Evaluation of Activated Carbon Treatment on Overcoming the Interference of Rivaroxaban on the Detection of Functional Lupus Anticoagulant.

OBJECTIVE: The aim of this study was to review the role of activated carbon (AC) in eliminating the interference of rivaroxaban in the detection of lupus anticoagulants (LAs). METHODS: Normal pooled plasma was obtained as group N1, group N2 took 1 mL plasma from N1 and added AC, group N3 was prepared by mixing normal plasma with rivaroxaban, and group N3 was treated with AC according to our procedure, as group N4. Plasma from 22 patients was collected before and 6-12 h after rivaroxaban therapy, described as group P1 and group P2, respectively, and 1 mL plasma was taken from group P2 and treated with AC, as group P3. Anti-Xa and diluted Russell's viper venom time (dRVVT)/silica clotting time (SCT) index in each group were measured and compared. RESULTS: Rivaroxaban concentrations and anti-Xa had high intercorrelations in group N3, and the levels of anti-Xa and dRVVT/SCT index had high intercorrelations. After treatment with AC, influence of rivaroxaban was removed, with LA and coagulation factor assays not influenced. Rivaroxaban administration could affect LA assay results in patients, with all LA results increased. After treatment with AC, results of anti-Xa and LA tests recovered to the level before rivaroxaban therapy. CONCLUSIONS: We proposed a reference procedure for the LA detection of patients using rivaroxaban by AC, and activated carbon was proven to be a simple product to eliminate the interference of rivaroxaban.

Ascorbic acid specifically reduces the misclassification of nonirritating reactive chemicals in the OptiSafe™ macromolecular eye irritation test.

Recently, we showed that the addition of physiological concentrations of ascorbic acid, a tear antioxidant, to the OptiSafe™ macromolecular eye irritation test reduced the false-positive (FP) rate for chemicals that had reactive chemistries, leading to the formation of reactive oxygen species (ROS) and molecular crosslinking. The purpose of the current study was to 1) increase the number of chemicals tested to comprehensibly determine whether the antioxidant-associated reduction in OD is specific to FP chemicals associated with ROS chemistries and 2) determine whether the addition of antioxidants interferes with the detection of true positive (TP) and true negative (TN) ocular irritants. We report that when ascorbic acid is added to the test reagents, retesting of FP chemicals with reactive chemistries show significantly reduced OD values (P < 0.05). Importantly, ascorbic acid had no significant effect on the OD values of TP or TN chemicals regardless of chemical reactivity. These findings suggest that supplementation of ascorbic acid in alternative ocular irritation tests may help improve the detection of TN for those commonly misclassified reactive chemicals.

Sense and nonsense concerning biotin interference in laboratory tests.

INTRODUCTION: Biotin supplementation (mainly OTC preparations) has gained popularity. There are concerns about biotin interference in immunoassays and potential misdiagnosis, especially since the discovery of high dose therapy in MS. This review summarizes the dangers of biotin usage and possible countermeasures. METHODS: Immunoassays design determines whether positive or negative analytical errors may occur. Techniques using biotinylated reagent and biotin binding proteins may generate errors. In sandwich immunoassays, biotin causes lowered results. Competitive immunoassays are more vulnerable: biotin usage causes false increased results. The interference is platform dependent. Parameters vary in their susceptibility: a combination of false positives and negatives mimicking a coherent profile is dangerous, e.g. combining falsely lowered TSH with falsely elevated FT4/FT3 mimicking hyperthyreosis. Other susceptible parameters are thyroglobulin, DHEA-S, estradiol, testosterone, ferritin, progesterone, Vitamin D, Vitamin B12, PSA, PTH, LH, FSH, Troponins I and T, Pro-BNP. Digoxin and PSA may also be affected. Tumor markers and ß-hCG are robust. Inserts of serological markers of HIV, hepatitis B and C warn for biotin interference. RESULTS: Manufacturers have made assays less vulnerable for biotin interference. In doubtful cases, it is helpful to determine testosterone in females and estrogen in males. Both are elevated if biotin interference is present. Biotin supplementation should be discontinued. However, this is impossible in MS patients needing biotin, as interrupting this medication is discouraged. CONCLUSIONS: Solutions to overcome this interference are: informing patients prior to analysis (avoiding peak biotin values when sampling), choice of appropriate immunoassays, and use of biotin removing steps prior to analysis.

Newborn Pulse Oximetry for Infants Born Out-of-Hospital.

BACKGROUND AND OBJECTIVES: Conventional timing of newborn pulse oximetry screening is not ideal for infants born out-of-hospital. We implemented a newborn pulse oximetry screen to align with typical midwifery care and measure its efficacy at detecting critical congenital heart disease. METHODS: Cohort study of expectant mothers and infants mainly from the Amish and Mennonite (Plain) communities with limited prenatal ultrasound use. Newborns were screened at 1 to 4 hours of life ("early screen") and 24 to 48 hours of life ("late screen"). Newborns were followed up to 6 weeks after delivery to report outcomes. Early screen, late screen, and combined results were analyzed on the basis of strict algorithm interpretation ("algorithm") and the midwife's interpretation in the field ("field") because these did not correspond in all cases. RESULTS: Pulse oximetry screening in 3019 newborns (85% Plain; 50% male; 43% with a prenatal ultrasound) detected critical congenital heart disease in 3 infants. Sensitivity of combined early and late screen was 66.7% (95% confidence interval [CI] 9.4% to 99.2%) for algorithm interpretation and 100% (95% CI 29.2% to 100%) for field interpretation. Positive predictive value was similar for the field interpretation (8.8%; 95% CI 1.9% to 23.7%) and algorithm interpretation (5.4%; 95% CI 0.7% to 18.2%). False-positive rates were ≤1.2% for both algorithm and field interpretations. Other pathologies (noncritical congenital heart disease, pulmonary issues, or infection) were reported in 12 of the false-positive cases. CONCLUSIONS: Newborn pulse oximetry can be adapted to the out-of-hospital setting without compromising sensitivity or prohibitively increasing false-positive rates.

Toxic transdermal absorption of isopropyl alcohol with falsely elevated creatinine.

Transdermal absorption of isopropyl alcohol (IPA) can cause toxicity at high doses, but case reports of this phenomenon are limited. This is a single patient encounter and chart review describing a 33-year-old previously healthy female who presented obtunded, wrapped in IPA soaked round cotton pads with overlying shrink wrap, her family's home remedy for a mild persistent rash. This case highlights several interesting aspects of IPA toxicity, including evidence that toxic doses of IPA are possible through transdermal absorption and creatinine may be falsely elevated due to acetone's interference with the measurement of creatinine on some assays.

Electrophysiological Study-Guided Permanent Pacemaker Implantation in Patients With Conduction Disturbances Following Transcatheter Aortic Valve Implantation.

Conduction disturbances remain common following transcatheter aortic valve implantation (TAVI). Aside from high-degree atrioventricular block (HAVB), their optimal management remains elusive. Invasive electrophysiological studies (EPS) may help stratify patients at low or high risk of HAVB allowing for an early discharge or permanent pacemaker (PPM) implantation among patients with conduction disturbances. We evaluated the safety and diagnostic performances of an EPS-guided PPM implantation strategy among TAVI recipients with conduction disturbances not representing absolute indications for PPM. All patients who underwent TAVI at a single expert center from June 2017 to July 2020 who underwent an EPS during the index hospitalization were included in the present study. False negative outcomes were defined as patients discharged without PPM implantation who required PPM for HAVB within 6 months of the initial EPS. False positive outcomes were defined as patients discharged with a PPM with a ventricular pacing percentage <1% at follow-up. A total of 78 patients were included (median age 83.5, 39% female), among whom 35 patients (45%) received a PPM following EPS. The sensitivity, specificity, positive and negative predictive values of the EPS-guided PPM implantation strategy were 100%, 89.6%, 81.5%, and 100%, respectively. Six patients suffered a mechanical HAVB during EPS and received a PPM. These 6 patients showed PPM dependency at follow-up. In conclusion, an EPS-guided PPM implantation strategy for managing post-TAVI conduction disturbances appears effective to identify patients who can be safely discharged without PPM implantation.

Possibility of Japanese Cedar Pollen Causing False Positives in the Deep Mycosis Test.

Because Japanese cedar pollen (JCP) contains beta-1,3-d-glucan (BG), there is concern that its lingering presence in the atmosphere, especially during its scattering period, may cause false positives in the factor-G-based Limulus amebocyte lysate (LAL) assay used to test for deep mycosis (i.e., G-test). Hence, we examined whether the LAL assay would react positively with substances contained in JCP by using the G-test to measure JCP particles and extracts. BG was purified from the JCP extract on a BG-specific affinity column, and the percentage extractability was measured using three different BG-specific quantitative methods. The G-test detected 0.4 pg BG in a single JCP particle and 10 fg from a single particle in the extract. The percentage extractability of JCP-derived BG was not significantly different among the three quantitative methods. As the JCP particles should technically have been removed during serum separation, they should be less likely to be a direct false-positive factor. However, given that the LAL-assay-positive substances in the JCP extract were not distinguishable by the three BG-specific quantitative methods, we conclude that they may cause the background to rise. Therefore, in Japan false positives arising from JCP contamination should be considered when testing patients for deep mycosis.

Posttraumatic Scab on 131I Whole-Body Scan-A False-Positive Finding.

ABSTRACT: 131I scan plays a crucial role in the management of patients with differentiated thyroid cancer for the evaluation of remnant thyroid tissue, residual/recurrent metastatic disease, posttherapy tracer distribution, and response assessment to high-dose 131I therapy. Different causes secondary to physiological, pathological, and anatomical variations have been described for false-positive findings in the whole-body planar images. This case report of a patient of differentiated thyroid cancer with undocumented trauma to the left knee region a day before receiving the high-dose radioiodine therapy showed an interesting image finding of tracer uptake at unusual site in the posttherapy whole-body 131I scan.

A simple equation to correct for gadolinium interference on plasma selenium measurement using inductively coupled plasma mass spectrometry.

BACKGROUND: The measurement of selenium in human plasma is useful to assess deficiency or toxicity. The presence of gadolinium in clinical samples following administration of certain contrast agents used for magnetic resonance imaging can cause a significant positive bias in selenium results when measured using quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS). METHODS: A mathematical equation to correct for gadolinium interference was assessed using both patient samples and commercial quality control/external quality assurance (QC/EQA) materials spiked with gadolinium. Samples were analysed using an Agilent 7900 ICP-MS operated in 'narrow peak' (half-mass) mode. Accuracy was evaluated by comparing corrected selenium results with target concentrations. RESULTS: Corrected results were found to be accurate at all gadolinium concentrations tested (2, 4, 10 and 20 mg/L). Average recoveries ranged from 97.4 to 106.5%. Results for QC/EQA materials were within specified target ranges. Within-run imprecision was <3%, and between-run imprecision was <4.3%, demonstrating robustness. CONCLUSIONS: The correction equation described here is a simple method to correct for gadolinium interference on plasma selenium measurement using ICP-MS. This approach eliminates the need for specimen recollections, and improves patient care by reducing laboratory turnaround times and preventing delays in diagnosis/treatment.

Faster automatic ASSR detection using sequential tests.

Objective: Objective Response Detection (ORD) can be used for auditory steady-state response (ASSR) detection. In conventional ORD methods, the statistical tests are applied at the end of data collection ('single-shot tests'). In sequential ORD methods, statistical tests are applied repeatedly, while data is being collected. However, repeated testing can increase False Positive (FP) rates. One solution is to infer that response is present only after the test remains significant for a predefined number of consecutive detections (NCD). Thus, this paper describes a new method for finding the required NCD that control the FP rate for ASSR detection.Design: NCD values are estimated using Monte Carlo simulations.Study sample: ASSR signals were recorded from 8 normal-hearing subjects.Results: The exam time was reduced by up to 38.9% compared to the single-shot test with loss of approximately 5% in detection rate. Alternatively, lower gains in time were achieved for a smaller (non-significant) loss in detection rate. The FP rates at the end of the test were kept at the nominal level expected (1%).Conclusion: The sequential test strategy with NCD as the stopping criterion can improve the speed of ASSR detection and prevent higher than expected FP rates.

Assessment of a rapid diagnostic test to exclude bacteraemia and effect on clinical decision-making for antimicrobial therapy.

Unnecessary antimicrobial treatment promotes the emergence of resistance. Early confirmation that a blood culture is negative could shorten antibiotic courses. The Cognitor Minus test, performed on blood culture samples after 12 hours incubation has a negative predictive value (NPV) of 99.5%. The aim of this study was to determine if earlier confirmation of negative blood culture result would shorten antibiotic treatment. Paired blood cultures were taken in the Critical Care Unit at a teaching hospital. The Cognitor Minus test was performed on one set >12 hours incubation but results kept blind. Clinicians were asked after 24 and 48 hours whether a result excluding bacteraemia or fungaemia would affect decisions to continue or stop antimicrobial treatment. Over 6 months, 125 patients were enrolled. The median time from start of incubation to Cognitor Minus test was 27.1 hours. When compared to 5 day blood culture results from both the control and test samples, Cognitor Minus gave NPVs of 99% and 100% respectively. Test results would have reduced antibiotic treatment in 14% (17/119) of patients at 24 and 48 hours (24% at either time) compared with routine blood culture. The availability of rapid tests to exclude bacteraemia may be of benefit in antimicrobial stewardship.

[What to do in the event of a suspicion of analytical interference during an immunoassay?] / Conduite à tenir devant une suspicion d'interférence analytique lors d'un immunodosage.

Identifying analytical interference is a challenge for the medical biologist in providing advice to the prescriber. Indeed, these analytical interferences often have deleterious consequences on the care of patients. Understanding their mechanisms and mastering corrective procedures is essential to limit these management errors. Faced with the many questions from clinicians in current practice, we propose an algorithm for managing a sample when interference is suspected.

[Intake of high dose biotin: A cause of artificial hyperthyroidism]. / La prise de biotine à fortes doses : une cause d'hyperthyroïdie biologique factice.

INTRODUCTION: Many hormone immunoassays use the biotin streptavidin interaction to immobilize immune complexes. The intake of high dose biotin can interfere with immunoassays using the biotin streptavidin interaction. The biotin-immunoassay interference generates falsely low or falsely high tests of hormones according to the type of immunoassay used. CASE REPORT: A 70-year-old patient, with progressive multiple sclerosis, was referred to our hospital for thyrotoxicosis. She was found to have markedly elevated thyroid hormones level (T3-T4) and decreased thyrotropin (TSH) level but she had no symptoms of hyperthyroidism. An ingestion of biotin, that is more and more frequent in patients with progressive multiple sclerosis, was found. Thyroid function tests normalized after discontinuation of biotin treatment. CONCLUSION: The discrepancy between a clinical exam which is not indicative of thyrotoxicosis and markedly abnormal thyroid function tests should lead to a search for biotin intake, which can interfere with thyroid function tests.

Discovering Cross-Reactivity in Urine Drug Screening Immunoassays through Large-Scale Analysis of Electronic Health Records.

BACKGROUND: Exposure to drugs of abuse is frequently assessed using urine drug screening (UDS) immunoassays. Although fast and relatively inexpensive, UDS assays often cross-react with unrelated compounds, which can lead to false-positive results and impair patient care. The current process of identifying cross-reactivity relies largely on case reports, making it sporadic and inefficient, and rendering knowledge of cross-reactivity incomplete. Here, we present a systematic approach to discover cross-reactive substances using data from electronic health records (EHRs). METHODS: Using our institution's EHR data, we assembled a data set of 698651 UDS results across 10 assays and linked each UDS result to the corresponding individual's previous medication exposures. We hypothesized that exposure to a cross-reactive ingredient would increase the odds of a false-positive screen. For 2201 assay-ingredient pairs, we quantified potential cross-reactivity as an odds ratio from logistic regression. We then evaluated cross-reactivity experimentally by spiking the ingredient or its metabolite into drug-free urine and testing the spiked samples on each assay. RESULTS: Our approach recovered multiple known cross-reactivities. After accounting for concurrent exposures to multiple ingredients, we selected 18 compounds (13 parent drugs and 5 metabolites) to evaluate experimentally. We validated 12 of 13 tested assay-ingredient pairs expected to show cross-reactivity by our analysis, discovering previously unknown cross-reactivities affecting assays for amphetamines, buprenorphine, cannabinoids, and methadone. CONCLUSIONS: Our findings can help laboratorians and providers interpret presumptive positive UDS results. Our data-driven approach can serve as a model for high-throughput discovery of substances that interfere with laboratory tests.

Residue concentration of cefquinome taking into account different milk fractions and comparing the performance of two screening tests.

This Research Communication describes the residue concentration of a dry cow antibiotic in two different milk fractions and describes effects of milk fraction and milk composition on the test performance of a rapid screening and a microbial inhibitor test. Thirteen dry cows were treated with an intramammary dry cow antibiotic containing 150 mg cefquinome. Quarter foremilk and stripping samples were collected on the first 10 d postpartum. All milk samples were analyzed for milk composition by the local Dairy Herd Improvement Association and were tested for antibiotic residues using the rapid screening test Milchtest BL and the microbial inhibitor test Delvotest BR Brilliant Plates. The residue concentration of cefquinome was determined in foremilk and stripping samples from milkings 1, 2, 3, 5, and 7 after calving using high performance liquid chromatography - tandem mass spectrometry. The logarithm of cefquinome concentration (logCef) was higher in foremilk than in stripping samples and higher in milk samples with lower lactose content. Furthermore, logCef decreased with the number of milkings (P < 0.001). The Milchtest BL was more likely to be not evaluated (i.e. no test and control line or no control line appeared) in stripping samples and milk samples with higher protein content. In the Delvotest BR Brilliant Plates milk samples with higher protein content were more likely to have a false positive result (i.e. the screening test result was positive, but the HPLC-MS/MS result was below the detection limit of the screening test). These results indicate that foremilk is the recommended milk fraction to be tested for residues of cefquinome and that a high protein content can be a cause of test failure and false positive results when milk during the first 10 d postpartum is tested for antibiotic residues using screening tests.

Background autofluorescence induced by plant extracts in human lymphocytes: A flow cytometric analysis of a critical bias.

The presence of background autofluorescence sources is considered as an important problem when performing fluorometric methods, due to the possible spectral overlap between it and the fluorescence emission of probes. Regarding that, we evaluated the presence of background autofluorescence in human lymphocytes after the treatment with extracts from three medicinal plants, including ethanolic extract from aerial parts of Ageratum fastigiatum, ethanolic extract from aerial parts of Eriosema campestre and the ethanolic extract from stem of Pseudobrickellia brasiliensis. Human peripheral blood mononuclear cells were treated with each extract in vitro during 24 h, followed by flow cytometric analysis. Additionally, the fluorescence emission of plant extracts was evaluated by fluorometry, using the same concentrations used in cell cultures. We identified that plant extracts treatment on lymphocytes induced background autofluorescence detectable in several wavelength ranges. Isolated extracts showed no expressive fluorescence emission in fluorometric analyses, suggesting that background autofluorescence was induced in lymphocytes by interactions between cellular components and extracts compounds. Here we discuss the importance to perform previous tests to evaluate a possible background autofluorescence induction after cell treatments with plant extracts or any other substance. In spite of being mandatory, background autofluorescence analysis of cells after treatments and stimulations is still underestimated on literature. In summary, following the precautions herein established should help to reduce the incidence of false positive results.

Dietary supplement product composed of natural ingredients as a suspected cause of erythema multiforme: A case report and identification for the confident false positivity of lymphocyte transformation test.

Growing and sustainable consumption of health-care products raises a controversial issue underlying the reliability of an in vitro diagnostic approach for adverse skin reaction. This report aimed to: (i) discuss the causative nature of a commercial dietary supplement composed of natural ingredients, particularly an Euglena-containing product, suspicious for erythema multiforme in our exemplified case; and (ii) to address the assay suitability of the lymphocyte transformation test (LTT) for identifying allergic reaction to any ingredient(s) of the product. A Japanese elderly man developed erythema multiforme after intake of a commercially available natural dietary product, whose LTT was positive. His clinical course and positive LTT suggested a provisional diagnosis of natural dietary product-induced eruption. We conducted an inquiry survey for the standard LTT with any commercial products containing Euglena in three major Japanese laboratory services and identified 22 subjects, almost all of whom (21/22, 95.6%) showed a positive LTT for any Euglena-containing products as a suspected causative. Seven normal healthy volunteers who had no intake history of Euglena-containing products showed an equivalent LTT positivity rate with the same product taken by our case; culprit components of the product included Euglena, Angelica keiskei, Barley grass and Chlorella. A cell-free culture system and enzyme-linked immunoassay suggest that the high LTT positivity relies on the non-specific lymphoproliferative activity, and not contamination of uncharacterized microorganisms and endotoxins. Because of the constitutive false positivity of LTT, this assay is unreliable for in vitro supportive diagnosis of adverse skin events caused by dietary products containing particular natural ingredients, as well as herbal materials.

Evaluation of Cytochrome P450 Selectivity for Hydralazine as an Aldehyde Oxidase Inhibitor for Reaction Phenotyping.

Hydralazine has been reported as a selective mechanism-based inactivator of aldehyde oxidase (AO) and it is widely used in the pharmaceutical industry for reaction phenotyping to estimate fraction metabolized by AO and to identify AO substrates. In this study, however, hydralazine was found to inhibit CYP1A2, 2B6, 2D6, and 3A in human suspension hepatocytes under reaction phenotyping assay conditions, at concentrations that chemically knocked out most of the AO activities (≥50 µM). Furthermore, hydralazine is a time-dependent inhibitor of CYP1A2. Based on these findings, precautions need to be taken when using hydralazine as an AO inhibitor for in vitro studies because fraction metabolized by AO is likely to be overestimated and the likelihood of false positives in identifying AO substrates increases.