Algeciras‐Schimnich, Alicia

Abstract Introduction Measurement of amyloid beta (Aβ40 and Aβ42) and tau (phosphorylated tau [p‐tau] and total tau [t‐tau]) in cerebrospinal fluid (CSF) can be utilized to differentiate clinical and preclinical Alzheimer's disease dementia (AD) from other neurodegenerative processes. Methods CSF biomarkers were measured in 150 participants from the Mayo Clinic Study of Aging and the Alzheimer's Disease Research Center. P‐tau/Aβ42 (Roche Elecsys, Fujirebio LUMIPULSE) and Aβ42/40 (Fujirebio LUMIPULSE) ratios were compared to one another and to amyloid positron emission tomography (PET) classification. Results Strong correlation was observed between LUMIPULSE p‐tau/Aβ42 and Aβ42/40, as well as Elecsys and LUMIPULSE p‐tau/Aβ42 and Aβ42/40 (Spearman's ρ = –0.827, –0.858, and 0.960, respectively). Concordance between LUMIPULSE p‐tau/Aβ42 and Aβ42/40 was 96% and between Elecsys p‐tau/Aβ42 and both LUMIPULSE ratios was 97%. All ratios had > 94% overall, positive, and negative percent agreement with amyloid PET classification. Discussion These data suggest that p‐tau/Aβ42 and Aβ42/40 ratios provide similar clinical information in the assessment of amyloid pathology.

Abstract Background: Measurement of parathyroid hormone related peptide (PTHrP) is helpful in the diagnosis and clinical management of patients suspected of humoral hypercalcemia of malignancy (HHM). In these patients uncontrolled release of PTHrP by tumor cells is responsible for the hypercalcemia and PTH concentrations are typically suppressed. Objective: Develop a sensitive and specific assay for quantitation of PTHrP in plasma. Method: Calibrators (PTHrP 1-86) and samples (50uL) were incubated with an anti-PTHrP goat polyclonal acridinium ester labeled antibody. Complexes were transferred and incubated in a microplate coated with an anti-PTHrP polyclonal rabbit antibody. After washing, the acridinium ester generated signal, which is directly proportional to the amount of PTHrP in sample, was quantified. Results: In this assay PTHrp was stable for 24 hours ambient, 3 days refrigerated, 34 days frozen and through 3 freeze/thaws. Intra and inter-assay imprecision in EDTA plasma (~0.16-35.0 pmol/L) ranged from 2.2-8.6% and 5-15%, respectively. The limit of detection was 0.04 pmol/L and the limit of quantitation was 0.16 pmol/L (15% CV). The analytical measuring range was 0.39-50.5 pmol/L (slope of 1.07 and r2 of 0.99). Average spike recovery was 98% (range 85-108%). The assay was not affected by hemoglobin of ≤500 mg/dL, triglycerides of ≤2000 mg/dL, or bilirubin of ≤50mg/dL. No hook effect was noted up to 500 pmol/L. PTH (1-84) did not cross-react in the assay. C-terminal PTHrP(107-139), and N-terminal PTHrP(1-36) had no significant cross-reactivity (≤1.1%). Mid-PTHrP(38-94) had 8.3% cross-reactivity. Comparison with an in-house PTHrP assay (n=267) showed an r2 of 0.96, and slope of 2.25 by Passing-Bablok regression fit. The 97.5% reference interval for PTHrP (n=114) was ≤0.7 pmol/L, however a higher concentration (≤4.2 pmol/L) was identified as a more specific clinical cut-off. A retrospective clinical validation study showed that using ≤4.2 pmol/L resulted in a 91% clinical sensitivity and a 98% clinical specificity. Conclusion: We have developed an analytically and clinically sensitive and specific PTHrP immunoassay. A cutoff of ≤4.2 pmol/L is clinically useful in the evaluation of patients suspected of hypercalcemia of malignancy.

Abstract Context The normal cortisol response 30 or 60 minutes after cosyntropin (ACTH[1–24]) is considered to be ≥18 μg/dL (500 nmol/L). This threshold is based on older serum cortisol assays. Specific monoclonal antibody immunoassays or LC-MS/MS may have lower thresholds for a normal response. Objective To calculate serum cortisol cutoff values for adrenocorticotropic hormone (ACTH) stimulation testing with newer specific cortisol assays. Methods Retrospective analysis of ACTH stimulation tests performed in ambulatory and hospitalized patients suspected of adrenal insufficiency (AI). Serum samples were assayed for cortisol in parallel using Elecsys I and Elecsys II immunoassays, and when volume was available, by Access immunoassay and LC-MS/MS. Results A total of 110 patients were evaluated. Using 18 μg/dL as the cortisol cutoff after ACTH stimulation, 14.5%, 29%, 22.4%, and 32% of patients had a biochemical diagnosis of AI using the Elecsys I, Elecsys II, Access, and LC-MS/MS assays, respectively. Deming regressions of serum cortisol were used to calculate new cortisol cutoffs based on the Elecsys I cutoff of 18 μg/dL. For 30-minute values, new cutoffs were 14.6 μg/dL for Elecsys II, 14.8 μg/dL for Access, and 14.5 μg/dL for LC-MS/MS. Baseline cortisol <2 μg/dL was predictive of subnormal stimulated cortisol values. Conclusion To reduce false positive ACTH stimulation testing, we recommend a new serum cortisol cutoff of 14 to 15 μg/dL depending on the assay used (instead of the historical value of 18 μg/dL with older polyclonal antibody assays). Clinicians should be aware of the new cutoffs for the assays available to them when evaluating patients for AI.

Objective This study was undertaken to describe a novel biomarker of germ cell tumor and associated paraneoplastic neurological syndrome (PNS). Methods Archival sera from patients with germ cell tumor–associated PNS were evaluated. We identified a common autoantigen in a human testicular cancer cell line (TCam‐2) by Western blot and mass spectrometry. Its identity was confirmed by recombinant‐protein Western blot, enzyme‐linked immunosorbent assay (ELISA), and cell‐based assay. Autoantibody specificity was confirmed by analyzing assorted control sera/cerebrospinal fluid. Results Leucine zipper 4 (LUZP4)–immunoglobulin G (IgG) was detected in 28 patients' sera, 26 of whom (93%) were men. The median age at neurological symptom onset was 45 years (range = 28–84). Median titer (ELISA) was 1:300 (1:50 to >1:6,400, normal value < 1:50). Coexistent kelchlike protein 11–IgG was identified in 18 cases (64%). The most common presenting phenotype was rhombencephalitis (17/28, 61%). Other presentations included limbic encephalitis (n = 5, 18%), seizures and/or encephalitis (n = 2, 7%), and motor neuronopathy/polyradiculopathy (n = 4, 14%). The most common malignancy among cancer‐evaluated PNS patients was seminoma (21/27, 78%). Nine of the 21 seminomas detected by whole‐body fluorodeoxyglucose positron emission tomography scan (43%) were extratesticular. Both female patients had ovarian teratoma. Regressed testicular germ cell tumors were found in 4 patients. Exposure of T‐cell–dendritic‐cell cocultures from chronic immunosuppression‐naïve LUZP4‐IgG–seropositive patients to recombinant LUZP4 protein evoked a marked increase in CD69 expression on both CD4+ and CD8+ T cells when compared to vehicle‐exposed and healthy control cultures. Interpretation LUZP4‐IgG represents a novel serological biomarker of PNS and has high predictive value for germ cell tumors. The demonstrated antigen‐specific T‐cell responses support a CD8+ T‐cell–mediated cytotoxic paraneoplastic and antitumor potential. ANN NEUROL 2021;89:1001–1010

Abstract Introduction: Transsphenoidal surgery is recommended as first line therapy in the vast majority of patients with acromegaly. Successful surgical intervention is determined by normalization of insulin like-growth factor (IGF) - 1 and adequate suppression of growth hormone (GH) during glucose GH suppression test or random GH levels &lt;1.0 ng/mL. Given the long half-life of IGF-1, evolution of IGF-1 and GH assays and limitations of GH suppression test, clinicians remain reliant on IGF-1 results 3–6 months following surgery to assess disease remission following surgical intervention. This can lead to delayed treatment of patients with persistent disease and significantly increase patient anxiety. Aim: To determine if IGF-1 levels at 6 weeks were equally predictive of surgical outcomes when compared to IGF-1 levels at 3–6 months postoperative. Methods: Retrospective review of patients with newly diagnosed acromegaly who had surgery between 2010–2019 and had post-operative IGF-1 level measured at 6 weeks and 3–6 months. IGF-1 was measured using the Siemens Immulite assay until 2016 when it was replaced by a LC-MS/MS assay. IGF-1 measurements at 6 weeks are obtained based on clinician discretion. Results: 69 patients (mean age 49 ± 14.8, female 31/69, 44.9%) with acromegaly had surgery and IGF-1 follow-up measurements at 6 weeks and 3–6 months. Persistent acromegaly was noted in 45/69 at 3–6 months. The median IGF-1 pre-operative was 701 ng/ mL (289–1600), 6 weeks postoperative was 286 ng/ mL (109–1038) and at 3–6 months was 267 ng/ mL (77–996). The median pre-operative IGF-1 was significantly higher than the median IGF-1 level at 6 weeks and 3–6 months (P=&lt;0.001). Although a statistically significant difference was seen between IGF-1 levels at 6 weeks and 3–6 months, the mean difference between these time points was small (20 ng/mL, P=&lt;0.001). There was a greater percent reduction in IGF-1 at 6 weeks following surgery in those who had a normal IGF-1 at 3–6 months compared to those who did not (63% vs 35%, P=&lt;0.01). Among patients who were deemed in remission at 3–6 months (24/69, 35%), 3/24 patients (all male with macroadenoma and no cavernous sinus invasion) had mildly elevated IGF-1 levels at 6 weeks (≤1.12 upper limit of normal) which subsequently normalized. In all of these patients, GH was &lt;1 ng/mL post-op. In 1 male (macroadenoma and cavernous sinus invasion), IGF-1 levels increased from normal at 6 weeks to abnormal when measured at 3–6 months. Conclusion: In the vast majority of patients, 6 weeks post-operative IGF-1 can be used to assess response to surgery avoiding a delay in treatment. However, we would recommend repeating IGF-1 levels at 3–6 months in those who have marginally elevated IGF-1 above normal (≤ 1.12), without cavernous sinus invasion and a post-operative GH of &lt;1 ng/mL prior to intervening if the IGF-1 is elevated 6 weeks as the IGF-1 may normalize.

Abstract Introduction Varied presentations of vitamin B12 (B12) deficiency include hematologic (megaloblastic anemia) and neurologic (myelopathy, peripheral neuropathy). Delayed recognition and treatment may have serious consequences. Assessing B12 status can be challenging due to diverse laboratory assays and thresholds, resulting in a wide range of reported prevalence of B12 deficiency from 3-26%. Comorbidities may also spuriously elevate or suppress B12 levels. Methylmalonic acid (MMA) level, often used as a companion test to assess for B12 deficiency, may also be affected by differing laboratory thresholds and other medical comorbidities, such as renal dysfunction. Our institutional approach to B12 assessment, termed the pernicious anemia (PA) cascade, consists of reflexive testing to 1) document low B12 stores (B12 levels with or without MMA), and 2) diagnose pernicious anemia (intrinsic factor binding antibody [IFBA] with or without gastrin assay). In this study, our objectives were: (1) assess the usefulness of our B12 testing algorithm and associated laboratory thresholds for identifying B12 deficiency, and (2) evaluate clinical follow-up of test results as part of a quality project. Methods In this retrospective study, adult (age ≥18 years) inpatients who had B12 testing from 2007 to 2013 were identified. Medical records for those patients with B12 levels 150-400 ng/L were reviewed. Data abstracted included patient demographics, indication for B12 testing, B12 levels, results for MMA, IFBA, gastrin, serum creatinine, complete blood count, and clinical outpatient follow-up. The PA cascade algorithm is as follows: 1) for B12 <150 ng/L, IFBA is performed; 2) if IFBA is negative or indeterminate, then gastrin is performed; 3) for B12 150-400 ng/L, MMA is performed; 4) if MMA is >0.40 nmol/mL, then IFBA is performed. Reference range for B12 is 180-914 ng/L. Patients were determined to be B12 deficient if B12 level was <180 ng/L, or if B12 was 150-400 ng/L with elevated MMA and macrocytosis in the absence of significant renal dysfunction, defined as serum creatinine ≥2.0 mg/dL. Results Records of 326 patients (150 female) were reviewed. Indications for B12 testing were: hematologic, 175 patients (53.7%); neurologic, 127 patients (39.0 %), psychiatric, 18 patients (5.5%); other, 4 patients (1.2%). Fifty-nine of 326 (18.1%) patients were B12 deficient, of whom 17 of 59 (28.8%) had PA. There were 54 cases of elevated MMA, >0.40 nmol/mL, of which 30 cases had mildly elevated MMA, >0.40 nmol/mL and ≤0.60 nmol/mL, considered to be the MMA "gray zone". Thirty-two of the total 326 patients had serum creatinine ≥2.0 mg/dL, of which 23 patients also had elevated MMA. Elevated MMA in 13 of these 23 patients was more likely due to renal dysfunction than to B12 deficiency. B12 testing results were not mentioned in hospital discharge summaries for 173 patients, including 8 patients with B12 deficiency. For 22 B12-deficient patients, there was no documentation of B12 replacement. Conclusions The PA cascade detected B12 deficiency in a significant number of inpatients with low-normal B12 levels that might have otherwise been missed; 28.8% of this group had PA for whom long-term B12 replacement is indicated. As treatment for B12 deficiency is inexpensive, non-toxic, and non-invasive, it is reasonable to evaluate B12 status by cascade testing which may provide additional diagnostic data beyond B12 level. Notable clinical practice findings from this study include the lack of B12 results in 173 of 326 discharge summaries, and no record of B12 supplementation in 22 of 59 patients with B12 deficiency. These gaps in documentation and follow-up may be associated with the relatively long turnaround time of MMA testing. Efforts at improving documentation, communication, and treatment of B12 deficiency are ongoing. Disclosures No relevant conflicts of interest to declare.

Abstract Introduction The CLSI EP15-A3 guideline “User Verification of Precision and Estimation of Bias” provides a simple experimental approach to estimate a method’s imprecision and bias. The objective is to determine if the laboratory precision performance of repeatability (SR) and within-laboratory imprecision (SWL) are in accordance to the manufacturer specification claims (MSCs). Objectives Evaluate the utility of the EP15-A3 protocol to verify method precision during a troubleshooting investigation and after major instrument maintenance, using a carcinoembryonic antigen (CEA) immunoassay as an example. Methods CEA was performed on the Beckman Coulter DxI (Beckman Coulter, Brea, CA). Quality control (QC) levels (L1: 2.89; L2: 21.10; L3: 39.10 ng/mL) (Bio-Rad Laboratories, Irvine, CA) were used. Each QC level was measured before and after instrument maintenance as follows: five replicates per run, one run per day, and during 5 days. Imprecision estimates (IEs) for SR (%CVR) and SWL (%CVWL) were calculated by one-way analysis of variance using Microsoft Excel Analyse-it software. Estimated imprecision was compared to MSC and desirable imprecision specifications based on biological variation (BV). Results A change in the analytical performance of CEA was detected by a decreased sigma-metric indicator. After a bias problem was ruled out, the observed %CVR for L1, L2, and L3 were 7.2%, 3.7%, and 4.8%, respectively. The %CVWL were 8.3%, 5.0%, and 5.5%, which exceeded the MSC of %CVWL~4.0% to 4.5%. After a laboratory investigation, major instrument maintenance was performed by the manufacturer. The %CVR and %CVWL estimates for L1, L2, and L3 after maintenance were 3.2%, 3.8%, 3.5% and 3.9%, 4.2%, 4.0%, respectively. After maintenance, the CEA performance was consistent with the MSC for each of the levels analyzed and within the BV impression goal of %CV ≤6.4. Conclusion CLSI EP15-A3 guideline is an alternative troubleshooting tool that can be used to investigate and verify method precision performance before and after significant instrument maintenance.

Abstract Background Pathologic causes of hyperprolactinemia include prolactin-secreting pituitary adenoma (prolactinoma), diseases of the hypothalamus, primary hypothyroidism, and renal failure. Another cause of hyperprolactinemia is the presence of macroprolactin, a high-molecular-mass complex of prolactin and immunoglobulins, which constitutes a biologically inactive form of prolactin. Detection of macroprolactin is important to avoid misdiagnosis and inappropriate treatment; however, relatively little is known about the persistence of macroprolactin in patients over time or how macroprolactin concentrations evolve within patients. The objective of this study was to examine the changes in macroprolactin and prolactin over time in a large clinical population. Methods All physician-ordered macroprolactin tests from December 2011 to October 2018 (n = 5,318 unique patients) were examined. Data were extracted from patients with repeat collections (≥2 timepoints) during this 7-year period (n = 269). Macroprolactin testing was performed using the Roche Elecsys Prolactin II assay. Prior to analysis, an equal volume of 25% polyethylene glycol (PEG) was added to patient serum, causing macroprolactin to precipitate. Following centrifugation, unprecipitated prolactin was measured in the supernatant, as well as an aliquot of the native sample (measuring total prolactin). Macroprolactin (precipitated prolactin) was calculated by subtracting the unprecipitated prolactin from the total prolactin concentration. For this study, a specimen was considered positive for macroprolactin if the percentage of precipitated prolactin was ≥60%. Results A total of 14% (37/269) of patients tested positive for macroprolactin in at least one of the sequential determinations. For all patients with two or more timepoints, the mean interdetermination change in percent macroprolactin was +0.6% and the mean interdetermination change in total prolactin was –11.6 ng/mL. The mean time between determinations in these patients was 303 days. For the 37 patients that had a positive macroprolactin determination, 25 remained positive across all sample collections (mean interdetermination change of +0.5% macroprolactin, mean interdetermination change in total prolactin of +0.4 ng/mL), seven samples went from positive to negative (mean interdetermination change of –10% macroprolactin, mean change in total prolactin of +0.2 ng/mL), and two samples went from negative to positive (mean interdetermination change of +5.5% macroprolactin, mean change in total prolactin of +1.3 ng/mL). The remaining 3 of the 37 specimens had more than two determinations that fluctuated above and below the predefined cutoff. Conclusions The results from this study suggest that the presence of macroprolactin largely but not exclusively persists over time. Additionally, macroprolactin rarely appears after a previously negative assessment (2/235 patients). Furthermore, only small increases in sequential percent macroprolactin determinations were observed in this data set. The prevalence of the persistence of macroprolactin protein over time might have important implications for patient prolactin monitoring.