scholarly journals Follow-Up SARS-CoV-2 PCR Testing Outcomes From a Large Reference Lab in the US

2021 ◽  
Vol 9 ◽  
Author(s):  
Adam Sullivan ◽  
David Alfego ◽  
Brian Poirier ◽  
Jonathan Williams ◽  
Dorothy Adcock ◽  
...  
Keyword(s):  
United States ◽  
Cohort Study ◽  
False Positive ◽  
False Positive Rate ◽  
The United States ◽  
Positive Test ◽  
Test Results ◽  
Rt Pcr ◽  
Positive Rate

By analyzing COVID-19 sequential COVID-19 test results of patients across the United States, we herein attempt to quantify some of the observations we've made around long-term infection (and false-positive rates), as well as provide observations on the uncertainty of sampling variability and other dynamics of COVID-19 infection in the United States. Retrospective cohort study of a registry of RT-PCR testing results for all patients tested at any of the reference labs operated by Labcorp® including both positive, negative, and inconclusive results, from March 1, 2020 to January 28, 2021, including patients from all 50 states and outlying US territories. The study included 22 million patients with RT-PCR qualitative test results for SARS-CoV-2, of which 3.9 million had more than one test at Labcorp. We observed a minuscule <0.1% basal positive rate for follow up tests >115 days, which could account for false positives, long-haulers, and/or reinfection but is indistinguishable in the data. In observing repeat-testing, for patients who have a second test after a first RT-PCR, 30% across the cohort tested negative on the second test. For patients who test positive first and subsequently negative within 96 h (40% of positive test results), 18% of tests will subsequently test positive within another 96-h span. For those who first test negative and then positive within 96 h (2.3% of negative tests), 56% will test negative after a third and subsequent 96-h period. The sudden changes in RT-PCR test results for SARS-CoV-2 from this large cohort study suggest that negative test results during active infection or exposure can change rapidly within just days or hours. We also demonstrate that there does not appear to be a basal false positive rate among patients who test positive >115 days after their first RT-PCR positive test while failing to observe any evidence of widespread reinfection.

Improving diagnosis of acute appendicitis with atypical findings by Tc-99m HMPAO leukocyte scan

2002 ◽  
Vol 41 (01) ◽  
pp. 37-41 ◽  
Author(s):  
S. Shung-Shung ◽  
S. Yu-Chien ◽  
Y. Mei-Due ◽  
W. Hwei-Chung ◽  
A. Kao
Keyword(s):  
Acute Appendicitis ◽  
False Positive ◽  
False Positive Rate ◽  
Accurate Method ◽  
Clinical Findings ◽  
Pathological Findings ◽  
Lower Quadrant ◽  
Predictive Values ◽  
Positive Rate

Summary Aim: Even with careful observation, the overall false-positive rate of laparotomy remains 10-15% when acute appendicitis was suspected. Therefore, the clinical efficacy of Tc-99m HMPAO labeled leukocyte (TC-WBC) scan for the diagnosis of acute appendicitis in patients presenting with atypical clinical findings is assessed. Patients and Methods: Eighty patients presenting with acute abdominal pain and possible acute appendicitis but atypical findings were included in this study. After intravenous injection of TC-WBC, serial anterior abdominal/pelvic images at 30, 60, 120 and 240 min with 800k counts were obtained with a gamma camera. Any abnormal localization of radioactivity in the right lower quadrant of the abdomen, equal to or greater than bone marrow activity, was considered as a positive scan. Results: 36 out of 49 patients showing positive TC-WBC scans received appendectomy. They all proved to have positive pathological findings. Five positive TC-WBC were not related to acute appendicitis, because of other pathological lesions. Eight patients were not operated and clinical follow-up after one month revealed no acute abdominal condition. Three of 31 patients with negative TC-WBC scans received appendectomy. They also presented positive pathological findings. The remaining 28 patients did not receive operations and revealed no evidence of appendicitis after at least one month of follow-up. The overall sensitivity, specificity, accuracy, positive and negative predictive values for TC-WBC scan to diagnose acute appendicitis were 92, 78, 86, 82, and 90%, respectively. Conclusion: TC-WBC scan provides a rapid and highly accurate method for the diagnosis of acute appendicitis in patients with equivocal clinical examination. It proved useful in reducing the false-positive rate of laparotomy and shortens the time necessary for clinical observation.

scholarly journals Does neighborhood socioeconomic status predict the risk of preterm birth? A community-based Canadian cohort study

BMJ Open ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. e025341 ◽  
Author(s):  
Kamala Adhikari ◽  
Scott B Patten ◽  
Tyler Williamson ◽  
Alka B Patel ◽  
Shahirose Premji ◽  
...  
Keyword(s):  
Socioeconomic Status ◽  
Cohort Study ◽  
Preterm Birth ◽  
Cohort Studies ◽  
False Positive ◽  
False Positive Rate ◽  
Community Based ◽  
Individual Level ◽  
Risk Threshold ◽  
Positive Rate

ObjectiveThis study developed and internally validated a predictive model for preterm birth (PTB) to examine the ability of neighbourhood socioeconomic status (SES) to predict PTB.DesignCohort study using individual-level data from two community-based prospective pregnancy cohort studies (All Our Families (AOF) and Alberta Pregnancy Outcomes and Nutrition (APrON)) and neighbourhood SES data from the 2011 Canadian census.SettingCalgary, Alberta, Canada.ParticipantsPregnant women who were <24 weeks of gestation and >15 years old were enrolled in the cohort studies between 2008 and 2012. Overall, 5297 women participated in at least one of these cohorts: 3341 women participated in the AOF study, 2187 women participated in the APrON study and 231 women participated in both studies. Women who participated in both studies were only counted once.Primary and secondary outcome measuresPTB (delivery prior to 37 weeks of gestation).ResultsThe rates of PTB in the least and most deprived neighbourhoods were 7.54% and 10.64%, respectively. Neighbourhood variation in PTB was 0.20, with an intra-class correlation of 5.72%. Neighbourhood SES, combined with individual-level predictors, predicted PTB with an area under the receiver-operating characteristic curve (AUC) of 0.75. The sensitivity was 91.80% at a low-risk threshold, with a high false-positive rate (71.50%), and the sensitivity was 5.70% at a highest risk threshold, with a low false-positive rate (0.90%). An agreement between the predicted and observed PTB demonstrated modest model calibration. Individual-level predictors alone predicted PTB with an AUC of 0.60.ConclusionAlthough neighbourhood SES combined with individual-level predictors improved the overall prediction of PTB compared with individual-level predictors alone, the detection rate was insufficient for application in clinical or public health practice. A prediction model with better predictive ability is required to effectively find women at high risk of preterm delivery.

scholarly journals False-Positive Gen-Probe Direct Mycobacterium tuberculosis Amplification Test Results for Patients with Pulmonary M. kansasii and M. aviumInfections

1999 ◽  
Vol 37 (1) ◽  
pp. 175-178 ◽  
Author(s):  
James H. Jorgensen ◽  
Jesse R. Salinas ◽  
Rosemary Paxson ◽  
Karen Magnon ◽  
Jan E. Patterson ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
False Positive ◽  
Disease Patient ◽  
The United States ◽  
Positive Test ◽  
Test Results ◽  
High Power Field ◽  
Low Level ◽  
False Positive Test ◽  
Abnormal Chest

The Gen-Probe Amplified Mycobacterium Tuberculosis Direct (MTD) test has been approved for use in the United States for the rapid diagnosis of pulmonary tuberculosis in patients with acid-fast smear-positive sputum samples since 1996. Four patients infected with human immunodeficiency virus and one chronic pulmonary-disease patient seen in our institutions with abnormal chest radiographs and fluorochrome stain-positive sputa were evaluated for tuberculosis, including performance of the MTD test on expectorated sputum samples. Three of these five patients’ sputa were highly smear-positive (i.e., more than 100 bacilli per high-power field), while two patient’s sputa contained 1 to 10 bacilli per field. MTD results on sputum specimens from these patients ranged from 43,498 to 193,858 relative light units (RLU). Gen-Probe has defined values of at least 30,000 RLU as indicative of a positive test, i.e., the presence ofMycobacterium tuberculosis RNA. Four of the patients’ sputum cultures yielded growth of M. kansasii within 6 to 12 days, and the fifth produced growth of M. avium only. One patient’s culture contained both M. kansasii andM. avium, but none of the initial or follow-up cultures from these five patients revealed M. tuberculosis. However, subsequent cultures from three of the patients again revealed M. kansasii. During the period of this study, in which MTD tests were performed on smear-positive sputum specimens from 82 patients, four of seven patients with culture-proven M. kansasiipulmonary infections yielded one or more false-positive MTD tests. The MTD sensitivity observed in this study was 93.8%, and the specificity was 85.3%. Five cultures of M. kansasii (including three of these patients’ isolates and M. kansasii ATCC 12478), and cultures of several other species were examined at densities of 105 to 107 viable CFU/ml by the MTD test. All five isolates of M. kansasii and three of three isolates ofM. simiae yielded false-positive test results, with readings of 75,191 to 335,591 RLU. These findings indicate that low-level false-positive MTD results can occur due to the presence ofM. kansasii, M. avium, and possibly otherMycobacterium species other than M. tuberculosis in sputum. Low-level positive MTD results of 30,000 to 500,000 RLU should be interpreted in light of these findings. It remains to be determined if the enhanced MTD test (MTD 2) recently released by Gen-Probe will provide greater specificity than that observed in this report with its first-generation test.

scholarly journals LOW FALSE POSITIVE RATE OFKEPLERCANDIDATES ESTIMATED FROM A COMBINATION OFSPITZERAND FOLLOW-UP OBSERVATIONS

2015 ◽  
Vol 804 (1) ◽  
pp. 59 ◽  
Author(s):  
Jean-Michel Désert ◽  
David Charbonneau ◽  
Guillermo Torres ◽  
François Fressin ◽  
Sarah Ballard ◽  
...  
Keyword(s):  
False Positive ◽  
False Positive Rate ◽  
Positive Rate

scholarly journals Using Z-score to optimize population-specific DDH screening: a retrospective study in Hangzhou, China

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Haomin Li ◽  
Liqi Shu ◽  
Jin Yu ◽  
Zeng Xian ◽  
Huilong Duan ◽  
...  
Keyword(s):  
False Positive ◽  
False Positive Rate ◽  
Developmental Dysplasia ◽  
Z Score ◽  
Local Regression ◽  
X Ray ◽  
Positive Rate ◽  
Z Scores ◽  
Highly Correlated

Abstract Background DDH (Developmental Dysplasia of the Hip) screening can potentially avert many morbidities and reduce costs. The debate about universal vs. selective DDH ultrasonography screening in different countries revolves to a large extent around effectiveness, cost, and the possibility of overdiagnosis and overtreatment. In this study, we proposed and evaluated a Z-score enhanced Graf method to optimize population-specific DDH screening. Methods A total of 39,710 history ultrasonography hip examinations were collected to establish a sex, side specific and age-based Z-scores model using the local regression method. The correlation between Z-scores and classic Graf types was analyzed. Four thousand two hundred twenty-nine cases with follow-up ultrasonographic examinations and 5284 cases with follow-up X-ray examinations were used to evaluate the false positive rate of the first examination based on the subsequent examinations. The results using classic Graf types and the Z-score enhanced types were compared. Results The Z-score enhanced Graf types were highly correlated with the classic Graf’s classification (R = 0.67, p < 0.001). Using the Z-scores ≥2 as a threshold could reduce by 86.56 and 80.44% the false positives in the left and right hips based on the follow-up ultrasonographic examinations, and reduce by 78.99% false-positive cases based on the follow-up X-ray examinations, respectively. Conclusions Using an age, sex and side specific Z-scores enhanced Graf’s method can better control the false positive rate in DDH screening among different populations.

scholarly journals Clinical and Epidemiologic Evaluation of Inconclusive COVID-19 PCR Results Using a Quantitative Algorithm

2020 ◽  
Author(s):  
Shangxin Yang ◽  
Nicholas Stanzione ◽  
Daniel Z Uslan ◽  
Omai B Garner ◽  
Annabelle de St Maurice
Keyword(s):  
False Positive ◽  
Infection Prevention ◽  
False Positive Rate ◽  
Antibody Test ◽  
Test Results ◽  
Asymptomatic Patients ◽  
Positive Rate ◽  
Control And Prevention ◽  
Polymerase Chain ◽  
Asymptomatic Individuals

Abstract Objectives The inconclusive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) polymerase chain reaction (PCR) result causes confusion and delay for infection prevention precautions and patient management. We aimed to develop a quantitative algorithm to assess and interpret these inconclusive results. Methods We created a score-based algorithm by combining laboratory, clinical, and epidemiologic data to evaluate 69 cases with inconclusive coronavirus disease 2019 (COVID-19) PCR results from the Centers for Disease Control and Prevention (CDC) assay (18 cases) and the TaqPath assay (51 cases). Results We determined 5 (28%) of 18 (CDC assay) and 20 (39%) of 51 (TaqPath assay) cases to be false positive. Lowering the cycle threshold cutoff from 40 to 37 in the TaqPath assay resulted in a dramatic reduction of the false-positive rate to 14%. We also showed testing of asymptomatic individuals is associated with a significantly higher probability of having a false-positive result. Conclusions A substantial percentage of inconclusive SARS-CoV-2 PCR results can be false positive, especially among asymptomatic patients. The quantitative algorithm we created was shown to be effective and could provide a useful tool for clinicians and hospital epidemiologists to interpret inconclusive COVID-19 PCR results and provide clinical guidance when additional PCR or antibody test results are available.

scholarly journals Prenatal Testing, Disability, and Termination: An Examination of Newspaper Framing

2012 ◽  
Vol 32 (3) ◽  
Author(s):  
Carol Bishop Mills ◽  
Elina Erzikova
Keyword(s):  
United States ◽  
Full Text ◽  
Print Media ◽  
Prenatal Testing ◽  
The United States ◽  
Positive Test ◽  
Test Results ◽  
Positive Representations

<p>Keywords: disability, genetics, prenatal testing, health, framing</p><p>Given the increase in the prevalence of prenatal testing for disabilities and the options following positive test results, this study investigates how information about prenatal testing and disability is represented in the top 30 newspaper markets in the United States. The goal is to examine how print media convey information about prenatal testing for disabilities to its readers. Analyses of 148 full-text articles from 1998 to 2006 indicate that disability is represented in negative terms. The negative framing of disability is paired with positive representations of prenatal testing, and to a slightly lesser extent, positive representations of termination of pregnancies involving a fetus diagnosed with disabilities.</p>

scholarly journals SARS-CoV-2 RT-PCR profile in 298 Indian COVID-19 patients : a retrospective observational study

2020 ◽  
Author(s):  
Bisakh Bhattacharya ◽  
Rohit Kumar ◽  
Ved Prakash Meena ◽  
Manish Soneja ◽  
Saurabh Vig ◽  
...  
Keyword(s):  
Observational Study ◽  
Symptom Onset ◽  
Positive Test ◽  
Retrospective Observational Study ◽  
New Delhi ◽  
Test Results ◽  
Rt Pcr ◽  
Prolonged Duration ◽  
The Mean

AbstractBackgroundDespite being in the 5th month of pandemic, knowledge with respect to viral dynamics, infectivity and RT-PCR positivity continues to evolve.AimTo analyse the SARS CoV-2 nucleic acid RT-PCR profiles in COVID-19 patients.DesignIt was a retrospective, observational study conducted at COVID facilities under AIIMS, New Delhi.MethodsPatients admitted with laboratory confirmed COVID-19 were eligible for enrolment. Patients with incomplete details, or only single PCR tests were excluded. Data regarding demographic details, comorbidities, treatment received and results of SARS-CoV-2 RT-PCR performed on nasopharyngeal and oropharyngeal swabs, collected at different time points, was retrieved from the hospital records.Results298 patients were included, majority were males (75·8%) with mean age of 39·07 years (0·6-88 years). The mean duration from symptom onset to first positive RT-PCR was 4·7 days (SD 3·67), while that of symptom onset to last positive test was 17·83 days (SD 6·22). Proportions of positive RT-PCR tests were 100%, 49%, 24%, 8·7% and 20·6% in the 1st, 2nd, 3rd, 4th & >4 weeks of illness. 12 symptomatic patients had prolonged positive test results even after 3 weeks of symptom onset. Age >= 60 years was associated with prolonged RT-PCR positivity (statistically significant).ConclusionThis study showed that the average period of PCR positivity is more than 2 weeks in COVID-19 patients; elderly patients have prolonged duration of RT-PCR positivity and requires further follow up.

scholarly journals Audit of the first > 7500 noninvasive prenatal aneuploidy tests in a Swiss genetics center

2021 ◽  
Author(s):  
Anahita Bajka ◽  
Michael Bajka ◽  
Fabian Chablais ◽  
Tilo Burkhardt
Keyword(s):  
Pregnancy Outcome ◽  
False Positive Rate ◽  
Prenatal Testing ◽  
Accurate Method ◽  
Test Results ◽  
Data Set ◽  
Single Nucleotide ◽  
Noninvasive Prenatal Testing ◽  
Positive Rate

Abstract Objectives Noninvasive prenatal testing (NIPT) is actually the most accurate method of screening for fetal chromosomal aberration (FCA). We used pregnancy outcome record to evaluate a complete data set of single nucleotide polymorphism-based test results performed by a Swiss genetics center. Materials and methods The Panorama® test assesses the risk of fetal trisomies (21, 18 and 13), gonosomal aneuploidy (GAN), triploidy or vanishing twins (VTT) and five different microdeletions (MD). We evaluated all 7549 test results meeting legal and quality requirements taken in women with nondonor singleton pregnancies between April 2013 and September 2016 classifying them as high or low risk. Follow-up ended after 9 months, data collection 7 months later. Results The Panorama® test provided conclusive results in 96.1% of cases, detecting 153 FCA: T21 n = 76, T18 n = 19, T13 n = 15, GAN n = 19, VTT n = 13 and MD n = 11 (overall prevalence 2.0%). Pregnancy outcome record was available for 68.6% of conclusive laboratory results, including 2.0% high-risk cases. In this cohort the Panorama® test exhibited 99.90% sensitivity for each trisomy; specificity was 99.90% for T21, 99.98% for T18 and 99.94% for T13. False positive rate was 0.10% for T21, 0.02% for T18 and 0.06% for T13. Conclusion SNP-based testing by a Swiss genetics center confirms the expected accuracy of NIPT in FCA detection.

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