Nucleic Acid Amplification Tests Testing Research Articles

SARS-CoV-2 seroprevalence in Nova Scotia blood donors.

SARS-CoV-2 seroprevalence monitors cumulative infection rates irrespective of case testing protocols. We aimed to describe Nova Scotia blood donor seroprevalence in relation to public health policy and reported data over the course of the COVID-19 pandemic (May 2020 to August 2022). Monthly random Nova Scotia blood donation samples (24,258 in total) were tested for SARS-CoV-2 infection antibodies (anti-nucleocapsid) from May 2020 to August 2022, and vaccination antibodies (anti-spike) from January 2021 to August 2022. Multivariable logistic regression for infection antibodies and vaccination antibodies separately with month, age, sex, and racialization identified independent predictors. The provincial nucleic acid amplification test (NAAT)-positive case rate over the pandemic was calculated from publicly available data. Anti-N seroprevalence was 3.8% in January 2022, increasing to 50.8% in August 2022. The general population COVID-19 case rate was 3.5% in January 2022, increasing to 12.5% in August 2022. The percentage of NAAT-positive samples in public health laboratories increased from 1% in November 2021 to a peak of 30.7% in April 2022 with decreasing numbers of tests performed. Higher proportions of younger donors as well as Black, Indigenous, and racialized blood donors were more likely to have infection antibodies (p < 0.01). Vaccination antibodies increased to 100% over 2021, initially in older donors (60+ years), and followed by progressively younger age groups. SARS-CoV-2 infection rates were relatively low in Nova Scotia until the more contagious Omicron variant dominated, after which about half of Nova Scotia donors had been infected despite most adults being vaccinated (although severity was much lower in vaccinated individuals). Most COVID-19 cases were detected by NAAT until Omicron arrived. When NAAT testing priorities focused on high-risk individuals, infection rates were better reflected by seroprevalence.

Comparison of Clostridioides difficile nucleic acid amplification test (NAAT) results using fresh and frozen stool specimens and rectal swabs.

Nucleic acid amplification tests (NAATs) are frequently used in Clostridioides difficile research and diagnostic testing, but the effect of freezing specimens on C. difficile NAAT performance is not well characterized. This study evaluated the concordance of NAAT results between fresh and frozen specimens (fecal and rectal swabs) and found it to be very good to excellent. The results indicate that frozen fecal and rectal swab specimens may be used for C. difficile NAAT testing in research when fresh specimens are not available.

699. Clinical Outcomes and Management of NAAT-Positive/Toxin-Negative Clostridium difficile Infection: A Systematic Review and Meta-Analysis

Abstract Background Standalone nucleic acid amplification tests (NAATs) are increasingly used to diagnose Clostridium difficile infections (CDI), although they may be unable to distinguish colonization from disease. A two-stage algorithm pairing NAAT with a toxin immunoassay (Toxin) has been proposed to improve specificity. We sought to evaluate clinical outcomes among patients testing NAAT+/Toxin+ vs NAAT+/Toxin- by conducting a systematic review and meta-analysis. We further compared outcomes between NAAT+/Toxin- patients who were and were not treated. Methods We searched EMBASE and MEDLINE from inception to September 17, 2022 for articles comparing CDI outcomes among symptomatic patients tested by NAAT and Toxin tests. The risk differences (RD) of all-cause mortality and CDI recurrence were computed by random effects meta-analysis between NAAT+/Toxin+ and NAAT+/Toxin- patients, as well as between treated and untreated NAAT+/Toxin- patients. Results Twenty-three observational studies comprising 11749 patients were included. 30-Day all-cause mortality was not significantly different between NAAT+/Toxin+ and NAAT+/Toxin- patients (8.4% vs 6.8%, respectively; RD=0.2%, 95%CI -2.4, 2.9; I2=52.9%). Recurrence at 60 days was significantly higher among NAAT+/Toxin+ (19.8%) vs NAAT+/Toxin- patients (11.0%) (RD=7.7%, 95%CI=4.6, 10.7, I2=37.4%). Among treated compared to untreated NAAT+/Toxin- patients, the all-cause 30-day mortalities were 5.0% and 14.9%, respectively (RD=-9.5%, 95%CI=-15.0, -3.9, I2=0.0%), but 60-day recurrence was not significantly different (11.6% vs 7.0%, respectively; RD=5.3%, 95%CI -1.7, 12.2; I2=47.0%). Conclusion Compared to NAAT+/Toxin- patients, NAAT+/Toxin+ patients had a greater risk of recurrence at 60 days, but not all-cause mortality. Treatment of NAAT+/Toxin- patients was associated with reduced all-cause mortality, but not recurrence. While subject to the limitations of observational studies including the potential for confounding by indication and immortal time bias, these results suggest that treatment of NAAT+/Toxin- patients may be beneficial. A strategy comparing standalone NAAT or staged testing with up front combined NAAT/Toxin testing could be the topic of a randomized controlled trial to determine cost and efficacy. Disclosures All Authors: No reported disclosures

136. Impact of a Tele-Stewardship and Tele-Infection Prevention Program on Hospital-Onset Clostridioides Difficile Rates in a Community Three-Hospital Health System

Abstract Background Clostridioides difficile infection (CDI) is a common hospital-acquired infection (HAI) that can be difficult to diagnose accurately given the numerous test modalities with differing performance characteristics. Inaccurate diagnosis of CDI can negatively affect patient care decisions as well as reimbursement rates. Community and rural hospitals (CARH) may lack specialized personnel or knowledge to implement diagnostic best practices, but telehealth solutions like tele-infection prevention (TIP) and tele-antimicrobial stewardship (TASP) can provide specialist support for CARHs to optimize diagnostic pathways, improve accuracy, and reduce unnecessary treatment. Methods In June 2021 under the guidance of TIP and TASP recommendations, C. difficile testing was transitioned from a 1-step nucleic acid amplification test (NAAT)-only algorithm to a 2-step algorithm that included NAAT and toxin enzyme immunoassay (EIA) testing. A 6-month pre- and post-implementation assessment was conducted to assess the impacts of this change in hospital-onset CDI (HO-CDI) case rate. Additionally, total C. difficile (community- and hospital-onset CDI) rates per 1000 patient days (PD) and consumption of CDI therapeutics were assessed. For statistical analysis, Wilcoxon ranked-sum test to assess changes in CDI rates. Estimated annualized cost-savings for therapeutics were calculated based on institutional purchasing costs. Results Following implementation, a 35.9% reduction in HO-CDI was observed (pre 0.96 cases/1000PD vs. 0.61 cases/1000PD; p = 0.054). A 10.2% reduction was observed in total CDI (pre 3.66 cases/1000PD vs. 3.28 cases/1000PD; p = 0.37). Additionally, a 30.6% reduction was observed in consumption of CDI therapeutics (20.1 doses/1000PD vs. 14.0 doses/1000PD) resulting in an annualized cost-savings of approximately $9200. Conclusion Our TIP and TASP advised a community three-hospital health system on optimal diagnostics resulting in a change in their algorithm. Following this, considerable reductions were observed in HO-CDI, total CDI, consumption of CDI therapeutics, and the associated costs of care. Disclosures Erin K. McCreary, PharmD, Abbvie: Advisor/Consultant|Ferring: Advisor/Consultant|GSK: Honoraria|La Jolla (Entasis): Advisor/Consultant|LabSimply: Advisor/Consultant|Merck: Advisor/Consultant|Shionogi: Advisor/Consultant|Shionogi: Honoraria

Clinical Outcomes and Management of NAAT-Positive/Toxin-Negative Clostridioides difficile Infection: A Systematic Review and Meta-Analysis.

Standalone nucleic acid amplification tests (NAATs) are frequently used to diagnose Clostridioides difficile infections (CDI), although they may be unable to distinguish colonization from disease. A 2-stage algorithm pairing NAATs with toxin immunoassays (Toxin) may improve specificity. We evaluated clinical outcomes of patients who were NAAT+/Toxin+ versus NAAT+/Toxin- and treated versus untreated NAAT+/Toxin- cases through systematic review and meta-analysis. We searched EMBASE and MEDLINE from inception to April 1, 2023 for articles comparing CDI outcomes among symptomatic patients tested by NAAT and Toxin tests. The risk differences (RD) of all-cause mortality and CDI recurrence were computed by random effects meta-analysis between patients who were NAAT+/Toxin+ and NAAT+/Toxin-, as well as between patients who were NAAT+/Toxin- and treated or untreated. Twenty-six observational studies comprising 12 737 patients were included. The 30-day all-cause mortality was not significantly different between those who were NAAT+/Toxin+ (8.4%) and NAAT+/Toxin- (6.7%) (RD = 0.41%, 95% confidence interval [CI] = -.67, 1.49). Recurrence at 60 days was significantly higher among patients who were NAAT+/Toxin+ (19.8%) versus NAAT+/Toxin- (11.0%) (RD = 7.65%, 95% CI = 4.60, 10.71). Among treated compared to untreated NAAT+/Toxin- cases, the all-cause 30-day mortalities were 5.0% and 12.7%, respectively (RD = -7.45%, 95% CI = -12.29, -2.60), but 60-day recurrence was not significantly different (11.6% vs 7.0%, respectively; RD = 5.25%, 95% CI -1.71, 12.22). Treatment of patients who were NAAT+/Toxin- was associated with reduced all-cause mortality but not recurrence. Although subject to the inherent limitations of observational studies, these results suggest that some patients who are NAAT+/Toxin- may benefit from treatment.

Effectiveness of Using Nucleic Acid Amplification Test to Screen Blood Donors for Hepatitis B, Hepatitis C, and HIV: A Tertiary Care Hospital Experience From Pakistan.

Background Ensuring blood safety is the primary goal of transfusion medicine. Despite extensive serological tests and strict safety measures, the risk of transfusion-transmitted infections (TTIs) still exists. As applied to blood screening, Nucleic Acid Amplification Test (NAT)offers much higher sensitivity for detecting viral infections. It is, however, currently available to a handful of centers due to the high cost. This study aims to establish the Effectiveness of NAT by assessing the NAT yield and residual risk of transmission of Hepatitis B virus (HBV), hepatitis C virus (HCV)and HIV with and without NAT testing. Material and method This prospective cross-sectional study recruited blood donors from January 2020 to November 2022. All donors underwent routine serologic screening. Only serologically negative donors were tested for HBV, HCV, and HIV by NAT. The NAT yield and residual risk (RR) per million donors were computed for viral infections in seronegative blood donors and calculated using the incidence/window period model. Result A total of 59708 donors were included during the study period. The overall prevalence of TTI's were: For HCV 1.7% (n = 1018), HBV 1.5% (n = 918), HIV 0.07% (n = 47), Syphilis 1.2% (n = 758) and malaria 0.3% (n = 218). Out of 57759 seronegative donors, thirty-four NAT-reactive samples were identified, with 3 cases of HCV, 31 cases of HBV, and Nil HIV cases. NAT yield of HBV was 1 in 1863 with an RR of 8.6 per million, followed by HCV with a NAT yield of 1 in 19253 and RR of 0.8 per million donations. NAT testing reduced RR for HBV by 48.9% and HCV by 94.5%. Conclusion Our study showed that NAT detected 34 out of 57759 cases initially missed by serological tests. The study suggests that the parallel use of serology and NAT screening of donated blood would be beneficial.

Long-acting injectable cabotegravir: implementation science needed to advance this additional HIV prevention choice.

Long-acting injectable cabotegravir: implementation science needed to advance this additional HIV prevention choice.

Adaptation of a Public-Private Partnership Model for the Implementation of Minipool Nucleic Acid Testing for Screening Routine Blood Donations and Assay Evaluation.

Background Nucleic acid amplification testing (NAT) for the screening of blood donations is known to improve blood safety. The decision to initiate NAT requires careful deliberation of infrastructure, skilled manpower, and financial resources. This report outlines the initiative of the Government of Odisha to implement NAT screening in government blood banks in the state of Odisha, India, through public–private partnership (PPP) and evaluates the incremental yield of minipool NAT screening over serology testing of blood donations. Methods Blood donations collected between June 2016 and September 2018 were initially screened for HBV (HBsAg), HCV (anti-HCV), and HIV (anti-HIV-1 and HIV-2) by ELISA, and syphilis and malaria. Sero-nonreactive donations were further screened in pools of six by Roche cobas TaqScreen MPX test version 2.0 (MPX2) NAT. Results On screening 3,39,472 blood donations, 1.34% seroreactive donations were detected. In all, 847 NAT-reactive donations (0.26%): 693 HBV, 58 HCV, and 96 HIV were detected. The NAT yields were 1:386 overall, 1:472 for HBV, 1:5642 for HCV, and 1:3409 for HIV. Conclusion NAT testing using the highly sensitive MPX2 assay leads to incremental detection of TTIs over serology. Implementation of NAT along with serological testing in blood centers all over India will be an important step towards providing safe blood. Our study not only highlights the benefits of minipool NAT testing but also presents a scalable PPP model that can serve as a template for application across other states.

Rapid molecular tests for tuberculosis and tuberculosis drug resistance: a qualitative evidence synthesis of recipient and provider views.

Rapid molecular tests for tuberculosis and tuberculosis drug resistance: a qualitative evidence synthesis of recipient and provider views.

Role of Diagnostics in Epidemiology, Management, Surveillance, and Control of Leptospirosis.

A One Health approach to the epidemiology, management, surveillance, and control of leptospirosis relies on accessible and accurate diagnostics that can be applied to humans and companion animals and livestock. Diagnosis should be multifaceted and take into account exposure risk, clinical presentation, and multiple direct and/or indirect diagnostic approaches. Methods of direct detection of Leptospira spp. include culture, histopathology and immunostaining of tissues or clinical specimens, and nucleic acid amplification tests (NAATs). Indirect serologic methods to detect leptospiral antibodies include the microscopic agglutination test (MAT), the enzyme-linked immunosorbent assay (ELISA), and lateral flow methods. Rapid diagnostics that can be applied at the point-of-care; NAAT and lateral flow serologic tests are essential for management of acute infection and control of outbreaks. Culture is essential to an understanding of regional knowledge of circulating strains, and we discuss recent improvements in methods for cultivation, genomic sequencing, and serotyping. We review the limitations of NAATs, MAT, and other diagnostic approaches in the context of our expanding understanding of the diversity of pathogenic Leptospira spp. Novel approaches are needed, such as loop mediated isothermal amplification (LAMP) and clustered regularly interspaced short palindromic repeats (CRISPR)-based approaches to leptospiral nucleic acid detection.

The impact of nucleic acid testing to detect human immunodeficiency virus, hepatitis C virus, and hepatitis B virus yields\xa0from a single blood center in China with 10-years review

BackgroundSince 2010, the Blood Center of Zhejiang province, China, has conducted a pilot nucleic acid amplification testing (NAT) screening of blood donors for Hepatitis B virus (HBV), Hepatitis C virus (HCV), and Human immunodeficiency virus (HIV). This study aims to assess the results of NAT testing over 10 years to establish the effects and factors influencing NAT yields of HBV, HCV, and HIV.MethodsBlood donations from seven different blood services were screened for HBV DNA, HCV RNA, and HIV RNA using 6 mini pools (6MP) or individual donation (ID)-NAT method between August 1, 2010, and December 31, 2019, at the NAT centralized screening center. We compared 3 transcription-mediated amplification (TMA) assays and 2 polymerase chain reaction (PCR) assays. Further, HBV, HCV, and HIV NAT yields were calculated and donor characteristics and prevalence of HBV NAT yields analyzed. Donors with HCV and HIV NAT yield were also followed up.Results1916.31 per million donations were NAT screening positive overall. The NAT yields for HBV, HCV, HIV and non-discriminating reactive were 1062.90 per million, 0.97 per million, 1.45 per million, and 850.99 per million, respectively, which varied in the seven blood services and different years. HBV NAT yields were higher than those of HCV and HIV and varied across demographic groups. Risk factors included being male, old age, low education level, and first-time donors. We found no differences in NAT yields of HBV, HCV, and HIV between the 3 TMA and 2 PCR assays; nonetheless, statistically, significant differences were noted between the five assays.ConclusionIn summary, NAT screening in blood donations reduces the risk of transfusion-transmitted infections and shortens the window period for serological marker screening. Therefore, a sensitive NAT screening method, ID-NAT workflow, and recruitment of regular low-risk donors are critical for blood safety.

754. A Two-step Testing Algorithm for Hospital-onset Clostridioides difficile Infection (CDI) Reduces Prescribing of C. difficile (CD) Therapy but Its Ability to Guide Treatment Decisions Remains Unclear

BackgroundDetermining true CDI versus CD colonization through CD testing is a continuing challenge. A previously introduced decision support tool at UVA Health significantly reduced inappropriate testing without adverse outcomes. More recently, our methodology changed from nucleic acid amplification test (NAAT) alone to an initial NAAT followed by ELISA for toxin to improve specificity. The purpose of this analysis was to assess provider interpretation of test results, using targeted CD therapy as a surrogate.MethodsThis single-center, retrospective study evaluated all patients with a positive NAAT (Cepheid Xpert® C. difficile) on day 4 or later of hospitalization following 2-step algorithm implementation from Feb 2020 through Feb 2021. Toxin negative (TOX-) test results (C. DIFF QUIK CHEK COMPLETE®) were accompanied by a comment that discordance may represent colonization or CDI and to consider ID consult. The proportion of toxin positive (TOX+) versus TOX- patients receiving ≥ 1 dose of CD therapy served as the primary outcome with partial courses considered < 10 days. Clinical outcomes were also compared.ResultsNinety patients with NAAT+ results were included, of whom 58 (64%) were TOX-. Thirty-two (100%) TOX+ (median days of therapy [IQR] = 14 [11-17]) versus 51 (88%) TOX- patients (median days of therapy [IQR] = 11 [7-14]) received CD therapy (p=0.04). Treatment decisions were guided by ID physicians for 32 (63%) TOX- patients; ID recommendations to discontinue CD therapy were followed in 2 out of 9 (22%) cases. TOX- patients received partial therapy due to patient death (n=5), presumptive colonization (n=3), and provider error (n=1). Of TOX- patients receiving partial or no treatment, there were no CDI-related adverse outcomes during the admission. CDI-related colectomy occurred in 2 (6%) and 1 (2%) TOX+ and TOX- patients, respectively. Five in-hospital deaths with CDI as a contributing factor occurred in the TOX+ group. ConclusionAdoption of a 2-step NAAT plus toxin testing algorithm for hospital-onset CDI reduced the frequency with which TOX- patients received CD therapy but the vast majority were still treated. Most providers considered a positive NAAT indicative of CDI, regardless of TOX status. Disclosures All Authors: No reported disclosures

Diagnostic Performance of an Antigen Test with RT-PCR for the Detection of SARS-CoV-2 in a Hospital Setting - Los Angeles County, California, June-August 2020.

Prompt and accurate detection of SARS-CoV-2, the virus that causes COVID-19, has been important during public health responses for containing the spread of COVID-19, including in hospital settings (1-3). In vitro diagnostic nucleic acid amplification tests (NAAT), such as real-time reverse transcription-polymerase chain reaction (RT-PCR) can be expensive, have relatively long turnaround times, and require experienced laboratory personnel.* Antigen detection tests can be rapidly and more easily performed and are less expensive. The performance† of antigen detection tests, compared with that of NAATs, is an area of interest for the rapid diagnosis of SARS-CoV-2 infection. The Quidel Sofia 2 SARS Antigen Fluorescent Immunoassay (FIA) (Quidel Corporation) received Food and Drug Administration Emergency Use Authorization for use in symptomatic patients within 5 days of symptom onset (4). The reported test positive percentage agreement§ between this test and an RT-PCR test result is 96.7% (95% confidence interval [CI]=83.3%-99.4%), and the negative percentage agreement is 100.0% (95% CI=97.9%-100.0%) in symptomatic patients.¶ However, performance in asymptomatic persons in a university setting has shown lower sensitivity (5); assessment of performance in a clinical setting is ongoing. Data collected during June 30-August 31, 2020, were analyzed to compare antigen test performance with that of RT-PCR in a hospital setting. Among 1,732 paired samples from asymptomatic patients, the antigen test sensitivity was 60.5%, and specificity was 99.5% when compared with RT-PCR. Among 307 symptomatic persons, sensitivity and specificity were 72.1% and 98.7%, respectively. Health care providers must remain aware of the lower sensitivity of this test among asymptomatic and symptomatic persons and consider confirmatory NAAT testing in high-prevalence settings because a false-negative result might lead to failures in infection control and prevention practices and cause delays in diagnosis, isolation, and treatment.

Fourth-Generation ELISA Screening of Blood Donors: A Reliable Alternative to Nucleic Acid Testing

The gold standard for HIV screening of blood donors is individual nucleic acid amplification testing (NAT). However, individual NAT testing is cost-prohibitive, especially in a resource-limited setting. The fourth-generation ELISA that detects both p24 antigen and antibody to HIV-1 and 2 has been recommended as the minimum test for HIV to enhance blood transfusion safety and can be an alternative to NAT testing in resource-limited settings. The aim was to assess the performance of a fourth-generation ELISA in use at a regional blood transfusion service using nucleic acid amplification testing on units of screened blood negative to HIV. The study was a cross-sectional study conducted at the National Blood Transfusion Service center and the Plateau State Virology Research Centre, both in Jos, Nigeria. Between August and October 2016, one thousand and eighteen voluntary blood donors were recruited consecutively and had their samples tested using fourth-generation ELISA. One thousand p24 antigen-negative samples were pooled for NAT in an aliquot of 50 samples. All the pools of fifty samples of 1,000 HIV p24 antigen-antibody negative donor blood screened by the fourth-generation ELISA tested negative for HIV RNA on nucleic acid amplification. The yield of pooled NAT for HIV after a fourth-generation ELISA screening of blood donors was found to be zero in this study, thus establishing the fourth-generation ELISA's reliability. Therefore, we recommend adopting the fourth-generation ELISA test as a minimum requirement for blood donor screening.

Nucleic Acid Amplification Testing Compared With Cultures, Gram Stain, and Microscopy in the Diagnosis of Vaginitis

The aim of the study was to evaluate the performance of nucleic acid amplification testing (NAAT) for the diagnosis of vulvovaginal candidiasis (VVC), bacterial vaginosis, and Trichomonas vaginalis. A cross-sectional analysis of women with (n = 200) and without (n = 100) vulvovaginal symptoms was enrolled from outpatient gynecology offices and a vulvovaginal referral clinic. Vaginal swabs were analyzed by wet mount microscopy, yeast culture, Gram stain, T. vaginalis culture, and NAAT. Sensitivity and specificity analyses were performed. Among symptomatic women, the sensitivity of microscopy was 48.5% for VVC and 75% for T. vaginalis. Sensitivities of NAAT and culture for diagnosing VVC were 92.4% and 83.3%, respectively, whereas these methods were 100% and 93.8% for T. vaginalis. The sensitivity for bacterial vaginosis diagnosis by clinical criteria ("Amsel criteria"), Gram stain, and NAAT were 98.7%, 82.7%, and 78.7%, respectively. Test concordance rates were high between culture and NAAT for Candida species (91%) and between Gram stain and NAAT for the detection of bacterial vaginosis (88%). Among asymptomatic women, 20%-21% tested positive for bacterial vaginosis by Gram stain or NAAT, and 8%-13% were colonized with Candida species based on culture or NAAT. Given the limitations of wet mount sensitivity for VVC and T. vaginalis, culture or NAAT testing should be considered when evaluating women with symptoms of vaginitis who test negative by microscopy. Although Amsel criteria accurately diagnosed bacterial vaginosis, NAAT is preferred for detection of T. vaginalis and performed similarly to culture for the diagnosis of VVC.

Comparison of Total Immunoglobulin G in Ante- and Postmortem Blood Samples from Tissue Donors

Background: A serology testing for infectious diseases (HIV, hepatitis B and C, syphilis) is mandatory in tissue donors. In many donors postmortem blood is the only sample available. Even though serological tests and nucleic acid amplification tests (NAT) used are validated for postmortem blood, a characterization of those blood samples is not yet established. We therefore investigated the total immunoglobulin G (IgG) content in postmortem blood of tissue donors and compared it to a corresponding antemortem blood sample. Methods: Ante- and postmortem blood samples were obtained from 100 consecutive tissue donors. The total IgG of all samples was measured using an immune-turbidometric test on the AU 480 Chemistry Analyzer (Beckman Coulter). Results: The mean total IgG concentration of antemortem blood samples from all 100 donors was 8.9 g/L ± 3.7 g/L (median 8.9 g/L, range 1.5 to 23.8 g/L). In 80 donors the IgG concentration in the antemortem blood sample was within the normal range with values ≥6 g/L (mean 10.0 g/L ± 3.3 g/L, median 9.3 g/L,). The total IgG concentration of the postmortem blood samples was lower with 7.2 g/L ± 3.2 g/L (median 6.7 g/L, range 0.6 to 18.2 g/L). The difference between the values of the antemortem and postmortem blood samples was 1.7 g/L ± 2.6 g/L (16.3%) (median 1.6 g/L, range –7.7 to 10.1 g/L). In 36 donors this difference was less than 10%, in 23 it was between 10 and 25%, in 33 between 26 and 50%, and in 8 over 50%. In 57 donors the total IgG in the postmortem blood sample was within the normal range with ≥6 g/L, in 53 of them also the value of the antemortem blood sample was within the normal range. No correlation for total IgG was found regarding the donor characteristics (age, sex, disease) and the sample characteristics (hemolysis, postmortem time). Conclusion: Total IgG values in antemortem samples were below the lower limit of 6 g/L in 20% of the cases. Total IgG was significantly lower in the postmortem samples compared to the antemortem samples, while 57% were still above the lower limit. No correlation with the postmortem time could be found. This lowered IgG levels should be payed attention to when using postmortem blood for infectious serology testing. Additional NAT testing should be considered.

Clinical, Laboratory, and Radiologic Characteristics of Patients With Initial False-Negative Severe Acute Respiratory Syndrome Coronavirus 2 Nucleic Acid Amplification Test Results.

BackgroundConcerns about false-negative (FN) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid amplification tests (NAATs) have prompted recommendations for repeat testing if suspicion for coronavirus disease 2019 (COVID-19) infection is moderate to high. However, the frequency of FNs and patient characteristics associated with FNs are poorly understood.MethodsWe retrospectively reviewed test results from 15 011 adults who underwent ≥1 SARS-CoV-2 NAATs; 2699 had an initial negative NAAT and repeat testing. We defined FNs as ≥1 negative NAATs followed by a positive NAAT within 14 days during the same episode of illness. We stratified subjects with FNs by duration of symptoms before the initial FN test (≤5 days versus >5 days) and examined their clinical, radiologic, and laboratory characteristics.ResultsSixty of 2699 subjects (2.2%) had a FN result during the study period. The weekly frequency of FNs among subjects with repeat testing peaked at 4.4%, coinciding with peak NAAT positivity (38%). Most subjects with FNs had symptoms (52 of 60; 87%) and chest radiography (19 of 32; 59%) consistent with COVID-19. Of the FN NAATs, 18 of 60 (30%) were performed early (ie, ≤1 day of symptom onset), and 18 of 60 (30%) were performed late (ie, >7 days after symptom onset) in disease. Among 17 subjects with 2 consecutive FNs on NP NAATs, 9 (53%) provided lower respiratory tract (LRT) specimens for testing, all of which were positive.ConclusionsOur findings support repeated NAATs among symptomatic patients, particularly during periods of higher COVID-19 incidence. The LRT testing should be prioritized to increase yield among patients with high clinical suspicion for COVID-19.

Extragenital testing increases case detection of gonorrhea and chlamydia: The impact of implementing nucleic acid amplification testing.

Nucleic acid amplification testing (NAAT) was validated in Ontario in 2018 to test for chlamydia and gonorrhea at extragenital (pharyngeal, rectal) sites. Prior to this validation, extragenital testing could be done only by culture in Ontario. The objective of this study was to determine the number and proportion of gonorrhea and chlamydia cases that were detected exclusively through extragenital (pharyngeal and/or rectal) testing after the implementation of extragenital NAAT for these two infections at Sexual Health Clinic among gay, bisexual, and other men who have sex with men (gbMSM). Case and laboratory data from before and after NAAT implementation were used to compare the rates of diagnosis of gonorrhea and chlamydia among gbMSM who presented at Sexual Health Clinics and the percent increase in diagnoses in gbMSM in the entire population. Among gbMSM seen at the clinic after implementation of NAAT testing, 70% of gonorrhea cases and 65% of chlamydia cases were detected exclusively at extragenital sites, corresponding to a four and two-fold increase, respectively, in the average annual number of cases diagnosed. As well, although approximately 50% more pharyngeal than rectal testing occurred, a higher proportion of chlamydia cases were detected rectally than would have been expected; this was not the case for gonorrhea, where most infections were pharyngeal. It is important that clinicians perform extragenital testing among gbMSM who have sexual contact involving extragenital sites with more than one partner.

Hepatitis B Virus Nucleic Acid Amplification Testing Assay in Detecting Window Period and Occult Hepatitis B Virus Infections in Blood Donors

SummaryTo reduce the residual risk of transfusion-transmitted infections, nucleic acid amplification testing (NAT) of donated blood with higher sensitivity for HBV, HCV, and HIV 1/2 was implemented in Bulgaria at the end of 2019. This study aimed to assess the clinical sensitivity of HBsAg testing and NAT testing of donated blood to detect all forms of HBV infection. A total of 9498 consecutive blood donations collected for six months, from February 10 to July 17, 2020, from first-time and repeat donors at the Regional Center of Transfusion Hematology Pleven, Bulgaria, were screened for HBsAg and HBV DNA. The detection of HBsAg was performed by enzyme-linked immunoassay and chemiluminescent immunoassay. Detection of HBV DNA was performed using the HIV1/2 /HCV / HBV multiplex Procleix Ultrio Elite assay in a fully automated and integrated Procleix Panther System. The overall HBsAg prevalence was 0.05%. HBV DNA was detected in 25 blood units (0.26%), but only 12 (0.13%) were found positive after repeat testing and were confirmed by a discriminatory test. The other 13 units were false positive, with the initial reactive result and negative results after repeat testing. HBV DNA’s overall incidence was significantly higher in HBsAg-positive donors than the HBsAg- negative (Fisher exact p=0.0063). In our study, blood donations were not tested for anti-HBc and anti-HBs, so it is difficult to determine whether HBV DNA-positive/HBsAg-negative results were associated with the early phase of infection or persistent occult infection. There was no statistical difference in the incidence of HBV DNA between repeat-donors (0.16%) and first-time donors (0.06%) (Fisher exact test p=0.239 NS), and also between the incidence in female donors (0.12%) and male donors (0.13%) (Fisher exact test p=1.0 NS). The results of this study showed a low rate of detection of the hepatitis B virus in donated blood. NAT testing demonstrates higher sensitivity for the detection of HBV, as compare to HBsAg screening.

Comparison of diagnostic accuracies of rapid serological tests and ELISA to molecular diagnostics in patients with suspected coronavirus disease 2019 presenting to the hospital

ObjectivesTo assess the diagnostic performance of rapid lateral flow immunochromatographic assays (LFAs) compared with an ELISA and nucleic acid amplification tests (NATs) in individuals with suspected coronavirus disease 2019 (COVID-19). MethodsPatients presenting to a Dutch teaching hospital were eligible between 17 March and 10 April 2020, when they had respiratory symptoms that were suspected for COVID-19. The performances of six different LFAs were evaluated in plasma samples obtained on corresponding respiratory sample dates of NATs testing. Subsequently, the best performing LFA was evaluated in 228 patients and in 50 sera of a historical patient control group. ResultsIn the pilot analysis, sensitivity characteristics of LFA were heterogeneous, ranging from 2/20 (10%; 95% CI 0%–23%) to 11/20 (55%; 95% CI 33%–77%). In the total cohort, Orient Gene Biotech COVID-19 IgG/IgM Rapid Test LFA had a sensitivity of 43/99 (43%; 95% CI 34%–53%) and specificity of 126/129 (98%; 95% CI 95%–100%). Sensitivity increased to 31/52 (60%; 95% CI 46%–73%) in patients with at least 7 days of symptoms, and to 21/33 (64%; 95% CI 47%–80%) in patients with C-reactive protein (CRP) ≥100 mg/L. Sensitivity and specificity of Wantai SARS-CoV-2 Ab ELISA was 59/95 (62%; 95% CI 52%–72%) and 125/128 (98%; 95% CI 95%–100%) in all patients, respectively, but sensitivity increased to 38/48 (79%; 95% CI 68%–91%) in patients with at least 7 days of symptoms. ConclusionsThere is large variability in diagnostic test performance between rapid LFAs, but overall limited sensitivity and high specificity in acutely admitted patients. Sensitivity improved in patients with longer existing symptoms or high CRP. LFAs should only be considered as additional triage tools when these may lead to the improvement of hospital logistics.