Elimination of False Negative Results with the FPN Forrest Test for Phenothiazine Derivatives in Urine

1966 ◽  
Vol 12 (6) ◽  
pp. 379-384 ◽  
Author(s):  
Irene S Forrest ◽  
Fred M Forrest ◽  
Saul L Kanter
Keyword(s):  
Reading Time ◽  
False Negative ◽  
False Positives ◽  
Phenothiazine Derivatives ◽  
False Negatives ◽  
Negative Results ◽  
Color Development ◽  
False Negative Results ◽  
Color Reactions ◽  
Urine Specimens

Abstract With the FPN Forrest test for urinary phenothiazine derivatives, omission of drug intake was found to be the most frequent cause of negative color reactions; accordingly, these negative reactions are true negatives. Excessive dilution of urine specimens occasionally yielded "apparent false negatives" by producing traces of drug metabolites, which cannot be detected without modification of the test. When measures to eliminate these conditions are taken, the previously specified reading time (10 sec. after mixing urine and reagent) is reliable. Unspecific color development due to reaction between endogenous urinary constituents and reagent appeared with a delay of 30 sec. or more, and hence recent recommendations of delaying reading times for the test were found to be unsuitable and productive of false positives.

Phenothiazine Derivatives in Urine: "False Nagative Results" With the Forrest Color Test (FPN), and a Method for Their Elimination

1965 ◽  
Vol 11 (10) ◽  
pp. 914-919
Author(s):  
K N Campbell
Keyword(s):  
False Negative ◽  
False Positives ◽  
Phenothiazine Derivatives ◽  
Color Test ◽  
False Negatives ◽  
Delayed Reaction ◽  
Negative Results ◽  
False Negative Results ◽  
Phenothiazine Drugs ◽  
Urine Specimens

Abstract More than 100 Forrest color tests (FPN) were performed on urine specimens from patients taking phenothiazine drugs. The results obtained showed > 20% "false negatives" and 6% "false positives." A delayed reaction due to possible individual patient variation seems to have been the cause for false-negative results. These false negatives were shown to disappear when test readings were delayed for 1-5 min. Some false positives were due to liver dysfunction.

Detection of Phenothiazine Derivatives in Urine

1966 ◽  
Vol 12 (12) ◽  
pp. 844-848 ◽  
Author(s):  
Herman Brownstein ◽  
Alfred R Roberge
Keyword(s):  
False Negative ◽  
Control Group ◽  
Phenothiazine Derivatives ◽  
False Negatives ◽  
Negative Results ◽  
False Negative Results ◽  
Positive Results ◽  
Urine Specimens ◽  
Modified Test

Abstract Findings of the present study agree with published results that showed an incidence of approximately 25% "false negative" results with the Forrest FPN test for phenothiazine derivatives in urine. A recently published modification purportedly decreased these "false negatives" to less than 5%. However, our control group of negative urine specimens omitted in Campbell's study, yielded 100% negative results with the FPN test and 81% positive results with the modified test. Phenistix (Ames) was evaluated for elimination of false negative readings but was found not to have any advantage for this purpose. Data are also presented indicating differing sensitivities of the Forrest FPN test to various phenothiazine derivatives.

scholarly journals False-Negative Results in Point-of-Care Qualitative Human Chorionic Gonadotropin (hCG) Devices Due to Excess hCGβ Core Fragment

2009 ◽  
Vol 55 (7) ◽  
pp. 1389-1394 ◽  
Author(s):  
Ann M Gronowski ◽  
Mark Cervinski ◽  
Ulf-Håkan Stenman ◽  
Alison Woodworth ◽  
Lori Ashby ◽  
...  
Keyword(s):  
Chorionic Gonadotropin ◽  
Human Chorionic Gonadotropin ◽  
Point Of Care ◽  
False Negative ◽  
The Core ◽  
Core Fragment ◽  
Negative Results ◽  
False Negative Results ◽  
Positive Results ◽  
Urine Specimens

Abstract Background: During pregnancy, human chorionic gonadotropin (hCG) immunoreactivity in urine consists of intact hCG as well as a number of hCG variants including the core fragment of hCGβ (hCGβcf). We identified 3 urine specimens with apparent false-negative results using the OSOM® hCG Combo Test (Genzyme Diagnostics) qualitative hCG device and sought to determine whether an excess of 1 of the fragments or variants might be the cause of the interference. Methods: We measured concentrations of hCG variants in the urine from 3 patients with apparent false-negative hCG results. Purified hCG variants were added to urines positive for hCG and tested using the OSOM, ICON® 25 hCG (Beckman Coulter), and hCG Combo SP® Brand (Cardinal Health) devices. Results: Dilution of these 3 urine samples resulted in positive results on the OSOM device. Quantification of hCG variants in each of the 3 patient urine specimens demonstrated that hCGβcf occurred in molar excess of intact hCG. Addition of purified hCGβcf to hCG-positive urines caused false-negative hCG results using the OSOM and ICON qualitative urine hCG devices. Conclusions: Increased concentrations of hCGβcf can cause false-negative results on the OSOM and ICON qualitative urine hCG devices. .

Ratio of urinary free immunoglobulin light chain κ to λ in the diagnosis of Bence Jones proteinuria

2004 ◽  
Vol 42 (4) ◽  
Author(s):  
Takanari Nakano ◽  
Atsuo Nagata ◽  
Hidenori Takahashi
Keyword(s):  
Light Chain ◽  
False Negative ◽  
Combination Method ◽  
Immunoglobulin Light Chain ◽  
Bence Jones Protein ◽  
Diagnostic Efficacy ◽  
Complementary Method ◽  
Negative Results ◽  
False Negative Results ◽  
Urine Specimens

AbstractThe aim of this study was to evaluate the diagnostic efficacy of the ratio of urinary free light chain (FLC) kappa to lambda (κ/λ ratio) for the detection of Bence Jones protein (BJP). Urine specimens were collected from 243 patients suspected of having BJP. Immunofixation identified 59 BJP-positive specimens among them. The κ/λ ratios of all specimens were determined by FLC immunoassays and then the cutoffs for the κ/λ ratio were defined as 5.5 for BJP κ and 0.1 for BJP λ by ROC curve analyses. Using the cutoffs, we detected abnormal κ/λ ratios in 51 (86%) of the 59 BJP-positives and 11 (6%) of the 184 BJP-negatives identified by the results of immunofixation. High-resolution urinary protein electrophoresis (UPE), a sensitive method for BJP screening, showed almost equal sensitivity to the κ/λ ratio, detecting monoclonal band(s) in 52 (88%) of the 59 BJP-positives. However, in UPE analysis these positive specimens should be followed by redundant immunofixation analysis to determine the isotypes. We further evaluated the combination method of FLC assays with UPE that correctly diagnosed 82% of the specimens as positive or negative for BJP, with only two false-negative results. These results suggest that quantitative FLC immunoassays provide an alternative or complementary method for the detection of BJP.

Decreased signal in Emit assays of drugs of abuse in urine after ingestion of aspirin: potential for false-negative results

1994 ◽  
Vol 40 (4) ◽  
pp. 608-612 ◽  
Author(s):  
R E Wagener ◽  
M W Linder ◽  
R Valdes
Keyword(s):  
High Frequency ◽  
Drugs Of Abuse ◽  
False Negative ◽  
Drug Analysis ◽  
Negative Bias ◽  
Negative Results ◽  
False Negative Results ◽  
Therapeutic Doses ◽  
Drug Free ◽  
Urine Specimens

Abstract During routine drug analysis with the Syva d.a.u. Emit immunoassays we observed a high frequency of urines with lower rates of changes in absorbance (delta A R) than the rate for a drug-free urine calibrator. Many of these urines contained salicylates. Among 40 urines with apparent salicylate concentrations between 15 and 420 mg/dL tested for benzoylecgonine (BE), 20 had delta A R < -4 (range +2 to -28 mA/min). The rates decreased with increasing salicylate: delta A R = -0.057 x (salicylate, mg/dL) -0.22 mA/min (r = 0.85, n = 40, P < 0.01). Urines from 100 control subjects (no salicylate) had mean +/- SD delta A R values of -1.05 +/- 2.2 mA/min (range +3 to -7; only two were < -4 mA/min). Although direct addition of salicylic acid (200 mg/dL) to urine specimens did not reproduce the negative bias, ingestion of aspirin (acetylsalicylic acid) did by -0.09 mA/min per 1 mg/dL (72.4 mumol/L) salicylate. Negative biases observed for other Emit d.a.u. assays after salicylate ingestion lead us to conclude that ingestion of therapeutic doses of aspirin may cause false-negative results for drug screens in urines by this technology.

Onychomycosis Infections

2017 ◽  
Vol 107 (4) ◽  
pp. 280-286 ◽  
Author(s):  
Aditya K. Gupta ◽  
Kerry-Ann Nakrieko
Keyword(s):  
False Negative ◽  
Kappa Statistic ◽  
False Negatives ◽  
Negative Results ◽  
False Negative Results ◽  
Repeated Sampling ◽  
Polymerase Chain ◽  
Serial Samples ◽  
Repeated Samples ◽  
Infecting Organisms

Background: Mycological culture is the traditional method for identifying infecting agents of onychomycosis despite high false-negative results, slower processing, and complications surrounding nondermatophyte mold (NDM) infections. Molecular polymerase chain reaction (PCR) methods are faster and suited for ascertaining NDM infections. Methods: To measure agreement between culture and PCR methods for identification of infecting species of suspected onychomycosis, single toenail samples from 167 patients and repeated serial samples from 43 patients with suspected onychomycosis were processed by culture and PCR for identification of 16 dermatophytes and five NDMs. Agreement between methods was quantified using the kappa statistic (κ). Results: The methods exhibited fair agreement for the identification of all infecting organisms (single samples: κ = 0.32; repeated samples: κ = 0.38). For dermatophytes, agreement was moderate (single samples: κ = 0.44; repeated samples: κ = 0.42). For NDMs, agreement was poor with single samples (κ = 0.16) but fair with repeated samples (κ = 0.25). Excluding false-negative reports from analyses improved agreement between methods in all cases except the identification of NDMs from single samples. Conclusions: Culture was three or four times more likely to report a false-negative result compared with PCR. The increased agreement between methods observed by excluding false-negative reports statistically clarifies and highlights the major discord caused by false-negative cultures. The increased agreement of NDM identification from poor to fair with repeated sampling along with their poor agreement in the single samples, with and without false-negatives, affirms the complications of NDM identification and supports the recommendation that serial samples help confirm the diagnosis of NDM infections.

scholarly journals FALSE-NEGATIVE RESULTS IN SCREENING PROGRAMS

2001 ◽  
Vol 17 (2) ◽  
pp. 164-170 ◽  
Author(s):  
Mark Petticrew ◽  
Amanda Sowden ◽  
Deborah Lister-Sharp
Keyword(s):  
Negative Impact ◽  
Relevant Literature ◽  
False Negative ◽  
Quantitative Information ◽  
Public Confidence ◽  
Psychological Consequences ◽  
False Negatives ◽  
Screening Programs ◽  
Negative Results ◽  
False Negative Results

Objectives: Assessment of the appropriateness of screening programs involves consideration of the harms as well as the benefits. These harms include the risk of false-negative results, the consequences of which have remained underinvestigated. This paper reports the results of a systematic literature review that aimed to assess the medical psychological, economic, and legal consequences of false-negative results in national screening programs.Methods: The review included a comprehensive literature search and contact with experts to identify relevant literature. Most studies that were identified presented only anecdotal evidence. However, thirteen studies presented quantitative information on medical consequences of false negatives, eight studies presented information on psychological consequences, and two studies presented information on economic consequences.Results: The strength of evidence from most of the primary studies was low. There is some evidence, however, that false-negative results may have a large legal impact. There is also a consensus in the literature that false negatives may have a negative impact on public confidence on screening; evidence is however limited.Conclusions: False negatives are evident even in high-quality screening programs. They may have the potential to delay the detection of breast and cervical cancer, but there is little evidence to help in assessing their psychological consequences. They also may lead to legal action being taken by those affected and may reduce public confidence in screening. Their impact may be reduced by provision of full information to participants about the benefits and limitations of screening programs and by increasing public education on these issues.

scholarly journals Simplified microscopy for rapid detection of significant bacteriuria in random urine specimens

1978 ◽  
Vol 7 (3) ◽  
pp. 286-289
Author(s):  
G K Barbin ◽  
J D Thorley ◽  
J A Reinarz
Keyword(s):  
False Negative ◽  
Rapid Screening ◽  
Negative Results ◽  
Microscopy Technique ◽  
Gram Staining ◽  
False Negative Results ◽  
Significant Bacteriuria ◽  
Urine Microscopy ◽  
Positive Results ◽  
Urine Specimens

Simplified urine microscopy, nitrite testing, and dipstick culture were compared with urine loop streak culture colony counts in 219 random voided specimens to determine the accuracy of the three rapid screening techniques. Nitrite testing resulted in 65% false negative results, which could not be significantly improved by incubation at 37 degrees C but which could be improved by adding nitrate substrate before incubation. Dipstick culture could not be quantitated until after 18 h of incubation. A new, simplified microscopy technique, using unspun, unstained urine, resulted in 4% false negative results and 4% false positive results in specimens containing over 10(5) organisms per ml and was the best method Centrifuges, Gram staining reagents, and counting chambers are not necessary for accurate microscopic screening of random urine specimens for the presence of bacteriuria by this technique, and the results are immediately available.

scholarly journals Analysis and Prediction of COVID-19 Patients’ False Negative Results for SARS-CoV-2 Detection with Pharyngeal Swab Specimen: A Retrospective Study

2020 ◽  
Author(s):  
Hui Xu ◽  
Li Yan ◽  
Chun (Martin) Qiu ◽  
Bo Jiao ◽  
Yanyan Chen ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Time Window ◽  
Clinical Symptoms ◽  
False Negative ◽  
Ct Imaging ◽  
Nucleic Acid Detection ◽  
False Negatives ◽  
Negative Results ◽  
False Negative Results ◽  
Blood Routine

ABSTRACTBackgroundFalse negative results of SARS-CoV-2 nucleic acid detection pose threats to COVID-19 patients and medical workers alike.ObjectiveTo develop multivariate models to determine clinical characteristics that contribute to false negative results of SARS-CoV-2 nucleic acid detection, and use them to predict false negative results as well as time windows for testing positive.DesignRetrospective Cohort Study (Ethics number of Tongji Hospital: No. IRBID: TJ-20200320)SettingA database of outpatients in Tongji Hospital (University Hospital) from 15 January 2020 to 19 February 2020.Patients1,324 outpatients with COVID-19MeasurementsClinical information on CT imaging reports, blood routine tests, and clinic symptoms were collected. A multivariate logistic regression was used to explain and predict false negative testing results of SARS-CoV-2 detection. A multivariate accelerated failure model was used to analyze and predict delayed time windows for testing positive.ResultsOf the 1,324 outpatients who diagnosed of COVID-19, 633 patients tested positive in their first SARS-CoV-2 nucleic acid test (47.8%), with a mean age of 51 years (SD=14.9); the rest, which had a mean age of 47 years (SD=15.4), tested negative in the first test. “Ground glass opacity” in a CT imaging report was associated with a lower chance of false negatives (aOR, 0.56), and reduced the length of time window for testing positive by 26%. “Consolidation” was associated with a higher chance of false negatives (aOR, 1.57), and extended the length of time window for testing positive by 44%. In blood routine tests, basophils (aOR, 1.28) and eosinophils (aOR, 1.29) were associated with a higher chance of false negatives, and were found to extend the time window for testing positive by 23% and 41%, respectively. Age and gender also affected the significantly.LimitationData were generated in a large single-center study.ConclusionTesting outcome and positive window of SARS-CoV-2 detection for COVID-19 patients were associated with CT imaging results, blood routine tests, and clinical symptoms. Taking into account relevant information in CT imaging reports, blood routine tests, and clinical symptoms helped reduce a false negative testing outcome. The predictive AFT model, what we believe to be one of the first statistical models for predicting time window of SARS-CoV-2 detection, could help clinicians improve the accuracy and efficiency of the diagnosis, and hence, optimizes the timing of nucleic acid detection and alleviates the shortage of nucleic acid detection kits around the world.Primary Funding SourceNone.

scholarly journals Evaluation of an adenosine 5'-triphosphate assay as a screening method to detect significant bacteriuria

1976 ◽  
Vol 3 (1) ◽  
pp. 42-46
Author(s):  
D N Alexander ◽  
G M Ederer ◽  
J M Matsen
Keyword(s):  
False Negative ◽  
Screening Method ◽  
Culture Method ◽  
Clinical Microbiology Laboratory ◽  
University Of Minnesota ◽  
Atp Assay ◽  
Negative Results ◽  
False Negative Results ◽  
Significant Bacteriuria ◽  
Urine Specimens

The bioluminescent reaction of adenosine 5'-triphosphate (ATP) with luciferin and luciferase has been used in conjunction with a sensitive photometer (Lab-Line's ATP photometer) to detect significant bacteriuria in urine. This rapid method of screening urine specimens for bacteriuria was evaluated by using 348 urine specimens submitted to the clinical microbiology laboratory at the University of Minnesota Hospitals for routine culture using the calibrated loop-streak plate method. There was 89.4% agreement between the culture method and the ATP assay, with 7.0% false positive and 27.0% false negative results from the ATP assay using 10(5) organisms/ml of urine or greater as positive for significant bacteriuria and less than 10(5) organisms/ml as negative for significant bacteriuria.

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