakes pollutants.

Impact of testosterone assay standardization efforts assessed via accuracy-based proficiency testing.

BACKGROUND: We reported observations on analytical performance in testosterone measurements of various methods/assays from the study carried out using accuracy-based proficiency testing (PT) during 2012-2013. In 2016, we re-evaluated analytical performance of testosterone assays using accuracy-based PT to assess effectiveness of CDC efforts toward standardization. METHODS: Five single-donor human serum samples from female and male adult donors were analyzed for testosterone by New York State Department of Health-certified clinical laboratories using 16 immunoassays and LC-MS/MS methods. Target values were determined using the CDC reference measurement procedure. RESULTS: Testosterone targets for the 5 samples were 43.5, 160, 294, 457, and 534 ng/dL. The biases of individual result of the 65 participant laboratories against the target for each sample were calculated. Of participants, 87.7% had ≥4 of the 5 results within the minimum allowable total error limits (± 25.1%), a 14.7% increase from the previous study. The improved PT scores were attributed to better analytical accuracy and precision, and laboratories' selection of more accurate assays/methods. CONCLUSIONS: Improved analytical accuracy and precision for testosterone assays were demonstrated over a 3.5-year period after the first CDC-directed accuracy-based proficiency testing. Additional effort is needed to improve accuracy/precision of measurements, especially at low concentrations.

IFCC Working Group Recommendations for Assessing Commutability Part 1: General Experimental Design.

Commutability is a property of a reference material (RM) that relates to the closeness of agreement between results for an RM and results for clinical samples (CSs) when measured by ≥2 measurement procedures (MPs). Commutability of RMs used in a calibration traceability scheme is an essential property for them to be fit for purpose. Similarly, commutability of trueness controls or external quality assessment samples is essential when those materials are used to assess trueness of results for CSs. This report is part 1 of a 3-part series describing how to assess commutability of RMs. Part 1 defines commutability and addresses critical components of the experimental design for commutability assessment, including selection of individual CSs, use of pooled CSs, qualification of MPs for inclusion, establishing criteria for the determination that an RM is commutable, generalization of commutability conclusions to future measurements made with the MPs included in the assessment, and information regarding commutability to be included in the certificate for an RM. Parts 2 and 3 in the series present 2 different statistical approaches to commutability assessment that use fixed criteria related to the medical decisions that will be made using the laboratory test results.

IFCC Working Group Recommendations for Assessing Commutability Part 3: Using the Calibration Effectiveness of a Reference Material.

A process is described to assess the commutability of a reference material (RM) intended for use as a calibrator based on its ability to fulfill its intended use in a calibration traceability scheme to produce equivalent clinical sample (CS) results among different measurement procedures (MPs) for the same measurand. Three sources of systematic error are elucidated in the context of creating the calibration model for translating MP signals to measurand amounts: calibration fit, calibrator level trueness, and commutability. An example set of 40 CS results from 7 MPs is used to illustrate estimation of bias and variability for each MP. The candidate RM is then used to recalibrate each MP, and its effectiveness in reducing the systematic error among the MPs within an acceptable level of equivalence based on medical requirements confirms its commutability for those MPs. The RM is declared noncommutable for MPs for which, after recalibration, the CS results do not agree with those from other MPs. When a lack of agreement is found, other potential causes, including lack of calibration fit, should be investigated before concluding the RM is noncommutable. The RM is considered fit for purpose for those MPs where commutability is demonstrated.

IFCC Working Group Recommendations for Assessing Commutability Part 2: Using the Difference in Bias between a Reference Material and Clinical Samples.

A process is described to assess the commutability of a reference material (RM) intended for use as a calibrator, trueness control, or external quality assessment sample based on the difference in bias between an RM and clinical samples (CSs) measured using 2 different measurement procedures (MPs). This difference in bias is compared with a criterion based on a medically relevant difference between an RM and CS results to make a conclusion regarding commutability. When more than 2 MPs are included, the commutability is assessed pairwise for all combinations of 2 MPs. This approach allows the same criterion to be used for all combinations of MPs included in the assessment. The assessment is based on an error model that allows estimation of various random and systematic sources of error, including those from sample-specific effects of interfering substances. An advantage of this approach is that the difference in bias between an RM and the average bias of CSs at the concentration (i.e., amount of substance present or quantity value) of the RM is determined and its uncertainty estimated. An RM is considered fit for purpose for those MPs for which commutability is demonstrated.

Accuracy-based proficiency testing for testosterone measurements with immunoassays and liquid chromatography-mass spectrometry.

BACKGROUND: Accurate testosterone measurements are needed to correctly diagnose and treat patients. Proficiency Testing (PT) programs using modified specimens for testing can be limited because of matrix effects and usage of non-reference measurement procedure (RMP)-defined targets for evaluation. Accuracy-based PT can overcome such limitations; however, there is a lack of information on accuracy-based PT and feasibility of its implementation in evaluation for testosterone measurements. METHODS: Unaltered, single-donor human serum from 2 male and 2 female adult donors were analyzed for testosterone by 142 NYSDH-certified clinical laboratories using 16 immunoassays and LC-MS/MS methods. Testosterone target values were determined using an RMP. RESULTS: The testosterone target concentrations for the 4 specimens were 15.5, 30.0, 402 and 498ng/dl. The biases ranged from -17.8% to 73.1%, 3.1% to 21.3%, -24.8% to 8.6%, and -22.1% to 6.8% for the 4 specimens, respectively. Using a total error target of ±25.1%, which was calculated using the minimum allowable bias and imprecision, 73% of participating laboratories had ≥3 of the 4 results within these limits. CONCLUSIONS: The variability in total testosterone measurements can affect clinical decisions. Accuracy-based PT can significantly contribute to improving testosterone testing by providing reliable data on accuracy in patient care to laboratories, assay manufacturers, and standardization programs.

Perfluoroalkyl substances, thyroid hormones, and neuropsychological status in older adults.

Minimal data exist regarding the neurotoxicity of perfluoroalkyl substances (PFASs) in aging populations and the possible mediating effects of thyroid hormones (THs). Hence, the aims of this study were to: (i) assess associations between PFASs and neuropsychological function, and (ii) determine if such associations are mediated by changes in circulating THs in an aging population. We measured perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), total thyroxine (T4) and free thyroxine (fT4) in serum and performed neuropsychological tests in 126 men and women aged 55-74 years and living in upper Hudson River communities. Multivariable linear regressions were conducted to assess associations between PFASs and neuropsychological test scores. Mediation analyses were performed in a subset of 87 participants for whom information was available on both PFASs and THs. We calculated TH-mediated, non-TH mediated, and total effects of PFASs on neuropsychological test scores. Higher PFOA was associated with better performance in tasks of the California Verbal Learning Test and the Wisconsin Card Sorting Test. Higher PFOS was associated with improved performance in a Wechsler Memory Scale subtest and Block Design Subtest (BDT) total scores. There was no evidence of mediation by THs for PFOA-neuropsychological function associations. However, T4 and fT4 partially mediated the protective effect of PFOS on BDT total scores. Our findings do not suggest that PFASs are associated with poor neuropsychological function. There was some evidence of mediation for the association between PFASs and neuropsychological functions by THs, although some other modes of action also appear likely.

Thyroid function and neuropsychological status in older adults.

Overt thyroid dysfunction is recognized as a risk factor for neuropsychological deficits in aging populations, yet evidence for how changes in levels of circulatory thyroid hormones impact specific neuropsychological domains is limited. Here we report cross-sectional associations between serum thyroid hormone concentrations and several neuropsychological function domains among men and women aged 55-74years. We administered neuropsychological tests to assess memory, learning, executive function, measures of attention, visuospatial function, affective state, and motor function. Multivariable linear regression analyses were performed adjusting for age, sex, education, and cigarette smoking. Effects were reported as differences in test scores per one interquartile range (IQR) increase in hormone concentration. Higher total thyroxine (T4) and free thyroxine (fT4) were associated with improved visuospatial function, as measured by Block Design Subtest total scores; associated increments per IQR differences in T4 and fT4 were 15% and 19%, respectively (false discovery rate q-values <0.05). We also detected statistical interactions between age and fT4 for effects in tasks of memory and learning. Concurrent increases in age and fT4 were associated with deficits in memory and learning as measured by California Verbal Learning Test subtests (10% and 16% deficits in t-score and short delay free recall score, respectively). Our findings suggest that changes in thyroid hormones may have important implications for neuropsychological function in aging populations. Further large-scale studies with comprehensive thyroid function and neuropsychological outcome assessments are warranted to confirm these results.

Diabetes Prevalence in Relation to Serum Concentrations of Polychlorinated Biphenyl (PCB) Congener Groups and Three Chlorinated Pesticides in a Native American Population.

BACKGROUND: Exposure to persistent organic pollutants (POPs) is known to increase risk of diabetes. OBJECTIVE: To determine which POPs are most associated with prevalence of diabetes in 601 Akwesasne Native Americans. METHODS: Multiple logistic regression analysis was used to assess associations between quartiles of concentrations of 101 polychlorinated biphenyl (PCBs) congeners, congener groups and three chlorinated pesticides [dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB) and mirex] with diabetes. In Model 1, the relationship between quartiles of exposure and diabetes were adjusted only for sex, age, body mass index (BMI), and total serum lipids. Model 2 included additional adjustment for either total PCBs or total pesticides. RESULTS: Total serum PCB and pesticide concentrations were each significantly associated with prevalence of diabetes when adjusted only for covariates (Model 1), but neither showed a significant OR for highest to lowest quartiles after additional adjustment for the other (Model 2). When applying Model 2 to PCB congener groups and individual pesticides, there were significant omnibus differences between the four quartiles (all ps < 0.042) for most groups, with the exception of penta- and hexachlorobiphenyls, DDE and mirex. However, when comparing highest to lowest quartiles only non- and mono-ortho PCBs [OR = 4.55 (95% CI: 1.48, 13.95)], tri- and tetrachloro PCBs [OR = 3.66 (95% CI: 1.37, -9.78)] and HCB [OR = 2.64 (95% CI: 1.05, 6.61)] showed significant associations with diabetes. Among the non- and mono-ortho congeners, highest to lowest quartile of dioxin TEQs was not significant [OR = 1.82 (95% CI: 0.61, 5.40)] but the OR for the non-dioxin-like congeners was [OR = 5.01 (95% CI: 1.76, 14.24)]. CONCLUSION: The associations with diabetes after adjustment for other POPs were strongest with the more volatile, non-dioxin-like, low-chlorinated PCB congeners and HCB. Because low-chlorinated congeners are more volatile, these observations suggest that inhalation of vapor-phase PCBs is an important route of exposure. CITATION: Aminov Z, Haase R, Rej R, Schymura MJ, Santiago-Rivera A, Morse G, DeCaprio A, Carpenter DO, and the Akwesasne Task Force on the Environment. 2016. Diabetes prevalence in relation to serum concentrations of polychlorinated biphenyl (PCB) congener groups and three chlorinated pesticides in a Native American population. Environ Health Perspect 124:1376-1383; http://dx.doi.org/10.1289/ehp.1509902.

Perfluoroalkyl substances and thyroid function in older adults.

Current understanding of the thyroid disruptive properties of perfluoroalkyl substances (PFASs), particularly in aging populations, is limited. The objectives of this study were to (i) assess associations between thyroid function, as measured by serum thyrotropin (thyroid stimulating hormone, TSH), free thyroxine (fT4), total thyroxine (T4), and total triiodothyronine (T3), and serum perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in an aging population and (ii) determine if other persistent organic pollutants with thyroid disruptive properties including polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) modify such associations. We conducted a cross-sectional study of 87 men and women 55 to 74years of age, without clinically-diagnosed thyroid disease, who resided in upper Hudson River communities in New York. Geometric means (standard deviations) of serum PFOS and PFOA were 31.6 (1.7) ng/mL and 9.17 (1.72) ng/mL, respectively. Multivariable linear regression analyses indicated that one interquartile range difference in PFOS corresponded to 4% and 9% increases in fT4 and T4 respectively. We detected statistical interactions between PFOA and age for effects on fT4 and T4; joint increases in PFOA and age were associated with increases in fT4 and T4, of 3% and 7%, respectively. We also detected statistical interactions between PFOS and total PCBs for the effect on T3 and between PFOA and total PBDEs for the effect on TSH. Our results suggest that PFASs are associated with subtle alterations in thyroid hormone levels in this population, and that these associations are likely to vary by age, and levels of PCBs and PBDEs.

Thyroid hormones are associated with exposure to persistent organic pollutants in aging residents of upper Hudson River communities.

The aim of this study was to evaluate the association between persistent organic pollutants (POPs) and thyroid hormones in an aging population. Forty-eight women and 66 men, aged 55-74 years and living in upper Hudson River communities completed a questionnaire and provided blood specimens. Serum was analyzed for thyrotropin (thyroid stimulating hormone, TSH), free (fT4) and total thyroxine (T4), total triiodothyronine (T3), and for POPs. POPs included 39 polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) determined by gas chromatography with electron capture detection (GC-ECD), and nine polybrominated diphenyl ethers (PBDEs) determined by high-resolution gas chromatography with high-resolution mass spectrometry detection (HRGC-HRMS). Multivariable linear regression analysis was used to evaluate associations between thyroid hormones and sums of POPs, adjusted for covariates and stratified by sex. Effects were expressed as differences in thyroid hormone levels associated with a doubling in the level of exposure. Among women, DDT+DDE increased T4 by 0.34µg/dL (P=0.04) and T3 by 2.78ng/dL (P=0.05). Also in women, sums of PCBs in conjunction with PBDEs elicited increases of 24.39-80.85ng/dL T3 (P<0.05), and sums of PCBs in conjunction with DDT+DDE elicited increases of 0.18-0.31µg/dL T4 (P<0.05). For men estrogenic PCBs were associated with a 19.82ng/dL T3 decrease (P=0.003), and the sum of estrogenic PCBs in conjunction with DDT+DDE elicited an 18.02ng/dL T3 decrease (P=0.04). Given age-related declines in physiologic reserve, the influence of POPs on thyroid hormones in aging populations may have clinical implications and merits further investigation.

Effects of resin or charcoal treatment on fetal bovine serum and bovine calf serum.

INTRODUCTION: Charcoal- or resin-stripping of fetal bovine serum (FBS) or bovine calf serum (BCS) intended for supplementation of cell culture media is widely practiced to remove a variety of endogenous compounds, including steroid, peptide, and thyroid hormones. The possibility that stripping removes other biologically relevant factors from serum may not be appreciated. METHODS: In this report, standardized clinical laboratory testing methods were used to assess the effects of resin- and charcoal-stripping on content in FBS and BCS of more than 25 analytes in the sera. RESULTS AND CONCLUSION: In addition to hormones, the serum constituents affected by stripping are certain vitamins, electrolytes, enzyme activities, and metabolites.