false negative results
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2022 ◽  
Vol 43 (2) ◽  
pp. 585-598
Author(s):  
Ana Paula Molinari Candeias ◽  
◽  
Gabrieli Maria Huff ◽  
Adriana Fiorini Rosado ◽  
André Luis Vriesman Beninca ◽  
...  

The objective of this study is to compare the direct fecal smear (DFS) and centrifugal sedimentation (CS) methods in the detection of Cryptosporidium spp. oocysts in fecal samples of dairy calves. One hundred and fourteen fecal samples were collected from calves aged up to six months from 10 dairy farms located in Palotina and Francisco Alves, Paraná, Brazil. The microscopic analysis revealed the presence of Cryptosporidium spp. oocysts in 51.75% (59/114) of the samples in both methods. In CS, 48.25% (55/114) of the samples were positive, while in DFS slides, only 6.14% (7/114) were positive. Only 4 samples were positive exclusively in DFS. To ensure that there were no false-negative results in the microscopic analysis, the 55 samples that were negative in both DFS and CS were selected for molecular analysis using the nested PCR (nPCR). Of these 55 samples, 24% (13/55) were positive and forwarded for sequencing part of the genome, which made it possible to identify C. parvum, C. bovis and C. ryanae. Besides the characterization of the Cryptosporidium species, it was possible to identify bacteria of the genus Acinetobacter interfering directly in the analyzed samples. The microscopic analysis also revealed higher sensitivity when CS was used to make the fecal smears. However, some samples that were negative in this technique had positive PCR results. Thus, molecular analysis is indicated to confirm cases of Cryptosporidium spp. Further studies are necessary to prove the specificities of the used primers since the results obtained in nPCR were positive for the protozoan but, when genetic sequencing was performed, Acinetobacter spp. was identified.


Author(s):  
Gun Srijuntongsiri ◽  
Atiwat Mhoowai ◽  
Sukuma Samngamnim ◽  
Pornchalit Assavacheep ◽  
Janine T. Bossé ◽  
...  

Species-specific markers are crucial for infectious disease diagnostics. Mutations within a marker sequence can lead to false-negative results, inappropriate treatment, and economic loss.


2022 ◽  
Author(s):  
Divya Sharma ◽  
Chengjin Ye ◽  
Giusppe Lippi ◽  
Jordi B. Torrelles ◽  
Luis Martinez-Sobrido ◽  
...  

Abstract Background The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant of concern (VoC) Omicron (B.1.1.529) has rapidly spread around the world presenting a new threat to global public human health. Due to the large number of mutations possessed by Omicron, concerns have emerged over potentially reduced diagnostic accuracy of reverse transcription polymerase chain reaction (RT-qPCR), the gold standard diagnostic test for SARS-CoV-2. Here, we aimed to assess the impact of Omicron on the integrity and sensitivity of RT-qPCR assays used for coronavirus disease-2019 (COVID-19) diagnosis via in silico analysis employing whole genome sequencing data and evaluated the potential for false negatives or test failure due to mismatches between primers/probes and viral genome. Methods In silico sensitivity of 12 RT-qPCR tests (containing 30 primers and probe sets) developed for detection of SARS-CoV-2 reported by the World Health Organization (WHO) or available in the literature, was assessed for use in detecting SARS-CoV-2 Omicron BA.1 and BA.2 sublineages, obtained after removing redundancy from publicly available genomes from National Center for Biotechnology Information (NCBI) and Global Initiative on Sharing Avian Influenza Data (GISAID) databases. The mismatches between the amplicon regions of the SARS-CoV-2 Omicron VoC and primers and probe sets were evaluated, and the clustering analysis of the corresponding amplicon sequences was carried out. Results From the 232 representative SARS-CoV-2 BA.1 Omicron sublineage genomes analyzed, 229 showed substitutions at the forward primer annealing site for assay China-CDC N, 226 showed mismatches in the reverse primer annealing site for assay Thai N, and all 232 had substitution at the 3’ end of the reverse primer annealing site for assay HKUniv RdRp/Hel. Therefore, the lowest sensitivity was observed for assay ChinaCDC N, Thai N and HKUniv RdRp/Hel for SARS-CoV-2 BA.1 sublineage genomes. For 5 SARS-CoV-2 BA.2 Omicron sublineage genomes, false negative results were observed for assays ChinaCDC N, Thai N, HKUniv RdRp/Hel, SigmAldr S5, SigmAldr S6 and HKUniv S. Conclusion In this study, we observed three (25%) assays (ChinaCDC N, Thai N, and HKUniv RdRp/Hel) demonstrated potential for false negatives for the SARS-CoV-2 Omicron BA.1 sublineage, while four (33.3%) assays (ChinaCDC N, Thai N, HKUniv RdRp/Hel, HKUniv S, SigmAldr S5 and SigmAldr S6) demonstrated potential false negative results for the for SARS-CoV-2 Omicron BA.2 sublineage, which also has the potential for Spike (S) gene dropout despite lacking 69-70 deletion in the S gene. Further, amplicon clustering and additional substitutions analysis along with the sensitivity analysis could be used for modification and development of RT-qPCR assays for detection of SARS-CoV-2 Omicron VoC lineages.


2022 ◽  
Vol 2 (1) ◽  
pp. e0000106
Author(s):  
Alisha Chaudhry ◽  
Jane Cunningham ◽  
Qin Cheng ◽  
Michelle L. Gatton

Malaria rapid diagnostic tests (RDTs) are dominated by products which use histidine-rich protein 2 (HRP2) to detect Plasmodium falciparum. The emergence of parasites lacking the pfhrp2 gene can lead to high rates of false-negative results amongst these RDTs. One solution to restore the ability to correctly diagnose falciparum malaria is to switch to an RDT which is not solely reliant on HRP2. This study used an agent-based stochastic simulation model to investigate the impact on prevalence and transmission caused by switching the type of RDT used once false-negative rates reached pre-defined thresholds within the treatment-seeking symptomatic population. The results show that low transmission settings were the first to reach the false-negative switch threshold, and that lower thresholds were typically associated with better long-term outcomes. Changing the diagnostic RDT away from a HRP2-only RDT is predicted to restore the ability to correctly diagnose symptomatic malaria infections, but often did not lead to the extinction of HRP2-negative parasites from the population which continued to circulate in low density infections, or return to the parasite prevalence and transmission levels seen prior to the introduction of the HRP2-negative parasite. In contrast, failure to move away from HRP2-only RDTs leads to near fixation of these parasites in the population, and the inability to correctly diagnose symptomatic cases. Overall, these results suggest pfhrp2-deleted parasites are likely to become a significant component of P. falciparum parasite populations, and that long-term strategies are needed for diagnosis and surveillance which do not rely solely on HRP2.


2022 ◽  
Author(s):  
Elsayed Ghannam ◽  
Salah Rozaik ◽  
Ramy Hasan Agwa ◽  
Ahmed Marwan ◽  
Mervat El-Sayed Mashaly ◽  
...  

Abstract Background: Liver is the largest endocrine organ in the body. It is a key organ in insulin mediated metabolism, growth hormone and insulin like growth factors (IGF) pathway. Liver cirrhosis is the end result of many chronic diseases including hepatitis C virus infection. Child-Turcotte-Pugh (CTP) score is the standard used in assessment of hepatic reserve but it has its drawbacks in the form of subjective variables, hepatic encephalopathy and ascites. The aim of this work is to assess IGF-1 in patients with liver cirrhosis, correlate it with CTP score and assess value of modified combined CTP-IGF-1 score. Patients and Methods: 170 patients with CLD (liver cirrhosis) and 72 healthy controls in the study groups were enrolled in the study. All patients were subjected to thorough history, clinical examination and laboratory assessment. IGF-1 was measured and all patients were evaluated using CTP and CTP-IGF-1 scores. Results: IGF1 showed highly significant low values in the study group in comparison to controls (42.15 ± 27.976 and 66.31 ± 33.084 ng/ml respectively, p <0.001). It showed also highly significant negative correlation to CTP score in the study group (p < 0.001) with progressive decrements with CTP score stage progression where IGF1 levels were 48.32 ± 28.611, 40.28 ± 25.869 and 18.80 ± 15.953 ng/ml (mean ± standard deviation) in relation to CTP score groups A, B and C respectively (p value < 0.001). The combined CTP-IGF-1 score in comparison to the classic CTP score showed improved area under curve (0.848 and 0.854), sensitivity (71.2% and 88%), negative predictive value (41.7% and 53.7%), false negative results (49 and 19) and accuracy (75.73% and 83.98%) but decreased specificity (97.22% and 61.1%), positive predictive value (99.2% and 91.5%) and higher false positive results (1 and 14) respectively. Conclusion: IGF-1 show progressive decrements with progression of liver cirrhosis and is negatively correlated with CTP score. Addition of IGF-1 to CTP score to formulate combined score improves the AUC, sensitivity, negative predictive value and the accuracy of CTP score and decreases the false negative results.


Diagnostics ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 100
Author(s):  
Victor Mihai Sacerdotianu ◽  
Bogdan Silviu Ungureanu ◽  
Sevastita Iordache ◽  
Adina Turcu-Stiolica ◽  
Antonio Facciorusso ◽  
...  

This study aimed to evaluate the diagnostic value of endoscopic ultrasound (EUS) after neoadjuvant therapy (NT) for gastric cancer restaging by meta-analysis. We conducted a systematic search of studies published on PubMed and Web of Science up to 30th August 2021. Assessing the risk of bias in the included studies was done with the QUADAS-2 tool. We used R and Review Manager 5.4.1 for calculations and statistical analysis. To evaluate the diagnostic value of EUS after NT for gastric cancer restaging, we performed a meta-analysis on six studies, with a total of 283 patients, including true-positive, true-negative, false-positive, and false-negative results for T1-T4, N0. EUS as a diagnostic test for GC patients after chemotherapy has a relatively low DOR for the T2 (3.96) and T4 stages (4.79) and a relatively high partial AUC for the T2 (0.85) and T4 (0.71) stages. Our results reveal that the pooled sensitivity for T stages after chemotherapy is rather low (29–56%), except for the T3 stage (71%). A potential limitation of our study was the small number of included studies, but no significant heterogeneity was found between them. Our meta-analysis concludes that EUS is not recommended or is still under debate for GC restaging after NT.


2022 ◽  
Vol 42 ◽  
Author(s):  
Patrícia W.G. Balestrin ◽  
Eder Balestrin ◽  
Fábio Santiani ◽  
Thierry G. de Cristo ◽  
David G. Pereira ◽  
...  

ABSTRACT: Coccidiosis is a disease of great importance in industrial poultry. The correct diagnosis directs the poultry industry to its best treatment and control. Thus, a survey of Eimeria spp. was carried out in intestines of 64 broiler flocks, with an average age of 29 days. Eight broilers from each flock were randomly removed from the slaughter line, in a total of 512 samples. Macroscopic and histopathological lesions in the intestine were classified into Scores 0 to 4. Polymerase chain reaction (PCR) was used to research the oocysts from the seven species of Eimeria spp. in the intestinal content. The macroscopic evaluations showed that 59.4% (38/64) of the flocks were positive for E. acervulina, 32.8% (21/64) for E. maxima, 29.7% (19/64) for E. tenella, and 34.4% (22/64) for E. brunetti. The histopathological evaluation showed that 87.5% (56/64) of the flocks had at least one broiler with parasitic structures compatible with Eimeria spp. in the duodenum, 70.3% (45/64) in the jejunum, 18.8% (12/64) in the ileum, 46.9% (30/64) in the cecum, and 4.7% (3/64) in the colon. In PCR, 21.9% (14/64) of the flocks were positive for E. acervulina, 12.5% (8/64) for E. maxima, 3.1% (2/64) for E. mitis, and 32.8% (21/64) for E. tenella. The Kappa Cohen test between macroscopy, histopathology, and PCR demonstrated concordance ranging from weak to moderate with the exception of histopathology and PCR of the cecum, which was strong. In the comparison between macroscopy and histopathology, there were significative differences between Scores 0 and 1 (apart from the cecum). For Score 3, there were significative differences in duodenum, jejunum and cecum (p<0.05). In conclusion, the macroscopic diagnosis and PCR can generate false-negative results, and the histopathological exam proved to be effective, making it essential to associate different techniques for the correct diagnosis of Eimeria spp. in broiler chickens.


2022 ◽  
pp. 230-243
Author(s):  
Antonia Mourtzikou ◽  
Marilena Stamouli ◽  
Georgia Kalliora ◽  
Panagiotis Koumpouros ◽  
Ioanna Petraki ◽  
...  

Clinical laboratories produce test results that support the diagnosis, prognosis, and patient treatment. Test results must be relevant, accurate, and reliable for patient care. International bibliographic data estimate that approximately 62.0% of the errors made in clinical laboratories are due to errors during the pre-analytical stage. This chapter presents a failure modes and effects analysis (FMEA) to analyze potential failure risks within the pre-analytical phase and classify them according to severity and likelihood. FMEA allows molecular laboratories to lower costs and drive better outcomes through high-quality nucleic acid extraction, sensitive detection, and accurate quantification. RT-PCR technology continues to be the gold standard for the clinical detection of SARS-CoV-2 RNA in individuals suspected of COVID-19. It is essential to use highly sensitive assays to detect active infections and reduce the likelihood of false-negative results.


2021 ◽  
Vol 9 (1) ◽  
pp. 142
Author(s):  
Karan Dharamsi ◽  
Juthikaa Deherkar ◽  
Ankita Agarwal ◽  
Mrunal Ketkar

Background: Breast cancer is frequently associated with activation of the hemostatic system and the extent of this activation correlates with a more advanced tumor stage. D-dimer is a biomarker that indicates the activation of hemostasis and fibrinolysis.Methods: This is a prospective, observational, analytical study in which we compare plasma D-dimer levels among three groups’ i.e., healthy subjects, benign patients and breast cancer patients. We have also evaluated plasma D-dimer levels in patients with lymphadenopathy and in those patients who did not have palpable lymph nodes. Plasma D-dimer levels were further characterized based on TNM classification in breast cancer patients where quantitative D-dimer levels were correlated with clinical stage grouping.Results: Through our study we have observed that D-dimer level is inexpensive and a convenient method for diagnosis and prognosis of breast cancer. We have used a control group so as to evaluate a more accurate result. Comparison between benign and malignant lesions was made and we have achieved a significant p value, which proved our study positive for raised D-dimer levels in cancer breast.Conclusions: D-dimer proves to be a safe, convenient and easily available biomarker which can be combined with conventional sentinel node biopsy in clinically node negative breast cancer to assess metastatic disease in axilla and reduce false negative results. Plasma D-dimer level was positively correlated with clinical stage of solid cancers.


Diagnostics ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2373
Author(s):  
Matthew Oughton ◽  
Ivan Brukner ◽  
Shaun Eintracht ◽  
Andreas I. Papadakis ◽  
Alan Spatz ◽  
...  

Respiratory screening assays lacking Sample Adequacy Controls (SAC) may result in inadequate sample quality and thus false negative results. The non-adequate samples might represent a significant proportion of the total performed tests, thus resulting in sub-optimal infection control measures with implications that may be critical during pandemic times. The quantitative sample adequacy threshold can be established empirically, measuring the change in the frequency of positive results, as a function of the numerical value of “sample adequacy”. Establishing a quantitative threshold for SAC requires a big number/volume of tests to be analyzed in order to have a statistically valid result. Herein, we are offering for the first time clear clinical evidence that a subset of results, which did not pass minimal sample adequacy criteria, have a significantly lower frequency of positivity compared with the “adequate” samples. Flagging these results and/or re-sampling them is a mitigation strategy, which can dramatically improve infection control measures.


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