Matrix-matched calibrators are necessary for robust and high-quality dried blood spots lead screening assays by inductively coupled plasma-mass spectrometry.

Background and aims: Reliable lead screening methods are necessary to support early identification of lead exposure in children. Sample collection using dried blood spots (DBS) offers advantages compared to traditional venipuncture and capillary collection. Here, we describe and compare three lead DBS inductively coupled plasma-mass spectrometry (ICP-MS) methods for lead screening. Materials and methods: Lead was extracted from Whatman 903 protein saver cards punches and analyzed by ICP-MS across three independent clinical laboratories. Each laboratory evaluated the performance of aqueous and matrix-matched DBS calibrators using external quality control samples (WI State of Laboratory of Hygiene Program). Leftover patient samples (n = 39) were used for an interlaboratory comparison of lead DBS. Lead DBS results were compared to whole blood methods. Results: The DBS ICP-MS methods using matrix-matched DBS calibrators had superior performance to the aqueous calibrations. There was a strong correlation between lead measured in DBS (matrix-matched) and whole blood for the three methods evaluated. Conclusion: Lead can be measured accurately by ICP-MS in DBS samples when matrix-matched calibrators are used. External quality control programs are valuable to assess the performance of DBS methods. DBS lead ICP-MS methods are a robust analytical option for lead screening even though the limitations of DBS are well recognized.

Lead poisoning: Clinical and laboratory considerations.

Lead has been a known source of toxicity for millennia due to widespread use until the 20th century. Consequently, there remains significant, though decreasing, exposure to lead throughout the world. Clinical signs and symptoms of lead toxicity are well-documented but is particularly concerning for children six years of age and under, as brain development is rapid and therefore, is likely to be affected by even low levels of lead. Therefore, in the United States, it is recommended that young children to be routinely screened for blood lead levels. Blood lead levels can be measured by various methods in laboratories with blood collection greatly impacting possible lead contamination of samples. The history, presentation, and laboratory testing methodologies will be discussed.

Reference intervals: past, present, and future.

Clinical laboratory test results alone are of little value in diagnosing, treating, and monitoring health conditions; as such, a clinically actionable cutoff or reference interval is required to provide context for result interpretation. Healthcare practitioners base their diagnoses, follow-up treatments, and subsequent testing on these reference points. However, they may not be aware of inherent limitations related to the definition and derivation of reference intervals. Laboratorians are responsible for providing the reference intervals they report with results. Yet, the establishment and verification of reference intervals using conventional direct methods are complicated by resource constraints or unique patient demographics. To facilitate standardized reference interval best practices, multiple global scientific societies are actively drafting guidelines and seeking funding to promote these initiatives. Numerous national and international multicenter collaborations demonstrate the ability to leverage combined resources to conduct large reference interval studies by direct methods. However, not all demographics are equally accessible. Novel indirect methods are attractive solutions that utilize computational methods to define reference distributions and reference intervals from mixed data sets of pathologic and non-pathologic patient test results. In an effort to make reference intervals more accurate and personalized, individual-based reference intervals are shown to be more useful than population-based reference intervals in detecting clinically significant analyte changes in a patient that might otherwise go unrecognized when using wider, population-based reference intervals. Additionally, continuous reference intervals can provide more accurate ranges as compared to age-based partitions for individuals that are near the ends of the age partition. The advantages and disadvantages of different reference interval approaches as well as the advancement of non-conventional reference interval studies are discussed in this review.

Artificial Intelligence Applications in Clinical Chemistry.

Artificial intelligence (AI) applications are an area of active investigation in clinical chemistry. Numerous publications have demonstrated the promise of AI across all phases of testing including preanalytic, analytic, and postanalytic phases; this includes novel methods for detecting common specimen collection errors, predicting laboratory results and diagnoses, and enhancing autoverification workflows. Although AI applications pose several ethical and operational challenges, these technologies are expected to transform the practice of the clinical chemistry laboratory in the near future.

Quantitation of non-derivatized free amino acids for detecting inborn errors of metabolism by incorporating mixed-mode chromatography with tandem mass spectrometry.

Introduction: Amino acids are critical biomarkers for many inborn errors of metabolism, but amino acid analysis is challenging due to the range of chemical properties inherent in these small molecules. Techniques are available for amino acid analysis, but they can suffer from long run times, laborious derivatization, and/or poor resolution of isobaric compounds. Objective: To develop and validate a method for the quantitation of a non-derivatized free amino acid profile in both plasma and urine samples using mixed-mode chromatography and tandem mass spectrometry. Methods: Chromatographic conditions were optimized to separate leucine, isoleucine, and allo-isoleucine and maintain analytical runtime at less than 15 min. Sample preparation included a quick protein precipitation followed by LC-MS/MS analysis. Matrix effects, interferences, linearity, carryover, acceptable dilution limits, precision, accuracy, and stability were evaluated in both plasma and urine specimen types. Results: A total of 38 amino acids and related compounds were successfully quantitated with this method. In addition, argininosuccinic acid was qualitatively analyzed. A full clinical validation was performed that included method comparison to a reference laboratory for plasma and urine with Deming regression slopes ranging from 0.38 to 1.26. Conclusion: This method represents an alternative to derivatization-based methods, especially in urine samples where interference from metabolites and medications is prevalent.

Indirect reference intervals using an R pipeline.

BACKGROUND: Indirect reference intervals require robust statistical approaches to separate the pathological and healthy values. This can be achieved with a data pipeline created in R, a freely available statistical programming language. METHODS: A data pipeline was created to ingest, partition, normalize, remove outliers, and identify reference intervals for testosterone (Testo; n  = 7,207) and aspartate aminotransferase (AST; n  = 5,882) using data sets from NHANES. RESULTS: The estimates for AST and Testo determined by this pipeline approximated current RIs. Care should be taken when using this pipeline as there are limitations that depend on the pathology of the analyte and the data set being used for RI estimation. CONCLUSIONS: R can be used to create a robust statistical reference interval pipeline.

Preterm to term infant postmenstrual age reference intervals for thyroid-stimulating hormone and free thyroxine.

BACKGROUND: Infants born preterm are affected by a hypothalamic-pituitary-thyroid axis that is immature and still developing as they progress closer to corrected term gestation. Multiple risk factors place preterm infants at risk for a hypothyroid state. However, there is variability in thyroid-stimulating hormone cutoff values and limited data on free thyroxine reference intervals to guide clinicians. METHODS: 1584 thyroid-stimulating hormone and 1576 free thyroxine laboratory samples that were originally collected to screen hospitalized infants for delayed-onset of hypothyroidism were retrospectively evaluated from a group of 1087 infants who ranged in postmenstrual age from 25 to 43 weeks gestation at the time of laboratory sample collection. Median thyroid hormone values and reference intervals were established using R and the mixtools package. RESULTS: Thyroid-stimulating hormone reference intervals remained similar across gestational ages from 0.340-9.681 µIU/mL in 25-27 6/7-week infants to 1.090-7.627 µIU/mL in 40-43-weeks infants. For the same age groups, free thyroxine reference intervals increased from 0.42-0.91 ng/dL to 0.87-1.32 ng/dL. CONCLUSION: The reference intervals identified suggest that infants <31 weeks gestation have a higher thyroid-stimulating hormone and lower free thyroxine level at baseline than previously anticipated. IMPACT: The increasing free thyroxine values in preterm to term infants indicate a maturing hypothalamic-pituitary-thyroid axis. Clinicians need thyroid hormone reference intervals that also vary by postmenstrual age to aid the evaluation of sick preterm infants who are at risk of a delayed hypothyroidism diagnosis that can be missed on the initial newborn screen. This study provides one of the largest samples of thyroid-stimulating hormone and free thyroxine data to establish reference intervals in preterm infants. Clinicians may utilize the identified postmenstrual age-based reference intervals to inform follow-up thyroid testing in preterm infants at several weeks postnatal age.

First- and Second-Trimester Reference Intervals for Thyroid Function Testing in a US Population.

OBJECTIVES: Thyroid dysfunction in pregnancy is associated with increased risk of adverse outcomes to mother and child. Trimester-specific reference intervals for thyroid function tests are not routinely provided by clinical laboratories. In this study, we present first- and second-trimester-specific reference intervals in a US population for thyroid-stimulating hormone (TSH), free thyroxine (FT4), total thyroxine (T4), and total triiodothyronine (T3) measured on Roche analyzers. METHODS: We used patient samples from first- and second-trimester prenatal screening. Samples were limited to singleton pregnancies and negative screening results for thyroid peroxidase and thyroglobulin antibodies. Analytes (TSH, FT4, T4, and T3) were measured on a Roche Modular e170 then verified on a Roche cobas e801. RESULTS: The reference intervals established on the e170 and verified on the e801 for the first trimester were 0.16 to 2.82 mIU/L for TSH, 12.0 to 18.5 pmol/L for FT4, 62.8 to 177.9 nmol/L for T4, and 1.5 to 3.4 nmol/L for T3. The reference intervals for the second trimester were 0.40 to 3.62 mIU/L for TSH, 10.2 to 16.6 pmol/L for FT4, 66.6 to 176.0 nmol/L for T4, and 1.56 to 3.6 nmol/L for T3. CONCLUSIONS: This is the first report of trimester-specific reference intervals for thyroid function tests on Roche analyzers in the United States, and it is consistent with worldwide reports.

Urinary cannabinoid mass spectrometry profiles differentiate dronabinol from cannabis use.

BACKGROUND: Dronabinol is used to treat a variety of conditions, including loss of appetite in people with AIDS and severe nausea and vomiting caused by cancer chemotherapy. Its therapeutic potential for pain management is now being explored in specific populations. Monitoring dronabinol compliance is challenging because its active ingredient, Δ-9-tetrahydrocannabinol (THC), is also present in cannabis. We developed a rapid LC-MS/MS assay with minimal specimen preparation to quantitate 11 cannabinoids in urine. Using this assay coupled with urine samples from normal controls, cannabis, and dronabinol users, we show the ability to differentiate cannabis from dronabinol use. METHODS: Residual clinical urine samples from 55 cannabinoid positive subjects and 31 negative controls, as well as prospective samples from 5 patients receiving dronabinol therapy were obtained for analysis. RESULTS: In the dronabinol group, only the THC metabolites 11-nor-9-carboxy-tetrahydrocannabinol (THC-COOH) and 11-hydroxy-Δ-9-tetrahydrocannabinol (THC-OH) were detected. Minor cannabinoids were detected in 91% of cannabis group samples and their detection was more frequent in samples with increased THC metabolite concentrations. Of minor cannabinoids evaluated, cannabigerol (CBG) and cannabidiol (CBD) had the greatest sensitivity in detecting cannabis use. CONCLUSIONS: This method has a high sensitivity for the detection of cannabis use with implications for evaluating dronabinol compliance.

The 2018 AACC/SYCL PhD Clinical Chemist Compensation Survey.

BACKGROUND: Doctoral level board-certified clinical chemists play an invaluable role in many facets of laboratory medicine and healthcare. However, information concerning their total compensation is sparse. CONTENT: A confidential self-reported compensation survey was conducted by the American Association for Clinical Chemistry's Society for Young Clinical Laboratorians (AACC SYCL) Core Committee from April 1 to April 17, 2018. Respondents provided information on geographic location, employment sector, gender, and years of experience to account for the influence of these variables on compensation. There were 199 respondents in total from the United States and Canada, however, only respondents employed in the United States with an earned doctoral degree and certification by the American Board of Clinical Chemistry (n = 133), were included in the full analysis. In comparison to compensation reported in AACC SYCL salary surveys conducted in 2010 and 2013, early career median salaries are trending upwards after correction for inflation. SUMMARY: This survey is the first to collect the gender of respondents, and identify a pay gap for some geographic groups. However, this gap could be due in part to a difference in the years of experience, since males were highly represented in the group with >20 years of experience (25 out of 35, 71%). Future studies on compensation trends within clinical chemistry that do not rely on self-report are needed to ensure accuracy and completeness of the dataset.

Health Care and Precision Medicine Research: Analysis of a Scalable Data Science Platform.

BACKGROUND: Health care data are increasing in volume and complexity. Storing and analyzing these data to implement precision medicine initiatives and data-driven research has exceeded the capabilities of traditional computer systems. Modern big data platforms must be adapted to the specific demands of health care and designed for scalability and growth. OBJECTIVE: The objectives of our study were to (1) demonstrate the implementation of a data science platform built on open source technology within a large, academic health care system and (2) describe 2 computational health care applications built on such a platform. METHODS: We deployed a data science platform based on several open source technologies to support real-time, big data workloads. We developed data-acquisition workflows for Apache Storm and NiFi in Java and Python to capture patient monitoring and laboratory data for downstream analytics. RESULTS: Emerging data management approaches, along with open source technologies such as Hadoop, can be used to create integrated data lakes to store large, real-time datasets. This infrastructure also provides a robust analytics platform where health care and biomedical research data can be analyzed in near real time for precision medicine and computational health care use cases. CONCLUSIONS: The implementation and use of integrated data science platforms offer organizations the opportunity to combine traditional datasets, including data from the electronic health record, with emerging big data sources, such as continuous patient monitoring and real-time laboratory results. These platforms can enable cost-effective and scalable analytics for the information that will be key to the delivery of precision medicine initiatives. Organizations that can take advantage of the technical advances found in data science platforms will have the opportunity to provide comprehensive access to health care data for computational health care and precision medicine research.

Investigation of transition ion ratio variation for liquid chromatography-tandem mass spectrometry: A case study approach.

BACKGROUND: A transition ion ratio (TIR) is the ratio of one fragment over another from the same precursor and is frequently monitored in liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays for analyte identification. The Clinical and Laboratory Standards Institute (CLSI) C50-A guidelines give a static percent allowable TIR deviation based on the TIR level. Anecdotally, we observed failures of these rules for some of our LC-MS/MS assays. We determined what parameters may affect TIRs in a clinical setting and whether TIR variations may be analyte, matrix, instrument service, and/or concentration dependent. METHODS: Data was collected from the validation and selected periods after implementation for urine benzodiazepines (7 analytes) and plasma azole antifungals (6 analytes). TIRs for the calibrators and quality control materials on a Thermo TSQ™ Quantum Ultra from July 2016 to February 2017 for benzodiazepines in urine and Thermo TSQ™ Vantage from May 2016 to Oct 2016 for azoles in serum were monitored. RESULTS: The statistically significant day-to-day TIR shift ranged from 5.7 to 27.0% of the days studies for benzodiazepines and from 5.6 to 27.8% of the days studied for azoles excluding shifts caused by instrument services. Instrument service had significant impact on all benzodiazepines except oxazepam with p-values ranging from 1.79 × 10-6 to 1.53 × 10-39 and 4 of the 6 azoles (fluconazole, isavuconazole, voriconazole, and itraconazole) with (p from 7.89 × 10-3 to 1.98 × 10-12). Lorazepam, α-hydroxyalprazolam, and hydroxyitraconazole showed significant concentration dependent TIR variations. CONCLUSIONS: TIR variations may be affected by instrument services, and can be concentration and analyte dependent. Instead of using a static percent deviation rule, establishment of TIR variation criteria for each analyte during test development and validation may provide a more useful tool for analyte identification.

Variability of Late-Night Salivary Cortisol in Cushing Disease: A Prospective Study.

Background: The frequency of variable hormonogenesis in patients with Cushing disease (CD) but without cyclical symptoms is unclear. Aim: To assess the frequency of variable hormonogenesis in patients presenting with CD. Methods: Over a 6-month period, patients with confirmed or suspected CD provided late-night salivary samples for up to 42 consecutive nights. Results: Of 19 patients confirmed to have CD, 16 provided at least 7 consecutive salivary samples, and 13 provided at least 21; these 16 patients are the subjects of this report. Twelve patients had at least three peak and two trough levels of late-night salivary cortisol (LNSC) but in only two patients were strict criteria for cyclical hormonogenesis fulfilled; variation was assessed as random in the others. Eight patients had de novo CD, and eight had recurrent/persistent disease. All patients with recurrent/persistent CD had two or more normal results, and in four of these patients, >50% of LNSC were normal. In six patients with de novo disease with at least one normal LNSC level, the maximum levels ranged from 1.55 to 15.5 times the upper limit of normal. Conclusions: Extreme fluctuations of cortisol production, measured by sequential LNSC, are common in CD. In newly diagnosed disease, this may only occasionally impair diagnostic ability, whereas in most patients with recurrent/persistent disease after pituitary surgery, LNSC is frequently within the reference range, with potential to cause diagnostic problems.