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.

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. .

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.

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.

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 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.

Mechanism of false-negative urine cannabinoid immunoassay screens by Visine eyedrops.

1989 ◽  
Vol 35 (4) ◽  
pp. 636-638 ◽  
Author(s):  
S D Pearson ◽  
K O Ash ◽  
F M Urry
Keyword(s):  
Benzalkonium Chloride ◽  
Drugs Of Abuse ◽  
Urine Analysis ◽  
False Negative ◽  
Gas Chromatography Mass Spectrometry ◽  
Negative Results ◽  
False Negative Results ◽  
Aqueous Solvent ◽  
Glass Specimen ◽  
Urine Specimens

Abstract To drug-free urine specimens, we added the following drugs of abuse to give concentrations twice the cutoff value for positive test results: 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (9-carboxy-THC), oxazepam, secobarbital, morphine, benzoylecgonine, amphetamine, or phencyclidine (PCP). Visine was then added. Although measured concentrations of several drugs were decreased in the presence of Visine, false-negative results were obtained only for 9-carboxy-THC for the EMIT-d.a.u. and TDx urine cannabinoid assays. Visine also decreased 9-carboxy-THC as measured by the Abuscreen assay. At low concentrations of Visine, false-negative cannabinoid results were attributable to the benzalkonium chloride ingredient of Visine. The added Visine was not detectable by routine urine analysis and had no effect on the activity of the glucose-6-phosphate dehydrogenase-drug conjugate used in the EMIT-d.a.u. assays. Moreover, analysis by gas chromatography/mass spectrometry showed no chemical modification or loss of 9-carboxy-THC in the Visine-adulterated urine specimens. However, Visine did increase the adhesion of 9-carboxy-THC to the borosilicate glass specimen containers. Results of ultrafiltration studies with Visine suggest that 9-carboxy-THC partitions between the aqueous solvent and the hydrophobic interior of benzalkonium chloride micelles, thereby reducing the availability of 9-carboxy-THC in antibody-based assays.

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.

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.

Sign in / Sign up

Export Citation Format

Share Document