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Screening false-positive result

Shafiq Q, Mutgi A. Urine opiate screening false-positive result with levofloxacin. CMAJ 2010 182(15) 1644-5. [Pg.420]

A systematic study was carried out using in parallel 50 standard solutions for each concentration of three natural colorants (curcumin, carminic acid, and caramel as yellow, red, and brown, respectively). No false positive results for synthetics were obtained up to concentrations of 15 and 20 ng/ml for natural red and yellow colorants, respectively, or 110 ng/ml for natural brown colorant. The concentrations have to be high enough to prove that the screening method is able to accurately discriminate natural and synthetic colorants. To make a clear interpretation of the quantitative UV-Vis spectrum, linear regression analysis was used. Quantitative UV-Vis analysis of a dye ° can be calculated according to the following formula ... [Pg.540]

Structurally related compounds may cross-react with the antibody, yielding inaccurate results. In screening for the herbicide alachlor in well water by immunoassay, a number of false positives were reported when compared with gas chromatography (GC) analysis. A metabolite of alachlor was found to be present in the samples and it was subsequently determined that the cross-reactivity by this metabolite accounted for the false-positive results. On the other hand, cross-reactivity by certain structural analogs may not be an issue. For example, in an assay for the herbicide atrazine, cross-reactivity by propazine is 196% because of atrazine and propazine field use... [Pg.646]

An assay or screen is said to exhibit ROBUSTNESS when it has a high discriminatory power and produces a low number of FALSE NEGATIVE and FALSE POSITIVE results. [Pg.80]

Drug/Lab test interactions False-positive results may occur in screening tests for pheochromocytoma in patients who are being treated with prazosin. [Pg.562]

Abdenur JE, Chamoles NA, Guinle AE, Schenone AB, Fuertes AN (1998) Diagnosis of isovaleric acidaemia by tandem mass spectrometry false positive result due to pivaloylcarnitine in a newborn screening programme. J Inherit Metab Dis 21 624-630... [Pg.206]

The pattern of urinary GAGs should be assessed in a case of a positive urinary MPS screening result or when clinical symptoms are suggestive of MPS despite normal GAG excretion. This also facilitates the choice of further enzymatic studies. In addition, approximately 5-6% of abnormal samples in the quantitative DMB method are false-positive results that can usually be identified as such by checking the distribution of GAG excretion [16]. [Pg.299]

Screening tests for PBG are based on its reaction with DMAB (modified Ehrlichs reaction ). We recommend the trace PBG test kit available from Thermo Electron (UK), which isolates PBG from urine by ion-exchange resin before the reaction with DMAB. Older screening methods, such as those of Schwartz or Hoesch, give false-positive results due to the reaction of DMAB with urea, which is abundant in urine. [Pg.755]

Methods used in the screening phase should prevent false-negative results and provide an acceptable percentage of false-positive results with a high sample throughput at low cost. Methods used in the confirmation phase should prevent false-positive results such methods usually have low sample throughput and a high cost, but enable the surveillance to be spread more comprehensively than would be the case if all samples had to be initially analyzed by time-, labor- and cost-intensive laboratory methods. Finally methods used in the intermediate phase should tentatively identify and, sometimes, quantify the type of residues. [Pg.765]

Residues of TCs were quantified via the MCAC-HPLC method (26) in pork and chicken muscle tissue that had been previously screened with both a microbiological inhibition test using B. subtilis and an ELISA method. The correlation between the mean area of the inhibition zones and the DXC levels found in 28 samples by HPLC was 0.82 the correlation between the ELISA results and the DXC levels in the same samples was 0.73. The results indicated that an inhibition test was well suited to screen the mentioned samples for TCs residues. The authors found the more expensive ELISA screening test unnecessary, because only a minority of analyzed samples did not contain TCs. Confirmation with HPLC method was necessary because of the presence of some false-positive results. Moreover, the positive results from LC-fluorescence assay were confirmed using LC-MS-MS assay with electrospray ionization working in positive-ion mode (31). [Pg.629]

However, problems associated with the reproducibility between electrodes derived from the screen-printing process and the partial electrode fouling have compromised the sensitivity of the biosensors. Work is in progress to improve both the reproducibility and the limits of detection by the use of new types of electrodes. The toxin overestimation observed with the amperometric biosensor, in the case of the microcystin analysis, suggests the use in parallel to other analytical techniques in order to minimise the risk of false-positive results. Nevertheless, the electrochemical strategy is appropriate to discriminate between toxic/non-toxic samples. [Pg.347]

This model was developed by Suswillo and Denham [22-24] for evaluation of filaricidal activity, in which jirds are infected by intraperitoneal implantation of ten female and five male B. pahangi. After 3 days, the compounds are administered either orally or by subcutaneous injection. The intraperitoneal injection of drugs may provide false positive results because some compounds remain concentrated at this site. This model is suitable for secondary screening of new drugs for micro- and macrofilaricidal activity. [Pg.235]

It is also desirable that a screening test should have a low incidence of false positive results. (False positives will occur if the test is sensitive to other, similar compounds - such as natural substances in the tissue - or metabolites.) A high incidence of false positives will limit the cost-effectiveness of the screening method because unnecessary and often costly confirmatory tests will need to be performed. [Pg.135]

What are the limitations of the screening method (false negative and false positive results) ... [Pg.175]

Free Thyroxine. Measurement of free T4 radioimmunoassay in dried blood samples has been found to be useful to avoid false-positive results for low TBG in neonatal hypothyroid screening. Enzyme immunoassay of free T4 in serum was developed by Weetall et al. (W7) and subsequently by us (16). [Pg.99]

TBG in dried blood samples on filter paper is stable for at least 1 month when kept dry at room temperature. The mean coefficients of variation are 6.6% (within assay) and 5.9% (between assays). The concentrations of TBG in dried blood samples determined by this method correlated well with those in serum determined by radioimmunoassay (r = 0.95) and by enzyme immunoassay (r = 0.96). This method is applicable for detecting patients with congenital TBG deficiency who do not need to be treated and avoids the false-positive results obtained on neonatal screening with T4. [Pg.102]


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See also in sourсe #XX -- [ Pg.85 ]




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Screening false positives

Screening positive

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