Bornhorst, Joshua

Context.— Clinical testing for Wilson disease (WD) is potentially challenging. Measuring the fraction of labile bound copper (LBC) to total copper may be a promising alternative diagnostic tool with better sensitivity and specificity than some current biomarker approaches. A dual filtration–based inductively coupled mass spectrometry (ICP-MS) assay to measure LBC in serum was developed. Objective.— To establish a reference interval for LBC and LBC to total copper (LBC fraction) in a healthy adult population, and to examine associations between total copper, LBC, and LBC fraction with age, sex, menopausal status, hormone replacement therapy, and supplement use. Design.— Serum samples were collected from healthy male (n = 110) and female (n = 104) patients between the ages of 19 and 80 years. Total copper and LBC were analyzed using ICP-MS. Results were used to calculate the LBC fraction. Reference intervals were calculated for the 2.5th and 97.5th percentiles for both LBC and LBC fraction. Results.— The reference intervals for LBC were determined to be 13 to 105 ng/mL and 12 to 107 ng/mL for female and male patients, respectively. The reference intervals for the LBC fraction were 1.0% to 8.1% and 1.2% to 10.5% for female and male patients, respectively. No significant associations were found regarding age, menopausal status, hormone replacement therapy, or vitamin and supplement use. Conclusions.— Sex-specific reference intervals have now been established for LBC and LBC fraction. These data in conjunction with further testing of WD populations can be used to assess the sensitivity and specificity of LBC fraction in screening, monitoring, and diagnosis.

Abstract Disclosure: D.Z. Erickson: None. D. Donegan: None. J. Van Gompel: None. J. Atkinson: None. M. Link: None. F. Meyer: None. M. Peris-Celda: None. G. Spears: None. J. Bornhorst: None. M. Hoplin: None. Dysnatremias are common after neurosurgical procedures. Depending on the cohort assessed, transient arginine vasopressin deficiency (AVD) following neurological procedures is seen in up to 46% of patients which can delay discharge. Copeptin (COPEP), a stable surrogate marker of arginine vasopressin, has demonstrated utility in the prediction of postoperative AVD, however COPEP cutoff and sample timing has varied. Aim: To assess the optimal sampling time and cut point concentration of COPEP to predict the development of post-surgical AVD. Method: Adults who had transsphenoidal surgery (TSS) for a sellar or suprasellar mass between February 2020 and April 2022 without pre-existing AVD were prospectively enrolled if agreeable. Two COPEP samples (immunofluorescent assay on B.R.A.H.M.S Kryptor Compact PLUS) included “early” sample 1-6 hours following extubation, and another post-op day 1 (POD1, 10-30 hours of extubation). Patients were assessed for the development of AVD; defined as new onset hypotonic (< 295 mmol/kg) polyuria (>50 ml/kg/d) without other causes. Patient demographics and tumor characteristics were collected. Results: 192 patients (median age 54.5 (39.8-67.0) years with 54.2% female) were included. Surgical indications included non-functioning pituitary adenoma (N=101), functioning pituitary adenoma (N= 78), disorders or the craniopharyngeal duct (N=10) and other (N=3). Median COPEP levels were associated with age, but not sex. Median COPEP levels were significantly lower at both time points in patients who developed AVD (N=20, 10.4%) vs those who did not, (early: 4.9 vs 18.7 pmol/L, P= <0.001; POD1: 3.35 vs 4.9 pmol/L, P=<0.001). Change in median COPEP level between the 2 sample times was lower in those who developed AVD -1.8 pmol/L vs who did not -12.6 pmol/L (P<0.001). ROC curve analysis of early COPEP indicated that a level >20.3 pmol/L had a negative predictive value (NPV) of 97% whereas POD1 level >6.7 pmolL had a NPV of 96%. In univariate logistic analysis, lower early COPEP was associated with higher risk of AVD (OR=0.34, CI 0.26 -0.62, p=0.008), with an optimal cut point of 8.5 pmol/L. A similar association was seen for POD1 COPEP (OR=0.19, CI 0.07- 0.53, p= 0.002), which had an optimal cut point of 4.3 pmol/L. In patients with disorders of the craniopharyngeal system vs those who had TSS for other reasons, AVD was more common (60% vs 9%, P<0.001) and median COPEP levels were lower at both time points. Those without AVD who received stress dose steroids intraoperatively had lower median early COPEP (11.7 vs 19.1 pmol/L, P=0.27). Conclusion: In early samples taken following extubation, the optimal COPEP cut point for AVD diagnosis was 8.5 pmol/L and a level of >20.3 pmol/L has predicative utility in excluding AVD. However, caution should be used in patients who are administered glucocorticoids intra-operatively as this was associated with a lower median COPEP level. Presentation: Thursday, June 15, 2023

e16242 Background: Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare cancers with highly heterogeneous growth rates, yielding very broad ranges of radiographic imaging intervals in standard guidelines, with a multitude of risk for patients. Better tools are needed to reduce risks for these patients. Chromogranin A (CgA) is released by GEP-NET cells and has been associated with increased tumor burden. The European Neuroendocrine Tumor Society (ENETS) considers CgA to be the most practical and useful general serum tumor marker in patients with NETs. However, clinical utility has been limited by the lack of prospective validation studies and by different sensitivity of CgA according to NET tumor type and volume. Accordingly, expert consensus guidelines have offered varying advice regarding the use of CgA to practicing clinicians. The aim was to evaluate the performance of the B·R·A·H·M·S CgA II KRYPTOR immunoassay to monitor the course of disease in patients with well-differentiated GEP-NETs (grade 1 and grade 2). This is the first prospective validation of a clinical algorithm for the interpretation of CgA values in patients with advanced GEP-NETs. Methods: This prospective, multi-center, observational study was designed to validate the performance of the B·R·A·H·M·S CgA II KRYPTOR assay in monitoring disease progression in a defined population of GEP-NET patients with minimal confounding from end organ dysfunction or concomitant medications (e.g. PPIs). Patients were followed for up to 36 months including the evaluation of tumor burden with RECIST 1.1 categorization by imaging (CT/MRI scans). A clinical cut-off for changes in CgA levels over time to indicate the risk that a tumor progression occurred was derived from a retrospective, bicentric observational pilot study. A change in CgA levels between visits was considered positive, if the CgA concentration increased by more than 50% to an absolute value of >100 ng/ml. Results: A total of 175 adult patients were enrolled, and 153 patients had measurable disease at baseline and ≥1 follow-up visit. Using the cut-off for CgA increase defined above resulted in a sensitivity of 34.4% (95%-CI: 25.6% - 44.3%, p < 0.001) and a specificity of 93.4% (95%-CI: 90.4% – 95.5%, p < 0.001). Positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+) and negative likelihood ratio (LR-) to diagnose whether a tumor progression occurred according RECIST 1.1 criteria were 57.9% (95% CI: 45.0-69.8), 84.3% (95% CI: 80.5-87.6), 5.20 (95% CI: 3.23-8.36), and 0.70 (95% CI: 0.61-0.81), respectively. The AUC was estimated at 0.731 (95% CI: 0.670-0.793). Conclusions: B·R·A·H·M·S CgA II KRYPTOR can be used in conjunction with other clinical methods as an aid in monitoring of disease progression during the course of disease and treatment in patients with gastroentero-pancreatic neuroendocrine tumors (GEP-NETs, grade 1 and grade 2).

Abstract Background Kidney stones are a highly prevalent disease worldwide. Additionally, both environmental and occupational exposure to Pb and Cd continue to be prevalent globally and can result in renal toxicity. The objective of this study was to examine the potential presence of Pb and Cd in kidney stones, and to assess for correlation with demographic factors including smoking, gender, age, and kidney stone matrix composition. Methods Patient kidney stones (n = 96) were analyzed using Fourier transform infrared spectroscopy to identify the stone constituents. Cd and Pb concentrations (µg/g) were determined by inductively coupled plasma mass spectrometry. Cd and Pb concentrations were correlated using bivariable and multivariable statistical analysis with demographic factors (age, gender, smoking status), and kidney stone composition. Results Kidney stone Cd (median 0.092 µg/g, range 0.014 to 2.46) and Pb concentrations (median 0.95 µg/g, range 0.060 to 15.4) were moderately correlated (r = 0.56, P &lt; 0.0001). Cd concentrations were positively associated with patient history of smoking, patient age, and calcium oxalate monohydrate levels while negatively associated with struvite and uric acid/uric acid dihydrate. Pb concentrations were positively associated with females and apatite levels while negatively associated with uric acid/uric acid dihydrate. After holding constant other stone type composition levels, smoking status, and age, both Pb and Cd were positively associated with apatite and negatively associated with uric acid/uric acid dihydrate, struvite, and calcium carbonate. Conclusions Cd and Pb kidney stone concentrations are associated with specific kidney stone types. Cd and Pb kidney stone concentrations are both associated with smoking.

AbstractBackgroundNeurofilament light chain (NfL) is an emerging blood‐based biomarker useful for assessing neuro‐axonal injury in several neurological conditions. Plasma NfL concentrations reflect the extent of axonal damage, making it a general marker of neurodegenerative disease progression. This study evaluates the analytical performance characteristics of the Quanterix NfL Advantage method in EDTA‐plasma.MethodThe assay was performed per manufacturer’s instructions on the Quanterix Simoa HD‐X Analyzer. Analytical validation included analyte stability, imprecision, lower limit of quantification (LLOQ), analytical measurement range (AMR), accuracy, and interferences. One‐sided reference intervals were established using quantile regression methods among 1100 cognitive normal individuals, age 20 to 95 years without known chronic kidney disease, stroke, or myocardial infarction.ResultNfL was stable in plasma three days ambient, seven days refrigerate, 90 days frozen (‐20C), and over 3 freeze/thaw cycles. Intra and inter‐assay imprecision, expressed as % coefficient of variation (%CV), ranged from 3.4 – 6.0% and 5.9 – 11.6% respectively. The LLOQ was evaluated using patient plasma pools at concentrations of 1.7 and 3.6 pg/mL. %CVs were 16.8% and 9.7% respectively, and the LLOQ was set at 3.0 pg/mL. Accuracy was assessed by spiking 5 plasma samples with NfL calibratoran 87% average recovery (range 81‐94%) was observed. The AMR of 3.0 – 1500 pg/mL was verified with a regression slope of 0.93 and r2 > 0.99. Additionally, plasma admixtures covering the AMR showed acceptable linear response (slope of 1.02 and r² >0.99). The assay was not affected by icterus to 100 mg/dL, lipemia to 1000 mg/dL, hemolysis to 1000 mg/dL at NfL concentrations >30 pg/mL or to 200 mg/dL at NfL concentrations ≤30 pg/mL. NfL increased with age but did not differ by sex. The data supported age‐based reference intervals broken down into 10‐year intervals. The 97.5th percentile limits were: 20s: ≤8.4 pg/mL, 30s: ≤11.4 pg/mL, 40s: ≤15.4 pg/mL, 50s: ≤20.8 pg/mL, 60s: ≤28.0 pg/mL, 70s: ≤37.9 pg/mL, 80+: ≤51.2 pg/mL.ConclusionThe analytical performance characteristics of the plasma Quanterix NfL advantage assay were deemed acceptable for clinical laboratory implementation. The establishment of NfL reference intervals will aid in the clinical interpretation of patient plasma NfL concentrations.

AbstractContextThyroglobulin autoantibodies (TgAbs) affect thyroglobulin immunometric assays (TgIMAs), causing falsely low results. Conversely, heterophilic antibodies (HAs) may cause falsely elevated results. Thyroglobulin (Tg) measurements by mass spectrometry (MS) resist antibody interference. The most effective use of TgIMA/TgMS in the evaluation of Tg remains unclear.ObjectiveThe objective of this work was to study the usefulness of TgMS vs TgIMA in the presence of Tg measurement interference by HA and TgAb.MethodsIn 163 thyroid cancer patients, Tg was postoperatively measured by TgIMA and TgMS. When TgIMA was elevated and TgMS undetectable, HA was assessed by serial dilution and pretreatment with HA blocking reagent. TgIMA and TgMS were compared in TgAb-positive patients with well-characterized clinical status.Results6 out of 45 cases with TgIMA &gt;1 ng/mL had undetectable TgMS. HA interference was confirmed by serial dilution and HA blocking reagent addition. In TgAb-positive cases, TgIMA and TgMS were highly correlated (R2 = 0.86). In patients with structural disease and TgAb, TgIMA and TgMS were detectable in 6/19 patients, and 9/19 cases, respectively. The TgMS concentration range in the 3 discrepant cases ranged from 0.5 to 2.0 ng/mL. Hence, the presence of TgAb was associated with inappropriately reduced Tg concentrations with both TgIMA and TgMS.ConclusionHA cause falsely elevated TgIMA with undetectable TgMS with significant frequency. TgMS can be used to rule out HA interference. Albeit resistant to TgAb in vitro, TgMS detects little Tg in patients with TgAb and structural disease. Hence, TgAb may reduce Tg concentrations in vivo. The implication is that no assay design may be able to overcome this problem. TgMS may not detect structural disease in TgAb-positive patients.

AbstractObjectiveTo investigate the effect of CRYSVITA® (burosumab‐twza) on FGF23 measurements in an intact and a C‐terminal immunoassay.MethodsAn intact serum FGF23 (MedFrontier) and a C‐terminal plasma FGF23 assay (Immutopics) were used. Serum/plasma pools were spiked to span the burosumab therapeutic range (1.4–11.3 μg/ml) and FGF23 recovery was assessed. Patient serum and plasma samples obtained pre and post‐burosumab treatment were evaluated on both assays and compared with corresponding phosphorus measurementsResultsSpiking burosumab (1.4–11.3 μg/ml) into sample pools resulted in a dose‐dependent negative analytical interference on intact FGF23 measurements and no significant interference for C‐terminal FGF23 measurements. However, more than a 500‐fold median increase (post‐ vs. pre‐burosumab administration) in in vivo FGF23 concentrations were observed by both assays.ConclusionsTherapeutic concentrations of burosumab result in a negative analytical interference of the intact, but not the C‐terminal FGF23 immunoassay. Despite this in vitro analytical interference in the intact assay, relatively large elevations of both intact FGF23 and C‐terminal FGF23 measurements were observed in vivo following burosumab administration. Following burosumab administration, FGF23 measurements must be interpreted within the clinical context of the patient and other relevant biomarker results.SummaryThis article describes a negative analytical interference by burosumab in an intact FGF23 immunoassay. The recovery of C‐terminal FGF23 is not significantly affected by the presence of burosumab. In vivo, both assays demonstrate extreme FGF23 elevations in the presence of the drug. Furthermore, the measurement of FGF23 blocked by burosumab is not clinically useful regarding hypophosphataemia.

Abstract Introduction Orexin deficiency in cerebrospinal fluid (CSF) was first reported in human narcolepsy in 2001, included in diagnostic criteria for narcolepsy in 2014, and made clinically available at the Mayo Clinic in 2019. The purpose of this publication is to report orexin test utilization and results, and other clinically relevant findings from patients evaluated at Mayo Clinic. Methods We retrospectively reviewed CSF orexin samples and clinical records from patients evaluated at Mayo Clinic from 2019 to 2021. Results A total of 98 internal samples (Rochester, n=56; Arizona, n=25, and Florida, n=17) from 95 patients (mean age 32.4 +/- 16.6 years with 20 %, 52 %, and 28 % of patients &lt; 18, 18 – 40, and &gt; 40 years, respectively, at time of CSF collection; 62 % female) have been submitted for CSF orexin measurement (mean CSF orexin 335.17 +/- 158.3 pg/ml; deficient &lt; 110 pg/ml, n=11, 64 % &lt;=40 years with mean age 32.9 +/- 17.0 years; intermediate 110 – 200 pg/ml, n=8, 100 % &lt;= 40 years with mean age 21.1 +/- 12.8 years; normal &gt; 200 pg/ml, n=79, 57 % &lt;=40 years with mean age 33.5 +/- 16.7). No significant correlation was found between orexin levels, and time of collection (i.e., diurnal variation), gender, or age. Repeat testing was performed on three individuals (ages 10, 14, and 19 years) with a change in category of orexin level found in one patient from an intermediate to a normal level. Conclusion Orexin deficiency was found in 12 % of the patients (64 % of the deficient samples were found at ages &lt;= 40 years). This result may reflect the fact that this test is frequently pursued in clinical patients presenting with inconclusive findings and/or comorbidities. Intermediate orexin levels found in 8 % of the samples (100 % &lt;= 40 years). Although most of the patients tested were female (62.2%) and most were 40 years or younger (72%), no significant correlation was found between orexin levels, and time of collection (i.e., diurnal variation), gender, or age. Support (If Any) none