scholarly journals False positive antigen test for Dirofilaria immitis after heat treatment of the blood sample in a microfilaremic dog infected with Acanthocheilonema dracunculoides

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Viktor Szatmári ◽  
Martin Willem van Leeuwen ◽  
Christine Jantine Piek ◽  
Luigi Venco
Keyword(s):  
Heat Treatment ◽  
Blood Sample ◽  
Real Time ◽  
Real Time Pcr ◽  
False Positive ◽  
Dirofilaria Immitis ◽  
False Negative ◽  
Correct Identification ◽  
Test Results ◽  
Antigen Test

Abstract Background Dirofilaria immitis is responsible for heartworm disease in dogs in endemic areas worldwide. Screening for this infection is done by blood tests. Antigen testing is the most sensitive method to detect an infection with adult (female) worms. Microscopic examination of a blood smear or Knott’s test can be used to detect circulating microfilariae, the infective larvae. To increase the sensitivity of the antigen test by decreasing the false negative test results, heating of the blood sample has been recommended in recent guidelines. Heating is believed to remove blocking immune-complexes. Circulating microfilariae are not specific findings for heartworm infection, as other nematodes (among others, Acanthocheilonema dracunculoides) can also result in microfilaremia. Although the type of microfilariae cannot be determined by microscopy alone, real-time PCR can reliably identify the infecting nematode species. Correct identification of the parasite is of major importance, as an infection with D. immitis requires antiparasitic therapy, whereas A. dracunculoides is thought to be a clinically irrelevant coincidental finding. The present case report describes a microfilaremic dog where the initial antigen test for D. immitis turned positive after heat treatment, whereas real-time PCR revealed that the microfilariae were A. dracunculoides (syn. Dipetalonema dracunculoides). Results A circa 5-year old, asymptomatic Spanish mastiff dog was referred for heartworm therapy because microfilariae were found via a screening blood test. The dog was recently imported to the Netherlands from Spain, where it had been a stray dog. Antigen tests on a plasma sample for D. immitis were performed with three different test kits, which all turned out to be negative. However, heat treatment of two of these samples were carried out and both of them led to a positive antigen test result. Real-time PCR showed that the circulating microfilariae belonged to A. dracunculoides species. Three administrations of moxidectin spot-on at monthly intervals resulted in a negative antigen and a negative Knott’s tests one month after the last treatment. Conclusions We conclude that heat treatment of initially negative blood samples for D. immitis could lead to false positive antigen test results if the dog is infected with A. dracunculoides.

Detection of Streptococcus pneumoniae in Sputum Samples by Real- Time PCR.

2020 ◽  
Vol 18 ◽  
Author(s):  
Pegah Shakib ◽  
Mohammad Reza Zolfaghari
Keyword(s):  
Streptococcus Pneumoniae ◽  
Real Time ◽  
Real Time Pcr ◽  
False Negative ◽  
Cross Sectional Study ◽  
Laboratory Culture ◽  
Cross Sectional ◽  
Negative Results ◽  
False Negative Results ◽  
Pcr Method

Background: Conventional laboratory culture-based methods for diagnosis of Streptococcus pneumoniae are time-consuming and yield false negative results. Molecular methods including real-time (RT)-PCR rapid methods and conventional PCR due to higher sensitivity and accuracy have been replaced instead traditional culture assay. The aim of the current study was to evaluate lytA gene for detection of Streptococcus pneumoniae in the cerebrospinal fluid of human patients with meningitis using real-time PCR assay. Material and Methods: In this cross-sectional study, a total of 30 clinical specimens were collected from patients in a period from September to December 2018. In order to evaluate the presence of lytA gene, conventional and real-time PCR methods were used without culture. Results: From 30 sputum samples five (16.66%) isolates were identified as S. pneumoniae by lytA PCR and sequencing. Discussion: In this research, an accurate and rapid real-time PCR method was used, which is based on lytA gene for diagnosis of bacteria so that it can be diagnosed. Based on the sequencing results, the sensitivity for detection of lytA gene was 100% (5/5).

scholarly journals A misleading false-negative result of Pneumocystis real-time PCR assay due to a rare punctual mutation: A French multicenter study

2016 ◽  
Vol 55 (2) ◽  
pp. 180-184 ◽  
Author(s):  
Solène Le Gal ◽  
Florence Robert-Gangneux ◽  
Yann Pépino ◽  
Sorya Belaz ◽  
Céline Damiani ◽  
...  
Keyword(s):  
Real Time ◽  
Multicenter Study ◽  
Real Time Pcr ◽  
False Negative ◽  
False Negative Result ◽  
Pcr Assay

Three Years of Experience With Random Urinary Homovanillic and Vanillylmandelic Acid Levels in the Diagnosis of Neuroblastoma

PEDIATRICS ◽  
1987 ◽  
Vol 79 (2) ◽  
pp. 203-205
Author(s):  
Mendel Tuchman ◽  
Margaret L. R. Ramnaraine ◽  
William G. Woods ◽  
William Krivit
Keyword(s):  
False Positive ◽  
Homovanillic Acid ◽  
False Negative ◽  
False Negative Rate ◽  
Urine Samples ◽  
Vanillylmandelic Acid ◽  
Test Results ◽  
Upper Limit ◽  
Positive Results ◽  
Rule Out

During the last 3 years, random urine samples from 408 patients were tested for elevated homovanillic acid (HVA) and vanillylmandelic acid (VMA) levels to rule out the diagnosis of neuroblastoma. Thirty-seven of these patients had elevated HVA and/or VMA levels, and neuroblastoma was subsequently diagnosed. In three additional patients with negative test results (normal HVA and VMA levels), tumors were subsequently diagnosed (false-negative rate of 7.5%). Ten percent of the patients with neuroblastoma had normal HVA and 27.5% had normal VMA levels at the time of diagnosis. Only one patient (2.5%) with neuroblastoma had elevated VMA levels in the presence of normal HVA levels. More than 60% of the patients with neuroblastoma had urinary HVA and/or VMA levels higher than twice the upper limit of normal. No false-positive results were encountered. Age and stage distributions of the patients are shown, and the significance of the results is discussed.

scholarly journals False Negative Results in High Viremia Parvovirus B19-Samples Tested with Real-Time PCR

2010 ◽  
Vol 59 (2) ◽  
pp. 129-132 ◽  
Author(s):  
PIOTR GRABARCZYK ◽  
ALEKSANDRA KALIŃSKA ◽  
EWA SULKOWSKA ◽  
EWA BROJER
Keyword(s):  
Positive Result ◽  
Real Time ◽  
Real Time Pcr ◽  
Parvovirus B19 ◽  
False Negative ◽  
Immunocompromised Patients ◽  
Negative Results ◽  
False Negative Results ◽  
Parvovirus B 19 ◽  
The Way

Extremely high viremia is observed during some viruses infection, especialy in immunocompromised patients. False negative results of Parvovirus B 19 DNA tests performed with real-time PCR in high viremic samples are reported. The way of fluorescence diagrams analysis and algorithm of positive result confirmation to exclude such phenomenon are proposed.

scholarly journals False-Positive Aspergillus Galactomannan Antigen Test Results

2004 ◽  
Vol 39 (2) ◽  
pp. 289-290 ◽  
Author(s):  
J. Maertens ◽  
K. Theunissen ◽  
G. Verhoef ◽  
J. Van Eldere
Keyword(s):  
False Positive ◽  
Test Results ◽  
Antigen Test ◽  
Galactomannan Antigen

Multivariate interpretation of laboratory tests used in monitoring patients

1990 ◽  
Vol 36 (5) ◽  
pp. 748-751 ◽  
Author(s):  
H B Slotnick ◽  
P Etzell
Keyword(s):  
Small Groups ◽  
False Positive ◽  
Laboratory Tests ◽  
False Negative ◽  
Test Results ◽  
Laboratory Findings ◽  
Bonferroni Inequality ◽  
The Impact

Abstract This study demonstrates an approach to the problem of minimizing false-negative and false-positive laboratory findings. In this approach, we consider the fact that results of laboratory tests are correlated, utilize within-person test results to interpret current results, and minimize the impact of multivariate conservatism by examining test results in small groups. The procedure requires panels of tests to be divided into related subpanels, testing each subpanel independently, and using the Bonferroni inequality to determine whether any of the observed values for a given subpanel is "out-of-range." The procedure is demonstrated, and its limitations are observed and discussed.

scholarly journals Performance and Verification of a Real-Time PCR Assay Targeting thegyrAGene for Prediction of Ciprofloxacin Resistance in Neisseria gonorrhoeae: TABLE 1

2016 ◽  
Vol 54 (3) ◽  
pp. 805-808 ◽  
Author(s):  
P. Hemarajata ◽  
S. Yang ◽  
O. O. Soge ◽  
R. M. Humphries ◽  
J. D. Klausner
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Real Time ◽  
Real Time Pcr ◽  
The United States ◽  
Test Results ◽  
Pcr Assay ◽  
Content Type ◽  
Agar Dilution ◽  
Ciprofloxacin Resistance ◽  
To Receive

In the United States, 19.2% ofNeisseria gonorrhoeaeisolates are resistant to ciprofloxacin. We evaluated a real-time PCR assay to predict ciprofloxacin susceptibility using residual DNA from the Roche Cobas 4800 CT/NG assay. The results of the assay were 100% concordant with agar dilution susceptibility test results for 100 clinical isolates. Among 76 clinical urine and swab specimens positive forN. gonorrhoeaeby the Cobas assay, 71% could be genotyped. The test took 1.5 h to perform, allowing the physician to receive results in time to make informed clinical decisions.

scholarly journals Effects of sample handling on the detection of porcine reproductive and respiratory syndrome virus in oral fluids by reverse-transcription real-time PCR

2018 ◽  
Vol 30 (6) ◽  
pp. 807-812 ◽  
Author(s):  
Ashley C. Weiser ◽  
Korakrit Poonsuk ◽  
Sarah A. Bade ◽  
Phillip C. Gauger ◽  
Marisa Rotolo ◽  
...  
Keyword(s):  
Real Time ◽  
Reverse Transcription ◽  
Real Time Pcr ◽  
False Negative ◽  
Rna Extraction ◽  
Free Water ◽  
Negative Control ◽  
Respiratory Syndrome Virus ◽  
Sample Handling ◽  
Oral Fluids

We evaluated effects of handling procedures on detection of porcine reproductive and respiratory syndrome virus (PRRSV) in oral fluids (OFs) by reverse-transcription real-time PCR (RT-rtPCR). The experiments were conducted using a composite sample of PRRSV-positive OF collected from 5-wk-old pigs vaccinated 15 d earlier with a modified-live PRRSV vaccine. Five pre-extraction sample-handling steps and all combinations thereof were evaluated: 1) thaw temperature (4°C or 25°C); 2) sample diluent (1:1 dilution with nuclease-free water or guanidinium thiocyanate–phenol); 3a) sonication of the sample (yes or no); 3b) temperature (4°C or 25°C) at which step 3a was conducted; and 4) temperature at which the sample was maintained after step 3b and until RNA extraction was initiated (4°C or 25°C). All combinations of the 5 sample-handling steps (i.e., 32 unique treatments) were tested in a completely randomized factorial design with 4 replicates and 1 negative control for each treatment. The entire experiment was repeated on 5 separate days to produce a total of 800 PRRSV RT-rtPCR results. Binary (positive or negative) data were analyzed by logistic regression and results (Ct) were analyzed using a generalized linear model. Overall, 1 false-positive result was observed among 160 negative controls (99.4% specificity), and 85 false-negative results were observed among the 640 known-positive samples (86.7% sensitivity). The most significant factor affecting test outcome was thaw temperature (4°C or 25°C); samples thawed at 4°C had higher positivity rate (94% vs. 80%, p < 0.0001) and lower Ct (36.2 vs. 37.5, p < 0.0001).

Sign in / Sign up

Export Citation Format

Share Document