scholarly journals Categorical performance characteristics of method ISO 7899-2 and indicator value of intestinal enterococci for bathing water quality monitoring

2018 ◽  
Vol 16 (5) ◽  
pp. 711-723 ◽  
Author(s):  
Ananda Tiwari ◽  
Anna-Maria Hokajärvi ◽  
Jorge W. Santo Domingo ◽  
Ari Kauppinen ◽  
Michael Elk ◽  
...  
Keyword(s):  
False Negative ◽  
False Negative Rate ◽  
Reference Method ◽  
Water Quality Monitoring ◽  
Performance Characteristics ◽  
Rrna Gene ◽  
Bathing Waters ◽  
Multiple Sample ◽  
Bathing Water Quality ◽  
Intestinal Enterococci

Abstract Intestinal enterococci indicate the fecal contamination of bathing waters. This study defines the performance characteristics of the reference method ISO 7899-2:2000 with water samples collected from inland and coastal bathing areas in Finland. From a total of 341 bacterial isolates grown on Slanetz and Bartley medium, 63.6% were confirmed as intestinal enterococci on bile aesculin agar. The partial 16S rRNA gene sequences showed that Enterococcus faecium and Enterococcus faecalis clades accounted for 93.1% of the confirmed isolates. The range of the false positive and false negative rate of the ISO 7899-2 was 0.0–18.5% and 5.6–57.1%, respectively, being affected by the presumptive colony count on the membrane. The analysis of multiple sample volumes is proposed to reach 10–100 colonies per membrane when 47 mm diameter membranes are used to prevent overestimation of low counts and underestimation of the high counts.

Comparison of the BAX System PCR Method to Brazil's Official Method for the Detection of Salmonella in Food, Water, and Environmental Samples

2008 ◽  
Vol 71 (12) ◽  
pp. 2442-2447 ◽  
Author(s):  
INGRID BOESCHE TOMAZELLI ◽  
JOSINETE BARROS de FREITAS ◽  
LEANIA MARIA FABBI ◽  
TEREZINHA AGNESE FILIPINI ◽  
CLÁUDIA MARIA da SILVA ◽  
...  
Keyword(s):  
Environmental Samples ◽  
Limit Of Detection ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Reference Method ◽  
Culture Method ◽  
Official Method ◽  
Positive Rate ◽  
Pcr Method

A two-stage study compared the BAX system PCR method with the reference culture method used by the Brazilian Ministry of Agriculture and Food Supply for the detection of Salmonella in food, water, and environmental samples. In stage 1, fish matrix samples (n = 258) were spiked at several levels with Salmonella and a combination of Salmonella and non-Salmonella competitive organisms. Replicates were analyzed by the BAX system PCR method and the reference method with comparable results (sensitivity ≥ 97.5%, specificity ≥ 83.3%) from both methods at the limit of detection. In stage 2, a total of 1,988 samples with 70 product types were analyzed with both methods. Five laboratories were involved in this study, and the samples used were from routine analyses. The BAX system PCR method was shown to be comparable to the reference method, with a limit of detection of 1.0 to 2.0 CFU/25 g of sample. Analysis of the results obtained in stage 2 and in the combination of stages 1 and 2 for the BAX system showed the following performance: sensitivity ≥ 99.0%, specificity ≥ 97.2%, false-negative rate ≤ 1.1%, and false-positive rate ≤ 2.8%. Therefore, the BAX system appears to be equivalent to the reference method, with ≥ 97.3% agreement.

Evaluation of an Immunomagnetic Separation–Real-Time PCR Assay for the Rapid Detection of Salmonella in Meat

2006 ◽  
Vol 69 (12) ◽  
pp. 2896-2901 ◽  
Author(s):  
ANGELIKA NOTZON ◽  
REINER HELMUTH ◽  
JOHANN BAUER
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Reference Method ◽  
Immunomagnetic Separation ◽  
Pcr Assay ◽  
Positive Rate ◽  
Meat Samples

The aim of this study was the comparison of an immunomagnetic separation (IMS)–real-time PCR assay for the detection of Salmonella with the cultural reference method according to §35 of the German Law on Food and Commodities (LMBG, L 00.00.20:1998). The IMS–real-time PCR assay includes a nonselective preenrichment step, an IMS, DNA extraction, as well as DNA purification followed by hybridization probe–based real-time PCR analysis. An accurate comparability was achieved, because both methods analyzed the same preenrichment. The evaluation was carried out using both artificially and naturally contaminated meat samples. The IMS–real-time PCR assay provides a result after 12 to 13 h. Compared with the reference method and regarding artificially contaminated meat samples, the IMS–real-time PCR assay achieved a specificity of 80% (false-positive rate of 20%) and a sensitivity of 100% (false-negative rate of 0%). The relative accuracy was 94%. The detection limit of both methods was 10 CFU/25 g. The concordance indexκ defines the statistical accordance, was 0.85 and indicated the agreement of both methods on statistical criteria. Compared to the reference method and analyzing naturally contaminated meat samples (n = 491), the IMS–real-time PCR assay showed a specificity of 99.3% (false-positive rate of 0.7%) and a sensitivity of 83.7% (false-negative rate of 16.3%). The relative accuracy was 98%. The concordance index κ had a value of 0.87 and highlighted the statistical agreement of both methods. In conclusion, the IMS–real-time PCR assay is suitable as specific, sensitive, and rapid screening method for the detection of Salmonella from meat.

scholarly journals Comparison of Colilert-18 with miniaturised most probable number method for monitoring of Escherichia coli in bathing water

2015 ◽  
Vol 14 (1) ◽  
pp. 121-131 ◽  
Author(s):  
Ananda Tiwari ◽  
Seppo I. Niemelä ◽  
Asko Vepsäläinen ◽  
Jarkko Rapala ◽  
Seija Kalso ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
False Negative ◽  
Reference Method ◽  
Water Quality Monitoring ◽  
Coliform Bacteria ◽  
Most Probable Number ◽  
Probable Number ◽  
E Coli ◽  
Negative Results ◽  
Bathing Water

The purpose of this equivalence study was to compare an alternative method, Colilert-18 Quanti-Tray (ISO 9308-2) with the European bathing water directive (2006/7/EC) reference method, the miniaturised most probable number (MMPN) method (ISO 9308-3), for the analysis of Escherichia coli. Six laboratories analysed a total of 263 bathing water samples in Finland. The comparison was carried out according to ISO 17994:2004. The recovery of E. coli using the Colilert-18 method was 7.0% and 8.6% lower than that of the MMPN method after 48 hours and 72 hours of incubation, respectively. The confirmation rate of presumptive E. coli-positive wells in the Colilert-18 and MMPN methods was high (97.8% and 98.0%, respectively). However, the testing of presumptive E. coli-negative but coliform bacteria-positive (yellow but not fluorescent) Colilert-18 wells revealed 7.3% false negative results. There were more false negatives in the naturally contaminated waters than in the samples spiked with waste water. The difference between the recovery of Colilert-18 and the MMPN method was considered not significant, and subsequently the methods are considered as equivalent for bathing water quality monitoring in Finland. Future bathing water method equivalence verification studies may use the data reported herein. The laboratories should make sure that any wells showing even minor fluorescence will be determined as positive for E. coli.

scholarly journals Somatic coliphages and bacterial indicators of bathing water quality in the beaches of Gipuzkoa, Spain

2007 ◽  
Vol 5 (3) ◽  
pp. 417-426 ◽  
Author(s):  
Jesús M. Ibarluzea ◽  
Belén Moreno ◽  
Elena Serrano ◽  
Karmele Larburu ◽  
María J. Maiztegi ◽  
...  
Keyword(s):  
Water Quality ◽  
Basque Country ◽  
Water Quality Monitoring ◽  
Bacterial Indicators ◽  
Somatic Coliphages ◽  
E Coli ◽  
Bathing Water ◽  
Bathing Waters ◽  
Viral Indicators ◽  
Bathing Water Quality

Monitoring the quality of the bathing waters of Gipuzkoa (the Basque Country, Spain) makes it possible to assess the suitability of its 15 beaches for bathing throughout each season. In 1998, the parameters E. coli, somatic coliphages (SOMCPH) and F-specific RNA bacteriophages (FRNAPH) were incorporated into the bathing water quality monitoring system. This enabled the study of the link between bacterial and viral indicators as well as the analysis of the ratios between both types of indicators in waters with different levels of pollution. Although bacterial indicators (total coliforms (TC) and faecal coliforms (FC)) and enterococci showed a strong correlation between them, the correlations between the viral indicators and between the viral and bacterial indicators were weaker, though significant in all cases. The ratio between SOMCPH and E. coli indicates that at low levels of bacterial pollution (E coli <100 MPN/100 ml) SOMCPH outnumber E coli. In contrast, at higher levels of pollution (E coli >100 MPN/100 ml), SOMCPH numbers are lower than those of E-coli. The data reveal the presence of viral indicators in waters classified as suitable for bathing by the European Directive and alert us to their suitability.

scholarly journals Comparison of the Accula SARS-CoV-2 Test with a Laboratory-Developed Assay for Detection of SARS-CoV-2 RNA in Clinical Nasopharyngeal Specimens

2020 ◽  
Vol 58 (8) ◽  
Author(s):  
Catherine A. Hogan ◽  
Natasha Garamani ◽  
Andrew S. Lee ◽  
Jack K. Tung ◽  
Malaya K. Sahoo ◽  
...  
Keyword(s):  
Viral Load ◽  
Test Performance ◽  
Point Of Care ◽  
False Negative ◽  
False Negative Rate ◽  
Kappa Coefficient ◽  
Performance Characteristics ◽  
Nasopharyngeal Swab ◽  
Percent Agreement ◽  
Gene Assay

ABSTRACT Several point-of-care (POC) molecular tests have received emergency use authorization (EUA) from the Food and Drug Administration (FDA) for the diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The test performance characteristics of the Accula (Mesa Biotech) SARS-CoV-2 POC test need to be evaluated to inform its optimal use. The aim of this study was to assess the test performance of the Accula SARS-CoV-2 test. The performance of the Accula test was assessed by comparing results of 100 nasopharyngeal swab samples previously characterized by the Stanford Health Care EUA laboratory-developed test (SHC-LDT), targeting the envelope (E) gene. Assay concordance was assessed by overall percent agreement, positive percent agreement (PPA), negative percent agreement (NPA), and Cohen’s kappa coefficient. Overall percent agreement between the assays was 84.0% (95% confidence interval [CI], 75.3 to 90.6%), PPA was 68.0% (95% CI, 53.3 to 80.5%), and the kappa coefficient was 0.68 (95% CI, 0.54 to 0.82). Sixteen specimens detected by the SHC-LDT were not detected by the Accula test and showed low viral load burden, with a median cycle threshold value of 37.7. NPA was 100% (95% CI, 94.2 to 100%). Compared to the SHC-LDT, the Accula SARS-CoV-2 test showed excellent negative agreement. However, positive agreement was low for samples with low viral load. The false-negative rate of the Accula POC test calls for a more thorough evaluation of POC test performance characteristics in clinical settings and for confirmatory testing in individuals with moderate to high pretest probability of SARS-CoV-2 who test negative on Accula.

scholarly journals Comparison of the Accula SARS-CoV-2 Test with a Laboratory-Developed Assay for Detection of SARS-CoV-2 RNA in Clinical Nasopharyngeal Specimens

2020 ◽  
Author(s):  
Catherine A. Hogan ◽  
Natasha Garamani ◽  
Andrew S. Lee ◽  
Jack K. Tung ◽  
Malaya K. Sahoo ◽  
...  
Keyword(s):  
Viral Load ◽  
Test Performance ◽  
Point Of Care ◽  
False Negative ◽  
False Negative Rate ◽  
Kappa Coefficient ◽  
Performance Characteristics ◽  
Nasopharyngeal Swab ◽  
Percent Agreement ◽  
Gene Assay

AbstractBackgroundSeveral point-of-care (POC) molecular tests have received emergency use authorization (EUA) from the Food and Drug Administration (FDA) for diagnosis of SARS-CoV-2. The test performance characteristics of the Accula (Mesa Biotech) SARS-CoV-2 POC test need to be evaluated to inform its optimal use.ObjectivesThe aim of this study was to assess test performance of the Accula SARS-CoV-2 test.Study designThe performance of the Accula test was assessed by comparing results of 100 nasopharyngeal swab samples previously characterized by the Stanford Health Care EUA laboratory-developed test (SHC-LDT) targeting the envelope (E) gene. Assay concordance was assessed by overall percent agreement, positive percent agreement (PPA), negative percent agreement (NPA), and Cohen’s kappa coefficient.ResultsOverall percent agreement between the assays was 84.0% (95% confidence interval [CI] 75.3 to 90.6%), PPA was 68.0% (95% CI 53.3 to 80.5%) and the kappa coefficient was 0.68 (95% CI 0.54 to 0.82). Sixteen specimens detected by the SHC-LDT were not detected by the Accula test, and showed low viral load burden with a median cycle threshold value of 37.7. NPA was 100% (95% CI 94.2 to 100%).ConclusionCompared to the SHC-LDT, the Accula SARS-CoV-2 test showed excellent negative agreement. However, positive agreement was low for samples with low viral load. The false negative rate of the Accula POC test calls for a more thorough evaluation of POC test performance characteristics in clinical settings, and for confirmatory testing in individuals with moderate to high pre-test probability of SARS-CoV-2 who test negative on Accula.

scholarly journals RapidChek SELECT Salmonella

2009 ◽  
Vol 92 (6) ◽  
pp. 1890-1894 ◽  
Author(s):  
Mark T Muldoon ◽  
Jingkun Li ◽  
Meredith Sutzko ◽  
Ann Christine Olsson-Allen ◽  
George Teaney ◽  
...  
Keyword(s):  
False Positive Rate ◽  
Peanut Butter ◽  
False Negative ◽  
False Negative Rate ◽  
Reference Method ◽  
Salmonella Spp ◽  
Chi Square ◽  
Negative Results ◽  
Significant Difference ◽  
Positive Rate

Abstract RapidChek SELECT Salmonella was previously validated in the Performance Tested MethodsSM program for the detection of Salmonella spp. in raw ground chicken, chicken carcass rinse, sliced cooked turkey, and liquid eggs. The present matrix extension study conducted under the AOAC Research Institute Emergency Response Validation program compared the RapidChek SELECT Salmonella method to the U.S. Food and Drug Administration's Bacteriological Analytical Manual (FDA-BAM) method for the detection of Salmonella Typhimurium in peanut butter. Overall, 27 samples were found positive by the RapidChek SELECT Salmonella method and 27 were found to be positive by the reference method. All RapidChek SELECT Salmonella presumptive positives were confirmed positive by the cultural reference method; additionally, all presumptive negative results were confirmed negative by the cultural reference method. Accordingly 0 false-negative rate and 0 false-positive rate were found. No significant difference between the RapidCheck SELECT Salmonella and FDA-BAM reference method was found; calculated Chi-square was 0. Results indicate that a low level of Salmonella in peanut butter can be successfully recovered and detected in the minimum 24 h enrichment protocol.

Validation of the Legipid® Bioalarm Legionella Assay

2012 ◽  
Vol 95 (5) ◽  
pp. 1440-1451 ◽  
Author(s):  
Guillermo Rodríguez Albalat ◽  
Begoña Bedrina Broch ◽  
Marisa Jiménez Bono
Keyword(s):  
Legionella Pneumophila ◽  
Water Samples ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Reference Method ◽  
Culture Method ◽  
Magnetic Microspheres ◽  
Test Volume ◽  
Significant Difference

Abstract Legipid® Bioalarm Legionella is a test based on combined magnetic immunocapture and enzyme-immunoassay (CEIA) for the detection of Legionella pneumophila in water. Anti-L. pneumophila antibodies are immobilized on magnetic microspheres. Immunomagnetic analysis is applied to preconcentrated water samples in a final test volume of 9 mL. The method was compared with the standard culture method on both spiked and naturally contaminated water samples. The test was evaluated in potable, industrial, and natural water matrixes, according to the scope of the ISO 11731 reference method. These waters were tested with the target at levels ranging from low (10–99 CFU/mL) to high (100–999 CFU/mL); a Chi-square value of 1.8 indicated that there was no significant difference between the test and the reference method. The false-positive rate was 7%, and the false-negative rate 2%. For the inclusivity study, all 17 strains of L. pneumophila of different serogroups reacted with the test. For the exclusivity study, 17 strains of other Legionella species and 16 non-Legionella strains were tested. There were no cross-reactions with non-Legionella strains. L. beliardensis, L. adelaidensis, and one environmentally isolated Legionella sp. produced a positive result at high concentrations of 1800, 230, and 3900 CFU/mL, respectively. Agreement between the two methods was 95.9%.

Diagnostic Performance of Contrast-enhanced Mammography: Comparison With MRI and Mammography

2021 ◽  
Author(s):  
Sabahattin Yüzkan ◽  
Duygu Cengiz ◽  
İlhan Hekimsoy ◽  
Özlem Sezgin Okçu ◽  
Ayşenur Oktay
Keyword(s):  
Predictive Value ◽  
False Positive ◽  
Diagnostic Performance ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Performance Characteristics ◽  
Histopathological Analysis ◽  
Contrast Enhanced ◽  
Improved Performance

Abstract Objective To compare the diagnostic performance of contrast-enhanced mammography (CEM) with MRI and mammography (MG) based on histopathological results. Methods In this IRB-approved study, written informed consent was obtained from all patients. Images from 40 patients (62 lesions) with suspicious findings on US between March 2018 and August 2018 were evaluated. Sensitivity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of CEM, MRI, and MG were evaluated and compared within a 95% confidence interval. Maximum dimensions of lesions were measured and correlations of results were evaluated with Spearman’s Rho test. Results In the histopathological analysis, 66% (41/62) of lesions were malignant and 34% (21/62) lesions were benign. Contrast-enhanced mammography, MRI, and MG had sensitivities of 100% (41/41), 100% (41/41), and 80% (33/41), respectively. The sensitivity of CEM and MRI was significantly better than that of MG (P = 0.03). The NPVs of CEM (100%, 7/7) and MRI (100%, 14/14) were statistically higher than the NPV of MG (60%, 12/20) (P = 0.03). The false-positive rates for CEM, MRI, and MG were 33% (7/21), 66% (14/21), and 42% (9/21), respectively. Contrast-enhanced mammography had a significantly lower false-positive rate than MRI (P < 0.001). Mammography had the highest false-negative rate, missing 19% (8/41) of malignant lesions. Conclusion Contrast-enhanced mammography has similar performance characteristics to MRI and improved performance characteristics relative to MG. In particular, CEM and MRI have similar sensitivity and NPVs and both are superior in each of these metrics to MG.

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