Assay Interference Research Articles

Anti‐factor IIa (FIIa) heparin assay for patients on direct factor Xa (FXa) inhibitors

BackgroundDirect factor Xa (FXa) inhibitors are increasingly prescribed for outpatients, and those transitioning to unfractionated heparin (UFH) for hospital admission are monitored via an anti‐FXa assay. Because of assay interference, UFH results would often be critically elevated, confounding dosing. ObjectivesAn anti‐factor IIa (FIIa) UFH assay was evaluated for clinical use. MethodsThe BIOPHEN ANTI‐IIa (Aniara Diagnostica) assay and anti‐FXa INNOVANCE Heparin assay (Siemens Healthcare Diagnostics Products GmbH) were compared on the Siemens BCS XP system. Samples included UFH controls and calibrators and specimens from patients transitioning from apixaban or rivaroxaban to UFH. Method comparison, linearity, recovery, precision, and interference by direct FXa inhibitors were evaluated. The effect of the BIOPHEN ANTI‐IIa assay on the rate of critically high UFH results was retrospectively reviewed 4 months after implementation. ResultsAccuracy studies using 0.24 and 0.50 IU/mL UFH yielded means and standard deviations of 0.26 ± 0.01 and 0.58 ± 0.01 IU/mL, respectively. Within‐run and between‐run coefficients of variation were 4.6% and 15.5% for the low control, and 1.8% and 10.6% for the high control. The method comparison slope was 0.9965 (r2 = 0.9468). The linear range was 0.1 to 1.3 IU/mL. The assay measured UFH in the presence of 192 ng/mL apixaban or 158 ng/mL rivaroxaban. Introduction of the assay for clinical use reduced the monthly percentage of critically high results from 9.4% to 3.8% for admitted heparinized patients who recently discontinued apixaban or rivaroxaban. ConclusionsThe BIOPHEN ANTI‐IIa assay is suitable for patients transitioning off apixaban or rivaroxaban.

Development of a Highly Specific Anti-drug Antibody Assay in Support of a Nanoparticle-based Therapeutic.

PEGylated biotherapeutics can elicit anti-PEG (polyethylene glycol) immune responses in patients treated with this category of drugs. While anti-PEG antibody assays for this class of biotherapeutics have become a common element of the clinical immunogenicity testing strategy, the overall antibody incidence induced by the nanoparticle (NP) delivery system (such as ACCURINS®) has not been fully studied to date. To support the immunogenicity assessment of one of Pfizer's NP-based therapeutics, consisting of gedatolisib (GEDA) encapsulated in ACCURINS® (GEDA-NP), we developed an anti-GEDA-NP antibody (ADA) assay on the MSD platform for the detection of GEDA-NP induced ADA in human serum. The focus of our strategy was on developing a clinically relevant ADA assay and systematically addressing assay interference through rigorous assay optimization. Our efforts led to a fit-for-purpose assay for the detection of anti-GEDA-NP ADA in serum samples obtained from breast cancer patients. Results from method qualification indicated robust assay performance, as highlighted by inter and intra-assay precision within 25% CV for all controls, and reproducible response profiles across multiple runs during the assessment of assay cut points with breast cancer samples. The assay sensitivity was between 4.3ng/mL and 123ng/mL for surrogate positive controls of IgG and IgM isotypes, respectively. Additionally, assay interference from nonspecific matrix proteins and circulating drug was addressed, which ensured accurate assessment of ADA incidence that can be attributed to GEDA-NP.

The effect of DOACs on laboratory tests and their removal by activated carbon to limit interference in functional assays.

We aimed to review the interfering effect of DOACs on tests for haemostatic function and then to discuss overcoming these with activated carbon (AC) products, thereby eliminating DOAC issues from test plasmas. Recent relevant articles were reviewed and are discussed. Laboratory tests for DOACs, lupus anticoagulant, factor assays and APC Resistance were carried out in such publications with and without an AC product on various instruments using reagents approved for diagnostic use in well-regulated clinical laboratories. All reports on this plasma pre-treatment by AC products agree that they extract DOACs from plasma samples with minimal effect on underlying clotting tests. The specific extraction of DOACs significantly reduced false positive lupus anticoagulant detection and provided more reliable results in clotting factor assays, APC resistance and other thrombophilia tests. Dabigatran and edoxaban seem to be adsorbed more thoroughly by AC from plasmas than rivaroxaban and apixaban. In summary, most of the AC products reviewed here appear to remove DOACs from test plasmas without significantly affecting underlying clotting tests and permit correct diagnosis of various haemostatic conditions despite the initial presence of DOACs. The application of such agents as a sample pre-treatment to overcome the effects of DOACs for routine coagulation testing is supported by the emerging literature.

SUN-493 A “Curve Ball” in the Management of an Infertile Hyperthyroid Patient

Introduction: We present the case of a young female patient referred for hyperthyroidism with persistently detectable TSH despite elevated free thyroxine (FT4) levels which, interestingly, failed to normalize following anti-thyroidal treatment. Further testing elucidated the underlying causation for detectable TSH in presence of hyperthyroxinemia to be due to interfering substances in the thyroid function assays. Case: A 35-year-old female is evaluated for hyperthyroidism discovered in preparation for embryo transfer. History includes transient hyperthyroidism two years ago while undergoing in vitro fertilization. Prior workup included negative antibodies and nuclear uptake scan revealing a right-sided autonomously functioning thyroid nodule with 24-hour uptake of 40.7%. She was briefly treated with PTU in first trimester and lost to follow-up. While once again undergoing fertility treatment with clomiphene, the patient developed tremor and heat intolerance. She was found to have TSH 0.3 (0.45-4.12 mU/L) and analog FT4 of 6.4 (0.8-1.8 ng/dL). She denied use of OTC supplements. PTU 50 mg twice daily was initiated with minimal improvement with TSH 0.7 mU/L, FT4 3.7 ng/dL. On evaluation, slight tremor and mild thyroid enlargement were noted. Our differential expanded to include TSH-secreting pituitary adenoma, thyroid hormone resistance (no family history), and assay interference. Both MRI pituitary and an alpha-subunit level (0.36) were normal. Symptoms improved gradually with repeat TSH 1.79 mU/L, FT4 2.4 ng/DL by standard analog methods. We suspected ‘assay interference’ for which FT4 via direct equilibrium dialysis was obtained and was indeed normal at 0.76 ng/dL. Further lab testing verified interference in both in the standard TSH and FT4 assays presumed secondary to heterophile antibodies. Discussion: Interpretation of thyroid studies discordant with the clinical picture or incongruent with each other requires understanding of thyroid physiology and the intricacies of commonly utilized assays. The differential of elevated thyroxine levels with detectable/normal TSH rests between thyroid hormone resistance syndromes, TSH secreting pituitary tumors and interfering substances in the assay. Most commercially available TSH assays are based on a ‘sandwich’ assay which is notoriously interfered with by heterophile antibodies and excess biotin. Determination of FT4 is also challenging as the assay must detect very low concentrations of free hormone relative to excess of protein-bound analyte. When in question, it is important consider utilization of laboratory expertise and retesting by alternative assays.

MON-480 Isolated Hyperthyroxinemia - Does Everyone Needs Treatment?

Background: Raised free thyroxine (T4) with normal thyroid stimulating hormone (TSH) levels should be identified and interpreted with caution. Some of these conditions do not need treatment. We present three cases with similar biochemical abnormalities from three different causes. Case 1: A 62-year-old clinically asymptomatic lady was referred to us with Free T4 34.9 pmol/L (10.0 – 24.0 pmol/L), TSH 0.81 mU/L (0.2 – 5.0 mu/L) and negative TSH receptor antibodies (<0.9 IU/L). She was trialled on antithyroid drugs for 6 months. Her Free T4 stayed elevated between 29.0 – 35.0 pmol/L with normal TSH. We worked up for assay interference by running tests on two analysers, Roche Cobas e801 and Siemens ADIVA Centaur CP, both yielded similar results. Alpha1 glycoprotein subunits and SHBG were normal with clinical euthyroid status making TSHoma less likely. Serum protein electrophoresis did not detect any abnormal albumin. We were unable to perform equilibrium dialysis due to non-availability of facility at our centre. Due to strong clinical suspicion and family history of thyroid dysfunction that never needed a treatment, we tested her genetically for familial dysalbumineic hyperthyroxinemia (FDH) using mutation surveyor and fluorescent sequence analysis showed her to be heterozygous for c.725G>A ALB variant confirming diagnosis of FDH. Case 2: A 65-year-old clinically asymptomatic lady, was referred to us with Free T4 28.8 pmol/L (10.0 – 24.0 pmol/L) and TSH 2.50 mU/L (0.2 – 5.0 mu/L). Given inappropriately normal TSH levels, we repeated her TFTs using 3 different analysers, Roche cobas e801, Siemens ADIVA centaur CP and Abbot ARCHITECT i1000SR. Roche and Siemens assays yielded similar results, however Abbot assay showed normal thyroid function tests with TSH 1.01 mu/L (0.4-5.0 mu/L) and free T4 18.7pmol/L (9.0-19.0 pmol/L), confirming assay interference. As Siemens and Roche uses streptavidin-biotin immobilizing system while Abbot uses a magnetic bead-based capture system, the abnormal results could be due to biotin interference. Case 3: A 65-year-old lady, clinically asymptomatic was referred to us with Free T4 29.2 pmol/L (10.0 – 24.0 pmol/L) and TSH 1.59 mU/L (0.2 – 5.0 mu/L), 3 months after stopping amiodarone, which she took for 3 weeks for atrial fibrillation. This was thought to be due to amiodarone, owing to its long half-life of 58 days. We repeated thyroid function tests in 3 months from first clinical encounter i.e. 6 months after stopping amiodarone that showed Free T4 24.2pmol/L and TSH 2.30 mU/L and repeated further 3 months later that were normal, confirming amiodarone induced abnormal biochemical profile requiring no treatment. Conclusion: Hyperthyroxinaemia with normal TSH need to be interpreted with caution as illustrated above. Some of them do not need treatment and inappropriate interpretation can potentially cause anxiety for the patient and harm due to unnecessary treatment.

MON-462 Rebel Nodule or Reluctant Gland? the Challenge Presented by Heterophile Antibodies

Introduction:Interpretation of thyroid function tests (TFTs) in background of non-specific symptoms concerning for hypothyroidism, has become challenging with assay interference. Heterophile antibody interferences are both test and laboratory platform dependent. We present a case of a toxic nodule erroneously diagnosed as isolated central hypothyroidism due to heterophile antibody interference.Case:A 38 year old lady was referred to Endocrinology for possible central hypothyroidism with symptoms of progressive fatigue, 40lb unintentional weight loss, poor appetite, nausea, intermittent diarrhea/constipation, occasional cold intolerance and intermittent lightheadedness. TFTs suggested low TSH 0.175 mcIU/ml (N 0.35-3.8 mcIU/ml) and low FT4 0.74 ng/dl (N 0.8-1.8 ng/dl). Pituitary hormone evaluation revealed normal ACTH, AM cortisol, IGF-1, prolactin and FSH. A pituitary MRI was normal.Two months later, she had worsening fatigue, anxiety with palpitations and tremors, and 14lb weight gain. TFTs again confirmed low TSH (0.575 mcIU/ml) and lower FT4 (0.70 ng/dl). Empirical weight-based levothyroxine (LT4) supplementation was initiated for central hypothyroidism. Six weeks later, TFTs showed hyperthyroidism (TSH <0.005 mcIU/ml, FT4 1.57 ng/dl). The patient endorsed worsening lightheadedness and palpitations on LT4, which resolved on LT4 discontinuation. One month later, TFTs were abnormal again (TSH 0.047 mcIU/ml, FT4 0.74 ng/dl).Due to persistent discordance in symptoms and biochemical tests, TFTs were evaluated for heterophile antibody interference. While HAMA-treated TSH remained low (0.04 mIU/l), FT4 by equilibrium dialysis (FT4 ED) was normal (1.1 ng/dl, regular assay 0.74 ng/dl), suggesting subclinical hyperthyroidism. A thyroid uptake scan confirmed an autonomous toxic right thyroid nodule with suppressed remaining gland. Patient ultimately underwent 15 mCi RAI ablation of the nodule. TFTs done 1 month post-RAI suggested normal TSH (1.2 mcIU/ml) and normal FT4 ED (1 ng/dl). Previous symptoms have since resolved.Conclusion:Current methods of TFTs are generally reliable in diagnosing and monitoring thyroid disease. Rarely, medications, supplements, and endogenous antibodies can bind to TSH, T4 or lab reagent, resulting in inaccurate values. This has become increasingly common with use of high dose biotin. TSH with HAMA/heterophile antibodies and FT4 ED are more accurate forms of diagnostic testing.When approaching patients with symptoms not consistent with typical hypo- or hyperthyroidism and are not responding as expected to therapy, it is important to consider more accurate testing to rule out assay errors.

Quantitative structure activity relationship and molecular simulations for the exploration of natural potent VEGFR-2 inhibitors: an in silico anti-angiogenic study

VEGFR-2 has recently become an eye-catching molecular target for the novel therapeutic designs against cancer for its well known role in persuading angiogenesis in tumor cells. The current study set sights on the exploration of novel potent natural compound targeting VEGFR-2 via computational ligand-based modeling and database screening followed by binding pattern analysis, reactivity site prediction and MD simulation studies. The known 53 VEGFR-2 inhibitors (with IC50 ranging from 0.7 nM to 9700 nM) were headed for development of Ligand based pharmacophore model using 3 D QSAR pharmacophore generation module of DS Client. Training set inhibitors (23 compounds) were exploited to create pharmacophore model based on their chemical features. The model was validated through 30 test set inhibitors and exploited further for screening of 62,082 natural compounds from InterBioscreen natural compound database. Screened compounds further went through Drug-Likeliness study, ADMET prediction, Binding pattern analysis, In silico prediction of reactivity sites, Biological activity spectra prediction, pan assay interference compound identification and MD simulation analysis. Out of 5 screened compounds, Compound A and Compound B exhibited highest binding energy judged against the standard drug “Sorafenib”. On further conducting reactivity site prediction, BAS prediction, and pan assay interference compound identification, Compound B exhibited better result which was carried forward for MD simulation study for 50 ns. MD simulation results suggested that Compound B exhibited more stable binding to the active site of VEGFR-2 without causing any conformational changes in protein-ligand complex. Thereby, the investigation proposes Compound B to hold potent antiangiogenic potential targeting VEGFR-2. Communicated by Ramaswamy H. Sarma

In silico strategies for probing novel DPP-IV inhibitors as anti-diabetic agents

Identification of new DPP-IV inhibitors by integrating validated in silico approach is being presented herein. Novel hits were identified by combining pharmacophore and structure based virtual screening of ZINC and Knowledge Base in house database followed by ADME profiling, consensus docking studies. Six potential hits were identified and analysed for their synthetic accessibility score, novelty analysis and pan assay interference compounds filtration. Out of six, three hits viz., ZINC25060187, ZINC53746227 and KB-10 were analysed for stability studies using Molecular Mechanics/Generalized Born Surface Area (MM/GBSA) and Molecular Dynamics (MD) simulation. The simulation studies of the identified hits revealed that these hits have good selectivity and stability in DPP-IV binding pocket. Important interactions with amino acids viz., Tyr547, Glu205 and Glu206 similar to co-crystallized ligand were also observed. One of the hits viz., KB-10 was synthesized and evaluated for its biological potential. The compound KB-10 showed good DPP-IV inhibition in both in vitro and in vivo studies with IC50: 22.69 µM. This study supports the fact that these techniques hold potential for efficient screening of compounds with unknown affinity for DPP-IV that could serve as candidates for therapeutic development. Communicated by Ramaswamy H. Sarma

Drug design: 4-thiazolidinones applications. Part 1. Synthetic routes to the drug-like molecules

4-Thiazolidinones, as examples of privileged scaffolds, have been the focus of medicinal chemistry since 60th. Among them, 5-substituted thiazolidinones with a C5 exocyclic bond (5-ene derivatives) are of special interest due to chemical characteristics and pharmacological profiles, possessing anticancer, antimicrobial, and antiviral properties, as well as being high-affinity ligands to a number of biological targets. A new medicinal chemistry trend claims that the aforementioned compounds are frequent hitters or pan assay interference compounds, which are useless because of the possible low selectivity. This is argued by the Michael acceptor property of 5-ene-4-thiazolidinones, which is actively discussed in the literature and requires further investigation. Based on SAR analysis, the main vectors for the design of 5-ene-4-thiazolidinone-based molecules were proposed: complication of C5 fragment; introduction of the substituents in the N3 position; synthesis of isosteric heterocycles; combination with other pharmacologically attractive fragments; annealing of thiazolidinone core; utilisation of 5-ene-thiazolidinones in synthesis of other compounds. The affinity of 5-ene-4-thiazolidinones toward various targets can be regarded as an advantage in polypharmacological approaches. Michael acceptors are considered as the “new old tool” for new drug creation, especially anticancer agents. One of the possible solutions within privileged substructure-based diversity-oriented synthesis is the fixation of 5-ene-4-thiazolidinone fragment in the fused heterocycles, for example, thiopyrano[2,3-d]thiazoles obtained from 5-ene-thiazolidinones.

Pure T3 thyrotoxicosis from a Struma Ovarii characterised by a paradoxical rise in thyroxine on treatment.

SummaryA 33-year-old female presented with a right 11.6 cm ovarian cyst. Routine pre-operative thyroid function tests showed thyroid stimulating hormone (TSH) of less than 0.02 mU/L (0.3–3.05) and a free thyroxine (FT4) of 5.5 pmol/L (10–28.2) suggesting either assay interference, triiodothyronine (T3) ingestion or hypopituitary hypothyroidism. A free triiodothyronine (FT3) level was requested which was high normal 6.9 pmol/L (3.1–8.1). Parallel assays on a different platform were similar but with a raised FT3 of 7.2 pmol/L (3.1–6.8). TSH receptor stimulating antibody (TSHAb) and thyroid peroxidase antibodies (TPO) were negative. Antithyroglobulin antibody (TgAb) was positive at 155.6 IU/mL (0–115). She was clinically euthyroid. Thyroid ultrasound showed a normal sized mildly heterogeneous gland with low blood flow and a solitary 1.5 cm U3 (BTA) nodule with higher blood flow. Thyroid Tc99m uptake was very low 0.2% (0.6–3.0) with no nodule uptake. These results demonstrated an extrathyroidal source of excessive autonomous T3 production resulting in the low thyroxine (T4). With carbimazole her TSH rose to 11.9 mU/L, FT4 rose to 7.7 pmol/L and FT3 reduced to 3.6 pmol/L. Histological diagnosis was Struma Ovarii. Her TSH, FT4 and FT3 remained normal thereafter. In conclusion, an extrathyroidal source of high T3 secretion was diagnosed using routine thyroid tests and scans. We believe this is the first description of a Struma Ovarii exclusively secreting T3 hormone characterised by the paradoxical rise of a low FT4 to normal with treatment. Two years later she developed non-secreting peritoneal deposits of highly differentiated follicular carcinoma.Learning points:Abnormally low TSH and FT4 levels suggestive of possible T3 ingestion, or less likely, hypopituitary hypothyroidism should always be followed by an assay of FT3.The diagnosis of an extrathyroidal source of T3 can be made using conventional thyroid tests, thyroid ultrasound scanning and technetium thyroid uptake and scan imaging. In a pre-menopausal patient this avoids a radiation dose to the pelvis.Pelvic radioisotope scanning of a suspected Struma Ovarii causing thyrotoxicosis can be reserved for patients whose thyroid function remains abnormal after initial surgery.Carbimazole is effective in the treatment of extrathyroidal autonomous T3 hormone production from a Struma Ovarii.The pathological appearance of a Struma Ovarii is not a guide to its malignancy. Even with a benign appearance they can disseminate to peritoneum, as highly differentiated follicular carcinoma (previously known as peritoneal strumosis).Hyperthyroid secretion by a Struma Ovarii may not be replicated in the metastatic follicular carcinoma in the peritoneum.

High-Throughput Screening to Predict Chemical-Assay Interference

The U.S. federal consortium on toxicology in the 21st century (Tox21) produces quantitative, high-throughput screening (HTS) data on thousands of chemicals across a wide range of assays covering critical biological targets and cellular pathways. Many of these assays, and those used in other in vitro screening programs, rely on luciferase and fluorescence-based readouts that can be susceptible to signal interference by certain chemical structures resulting in false positive outcomes. Included in the Tox21 portfolio are assays specifically designed to measure interference in the form of luciferase inhibition and autofluorescence via multiple wavelengths (red, blue, and green) and under various conditions (cell-free and cell-based, two cell types). Out of 8,305 chemicals tested in the Tox21 interference assays, percent actives ranged from 0.5% (red autofluorescence) to 9.9% (luciferase inhibition). Self-organizing maps and hierarchical clustering were used to relate chemical structural clusters to interference activity profiles. Multiple machine learning algorithms were applied to predict assay interference based on molecular descriptors and chemical properties. The best performing predictive models (accuracies of ~80%) have been included in a web-based tool called InterPred that will allow users to predict the likelihood of assay interference for any new chemical structure and thus increase confidence in HTS data by decreasing false positive testing results.

Familial dysalbuminemic hyperthyroxinemia confounding management of coexistent autoimmune thyroid disease.

SummaryFamilial dysalbuminemic hyperthyroxinemia (FDH) is a cause of discordant thyroid function tests (TFTs), due to interference in free T4 assays, caused by the mutant albumin. The coexistence of thyroid disease and FDH can further complicate diagnosis and potentially result in inappropriate management. We describe a case of both Hashimoto’s thyroiditis and Graves’ disease occurring on a background of FDH. A 42-year-old lady with longstanding autoimmune hypothyroidism was treated with thyroxine but in varying dosage, because TFTs, showing high Free T4 (FT4) and normal TSH levels, were discordant. Discontinuation of thyroxine led to marked TSH rise but with normal FT4 levels. She then developed Graves’ disease and thyroid ophthalmopathy, with markedly elevated FT4 (62.7 pmol/L), suppressed TSH (<0.03 mU/L) and positive anti-TSH receptor antibody levels. However, propylthiouracil treatment even in low dosage (100 mg daily) resulted in profound hypothyroidism (TSH: 138 mU/L; FT4: 4.8 pmol/L), prompting its discontinuation and recommencement of thyroxine. The presence of discordant thyroid hormone measurements from two different methods suggested analytical interference. Elevated circulating total T4 (TT4), (227 nmol/L; NR: 69–141) but normal thyroxine binding globulin (TBG) (19.2 µg/mL; NR: 14.0–31.0) levels, together with increased binding of patient’s serum to radiolabelled T4, suggested FDH, and ALB sequencing confirmed a causal albumin variant (R218H). This case highlights difficulty ascertaining true thyroid status in patients with autoimmune thyroid disease and coexisting FDH. Early recognition of FDH as a cause for discordant TFTs may improve patient management.Learning points:The typical biochemical features of familial dysalbuminemic hyperthyroxinemia (FDH) are (genuinely) raised total and (spuriously) raised free T4 concentrations due to enhanced binding of the mutant albumin to thyroid hormones, with normal TBG and TSH concentrations.Given the high prevalence of autoimmune thyroid disease, it is not surprising that assay interference from coexisting FDH may lead to discordant thyroid function tests confounding diagnosis and resulting in inappropriate therapy.Discrepant thyroid hormone measurements using two different immunoassay methods should alert to the possibility of laboratory analytical interference. The diagnosis of FDH is suspected if there is a similar abnormal familial pattern of TFTs and increased binding of radiolabelled 125I-T4 to the patient’s serum, and can be confirmed by ALB gene sequencing.When autoimmune thyroid disease coexists with FDH, TSH levels are the most reliable biochemical marker of thyroid status. Measurement of FT4 using equilibrium dialysis or ultrafiltration are more reliable but less readily available.

Flavonoids interference in common protein assays: Effect of position and degree of hydroxyl substitution

Flavonoids interfere with colorimetric protein assays in a concentration- and structure-dependent manner. Degree (≥3) and position (C3) of –OH substitution was associated with intensified interference (p < 0.05). Significant overestimation of protein (~3–5 folds) could occur at higher flavonoid concentrations (>5 μM) and is particularly evident at lower protein concentrations (25–250 μg/ml). Since, healthy human urinary protein (<200 μg/ml) and flavonoids urinary excretion (0.5–2 μg/ml) levels fall in this range, overestimation of protein concentration with flavonoids consumption in diet, including natural supplements, remains relevant issue for diagnostic and research labs. Protein precipitation by acetone to remove interfering flavonoid successfully resolves the problem.

Biotin supplementation causes erroneous elevations of results in some commercial serum 25-hydroxyvitamin d (25OHD) assays

The Vitamin D External Quality Assessment Scheme (DEQAS) distributes serum samples globally, on a quarterly basis, to assess participants’ performance of specific methods for 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (1,25-(OH)2D). DEQAS occasionally circulates samples containing high levels of substances found in certain clinical situations e.g. 25-OHD2, 24,25-(OH)2D3, hypertriglyceridemia. The increased availability and use of health supplements containing biotin has led to case reports of assay interference in methods utilizing a biotin-streptavidin detection system. In October 2018, DEQAS included a serum sample (545) containing exogenous biotin (concentration =586 μg/L) which was analyzed by a total of 683 laboratories using 35 different methods. The same serum sample (544) without exogenous biotin was also included in the 5-sample set. All methods (760 laboratories) performed satisfactorily on sample 544 giving an All-Laboratory Trimmed Mean = 50.2 ± 6.5 nmol/L (±SD, CV = 12.9 %). The target value for this sample 544 (& 555) was 47.4 nmol/L as determined by Centers for Disease Control and Prevention (CDC) Atlanta, Georgia using their LC–MS/MS reference method. In contrast, #545 containing the exogenous biotin was reported by only 683 laboratories and gave an All-Laboratory Trimmed Mean = 66.8 ± 37.6 nmol/L (±SD, CV = 56.3 %). As expected, LC-MS/MS methods (143 labs) reported similar results for both 544 = 48.9 ± 4.4 nmol/L (±SD) and 545 = 48.3 ± 4.5 nmol/L (±SD) showing that assays involving chromatographic steps are unaffected by the presence of biotin. Several of the antibody-based assays including Abbott Architect, DiaSorin Liaison, Beckman Unicel and Siemens Centaur are also unaffected by the addition of biotin. Two assays, IDS-iSYS and Roche Total 25OHD, both of which use biotin-streptavidin, exhibit biotin interference yielding values with a significant positive bias for 545 of 102.6 nmol/L ± 78.7 nmol/L (±SD) and 517.8 nmol/L ± 209.8 nmol/L (±SD) respectively. Interestingly, the failure to report sample 545 data from 77 laboratories is due solely to those running Roche Total 25OHD or Roche Vitamin D Total II assays. Given the prevalence of the adversely affected assays (25 % of DEQAS users) and the high volume of 25OHD testing, clinicians using these assays should, where possible, only measure 25OHD when patients are off biotin.

Hepatitis C-associated glomerulonephritis masquerading as Goodpasture’s syndrome

Anti-glomerular basement membrane (GBM) autoantibodies are associated with Goodpasture’s syndrome, characterised by lung and kidney involvement. We report a case with clinical disease demonstrating discrepant anti-GBM antibody results between assay platforms. A 39-year-old male presented with an eight-week history of haemoptysis and acute renal impairment, on a background of active hepatitis C infection. Creatinine was 256 μmol/L with haemoproteinuria, hypocomplementaemia, and positive anti-GBM level (65 U/mL Phadia ELiA; reference range >10 U/mL) which was confirmed on repeat testing. Treatment for Goodpasture’s syndrome was initiated with plasma exchange (PLEX) and intravenous cyclophosphamide. However, renal biopsy performed in parallel to treatment did not demonstrate characteristic linear GBM binding on direct immunofluorescence. Findings were instead consistent with hepatitis C-associated glomerulonephritis. ANCA by immunofluorescence was negative. Anti-PR3, anti-MPO and anti-CCP tested retrospectively by Phadia ELiA methods were also positive, raising suspicion for an interfering factor. Pre-treatment sera tested for anti-GBM antibodies via indirect immunofluorescence (INOVA primate kidney) and chemiluminescence assay (INOVA BIO-FLASH) were negative. Unfortunately, pre-treatment cryoglobulins had not been tested. However, testing 6 months after presentation confirmed type 2 cryoglobulins, and anti-GBM levels had normalised. Cryoglobulins or another interfering factor may have caused platform-specific assay interference, affecting anti-GBM and other autoantibody detection on the same platform.

Interference From High-Dose Biotin Intake in Immunoassays for Potentially Time-Critical Analytes by Roche.

Immunoassays using the interaction between streptavidin and biotin are used for clinical chemical analytes on platforms by many different manufacturers. The design can be susceptible to interference from high-dose biotin intake in patients, which remains an often-overlooked confounder despite recently increased awareness. To evaluate an easily implementable method of in vitro biotin depletion for the removal of biotin interference in immunoassays for potentially time-critical analytes. A biotin stock solution was made and de-identified patient samples were spiked to reach a biotin concentration of 1.126 × 106 pg/mL, the maximum reported biotin concentration 1 to 2 hours after a single oral dose of 300 mg biotin. Then, the resulting interference in Elecsys immunoassays for cortisol, cyclosporine A, tacrolimus, digitoxin, thyroid-stimulating hormone, free triiodothyronine, free thyroxine, C-peptide, insulin, N-terminal pro-B-type natriuretic peptide, troponin T high sensitive, human immunodeficiency virus, procalcitonin, β human chorionic gonadotropin, toxoplasma immunoglobulin M, and toxoplasma immunoglobulin G was evaluated before and after biotin depletion using streptavidin particles. All tested immunoassays, with the exception of toxoplasma immunoglobulin M and toxoplasma immunoglobulin G, suffered from significant biotin interference. The depletion protocol removed assay interference due to biotin and produced results that were close or identical to initial prespike measurements. Despite an increase in turnaround times, biotin adsorption is a feasible countermeasure for biotin interference in Elecsys immunoassays. Until test kits with an increased resistance to the interference from high-dose biotin intake are distributed, the evaluated protocol can provide results properly reflecting the patient's clinical condition.

Neutral analogs of the heat shock protein 70 (Hsp70) inhibitor, JG-98

The heat shock protein 70 (Hsp70) family of molecular chaperones are highly expressed in tumors. Inhibitors containing a pyridinium-modified benzothiazole, such as JG-98, bind to a conserved, allosteric site in Hsp70, showing promising anti-proliferative activity in cancer cells. When bound to Hsp70, the charged pyridinium makes favorable contacts; however, this moiety also increases the inhibitor’s fluorescence, giving rise to undesirable interference in biochemical and cell-based assays. Here, we explore whether the pyridinium can be replaced with a neutral pyridine. We report that pyridine-modified benzothiazoles, such as compound 17h (JG2-38), have reduced fluorescence, yet retain promising anti-proliferative activity (EC50 values ~0.1 to 0.07 µM) in breast and prostate cancer cell lines. These chemical probes are expected to be useful in exploring the roles of Hsp70s in tumorigenesis and cell survival.

Circular RNA circ_0006282 Contributes to the Progression of Gastric Cancer by Sponging miR-155 to Upregulate the Expression of FBXO22.

BackgroundThere is increasing evidence that circular RNAs (circRNAs) play an important role in human cancers. As a newly identified human circular RNA, circ_0006282 is abnormally expressed in several types of cancers and promotes the development of cancers. However, the expression and function of circ_0006282 in gastric cancer (GC) remain unclear.MethodsThe expression of circ_0006282 in cancer tissues and adjacent non-cancer tissues was detected by quantitative real-time polymerase chain reaction (qRT-PCR) method, and the relationship between circ_0006282 expression and clinicopathological parameters was analyzed. After knockdown of circ_0006282 by RNA interference in GC cells, CCK-8 assay, colony formation and transwell assays were conducted to examine the effects of circ_0006282 on GC cells. The influence of circ_0006282 on tumor growth in vivo was assessed in a xenograft model. Furthermore, regulatory relationship between circ_0006282, miR-155 and FBXO22 was detected by luciferase assay, qRT-PCR and Western blot.ResultsThe expression of circ_0006282 in GC tissues was significantly higher than its adjacent non-cancer tissues and over-expression of circ_0006282 was associated with tumor size, lymph nodes metastasis and TNM stage, but no obvious links with other pathological parameters. Knockdown of circ_0006282 inhibited the proliferation and metastasis ability of GC cells in vitro and suppressed the tumor growth in vivo. Furthermore, mechanistic investigations suggested that circ_0006282 served as a competing endogenous RNA (ceRNA) of miR-155. Moreover, FBXO22 was identified as the functional target of miR-155 and down-expression of circ_0006282 inhibited FBXO22 expression. Rescue assays also demonstrated that the oncogenic function of circ_0006282 is partly attributed to its regulation on miR-155/FBXO22 axis.ConclusionOur findings indicated that over-expression of circ_0006282 down‑regulated miR-155 to activate the expression of FBXO22, thus promoting proliferation and metastasis of GC cells, which provides a promising therapeutic target for GC treatment.

Estimation of lipemia interference with automated HIL-test on d-dimer ACL TOP 50 series analysis – reveals a higher cut-off than manufacturer’s recommendations

Fibrin-d-dimer (d-dimer) is essential for the diagnosis and treatment of thrombosis patients. The new ACL TOP 50- series used for d-dimer determination, integrates a preanalytical interference check for hemolysis, icterus and lipemia (HIL-test). Using earlier versions of ACL TOP, HIL was evaluated by visual inspection by the biomedical laboratory scientist. With the new integrated HIL-test, lipemia is determined by measuring turbidity in the sample at 671 nm, reflecting the lipid content in the sample. Using the new ACL TOP 50- series, we observed more samples being rejected for d-dimer analysis due to lipemia-interference evaluated by the integrated HIL-test suggesting a discrepancy between the former triglyceride-based cut-off and the new turbidity-based cut-off. Therefore, to re-evaluate the lipemia interference cut-off with the turbidimetric measurement, we did a spike-in experiment, using intralipid as lipemia simulation. Three × six different patient pools were prepared from sodium-citrate plasma. We observed no interference in the d-dimer assay by intralipid concentrations resulting in milli absorbances (mAbs) below 3000 mAbs. Thus, the cut-off for lipemia interference using the integrated HIL-test on ACL TOP 550 should be 3000 mAbs. This cut-off will reduce the number of samples rejected due to false positive interference and at the same time reduce ‘hands on’ time for the biomedical laboratory scientists and minimize the risk of subjective evaluation by a visual inspection.

CRISPR-Cas13d mediates robust RNA virus interference in plants

BackgroundCRISPR-Cas systems endow bacterial and archaeal species with adaptive immunity mechanisms to fend off invading phages and foreign genetic elements. CRISPR-Cas9 has been harnessed to confer virus interference against DNA viruses in eukaryotes, including plants. In addition, CRISPR-Cas13 systems have been used to target RNA viruses and the transcriptome in mammalian and plant cells. Recently, CRISPR-Cas13a has been shown to confer modest interference against RNA viruses. Here, we characterized a set of different Cas13 variants to identify those with the most efficient, robust, and specific interference activities against RNA viruses in planta using Nicotiana benthamiana.ResultsOur data show that LwaCas13a, PspCas13b, and CasRx variants mediate high interference activities against RNA viruses in transient assays. Moreover, CasRx mediated robust interference in both transient and stable overexpression assays when compared to the other variants tested. CasRx targets either one virus alone or two RNA viruses simultaneously, with robust interference efficiencies. In addition, CasRx exhibits strong specificity against the target virus and does not exhibit collateral activity in planta.ConclusionsOur data establish CasRx as the most robust Cas13 variant for RNA virus interference applications in planta and demonstrate its suitability for studying key questions relating to virus biology.