False-positive Reactions Research Articles

Using Soluble CD38 to Overcome Daratumumab Interference in Pretransfusion Compatibility Testing

Background: CD38 is a protein highly expressed on myeloma (MM) cells that has been shown to be an effective target antigen for monoclonal antibody therapies, so treatment with anti-CD38 monoclonal antibodies is a first line therapy for patients with MM. Although CD38 is weaker expressed on erythocytes anti-CD38 binds to CD38 on reagent RBCs and cause panreactivity in vitro and subsequent false positive reactions in indirect antiglobulin tests (IAT), antibody detection (screening) tests, antibody identification panels, and anti-human globulin (AHG) crossmatches. These findings suggest that the soluble CD38 method could improve transfusion safety for patients receiving anti-CD38 therapy, particularly in urgent clinical settings This study aims to evaluate the effectiveness of a new soluble CD38-based method in mitigating Daratumumab interference during pretransfusion compatibility testing." Methods: We evaluated the Grifols sCD38 method in 20 patients and compared it with the DTT method Results: In our experience the sCD38 method reduced testing time from 150 to 50 minutes and demonstrated 100% efficacy, compared to 90% with DTT. The sCD38 effectively mitigated the interference caused by anti-CD38 antibodies in 10 (100% efficacy) of patient samples tested while DTT was successful in only 9/10 (90% efficacy); no interference was observed in patients presenting anti erythrocyte antibodies. Moreover, there was no negative influence on DTT sensitive blood group systems such as KEL upon sCD38 treatment. Conclusions: In our Laboratory, in the year 2023, we processed 129 patients treated with anti-CD38. Therefore the reduction from 150 to 50 minutes in the time needed to perform tests for mitigation of anti-CD38 interference appears to be relevant with a recovery of approximately 210 technical-hours per year. Another highly appreciated operational aspect was the possibility of treating the patient's plasma and perform tests using automatic instruments (Erytra Grifols) available in our laboratory. In the evaluation of this new method, we did not observe failures in the mitigation of anti-CD38 interference. Furthermore, the results obtained in the samples that presented allo or auto antibodies were not affected by the treatment with sCD38. In our experience Grifols sCD38 assay is straightforward and quick to perform ant it is superior to DTT treatment in the mitigation of anti-CD38 antibody interference in MM patients treated with Daratumumab.

A Study on a Method of Detecting Heavy Metal Content Using Thioglycolic Acid and Quartz Crucible

In the Chinese Pharmacopoeia, the method of detecting heavy metals commonly uses thioglycolic acid. It is often used as a special method for the limit check of heavy metals in raw pharmaceutical or cosmetic raw materials. Traditional use of porcelain crucibles in sample pretreatment may result in false positive reactions. This study used quartz crucibles to replace the traditional porcelain crucibles to study the possibility of contamination. It was found that the false negative reactions caused by crucible material can be eliminated, and the precision of the method was verified by detecting three batches of samples. The method has good repeatability and accuracy. It can replace the use of traditional porcelain crucibles in the method of detecting heavy metals with thioglycolic acid.

PreSorb is superior to Adsorb Out in reducing high background and false positive reactivity in HLA single antigen bead assay

PreSorb is superior to Adsorb Out in reducing high background and false positive reactivity in HLA single antigen bead assay

Introduction of the donor centre virtual crossmatch in Eurotransplant.

On 24 January 2023, Eurotransplant has introduced the virtual crossmatch for kidney and pancreas allocation as a better alternative for the physical Complement Dependent Cytotoxicity (CDC) crossmatches at the donor centre, which were associated with a longer cold ischaemia time and false positive reactions. For the time being, the physical CDC crossmatch at the recipient centre will remain in place as the final histocompatibility check. While Eurotransplant is certainly not the first organ allocation organisation to introduce virtual crossmatching, several novel aspects have been introduced, such as calculation of the virtual panel reactive antibody (vPRA) on 11 loci at the second-field level in addition to the serological broad and split level, electronic HLA typing data transmission using Histoimmunogenetics Markup Language (HML) file format, and the actual virtual crossmatch based on ambiguous, second-field HLA typing of the donor on all 11 loci. This short communication will focus on these novel aspects of the virtual crossmatch in Eurotransplant.

Identification of Salmonella Enterica Serovar Typhi DNA by loop-mediated isothermal amplification with fluorescent detection

Introduction. Real-time PCR may be used along with loop isothermal amplification method (LAMP) allowing to conduct the study in 30–40 minutes to diagnose typhoid fever. Several LAMP assay variations for detecting Salmonella enterica serovar Typhi have been described. The studies report that relevant primers were tested on strains specific for Malaysia and China. We attempted to evaluate the LAMP primers described above for identifying S. Typhi strains specific for the Russian Federation and compare their sensitivity and specificity with each other. Materials and methods. A comparative in silico analysis of target sequences was carried out both in the open NCBI database and among the genetic sequences of collection strains at the St. Petersburg Pasteur Institute. Several sets of primers for LAMP amplification of various S. Typhi genome regions were tested. The tested primers amplify the following fragments: SalTyp1 — region of the STY1607 gene, SalTyp2 — region of the STY2879 gene, SalTyp3 — region of the STBHUCCB_38510 gene of the PapD chaperone. Results. In silico analysis of LAMP primers showed that only the SalTyp 3 set has strict specificity for Salmonella enterica serovar Typhi. For the SalTyp 1 and SalTyp 2 an opportunity of false-positive reactions with some E. coli strains was shown. A LAMP method for DNA fluorescent detection of the typhoid fever causative agent was chosen. Assay has been based on a marker gene termed STBHUCCB_38510 and amplification with six specific primers. The detection limit was 20 copies/reaction in reference plasmids and the reaction time lasted for 35 minutes. The specificity of the method was tested on DNA specimens of 20 S. Typhi isolates and 90 strains of other heterologous bacteria from 24 different species. No false positive or false negative results were identified. Conclusion. The developed method can be used in clinical practice for laboratory confirmation of typhoid fever diagnosis as a part of epidemiological monitoring of environmental objects as well as food products.

Concept of a six-fold multiplex planar bioassay to distinguish endocrine agonist, antagonist, cytotoxic and false-positive responses

To analyze a complex sample for endocrine activity, different tests must be performed to clarify androgen/estrogen agonism, antagonism, cytotoxicity, anti-cytotoxicity, and corresponding false-positive reactions. This means a large amount of work. Therefore, a six-fold planar multiplex bioassay concept was developed to evaluate up to the mentioned six endpoints or mechanisms simultaneously in the same sample analysis. Separation of active constituents from interfering matrix via high-performance thin-layer chromatography and effect differentiation via four vertical stripes (of agonists and end-products of the respective enzyme–substrate reaction) applied along each separated sample track were key to success. First, duplex endocrine bioassay versions were established. For the androgen/anti-androgen bioassay applied via piezoelectric spraying, the mean limit of biological detection of bisphenol A was 14 ng/band and its mean half maximal inhibitory concentration IC50 was 116 ng/band. Applied to trace analysis of six migrate samples from food packaging materials, 19 compound zones with agonistic or antagonistic estrogen/androgen activities were detected, with up to seven active compound zones within one migrate. For the first time, the S9 metabolism of endocrine effective compounds was studied on the same surface and revealed partial deactivation. Coupled to high-resolution mass spectrometry, molecular formulas were tentatively assigned to compounds, known to be present in packaging materials or endocrine active or previously unknown. Finally, the detection of cytotoxicity/anti-cytotoxicity and false-positives was integrated into the duplex androgen/anti-androgen bioassay. The resulting six-fold multiplex planar bioassay was evaluated with positive control standards and successfully applied to one migrate sample. The streamlined stripe concept for multiplex planar bioassays made it possible to assign different mechanisms to individual active compounds in a complex sample. The concept is generic and can be transferred to other assays.

Seroconversion in syphilis screening without positive confirmatory tests points at early infection

IntroductionThe chemiluminescence immunoassay (CLIA) is a widely used screening test for syphilis. A CLIA seroconversion in the absence of a positive line immunoassay (LIA) or rapid plasma reagin (RPR) could...

Comparative analysis of tuberculin and defined antigen skin tests for detection of bovine tuberculosis in buffaloes (Bubalus bubalis) in Haryana state, India

BackgroundBovine tuberculosis (bTB) is a chronic disease that results from infection with any member of the Mycobacterium tuberculosis complex. Infected animals are typically diagnosed with tuberculin-based intradermal skin tests according to World Organization of Animal Health which are presently in use. However, tuberculin is not suitable for use in BCG-vaccinated animals due to a high rate of false-positive reactions. Peptide-based defined skin test (DST) antigens have been identified using antigens (ESAT-6, CFP-10 and Rv3615c) which are absent from BCG, but their performance in buffaloes remains unknown. To assess the comparative performance of DST with the tuberculin-based single intradermal test (SIT) and the single intradermal comparative cervical test (SICCT), we screened 543 female buffaloes from 49 organized dairy farms in two districts of Haryana state in India.ResultsWe found that 37 (7%), 4 (1%) and 18 (3%) buffaloes were reactors with the SIT, SICCT and DST tests, respectively. Of the 37 SIT reactors, four were positive with SICCT and 12 were positive with the DST. The results show that none of the animals tested positive with all three tests, and 6 DST positive animals were SIT negative. Together, a total of 43 animals were reactors with SIT, DST, or both, and the two assays showed moderate agreement (Cohen’s Kappa 0.41; 95% Confidence Interval (CI): 0.23, 0.59). In contrast, only slight agreement (Cohen’s Kappa 0.18; 95% CI: 0.02, 0.34) was observed between SIT and SICCT. Using a Bayesian latent class model, we estimated test specificities of 96.5% (95% CI, 92–99%), 99.7% (95% CI: 98–100%) and 99.0% (95% CI: 97–100%) for SIT, SICCT and DST, respectively, but considerably lower sensitivities of 58% (95% CI: 35–87%), 9% (95% CI: 3–21%), and 34% (95% CI: 18–55%) albeit with broad and overlapping credible intervals.ConclusionTaken together, our investigation suggests that DST has a test specificity comparable with SICCT, and sensitivity intermediate between SIT and SICCT for the identification of buffaloes suspected of tuberculosis. Our study highlights an urgent need for future well-powered trials with detailed necropsy, with immunological and microbiological profiling of reactor and non-reactor animals to better define the underlying factors for the large observed discrepancies in assay performance, particularly between SIT and SICCT.

False-positive results of galactomannan assays in patients administered glucose-containing solutions

Galactomannan (GM) is a polysaccharide cell wall component released by Aspergillus spp., and an immunoenzymatic GM assay is used for the diagnosis of invasive pulmonary aspergillosis. We evaluated the cause of strong positivity for GM in patients with no typical signs of aspergillosis. Repeat assays were performed using different instruments and reagent lots, but there were no differences in results among the assays. Patients with strongly positive GM results were investigated. Medication histories revealed that 14 of 23 patients had been administered total parenteral nutrition solution from one manufacturer and 4 patients had been administered dextrose solution from a different manufacturer before being tested. The results of GM assays conducted on samples of dextrose solution and the glucose fraction of the total parenteral nutrition solution were strongly positive, confirming the causes of the false-positive reactions. We hypothesize that a trace amount of GM was introduced into the glucose-containing solutions because glucoamylase, which is necessary for the saccharification step of glucose synthesis, was derived from Aspergillus niger. To enhance patient care and prevent unnecessary antifungal prescriptions, healthcare providers and manufacturers of healthcare products need to be aware of the possibility of false-positive reactions for GM.

Cytochemical and Histochemical Staining with Peptide Antibodies.

Peptide antibodies are particularly useful for immunocytochemistry (ICC) and immunohistochemistry (IHC), where antigens may denature due to fixation of tissues and cells. Peptide antibodies can be made to any defined sequence, including unknown putative proteins and posttranslationally modified sequences. Moreover, the availability of large amounts of the antigen (peptide) allows inhibition/absorption controls, which are important in ICC/IHC, due to the many possibilities for false-positive reactions caused by immunoglobulin Fc receptors, nonspecific reactions and cross-reactivity of primary and secondary antibodies with other antigens and endogenous immunoglobulins, respectively. Here, simple protocols for ICC and IHC are described together with recommendations for appropriate controls.

Complement-dependent cytotoxicity crossmatch in solid organ transplantation: The gold standard or golden history?

Complement-dependent cytotoxicity crossmatch (CDC-XM) has been considered for many years the standard of practice for determining compatibility in solid organ transplantation (SOT). However, as this method is laborious, time intensive and lacks sensitivity and specificity, it has been replaced in many laboratories worldwide by flow cytometry crossmatch (FCXM) and/or virtual crossmatch (vXM).With this study we intend to show the relevance of performing CDC-XM in the era of virtual crossmatching. We retrospectively analyzed 1,007 consecutive T and B cell deceased donor (DD) CDC-XMs performed in parallel using non-treated and dithiothreitol (DTT) treated sera between May 2022 and January 2023 in waitlisted patients with no donor specific antibodies (DSA) against HLA-A, B and/or DR antigens. Thirty five of 1,007 (3.5%) T cell crossmatches and 132 of 1,007 (13.1%) B cell crossmatches were positive with non-treated sera. Correlation with the vXM demonstrated no DSA in any of the positive T cell crossmatches. DSA were also absent in 126/132 positive B cell crossmatches, indicating a high rate of false positive CDC-XM. Indeed, only 4/35 T cell and 13/132 B cell CDC-XM remained positive after treatment with DTT, confirming that false positive reactivity with non-treated sera is high. Class I HLA DSA against C locus antigens were present in 17/1,007 T cell crossmatches and none were detected by CDC-XM (sensitivity = 0%). Similarly, only 6/77 B cell crossmatches with DSA targeting HLA-C, DQ and/or DP antigens were CDC-XM positive (sensitivity = 7.8%). Furthermore, only 4/6 positive B cell CDC-XM were confirmed to have complement binding potential using the C1q assay, suggesting additional false positive reactivity in 2/6 of the positive CDC-XM.Our study demonstrates that CDC-XM exhibits poor sensitivity, high false positive reactivity (especially without DTT treatment) and does not meaningfully contribute to pre-transplant compatibility testing in the context of vXM based allocation. Furthermore, the use of CDC-XM can unnecessarily delay or even prevent safe and appropriate transplant allocation.

Red cell antibodies or noise? A case series on reactivity against the ingredients in column matrix

Abstract Noise in the immunohematological investigations can be described as a false reactivity of red blood cells (RBCs) in serologic testing that is not related to the interaction of RBC antigens and antibodies that the test system is intended to detect. These false-positive reactions can cause confusion during the cross-matching and RBC antibody screening and may result in delays in patient transfusion. Although these antibodies are predominantly clinically insignificant, proper laboratory work-up is indicated to avoid misidentification of a clinically significant antibody as a noise. In this report, we describe the three rare cases where the reactivity was found against the ingredients of the column matrix (glass beads). It is imperative that such reactivity is recognized and resolved during the investigation of blood group discrepancies, positive RBC antibody screens and in cases of positive cross-matches.

Albuminuria Is Affected by Urinary Tract Infection: A Comparison between Biochemical Quantitative Method and Automatic Urine Chemistry Analyzer UC-3500.

The automated urine reagent strip test is a cost-effective tool for detecting albuminuria in patients. However, prior research has not investigated how urinary tract infections (UTIs) affect the test's accuracy. Therefore, this study aims to assess the impact of UTIs on albuminuria diagnosis using both the biochemical quantitative method and the test strip method of the Fully Automatic Urine Chemistry Analyzer, UC-3500 (Sysmex, Kobe, Japan). From March to December 2019, we prospectively collected midstream urine from adult female UTI patients before and after one week of cephalexin treatment. The urine samples were subjected to culture, routine urinalysis, and albuminuria diagnosis using the biochemical quantitative method and UC-3500. Albuminuria was defined as a urine albumin to creatinine ratio (UACR) ≥ 30 mg/g in the biochemical quantitative method. The results were compared between the two methods. Among fifty-four female patients (average age: 50.5 ± 4.4 years) with UTIs, 24 (44.44%) had transient albuminuria. The quantitative UACR significantly decreased after one week of antibiotic treatment (median: 53 mg/g to 9 mg/g; median difference: -0.54, p < 0.0001). UC-3500 exhibited a higher false positive rate for diagnosing albuminuria during UTIs (42%) compared to after treatment (19%). Its agreement with the biochemical quantitative method was moderate during UTI (κ = 0.49, 95% confidence interval [CI]: 0.24-0.73) and good after treatment (κ = 0.65, 95% CI: 0.45-0.86). UC-3500's accuracy in diagnosing albuminuria is influenced by UTIs, leading to either transient albuminuria or a false positive reaction of the test strip. UTI should be excluded or treated before its application in albuminuria screening.

A Silent Outbreak of Hepatitis E Virus (HEV) Infection or False-Positive Reaction of Anti-HEV IgM after COVID-19 Vaccination? Epidemiological Investigation of an Outbreak in a Korean Factory Complex in 2022.

To investigate a reported outbreak of presumed hepatitis E virus (HEV) infection in a Korean food manufacturing facility and to explore the association between anti-HEV immunoglobulin M (IgM) positivity and coronavirus disease 2019 (COVID-19) infection or vaccination. Twenty-four cases of anti-HEV IgM positivity were reported among 646 workers at the facility in 2022. An epidemiological investigation was conducted, comprising HEV-RNA testing of blood and environmental samples, analysis of group meal records, and an association between anti-HEV IgM positivity and confirmed COVID-19 infection or vaccination. All 24 patients were asymptomatic, with cases spread sporadically across the facility. HEV RNA was not detected in the serum or environmental samples. Four out of 340 meals (1.2%) showed a significantly higher proportion of anti-HEV positivity in each meal intake group than in the non-intake group on certain days. Although the cumulative rate of COVID-19 infection showed no difference, the anti-HEV IgM positive group showed significantly higher proportions of >2 doses of COVID-19 vaccination (83.3% vs 48.7%, p=0.021), vaccination within 90 days (45.8% vs 19.7%, p=0.008), and having the Moderna vaccine administered as the last vaccine (75.0% vs 14.5%, p<0.001) than those of the anti-HEV negative group. In four multivariable models, three or more COVID-19 vaccinations and the Moderna vaccine as the last vaccine were consistently associated with anti-HEV IgM positivity, while the specific day group meal intake was also a significant factor. This epidemiological investigation showed that anti-HEV IgM positivity may occur as a false-positive result related to COVID-vaccination over three times and use of the Moderna vaccine, although a portion of true HEV infection may not be excluded.

A-285 Performance Evaluation of LIAISON® QuantiFERON®-TB Gold Plus Assay and Its Use in Long-Term Care Facilities

Abstract Background Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis with 7860 cases reported in 2021 in the United State and estimated 13 million people are living with Latent TB infection (LTBI); Early detection of TB infection is crucial to prevent the spread of the disease; there are two types of tests for TB and LTBI: Tuberculin Skin Test (TST) and Interferon-Gamma Release Assay (IGRA). Although TST has good sensitivity but false-negative reactions occur in certain population and the specificity of is decreased among persons with prior Bacillus Calmette-Guérin (BCG) vaccination, especially those vaccinated post-infancy and those with repeat vaccination. Similarly, persons living in areas where nontuberculous mycobacteria are common are at increased risk of having false-positive TST reactions. IGRA is blood-based laboratory test that measures responses to TB-specific peptide antigens in whole blood. Like the tuberculin skin test (TST), it is an indirect test for M. tuberculosis infection, but is more specific than TST and is unaffected by prior BCG vaccination and most environmental mycobacterial infections. Methods The LIAISON® QuantiFERON®-TB Gold Plus assay is an in vitro diagnostic test for the detection of interferon-γ (IFN-γ) in human lithium heparin plasma by chemiluminescence immunoassay (CLIA) using the LIAISON ® XL Analyzer. The clinical specificity and sensitivity were 96.9% and 84.4% respectively. Clinical studies have shown Positive Percent Agreement (PPA) of 97.4% and Negative Percent Agreement (NPA) of 98.6%. We evaluated the precision, reproducibility, and correlated patient results to our reference lab results. 452 samples collected from Long-Term Care facilities resident were run over 9 months. Statistical analyses were done using Analyse-it. Results The percentage agreement for precision, reproducibility, and accuracy were 100%. The correlation with the reference laboratory was 100% agreement. We found 14.8% of samples tested were positive, 83.2% were negative and 2.0% were indeterminate. Conclusion The LIAISON® QuantiFERON®-TB Gold Plus assay offers the benefit of a fully automated with high sensitivity and specificity. The faster turnaround will aid the physician in the diagnosing M. tuberculosis, eliminates the need for two-step testing, and is preferred in patients who received BCG vaccination. In addition, with the growing geriatric population, the availability of this test will give the physician the opportunity to follow the 2016 American Thoracic Society (ATS)/Infectious Disease Society of America (IDSA)/CDC clinical practice guidelines for using IGRAs in older patients.

Identification of Xenobiotic Biotransformation Products Using Mass Spectrometry-Based Metabolomics Integrated with a Structural Elucidation Strategy by Assembling Fragment Signatures.

The identification of xenobiotic biotransformation products is crucial for delineating toxicity and carcinogenicity that might be caused by xenobiotic exposures and for establishing monitoring systems for public health. However, the lack of available reference standards and spectral data leads to the generation of multiple candidate structures during identification and reduces the confidence in identification. Here, a UHPLC-HRMS-based metabolomics strategy integrated with a metabolite structure elucidation approach, namely, FragAssembler, was proposed to reduce the number of false-positive structure candidates. biotransformation product candidates were filtered by mass defect filtering (MDF) and multiple-group comparison. FragAssembler assembled fragment signatures from the MS/MS spectra and generated the modified moieties corresponding to the identified biotransformation products. The feasibility of this approach was demonstrated by the three biotransformation products of di(2-ethylhexyl)phthalate (DEHP). Comprehensive identification was carried out, and 24 and 13 biotransformation products of two xenobiotics, DEHP and 4'-Methoxy-α-pyrrolidinopentiophenone (4-MeO-α-PVP), were annotated, respectively. The number of 4-MeO-α-PVP biotransformation product candidates in the FragAssembler calculation results was approximately 2.1 times lower than that generated by BioTransformer 3.0. Our study indicates that the proposed approach has great potential for efficiently and reliably identifying xenobiotic biotransformation products, which is attributed to the fact that FragAssembler eliminates false-positive reactions and chemical structures and distinguishes modified moieties on isomeric biotransformation products. The FragAssembler software and associated tutorial are freely available at https://cosbi.ee.ncku.edu.tw/FragAssembler/ and the source code can be found at https://github.com/YuanChihChen/FragAssembler.

Proteomics and bioinformatics investigations to improve serological diagnosis of canine brucellosis.

Brucella canis is pathogenic for dogs and humans. Serological diagnosis is a cost-effective approach for disease surveillance, but a major drawback of current serological tests is the cross-reactivity with other bacteria that results in false positive reactions. Development of indirect tests with improved sensitivity and specificity that use selected B. canis proteins instead of the whole antigen remain a priority. A western blotting assay was developed to define the serum antibody patterns associated to infection using a panel of positive and negative dog sera. B. canis positive sera recognized immunogenic bands ranging from 7 to 30kDa that were then submitted to ESI-LC-MS/MS and analyzed by bioinformatics tools. A total of 398 B. canis proteins were identified. Bioinformatics tools identified 16 non cytoplasmic immunogenic proteins predicted as non-homologous with the most important Brucella cross-reactive bacteria and nine B. canis proteins non-homologous to B. ovis; among the latter, one resulted non-homologous to B. melitensis. Data are available via ProteomeXchange with identifier PXD042682. The western blotting test developed was able to distinguish between infected and non-infected animals and may serve as a confirmatory test for the serological diagnosis of B. canis. The mass spectrometry and in silico results lead to the identification of specific candidate antigens that pave the way for the development of more accurate indirect diagnostic tests.

A novel method for blood detection using fluorescent dye

Detection of the body fluid present at a crime scene is essential for any forensic investigation. Amongst all the body fluids (sweat, semen, vaginal fluid, saliva, etc.,) blood is the most frequently encountered evidence at the crime scene. Currently, reagents like benzidine, ortho-toluidine, tetramethylbenzidine, phenolphthalein, leucomalachite green, luminol, and fluorescein are used to screen the presence of blood on different surfaces (porous/nonporous). Most of these tests are based on colorimetric changes owing to the nature of hemoglobin to catalyze the oxidation of chromogenic compounds. Apart from aiding the investigation, these reagents show toxic behavior (DNA damage, carcinogenic, etc.) and false-positive results. Hence, to circumvent this issue, the present study attempts to develop a state-of-art methodology for preliminary blood detection and screening using fluorescein-derived 2′,7′-dichlorofluorescein di-acetate (DCFDA) dye. It is hereby proposed that the fluorescein-based dye can successfully detect blood and bloodstains aged up to 20 days. Moreover, supplemental experiments have suggested that the dye doesn't interfere with DNA integrity- causing any damage to DNA. Parallelly, no false-positive reactions have been observed as tested against similar-looking substances.

Patch testing hydroperoxides of limonene and linalool in consecutive patients-Results of the IVDK 2018-2020.

Hydroperoxides of limonene (Lim-OOHs) and linalool (Lin-OOHs) are potent contact sensitizers. To investigate the prevalence of positive patch test (PT) reactions to Lim-OOHs and Lin-OOHs in consecutive patients, their demographic factors and concomitant reactions. Between 7/2018 and 12/2020, Lim-OOHs 0.3% pet. and Lin-OOHs 1% pet. were patch tested in 5511 consecutive patients. We assessed PT reactivity and analysed data from patients with either positive or negative PTs to Lim-OOHs and Lin-OOHs. Positive PT results to Lim-OOHs (n = 170, 3.1%) and Lin-OOHs (n = 483, 8.8%) were frequent. Most of the positive reactions were weak (LimOOHs n = 134/LinOOHs n = 429), and even more frequently, doubtful (n = 252/n = 578) or irritant reactions (n = 81/n = 178) were documented. PT reactivity to Lim-OOHs and Lin-OOHs was increased in patients with irritant reactions to sodium lauryl sulphate (SLS). The proportion of leg dermatitis and concomitant positive reactions to fragrances and essential oils was increased in patients with reactivity to these hydroperoxides. The observed reaction pattern suggests that both test preparations display an irritant potential with an increased risk of false positive reactions. Preparations should be chemically monitored in order to reduce irritancy. Mindful interpretation of PT results and aimed patch testing of lower concentrations is recommended.

The relevance of false positive acid phosphatase reactions indicative of the presence of seminal fluid from oral and vaginal samples

The Body Fluid Forum of the Association of Forensic Science Providers recognised concerns raised by forensic practitioners regarding the lack of data to inform on the incidence of significant AP (Acid Phosphatase) reactions from vaginal and oral samples, i.e. those which might be misinterpreted as indicating the presence of semen. This is particularly relevant in the light of appeal court rulings regarding the need for data to support evaluations. This paper presents collaborative data on the nature and incidence of AP reactions from vaginal and oral swabs provided by donors. The results demonstrate that caution is required with mid to strong purple AP reactions from direct testing of oral swabs and with mid purple reactions from vaginal swabs. The use of a Bayesian approach to assist with the provision of opinions regarding the presence of seminal fluid is highlighted.