EVALUATION OF SCREENING TESTS FOR URINARY MUCOPOLYSACCHARIDES

PEDIATRICS ◽  
1973 ◽  
Vol 52 (1) ◽  
pp. 64-68
Author(s):  
Iraj Rezvani ◽  
P. J. Collipp ◽  
Angelo M. DiGeorge
Keyword(s):  
False Positive ◽  
Screening Test ◽  
False Positives ◽  
Spot Test ◽  
Screening Tests ◽  
Paper Test ◽  
Normal Children ◽  
Great Caution ◽  
Turbidity Test ◽  
Positive Results

A recently developed spot test, "MPS paper," has been added to other screening tests for urinary mucopolysaccharides. The effectiveness of this test has been compared to that of the cetytrimethylammonium bromide and the acid albumin gross turbidity tests in normal children and in patients with mucopolysaccharidoses. Although all these tests are effective in the detection of excessive mucopolysaccharides in urine, their excessive sensitivity yields many weak false-positives. We found "MPS paper" test to yield 34% false-positive tests, compared to 42% for cetytrimethylammonium bromide and 8% for the acid albumin gross turbidity test. We have concluded that the acid albumin gross turbidity is the most reliable screening test for detection of mucopolysaccharide disorders. "MPS paper" spot test has the advantage of being simple and practical, but weak positive results should be interpreted with great caution; it has the added disadvantage of being the most costly of the screening tests at the present time.

Recognition of the Mucopolysaccharidoses by Four Screening Tests, including a Refinement of the Albumin Turbidity Test, and Their Differentiation by Electrophoretic Separation of Urinary Glycosaminoglycans

1974 ◽  
Vol 11 (1-6) ◽  
pp. 67-71 ◽  
Author(s):  
P. W. Lewis ◽  
D. N. Raine ◽  
J. F. Kennedy
Keyword(s):  
Differential Diagnosis ◽  
Urinary Excretion ◽  
False Positive ◽  
Normal Subjects ◽  
Screening Tests ◽  
Electrophoretic Separation ◽  
Bovine Albumin ◽  
Turbidity Test ◽  
Urinary Glycosaminoglycans ◽  
Positive Results

Urinary excretion of mucopolysaccharides by normal subjects and patients with a mucopolysaccharidosis has been assessed by four screening tests including two quantitative determinations. Inclusion of a urine blank has been shown to reduce the number of false positive results given by the bovine albumin turbidity test. An electrophoretic technique has been developed and applied to urine concentrates. It has proved useful in the differential diagnosis of the mucopolysaccharidoses since four types are distinguished by characteristic glycosaminoglycan band patterns and another glycosaminoglycan pattern characterises two further types.

Properly collected plasma metanephrines excludes PPGL after false positive screening tests

2021 ◽  
Author(s):  
Gregory A Kline ◽  
Jessica Boyd ◽  
Brenda Polzin ◽  
Adrian Harvey ◽  
Janice L Pasieka ◽  
...  
Keyword(s):  
False Positive ◽  
Adrenal Mass ◽  
Chart Review ◽  
False Positive Rate ◽  
Total Positivity ◽  
Screening Tests ◽  
Positive Rate ◽  
Plasma Metanephrines ◽  
Positive Results ◽  
Urine Metanephrines

Abstract Context False positive results are common for pheochromocytoma/paraganglioma(PPGL) real-world screening. Objective Determine the correlation between screening urine and seated plasma metanephrines in outpatients where PPGL was absent, compared to meticulously prepared and supine-collected plasma metanephrines with age-adjusted references. Design Retrospective cohort study Setting Databases from a single-provider provincial laboratory(2012-2018), a validated PPGL registry and a manual chart review from a specialized endocrine testing unit. Patients PPGL registry data excluded known PPGL cases from the laboratory database. Outpatients having both urine and plasma metanephrines <90 days apart. Methods The correlation between urine and seated plasma measures along with the total positivity rate. All cases of plasma metanephrines drawn in the endocrine unit were reviewed for test indication and test positivity rate. Results There were 810 non-PPGL pairs of urine and plasma metanephrines in the laboratory database; 46.1% of urine metanephrines were reported high. Of seated outpatient plasma metanephrines drawn a median of 5.9 days later, 19.2% were also high (r=0.33 and 0.50 for normetanephrine and metanephrine, respectively). In contrast, the meticulously prepared and supine collected patients(n=139, 51% prior high urine metanephrines) had <3% rate of abnormal high results in patients without known PPGL/adrenal mass. Conclusions There was a poor-to-moderate correlation between urine and seated plasma metanephrines. Up to 20% of those with high urine measures also had high seated plasma metanephrines in the absence of PPGL. Properly prepared and collected supine plasma metanephrines had a false positive rate of <3% in the absence of known PPGL/adrenal mass.

scholarly journals Biosensor Analysis of β-Lactams in Milk Using the Carboxypeptidase Activity of a Bacterial Penicillin Binding Protein

2006 ◽  
Vol 89 (3) ◽  
pp. 832-837 ◽  
Author(s):  
Åse SternesjÖ ◽  
Eva Gustavsson
Keyword(s):  
False Positive ◽  
Polyclonal Antibodies ◽  
Active Form ◽  
False Negative ◽  
Screening Tests ◽  
Receptor Protein ◽  
Penicillin G ◽  
Penicillin Binding Protein ◽  
Spr Biosensor ◽  
Positive Results

Abstract The applicability of a -lactam receptor protein for detection of β-lactam antibiotics in milk using surface plasmon resonance (SPR) biosensor technology was investigated. The advantage of using a receptor protein instead of antibodies for detection of β-lactams is that a generic assay, specific for the active form of the β-lactam structure, is obtained. Two assays based on the enzymatic activity of the dd-carboxypeptidase from Actinomadura R39 were developed, using a Biacore SPR biosensor. The carboxypeptidase converts a tri-peptide into a di-peptide, a reaction which is inhibited in the presence of β-lactams. Polyclonal antibodies against the 2 peptides were developed and used to measure the amount of enzymatic product formed (di-peptide assay) or the amount of remaining enzymatic substrate (tri-peptide assay), respectively. The 2 assays showed similar performances with respect to detection limits (1.2 and 1.5 μg/kg, respectively) and precision (coefficient of variation <5%) for penicillin G in milk. Several other β-lactams were detected at or near their respective maximum residue limit. Furthermore, the 2 peptide assays were evaluated against 5 commercial kit tests in the screening of 195 producer milk samples. The biosensor assays showed 0% false-negative and 27% false-positive results, whereas the figures were 0% false-negative and 2753% false-positive results for other screening tests investigated.

Clinical Evaluation of the VMA Test Strip

PEDIATRICS ◽  
1973 ◽  
Vol 51 (1) ◽  
pp. 153-153
Author(s):  
Lawrence Helson ◽  
Victor Bethune ◽  
Morton K. Schwartz
Keyword(s):  
Clinical Evaluation ◽  
False Positive ◽  
Screening Test ◽  
Test Strip ◽  
False Positives ◽  
Vanillylmandelic Acid ◽  
Children With Cancer

The VMA test strip, based upon detection of increased amounts of vanillylmandelic acid (VMA) and metanephrine in urine has had wide publicity as a reliable screening test for neuroblastoma. Its authors report that of a total of 20,000 tests administered, 50, or roughly one per 400 were false-positives. Of these false-positive tests, 15, or 30% were in children with other cancers. Urines from each of 24 children with neuroblastoma tested positive.1 We evaluated the test strip in an ambulatory group of 50 children with cancer, which included eight children with disseminated neuroblastoma and seven other children with histologically proven, treated, and clinically inactive neuroblastoma.

scholarly journals Screening for Occult Gastrointestinal Bleeding in Hospital Patients

1981 ◽  
Vol 74 (1) ◽  
pp. 41-43 ◽  
Author(s):  
I G Barrison ◽  
E R Littlewood ◽  
J Primavesi ◽  
A Sharpies ◽  
I T Gilmore ◽  
...  
Keyword(s):  
General Practice ◽  
Gastrointestinal Bleeding ◽  
False Positive ◽  
Screening Test ◽  
False Positive Rate ◽  
False Positives ◽  
Occult Gastrointestinal Bleeding ◽  
Hospital Patients ◽  
Positive Rate ◽  
Hospital Inpatients

Stools have been tested for occult gastrointestinal bleeding in 278 outpatients and 170 hospital inpatients using the Haemoccult and Haemastix methods. Seventeen outpatients (6.1%) and 42 inpatients (24.7%) were positive with the Haemoccult technique. Thirty-three outpatients (11.9%) and 93 inpatients (54.7%) were positive with the Haemastix test. Following investigation of the Haemoccult-positive patients, only 2 cases (3.4%) were considered false positives. However, the false positive rate with Haemastix was 22.9% which is unacceptable in a screening test. Haemoccult may be useful as a screening test for asymptomatic general practice patients, but a test of greater sensitivity is needed for hospital patients.

scholarly journals Second Tier Molecular Genetic Testing in Newborn Screening for Pompe Disease: Landscape and Challenges

2020 ◽  
Vol 6 (2) ◽  
pp. 32 ◽  
Author(s):  
Laurie D. Smith ◽  
Matthew N. Bainbridge ◽  
Richard B. Parad ◽  
Arindam Bhattacharjee
Keyword(s):  
Genetic Testing ◽  
Newborn Screening ◽  
Pompe Disease ◽  
False Positive ◽  
Clinical Decision Making ◽  
Molecular Genetic ◽  
Screening Tests ◽  
Molecular Genetic Testing ◽  
Second Tier ◽  
Positive Results

Pompe disease (PD) is screened by a two tier newborn screening (NBS) algorithm, the first tier of which is an enzymatic assay performed on newborn dried blood spots (DBS). As first tier enzymatic screening tests have false positive results, an immediate second tier test on the same sample is critical in resolving newborn health status. Two methodologies have been proposed for second tier testing: (a) measurement of enzymatic activities such as of Creatine/Creatinine over alpha-glucosidase ratio, and (b) DNA sequencing (a molecular genetics approach), such as targeted next generation sequencing. (tNGS). In this review, we discuss the tNGS approach, as well as the challenges in providing second tier screening and follow-up care. While tNGS can predict genotype-phenotype effects when known, these advantages may be diminished when the variants are novel, of unknown significance or not discoverable by current test methodologies. Due to the fact that criticisms of screening algorithms that utilize tNGS are based on perceived complexities, including variant detection and interpretation, we clarify the actual limitations and present the rationale that supports optimizing a molecular genetic testing approach with tNGS. Second tier tNGS can benefit clinical decision-making through the use of the initial NBS DBS punch and rapid turn-around time methodology for tNGS, that includes copy number variant analysis, variant effect prediction, and variant ‘cut-off’ tools for the reduction of false positive results. The availability of DNA sequence data will contribute to the improved understanding of genotype-phenotype associations and application of treatment. The ultimate goal of second tier testing should enable the earliest possible diagnosis for the earliest initiation of the most effective clinical interventions in infants with PD.

The spot test is not a reliable screening procedure for mucopolysaccharidoses

1991 ◽  
Vol 37 (4) ◽  
pp. 572-575 ◽  
Author(s):  
J G N de Jong ◽  
J J F Hasselman ◽  
A A J van Landeghem ◽  
H L Vader ◽  
R A Wevers
Keyword(s):  
False Positive ◽  
False Negative ◽  
Spot Test ◽  
Urine Samples ◽  
Screening Procedure ◽  
Negative Results ◽  
False Negative Results ◽  
Spot Tests ◽  
Metabolic Screening ◽  
Positive Results

Abstract To check the reliability of the Ames MPS paper spot test, which is based on the Azure A dye, we sent a series of urine samples to three laboratories where the spot test is part of the metabolic screening for mucopolysaccharidoses. In these laboratories false-negative results ranged between 19% and 35% and false-positive results ranged between 12% and 29% of all samples submitted. In contrast, the quantitative dimethylmethylene blue test (Clin Chem 1989;35:1472-7) detected an increased glycosaminoglycan content in all urine samples from mucopolysaccharidosis patients and gave no false-positive results. In the latter procedure, glycosaminoglycan content is expressed per millimole of creatinine, and age-dependent reference values are used. We conclude that the Ames spot test and other spot tests are unreliable as a screening procedure for mucopolysaccharidoses and should not be used to screen for these diseases.

scholarly journals Efavirenz Treatment and False‐Positive Results in Benzodiazepine Screening Tests

2009 ◽  
Vol 48 (12) ◽  
pp. 1787-1789 ◽  
Author(s):  
Antje Blank ◽  
Victoria Hellstern ◽  
Dieter Schuster ◽  
Martin Hartmann ◽  
Anne K. Matthée ◽  
...  
Keyword(s):  
False Positive ◽  
Screening Tests ◽  
Positive Results

scholarly journals Do we cause false positives? An experimental series on droplet or airborne SARS-CoV-2 contamination of sampling tubes during swab collection in a test center

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Thomas Scheier ◽  
Cyril Shah ◽  
Michael Huber ◽  
Hugo Sax ◽  
Barbara Hasse ◽  
...  
Keyword(s):  
Infection Control ◽  
False Positive ◽  
False Positives ◽  
Experimental Series ◽  
Airborne Contamination ◽  
Rapid Spread ◽  
Time Periods ◽  
Short Time ◽  
Time Frames ◽  
Positive Results

AbstractThe rapid spread of the coronavirus disease 2019 pandemic urged immense testing capacities as one cornerstone of infection control. Many institutions opened outpatient SARS-CoV-2 test centers to allow large number of tests in comparatively short time frames. With increasing positive test rates, concerns for a possible airborne or droplet contamination of specimens leading to false-positive results were raised. In our experimental series performed in a dedicated SARS-CoV-2 test center, 40 open collection tubes placed for defined time periods in proximity to individuals were found to be SARS-CoV-2 negative. These findings argue against false-positive SARS-CoV-2 results due to droplet or airborne contamination.

The LaBrosse Spot Test: A Practical Aid in the Diagnosis and Management of Children with Neuroblastoma

PEDIATRICS ◽  
1971 ◽  
Vol 47 (5) ◽  
pp. 913-915
Author(s):  
Audrey E. Evans ◽  
Judith Blore ◽  
Richard Hadley ◽  
Sakir Tanindi
Keyword(s):  
False Positive ◽  
Mandelic Acid ◽  
Spot Test ◽  
Vanillylmandelic Acid ◽  
Diagnosis And Management ◽  
Quantitative Measurements ◽  
Routine Work ◽  
Strict Diet ◽  
Work Up ◽  
Positive Results

Measurement of vanillylmandelic acid (4-hydroxy-3 methoxy-mandelic acid or VMA) in the urine of patients with neuroblastoma has become part of the routine work up, since its presence was described by Voorhess and Gardner in 1960.1 When quantitative measurements of this catecholamine metabolite are performed, the patient must be placed on a strict diet for 2 to 3 days to eliminate substances whose breakdown products appear in the urine and give false positive results. The numerous items which must be excluded are beverages such as tea, colas, and Kcol-Aid, desserts and pastries flavored with chocolate and vanilla, and a variety of fruits including oranges, bananas, grapes, and tomatoes.

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