Number Of False-negative Results Research Articles

Interlaboratory validation and one-year retrospective review of hemp and marijuana decision-point assays

After the passage of the Agriculture Improvement Act of 2018 (Farm Bill) that defined hemp as Cannabis sativa L. if it contained ≤0.3 % Δ9-THC on a dry weight basis, forensic laboratories were faced with the challenge of distinguishing marijuana from hemp in seized drug samples. This study reports the results of an interlaboratory validation of a previously developed qualitative decision-point assay for the differentiation of illegal marijuana from legal hemp, utilizing gas chromatography-mass spectrometry (GC–MS) with a 1 % Δ9-THC threshold. The method was validated in terms of selectivity, linearity, carryover, precision, accuracy, extract stability, dilution integrity, and measurement uncertainty. Other elements such as decarboxylation rate and potential for CBD interference were also evaluated. Specificity and positive predictive value were both 100 % using known cannabis reference materials. A total of 8 false negative results were observed among the 280 analyses, resulting in an overall assay sensitivity of 94 % and a negative predictive value of 95 %. The small number of false negative results near the 1 % threshold were attributed to decarboxylation inefficiency in some laboratories. While qualitative in nature, the measurement uncertainty of the assay at the 0.3 % Δ9-THC cutoff (legal threshold) using a 95.45 % confidence interval (k = 2) ranged from 12.2 % to 21.8 % among laboratories (equivalent to 0.3 % ± 0.04 % to 0.07 % Δ9-THC by weight). A one-year retrospective study across three agencies and fifteen laboratories was undertaken. Among the three agencies participating in the original study, 93–96 % of all suspected cannabis seizures yielded results above the administrative threshold of 1 % Δ9-THC (n = 3,288). The interlaboratory method development highlighted differences in performance between sites, ultimately improving the overall robustness of the method. Observations highlight the need for site-specific validation and vigilance. While multi-agency collaborations and interlaboratory validations are valuable, they do not replace the necessity for full, independent, and rigorous validation.

Evaluation of CLINITEST® Rapid Covid-19 + Influenza antigen test in a cohort of symptomatic patients in an emergency department.

Rapid management of patients with respiratory tract infections in hospital emergency departments is one of the main objectives since the concurrent circulation of respiratory viruses following the SARS-CoV-2 pandemic. The use of new combined point-of-care antigen tests for detecting influenza A/B and SARS-CoV-2 represents an advantage in response time over the molecular tests. The objective was to evaluate the suitability of the CLINITEST® Rapid Covid-19 + Influenza Antigen test (Siemens Healthineers, Germany) (RCIA test) by measuring the sensitivity, specificity, Cohen's kappa, and cut-off values. Nasopharyngeal samples were collected from a randomised group of symptomatic patients of all ages at emergency department during January-February 2023. In parallel, these patients were screened for influenza A/B, and SARS-CoV-2 using RT-PCR. The Ct (cycle threshold) values were collected for positive [RT-PCR (+) /RCIA test (+)] and false negative [(RT-PCR (+) /RCIA test (-)] samples. A subanalysis was performed in the paediatric population (< 16 years-old). We included 545 patients (55.8% females) with a median age of 7 years-old (IQR: 1-66.5). The RCIA test showed a sensitivity of 59.7% [95%CI: 46.9-67.33] for influenza A, 65.6% [95%CI: 49.5-80.3] for influenza B, and 76.9% [95%CI: 45.8-84.8] for SARS-CoV-2. The specificity was between 90.7%-99.7% with a moderate/high level of agreement with RT-PCR (kappa score: 0.6-0.8) for the three respiratory viruses included in the RCIA test. The sensitivity of the RCIA test is insufficient for screening of patients, including patients with low Ct values (Ct > 20). Despite its good specificity and Cohen's kappa value, its use as a screening test is not comparable to RT-PCR systems in the ED environment with a high number of false negative results.

Modified ESR-based photosafety test (ESR-PT) detecting singlet oxygen and free radical formation.

The electron spin resonance-based photosafety test (ESR-PT) was modified using a new parameter, photoreactivity index (PRI), to detect singlet oxygen and free radical photoproducts simultaneously. With this modification, the modified ESR-PT is expected to reduce the number of false negative results due to chemicals producing free radical photoproducts other than singlet oxygen. The assay performance of the modified ESR-PT was evaluated using 56 chemicals, including hydrophobic chemicals. When using the PRI cutoff value of 2.0 in the modified ESR-PT, the accuracy relative to photosafety reference data was 91.1%, and the applicability (100%) was better than the other non-animal photosafety test. Among the chemicals producing positive results, bithionol, fenticlor, and doxycycline HCl were considered positive based on the detection of free radical photoproducts, suggesting that these three chemicals may have phototoxic or photoallergic potential via radical reactions. Additionally, this finding demonstrated the fundamental advantage of the modified ESR-PT using ESR spectroscopy, which can detect radicals selectively and quantitatively. Accordingly, the new parameter PRI is effective for photosafety evaluations based on not only singlet oxygen but also free radical photoproducts generated from chemicals. Therefore, the modified ESR-PT has a great potential for a photosafety test method applicable to various chemicals.

A-297 Usefulness of Non-Skin Samples in the PCR Diagnosis of Monkeypox

Abstract Background During 2022, human mpox cases were reported in several European countries. Until November 2022, in Spain, 7404 cases were detected, most of them linked to sexual intercourse. In that context, fast identification of cases and sources of infection were essential for an optimal management. Polymerase chain reaction (PCR) was the preferred laboratory test. Our objective was to evaluate the usefulness of sera and nasopharyngeal samples for MPXV detection, and its application in contact studies without skin or mucosal injuries. Methods In the Hospital Clínico Universitario of Zaragoza (Spain), 106 samples from 50 patients, 38 male and 12 female, aged between 11 to 62 years, with skin lesions suspected MPXV infection were analysed. Samples were collected between May and September 2022 in inactivating universal viral transport medium (Biocomma). Samples were obtained between 1 and 19 days of evolution. To perform the real-time PCR, the VIASURE Monkeypox Virus Real Time PCR Detection Kit and the VIASURE 48—Real Time PCR System were used. Nucleic acid extraction was performed with the automated nucleic acid extraction system MagLEAD12gC using the MagDEA®Dx SV reagents. Results Table 1 shows the results expressed in Ct values. Skin, anogenital and serum samples were the most efficient for MPXV diagnosis. Nevertheless, these data are influenced by the sample collection date. Conclusion Real-time PCR was positive in samples from all locations in 71,4% of the infected patients. Respiratory samples (pharyngeal and nasopharyngeal) were the ones that showed the highest number of false negative results, whereas there was only one skin sample and one serum sample with a negative result. This study shows that sera samples can be used in the diagnosis of MPXV infection because of ease of collection, applicability to contacts without lesions and the option of serology testing for other STI agents (HBV, HCV, HIV, Treponema pallidum…).

Development and validation of a video-assisted liver biopsy technique using a minimally-invasive device

BackgroundPercutaneous liver biopsy is the gold standard technique for establishing the cause of cirrhosis and liver disease activity assessment. However, some cases of steatohepatitis or other chronic liver diseases show a high number of false negative results in samples obtained via the percutaneous route. This fact justifies performing a liver biopsy via the laparoscopic route. However, this is an expensive technique, with morbidities associated with pneumoperitoneum and anesthetic complications. The main objective of this study is to develop a video-assisted technique that uses only a minimally-invasive device for the liver biopsy and the optical trocar. Without additional trocars, this technique constitutes a less invasive procedure than the existing techniques in clinical practice.MethodsThis is a device development and validation study and patients submitted to abdominal laparoscopic surgery and required liver biopsy for moderate to severe steatosis were recruited. The patients were randomized into two groups: laparoscopic liver biopsy technique (n = 10, control group) and mini-laparoscopic liver biopsy technique (n = 8, experimental group). The times associated with procedure performance in both groups were evaluated using the Mann–Whitney or Kruskal–Wallis tests according to data distribution.ResultsAt baseline, there was no statistical difference regarding gender and type of surgery. The experimental group had a significantly shorter time compared with the group that underwent the traditional procedure in mean procedure time (p = 0.003), biopsy time (p = 0.002) and hemostasis time (p = 0.003).ConclusionsThe mini-laparoscopic biopsy device and technique showed to be capable of safely obtaining sufficient tissue samples, which was minimally invasive and in a shorter time than the classic technique.

Fluctuations of antibody serum titers for Toxoplasma gondii and Neospora caninum in naturally infected crossbred cows during gestation.

This study aimed to assess the fluctuations of antibody serum titers for Toxoplasma gondii and Neospora caninum in naturally infected crossbred cows during gestation and to investigate transplacental transmission of T. gondii; 51 cows were monitored during pregnancy by monthly serologic testing by indirect fluorescent antibody test. 33 cows were seronegative for both N. caninum and T. gondii, 10 were seropositive only for N. caninum, 5 were seropositive only for T. gondii, and 3 were seropositive for both N. caninum and T. gondii. In both protozoan infections, great variation in antibody levels in pregnant cows was observed, and there was significant increase (p<0.05) in the comparison between the averages of serological titration per trimester. There was a significant correlation (p<0.05) between month and probability of seropositivity for T. gondii. We conclude that pregnancy influences antibody titers of crossbred cows naturally infected with N. caninum and/or T. gondii, and that serologic testing for T. gondii in pregnant cows from the sixth month of gestation onward may decrease the number of false negative results.

Importance of Cytological Screening in the Diagnosis of Cervical Diseases

The purpose of the study was to compare the conventional Pap smear with liquid-based cytology in the early diagnosis of cervical diseases. Materials and methods. The study included 150 women between the ages of 18 and 73 with cervical diseases. The comparison was held on the basis of the results of histology of liquid-based and conventional Pap smears taken from cervix. Bethesda classification was used to make the diagnosis. Diagnostic performance was calculated in terms of sensitivity, specificity, positive predictive value and negative predictive value. Results and discussion. During the sensitivity, specificity and prognostic assessment of liquid-based cytology with conventional Pap smears, the sensitivity of liquid-based cytology was higher than the conventional Pap test – 93.1%, and the conventional Pap test was 81.3%. The specificity of liquid-based cytology can be compared with a conventional Pap test (76.2% and 70.6%, respectively). The positive prognostic value was 84.4% in liquid-based cytology and 88.6% in the conventional Pap test. Negative prognostic value was significantly higher in liquid-based cytology than in conventional Pap tests (88.9% and 57.1%, respectively). The total diagnostic value was 86.0% in liquid-based cytology and 78.5% in the conventional Pap test. As a result of the study it has become clear that liquid-based cytology is an appropriate method for the diagnosis of cervical diseases. There are screening programs for cervical, breast, colorectal and prostate cancer in the country, but due to some psycho-social factors, restrictions and barriers, patients only seek medical attention when there is an urgent need. As a result, more than half of all cancers are diagnosed at a late stage. Thus, the study concluded that liquid-based cytology is more convenient than conventional smear screening for cervical cancer screening. As single-layer smears are easier to examine, cells with atypia are not covered by other cells (inflammation, blood, etc.). In addition, the amount of unsatisfactory smears is minimal. In general, many studies have been conducted comparing liquid-based cytology with conventional Pap smears. The results were different in both the initial studies and the meta-analysis. Conclusion. Thus, both screening methods predict the likelihood of disease in the same way, but with liquid-based cytology, the number of false-negative results is less, and the sample quality is improved by reducing the number of unsatisfactory smears. Also, women with liquid-based cytology are more likely to get a positive result than those with cervical disease. Liquid-based cytology is superior and more sensitive than conventional Pap tests in the detection of cervical neoplasms

Biomechanical modelling of the pelvic system: improving the accuracy of the location of neoplasms in MRI-TRUS fusion prostate biopsy

BackgroundAn accurate knowledge of the relocation of prostate neoplasms during biopsy is of great importance to reduce the number of false negative results. Prostate neoplasms are visible in magnetic resonance images (MRI) but it is difficult for the practitioner to locate them at the time of performing a transrectal ultrasound (TRUS) guided biopsy. In this study, we present a new methodology, based on simulation, that predicts both prostate deformation and lesion migration during the biopsy.MethodsA three-dimensional (3-D) anatomy model of the pelvic region, based on medical images, is constructed. A finite element (FE) numerical simulation of the organs motion and deformation as a result of the pressure exerted by the TRUS probe is carried out using the Code-Aster open-source computer software. Initial positions of potential prostate lesions prior to biopsy are taken into consideration and the final location of each lesion is targeted in the FE simulation output.ResultsOur 3-D FE simulations show that the effect of the pressure exerted by the TRUS probe is twofold as the prostate experiences both a motion and a deformation of its original shape. We targeted the relocation of five small prostate lesions when the TRUS probe exerts a force of 30 N on the rectum inner wall. The distance travelled by these lesions ranged between 5.6 and 13.9 mm.ConclusionsOur new methodology can help to predict the location of neoplasms during a prostate biopsy but further studies are needed to validate our results. Moreover, the new methodology is completely developed on open-source software, which means that its implementation would be affordable to all healthcare providers.

Associating Automated Breast Ultrasound (ABUS) and Digital Breast Tomosynthesis (DBT) with Full-Field Digital Mammography (FFDM) in Clinical Practice in Cases of Women with Dense Breast Tissue.

The purpose of the present study was to evaluate the value of full-field digital mammography (FFDM) and automated breast ultrasound (ABUS) in the diagnosis of breast cancer compared to FFDM associated with digital breast tomosynthesis (DBT). Methods: This retrospective study included 50 female patients with a denser framework of connective tissue fibers, characteristic of young women who underwent FFDM, DBT, handheld ultrasound (HHUS), and ABUS between January 2017 and October 2018. The sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV), and accuracy of FFDM+ABUS were 81.82% (95% CI [48.22–97.72]), 89.74% (95% CI [75.78–97.13]), 69.23% (95% CI [46.05–85.57]), 94.59% (95% CI [83.26–98.40]), and 88% (95% CI [75.69–95.47]), while for FFDM+DBT, the values were as follows: 91.67% (95% CI [61.52–99.79]), 71.79% (95% CI [55.13–85.00]), 50% (95% CI [37.08–62.92]), 96.55% (95% CI [80.93–99.46]), 76.47% (95% CI [62.51–87.21]). We found an almost perfect agreement between the two readers regarding FFDM associated with ABUS, and substantial agreement regarding FFDM+DBT, with a kappa coefficient of 0.896 and 0.8, respectively; p < 0.001. Conclusions: ABUS and DBT are suitable as additional diagnostic imaging techniques to FFDM in women at an intermediate risk of developing breast cancer through the presence of dense breast tissue. In this study, DBT reduced the number of false negative results, while the use of ABUS resulted in an increase in specificity.

Direct Detection of Feline Coronavirus by Three Rapid Antigen Immunochromatographic Tests and by Real-Time PCR in Cat Shelters.

The aim of this study was the direct detection of feline coronavirus by real-time PCR and by three different rapid immunochromatographic (RIM) tests detecting antigens in faecal samples of shelter cats. Based on sensitivity and specificity calculated for each of the RIM tests, the utility of RIM tests was compared. Seventy faecal samples originating from shelter cats housed in quarantine were examined. Out of 70 samples analyzed by real-time PCR, 44 (62.9%) were positive. Significantly more cats (p < 0.05) tested positive than negative. Neither age nor sex of the cats played a significant role (p > 0.05) in the shedding status of the virus. The sensitivity of the RIM tests was found to be at low (<35%; RIM tests A and C) to satisfactory level (>50%, RIM test B). The number of virus particles determined by real-time RT-PCR analysis did not significantly correlate with the results detected by any of the RIM tests (p > 0.05). The results of this study indicate that the use of rapid antigen RIM tests in routine screening of FCoV shedding status in shelter cats is limited due to the occurrence of a high number of false negative results.

Visualization of Lesions of Metaphyses and Epiphyses of Bones in Newborns and Young Children

The aim of this study was to determine the diagnostic capabilities of various methods of radiological diagnostics for lesions of the metaphyses and epiphyses of bones in newborns and young children.The study involved 108 children in the age group 5 days – 12 months with pathological changes in the pineal gland and bone metaphysis. The possibilities and advantages of standard radiography (СR), ultrasound examination (US) and magnetic resonance imaging (MRI) in the early and differential diagnosis of the osteomyelitis process and epiphyseolysis have been determined. High sensitivity (98 %), specificity (99 %) and accuracy (98 %) for ultrasound and sensitivity (94 %), specificity (89 %) and accuracy (95 %) of MRI in diagnosing osteomyelitis in patients of this age groups. At the same time, the possibilities of standard radiography at the stages of early diagnosis of inflammatory processes in the distal parts of the bones were limited due to a number of factors. The use of diagnostic algorithms greatly facilitates the work of a radiologist and reduces the number of false negative results during the initial treatment of patients.

COVID19-related and all-cause mortality risk among middle-aged and older adults across the first epidemic wave of SARS-COV-2 infection: a population-based cohort study in Southern Catalonia, Spain, March\u2013June 2020

BackgroundDirect and indirect COVID19-related mortality is uncertain. This study investigated all-cause and COVID19-related deaths among middle-aged and older adults during the first wave of COVID-19 pandemic period, assessing mortality risks by pre-existing socio-demographic and medical underlying conditions.MethodsPopulation-based cohort study involving 79,083 individuals ≥50 years-old in Tarragona (Southern Catalonia, Spain). Baseline cohort characteristics (age/sex, comorbidities and medications/vaccinations history) were established at study start (01/03/2020) and main outcomes were COVID19-related deaths (those occurred among patients with laboratory-confirmed COVID19) and all-cause deaths occurred among cohort members between 01/03/2020–30/06/2020. Mortality risks were assessed by Cox regression analyses.ResultsCohort members were followed for 1,356,358 persons-weeks, occurring 576 all-cause deaths (124 COVID19-related deaths). Of the 124 deceased patients with a laboratory-confirmed COVID19, 112 (90.3%) died by (due to) COVID-19, while 12 (9.7%) died with COVID-19 (but likely due to other concomitant causes). All-cause mortality rate among cohort members across study period was 42.5 deaths per 100,000 persons-week, being 22.8 among healthy/unrelated-COVID19 subjects, 236.4 in COVID19-excluded/PCR-negative subjects, 493.7 in COVID19-compatible/PCR-unperformed subjects and 4009.1 in COVID19-confirmed patients. Increasing age, sex male, nursing-home residence, cancer, neurologic, cardiac or liver disease, receiving diuretics, systemic corticosteroids, proton-pump inhibitors and benzodiazepines were associated with increased risk of all-cause mortality; conversely, receiving renin-angiotensin inhibitors and statins were associated with reduced risk. Age/years (hazard ratio [HR]: 1.08; 95% confidence interval [CI]: 1.06–1.10), sex male (HR: 1.82; 95% CI: 1.24–2.70), nursing-home residence (HR: 12.56; 95% CI: 8.07–19.54) and number of pre-existing comorbidities (HR: 1.14; 95% CI: 1.01–1.29) were significant predictors for COVID19-related mortality, but none specific comorbidity emerged significantly associated with an increased risk in multivariable analysis evaluating it.ConclusionCOVID19-related deaths represented more than 20 % of all-cause mortality occurred among middle-aged and older adults during the first wave of the pandemic in the region. A considerable proportion (around 10 %) of these COVID19-related deaths could be attributed to other concomitant causes. Theoretically COVID19-excluded subjects (PCR-negative) suffered ten-times greater all-cause mortality than healthy/unrelated-COVID19 subjects, which points to the existence of considerable number of false negative results in earlier PCR testing and could explain part of the global excess all-cause mortality observed during the pandemic.

The T2-FLAIR Mismatch Sign as an Imaging Indicator of IDH-Mutant, 1p/19q Non-Codeleted Lower Grade Gliomas: A Systematic Review and Diagnostic Accuracy Meta-Analysis.

The study’s objective was the evaluation of the diagnostic accuracy of the T2-FLAIR mismatch sign in terms of diagnosing IDH-mutant non-codeleted (IDHmut-Noncodel) lower grade gliomas (LGG) of the brain. We searched the MEDLINE, Scopus and Cochrane Central databases. The last database search was performed on 12 April 2021. Studies that met the following were included: MRI scan assessing the presence of T2-FLAIR mismatch sign, and available IDH mutation and 1p/19q codeletion status. The quality of studies was assessed using the QUADAS-2 tool. Twelve studies involving 14 cohorts were included in the quantitative analysis. The diagnostic odds ratio [DOR (95% confidence interval; CI)] was estimated at 34.42 (20.95, 56.56), Pz < 0.01. Pooled sensitivity and specificity (95% CI) were estimated at 40% (31–50%; Pz = 0.05) and 97% (93–99%; Pz < 0.01), respectively. The likelihood ratio (LR; 95% CI) for a positive test was 11.39 (6.10, 21.29; Pz < 0.01) and the LR (95% CI) for a negative test was 0.40 (0.24, 0.65; Pz < 0.01).The T2-FLAIR mismatch sign is a highly specific biomarker for the diagnosis of IDHmut-Noncodel LGGs. However, the test was found positive in some other tumors and had a high number of false negative results. The diagnostic accuracy of the mismatch sign might be improved when combined with further imaging parameters.

Computed tomography-guided pararectal prostate fusion biopsy

Background . Prostate cancer (PCa) is one of the most common malignancies. The gold standard of PCa diagnostics is morphological examination of prostate tissues obtained using 10-12-core biopsy. However, the number of false-negative results and detected clinically insignificant forms of cancer remain high. Magnetic resonance imaging (MRI) is the most sensitive and specific method of radiation diagnosis of PCa. The use of MRI data for prostate biopsy (fusion-biopsy) increases the accuracy of this procedure. Objective : to increase the accuracy of PCa diagnostics using targeted pararectal prostate biopsy guided by computed tomography (CT)/MRI. Materials and methods . A total of 95 patients underwent CT/MRI-guided targeted pararectal biopsy between March 2015 and March 2020. The mean level of prostate specific antigen (PSA) was 13.7 ± 12.6 ng/mL. All men were found to have 1 to 3 lesions with a PI-RADS score between 3 and 5. Patients were divided into 4 groups: 1 st group (n = 33) included patients in whom transrectal access was impossible; 2 nd group (n = 22) included patients with suspected local recurrence of PCa after brachytherapy; 3 rd group (n = 28) included patients with a negative result of primary biopsy, but with growing PSA level; 4th group (n = 12) included patients who preferred targeted biopsy. We performed targeted biopsy of each suspicious lesion according to MRIscans. Then we performed ‘blind’ systematic 10-14-core biopsy, where we did not take into account the location of suspicious foci and they could be, therefore, accidentally used for sample collection for the second time. Results . Histological examination revealed PCa in 71 out of 95 patients (74.7 %): in 27 out of 33 in 1 st group (81.8 %), in 19 out of 22 in 2 nd group (86.4 %), in 17 out of 28 in 3 rd group (60.7 %), and in 8 out of 12 in 4 th group (66.7 %). In 21 patients (29.6 %), PCa was diagnosed only in samples obtained using targeted biopsy; in 9 patients (12.7 %), PCa was diagnosed only in samples after systematic biopsy; in 41 patients (57.7 % PCa was detected by both targeted and systematic biopsy. Clinically significant cancer (Gleason score ≥7) was diagnosed in 84.5 % of cases after targeted biopsy and in 70.4 % of cases after systemic biopsy. Conclusion . CT/MRI-guided prostate fusion biopsy increases the accuracy of PCa diagnostics by additional detection of clinically significant tumors, including those in patients in whom the rectal access is impossible.

Sentinel Lymph Node Biopsy after Neoadjuvant Treatment for Breast Cancer. The Validation Protocol.

Introduction: The identification and biopsy of the sentinel lymph node (SLNB) in breast cancer patients requiring neoadjuvant cytostatic treatment (NAC), with clinically negative lymph nodes following treatment, may be an effective method of de-escalation of axillary surgery. Materials and methods: This prospective study includes 47 cases of breast cancer stage IIB-IIIA, with NAC treatment and complete axillary clinical and imaging response, surgeries performed at Prof. Dr. Alexandru Trestioreanu Oncological Institute in Bucharest (IOB) by the same team. In all the cases, SLNB was employed using the radioactive tracer method. The SLNB technique with Tc99 radioactive tracer involves: - injection of the radioactive tracer and preoperative lymphoscintigraphy, - intraoperative identification of the sentinel node/ lymph nodes and their excisional biopsy, - intraoperative histopathological examination, in paraffin blocks, and immunohistochemistry of the lymph node (SLN). Results: SLN was identified in 46 of 47 cases. In 19 cases SLN was positive, and in 2 cases we recorded false negative results. All patients underwent standard axillary lymphadenectomy (back-up lymphadenectomy). The correlation between the intraoperative and paraffin histopathological examination of SLN with the paraffin and immunohistochemical examination of the rest of the axillary nodes (N-SLN) led to the following results: sensitivity 91% (19/ 21), specificity 100% (25/ 25), positive predictive value 100% (19/ 19), negative predictive value 93% (25/ 27). The accuracy of the method was 96% (44/ 46). SLN invasion was more common in patients with residual tumor 2 cm (vs T 2 cm) (p = 0.01), positive N-SLN (vs non-invaded N-SLN) (p = 0.003). N-SLNs were more frequently invaded when there was peritumoral lymphocyte invasion (vs. no invasion) (p = 0.01). Conclusions: SLNB in patients with breast cancer who require NAC, with clinically and imaging negative lymph nodes following treatment, has a high rate of specificity and an acceptable number of false negative results. Node invasion is more common in patients with residual tumors 2 cm, with lymphovascular invasion or with multicenter/ multifocal disease.

Detection of SARS-CoV-2 RNA in nasopharyngeal swabs from COVID-19 patients and asymptomatic cases of infection by real-time and digital PCR.

In this work we tested two reagent kits developed by us for detecting SARS-CoV-2 RNA using a fragment of the ORF1ab gene in digital PCR and real-time PCR formats. Data were obtained on the detection of SARS-CoV-2 virus RNA in nasopharyngeal swabs of patients with COVID-19 and asymptomatic carriers. The developed reagent kits provided 100% sensitivity and a detection limit of 103 GE / ml for qPCR, and at least 200 copies / ml of viral RNA when performing digital PCR. These methods were tested using a panel of 1,328 samples collected from patients with suspected COVID-19 at the beginning of 2020 in the Russian Federation. It has been shown that dPCR is more sensitive and can be used to analyze samples with low viral load, including those from patients without clinical symptoms. dPCR significantly improves the accuracy of laboratory research and significantly reduces the number of false negative results in the diagnosis of SARS-CoV-2. Determination of the concentration of SARS-CoV-2 RNA in patients with different clinical course of the disease showed that the concentration of viral RNA can sharply decrease in the first days of the disease. A low concentration of viral RNA in samples from patients is also characteristic of asymptomatic disease. Digital PCR provides a higher detection rate for asymptomatic cases, which is approximately 75% of those infected, as opposed to 45% for real-time PCR. The results obtained on the use of the digital PCR method for detecting SARS-CoV-2 RNA showed that this method is especially suitable for detecting RNA in case of its low concentration in contacts, as well as for monitoring changes in viral load in convalescent patients.

The role of EBUS-TBNA in lung cancer restaging and mutation analysis

In recent years, several molecules targeting specific genetic aberrations were released for the treatment of patients affected by locally advanced and metastatic non-small cell lung cancer (NSCLC), leading to an improvement in survival. Moreover, inhibitors of PD-1 and PD-L1 immune checkpoints showed to improve survival, and they are now indicated as first-line treatment in selected patients. Hence, the collection of adequate samples for diagnosis, staging, genotyping and immunohistochemical analysis is a fundamental step in NSCLC treatment planning. When feasible, EBUS-TBNA is suggested as the first-choice diagnostic tool by most of the guidelines. Several studies demonstrated that mutation analysis is viable with high levels of accuracy on both cytological and histological samples obtained by EBUS-TBNA. No technical factor (type of needle, number of passes, use of rapid-on-site-examination, material processing, detection method) has been identified as uniquely influencing the diagnostic yield of molecular analysis. EBUS-TBNA demonstrated to be useful for the restaging of patients affected by locally advanced NSCLC who underwent induction chemotherapy or chemo-radiotherapy, as well as in those who show acquired resistance to targeted therapy and immunotherapy. Nevertheless, most authors agree that a high number of false negative results should be expected due to the likely presence of necrosis and fibrosis induced by neoadjuvant treatments. Therefore, in case of EBUS-TBNA negative sample, pathologic confirmation by surgical biopsy is recommended for the planning of definitive treatment. As suggested by a few preliminary experiences, a wide application of next-generation sequencing (NGS) on EBUS-TBNA specimens will lead to the development of better tailored treatments with simultaneous identification of a large number of gene alterations on a single sample at the time of diagnosis.

Dependence of quality on the completed standard x-ray dental installations on the diagnostic process

The article is devoted to determining the dependence of the quality of performance by an x-ray laboratory technician and, especially, by the dental assistant, of standard x-ray dental laying on the process of examining teeth and jaws. A retrospective analysis of 900 intraoral radiographs, orthopantomograms, enlarged panoramic radiographs in direct projection (analog and digital, performed in various medical facilities) of patients in the age group of 18-85 years was performed. The most signfTcant methodological errors of the paramedical staff (especially dental assistants) of the X-ray room were determined, which lead to the appointment of a re-examination, the implementation of additional projections, auxiliary visualization techniques and an increase in the number of false-negative results.

Development of a molecular xenomonitoring protocol to assess filariasis transmission

According to the World Health Organization, lymphatic filariasis (LF), a mosquito-borne neglected tropical disease (NTD), should be eliminated as a public health concern by the end of 2020. To this end, the goals of the Global Programme to Eliminate Lymphatic Filariasis (GPELF) include interrupting transmission through mass drug administration (MDA). After two decades, several countries have implemented MDA and are now ready to confirm whether transmission has been interrupted. The method for detecting the parasites in mosquito vectors known as xenomonitoring is a non-invasive tool for assessing the current transmission status of the filarial nematode Wuchereria bancrofti (which is responsible for 90% of cases) by their vectors. There are several methods available for detection of the worm in mosquito samples, such as dissection or polymerase chain reaction (PCR). However, most of these techniques still produce a considerable number of false-negative results. The present study describes a new duplex PCR protocol, which is an improvement on the traditional PCR methodology, enhanced by introducing the actin gene as an endogenous control gene. After adjusting the mosquito pool size, DNA extraction, and WbCx PCR duplex design, we achieved a reliable and sensitive molecular xenomonitoring protocol. This assay was able to eliminate 5% of false negative samples and detected less than one Wb larvae. This high sensitivity is particularly valuable after MDA, when prevalence declines. This new method could reduce the number of false-negative samples, which will enable us to improve our ability to generate accurate results and aid the monitoring strategies used by LF elimination programmes.

Reducing False Negative PCR Test for COVID-19.

As the SARS-CoV-2 (COVID-19) pandemic spreads rapidly, there is need for a diagnostic test with high accuracy to detect infected individuals especially those without symptoms. Real-time polymerase chain reaction (RT-PCR) is a common molecular test for diagnosing SARS-CoV-2. If some factors are not taken into consideration when performing this test, it can have a relatively large number of false negative results. In this article, we discuss important considerations that could lead to false negative test reduction.