Discrepant Test Results Research Articles

Analysis of Suspected Measles Cases with Discrepant Measles-Specific IgM and rRT-PCR Test Results, Japan.

We investigated clinically suspected measles cases that had discrepant real-time reverse transcription PCR (rRT-PCR) and measles-specific IgM test results to determine diagnoses. We performed rRT-PCR and measles-specific IgM testing on samples from 541 suspected measles cases. Of the 24 IgM-positive and rRT-PCR--negative cases, 20 were among children who received a measles-containing vaccine within the previous 6 months; most had low IgG relative avidity indexes (RAIs). The other 4 cases were among adults who had an unknown previous measles history, unknown vaccination status, and high RAIs. We detected viral nucleic acid for viruses other than measles in 15 (62.5%) of the 24 cases with discrepant rRT-PCR and IgM test results. Measles vaccination, measles history, and contact history should be considered in suspected measles cases with discrepant rRT-PCR and IgM test results. If in doubt, measles IgG avidity and PCR testing for other febrile exanthematous viruses can help confirm or refute the diagnosis.

Верифікація алгоритмів тестування на ВІЛ з використанням швидких тестів

Верифікація алгоритмів тестування на ВІЛ з використанням швидких тестів

678. Rapid Molecular SARS-CoV-2 Detection by Abbott ID NOW Is Reliable in Pediatric Patients

BackgroundThe COVID-19 Pandemic demonstrated the importance of rapid, accurate, point of care testing to control spread of the virus. The availability of this testing has been crucial to re-opening schools, keeping children safely in schools, and returning children to school quickly following illness. The Abbott ID Now molecular assay to detect SARS-CoV-2 was granted Emergency Use Authorization in March 2020. Reports of lower sensitivity compared with conventional PCR prompted some school districts to require confirmatory conventional PCR for negative rapid molecular results to return children to school. In this study we aim to determine the sensitivity and specificity of the Abbott ID NOW molecular SARS-CoV-2 test in a large pediatric primary care practice.MethodsA retrospective observational study was performed using data from 25 pediatric primary care sites in the Boston Children’s Health Physicians network, a large multispecialty pediatric practice in New York and Connecticut. Data were extracted from the electronic health record for all patients 0-22 years of age who had an Abbott ID NOW rapid molecular COVID-19 assay from October 1, 2020 - February 28, 2021. For all patients with rapid tests, we identified patients who had a conventional PCR test sent within 1 day before or 1 day after the ID NOW test. The result of the conventional PCR test was considered the “true” result. All discrepant test results were identified.ResultsDuring the study period, 14993 patients had ID NOW testing performed. The percent positivity was 8.5%. The percent positivity in our practices paralleled that in the surrounding community throughout the winter surge of COVID-19. 500 patients had confirmatory testing sent within 1 day before or after the ID NOW test (15 positive and 485 negative results). Based on the conventional PCR test results, 2 of 15 positive results were false positive and only 1 of 485 negative results was a false negative, resulting in a sensitivity of 93% and specificity of 99.6%. The false negative result was in a patient with nasal congestion whose mother was COVID positive.ConclusionRapid, molecular, point of care testing is an important tool to identify SARS-CoV-2 in pediatric patients and limit school absences. The ID NOW assay is highly sensitive and specific in a real-world pediatric setting. Disclosures All Authors: No reported disclosures

90. Impact of Discrepant Rapid Diagnostic Test (RDT) Results on Antimicrobial Stewardship Program (ASP) Interventions in Patients with Bloodstream Infections (BSI) due to Gram-Negative Bacilli (GNB)

BackgroundImplementation of the Accelerate PhenoTM Gram-negative platform (AXDX) paired with ASP intervention projects to improve time to definitive institutional-preferred antimicrobial therapy (IPT). However, few data describe the impact of discrepant RDT results from standard of care (SOC) methods on antimicrobial prescribing. Here we evaluate the prescribing outcomes for discrepant results following the first year of AXDX + ASP implementation.MethodsConsecutive, non-duplicate blood cultures for adult inpatients with GNB BSI following combined RDT + ASP intervention were included (July 2018 – July 2019). AXDX results were emailed to the ASP in real time then released into the EMR upon ASP review and communication with the treating team. SOC identification (ID; Vitek® MS/Vitek® 2) and antimicrobial susceptibility testing (AST; Trek SensititreTM) followed RDT as the reference standard. IPT was defined as the narrowest susceptible beta-lactam, and a discrepancy was characterized when there was categorical disagreement between RDT and SOC methods. When IPT by AXDX was found to be non-susceptible on SOC, this was characterized as “false susceptible“. Conversely, “false resistance” was assessed when a narrower-spectrum agent was susceptible by SOC. Results were also deemed discrepant when the AXDX provided no/incorrect ID for on-panel organisms, no AST, or a polymicrobial specimen was missed.ResultsSixty-nine of 250 patients (28%) had a discrepancy in organism ID or AST: false resistance (9%), false susceptible (5%), no AST (5%), no ID (4%), incorrect ID (2%), and missed polymicrobial (2%). A prescribing impact occurred in 55% of cases (Table 1), where unnecessarily broad therapy was continued most often. Erroneous escalation (7%) and de-escalation to inactive therapy (7%) occurred less frequently. In-hospital mortality occurred in 4 cases, none of which followed an inappropriate transition to inactive therapy. ConclusionThough the AXDX platform provides rapid ID and AST results, close coordination with Clinical Microbiology and continued ASP follow up are needed to optimize therapy. Although uncommon, the potential for erroneous ASP recommendations to de-escalate to inactive therapy following AXDX results warrants further investigation.DisclosuresAmy J. Mathers, MD, D(ABMM), Accelerate Diagnostics (Consultant)

Transmission of infection from non-isolated patients with COVID-19 to healthcare workers

Insufficiently protected healthcare workers (HCWs), defined as high-risk contacts of patients with coronavirus disease 2019 (COVID-19), are routinely quarantined. This study evaluated the transmission of infection from a symptomatic patient with COVID-19 to 60 HCWs exposed at ≤2 m for ≥15 min or during aerosol-generating procedures. Following ≥106 unique high-risk contacts, none of the HCWs tested positive for severe acute respiratory syndrome coronavirus-2 RNA or developed antibodies. The HCWs reported adherence to basic infection control procedures. These results are in accordance with other reports, and should reassure HCWs and further stimulate broader evaluation of the foundation for the current practice of home quarantining non-symptomatic HCWs.

Monitoring unfractionated heparin therapy. 4 hour-stability of anti-Xa activity in unspun citrated tubes

Current guidelines recommend performing laboratory tests aimed at monitoring unfractionated heparin (UFH) treatments within a delay not exceeding 1 to 2 h(s) after sampling when blood is collected into citrated tubes. As such a short delay could be an issue, we evaluated the potential impact of longer delays. For that purpose, two citrated tubes were obtained from patients on UFH: one was centrifuged and tested for anti-Xa activity and aPTT within 1 h after collection (T1 h) and one was stored for 4 h at room temperature (T4 h) before being processed. A total of 123 paired tubes were investigated. Anti-Xa activity was significantly lower at T4 h than at T1 h, with a mean bias, calculated according to Bland-Altman, of 0.05 IU/mL. Considering 0.30 to 0.70 IU/mL as the therapeutic range, there were 12 cases of discrepant test results (9.8%). Most of them being around the lower limit of the therapeutic range had no impact on patients' management. APTT was significantly shortened (p < 0.0001) at T4 h vs. T1 h, with a mean bias of −7.9 s. Considering anti-Xa correlated aPTT therapeutic range, 29 cases of discrepant test results (23.6%) were found, 10% would have induce dosage changes. The concordance between anti-Xa activities measured at T4 h and T1 h was excellent (kappa = 0.813) and good for aPTT (kappa = 0.661). In conclusion, extending the delay between blood collection and measurement of tests prescribed for monitoring UFH therapy up to 4 h was found to lead to a systematic reduction in both anti-Xa activity and aPTT in unspun citrated tubes. As changes at T4 h were limited and had few clinically relevance than the ones observed with aPTT testing, a 4 h-delay was found to be acceptable for anti-Xa activity. The maximum delay for aPTT should remain around 1–2 h as changes were more relevant.

Comparison of three commercial IgG and IgM ELISA kits for the detection of tick-borne encephalitis virus antibodies

Tick-borne encephalitis (TBE) is endemic in many parts of Europe and Asia. The diagnosis of this disease is essentially based on the demonstration of specific antibodies. For reasons of simplicity, automatization and quick availability of test results, enzyme-linked immunosorbent assays (ELISAs) are the method of choice for serological diagnosis of TBE. Here, we evaluated three commercially available anti-TBEV IgG and IgM ELISAs using 251 serum samples: the SERION ELISA classic FSME Virus/TBE Virus IgG and IgM kit (Virion\\Serion), the RIDASCREEN® FSME/TBE IgG and IgM kit (R-Biopharm), and the anti-FSME/TBE virus ELISA “Vienna” IgG/anti-FSME/TBE virus ELISA IgM kit (Euroimmun). In total, discrepant test results for IgG and/or IgM were observed for 37/251 (14.7 %) of tested samples; differences were statistically significant. Reference values defined by serum neutralization test (SNT, n = 25) or results provided by EQA organizers (n = 2) were established for a subset of samples. In relation to these values, false-positive results were observed mainly for Euroimmun Vienna IgG and RIDASCREEN IgG, whereas false-negative results were primarily observed for Virion\\Serion IgG and RIDASCREEN IgM kits. In routine diagnostics, specificity problems are of major relevance and may be addressed by analyzing the respective samples using SNT.

To err is human, to correct is public health: a systematic review examining poor quality testing and misdiagnosis of HIV status.

Introduction: In accordance with global testing and treatment targets, many countries are seeking ways to reach the “90-90-90” goals, starting with diagnosing 90% of all people with HIV. Quality HIV testing services are needed to enable people with HIV to be diagnosed and linked to treatment as early as possible. It is essential that opportunities to reach people with undiagnosed HIV are not missed, diagnoses are correct and HIV-negative individuals are not inadvertently initiated on life-long treatment. We conducted this systematic review to assess the magnitude of misdiagnosis and to describe poor HIV testing practices using rapid diagnostic tests. Methods: We systematically searched peer-reviewed articles, abstracts and grey literature published from 1 January 1990 to 19 April 2017. Studies were included if they used at least two rapid diagnostic tests and reported on HIV misdiagnosis, factors related to potential misdiagnosis or described quality issues and errors related to HIV testing. Results: Sixty-four studies were included in this review. A small proportion of false positive (median 3.1%, interquartile range (IQR): 0.4-5.2%) and false negative (median: 0.4%, IQR: 0-3.9%) diagnoses were identified. Suboptimal testing strategies were the most common factor in studies reporting misdiagnoses, particularly false positive diagnoses due to using a “tiebreaker” test to resolve discrepant test results. A substantial proportion of false negative diagnoses were related to retesting among people on antiretroviral therapy. Conclusions: HIV testing errors and poor practices, particularly those resulting in false positive or false negative diagnoses, do occur but are preventable. Efforts to accelerate HIV diagnosis and linkage to treatment should be complemented by efforts to improve the quality of HIV testing services and strengthen the quality management systems, particularly the use of validated testing algorithms and strategies, retesting people diagnosed with HIV before initiating treatment and providing clear messages to people with HIV on treatment on the risk of a “false negative” test result.

A public health approach to addressing and preventing misdiagnosis in the scale-up of HIV rapid testing programmes

Introduction: In accordance with global testing and treatment targets, many countries are seeking ways to reach the “90-90-90” goals, starting with diagnosing 90% of all people with HIV. Quality HIV testing services are needed to enable people with HIV to be diagnosed and linked to treatment as early as possible. It is essential that opportunities to reach people with undiagnosed HIV are not missed, diagnoses are correct and HIV-negative individuals are not inadvertently initiated on life-long treatment. We conducted this systematic review to assess the magnitude of misdiagnosis and to describe poor HIV testing practices using rapid diagnostic tests. Methods: We systematically searched peer-reviewed articles, abstracts and grey literature published from 1 January 1990 to 19 April 2017. Studies were included if they used at least two rapid diagnostic tests and reported on HIV misdiagnosis, factors related to potential misdiagnosis or described quality issues and errors related to HIV testing. Results: Sixty-four studies were included in this review. A small proportion of false positive (median 3.1%, interquartile range (IQR): 0.4-5.2%) and false negative (median: 0.4%, IQR: 0-3.9%) diagnoses were identified. Suboptimal testing strategies were the most common factor in studies reporting misdiagnoses, particularly false positive diagnoses due to using a “tiebreaker” test to resolve discrepant test results. A substantial proportion of false negative diagnoses were related to retesting among people on antiretroviral therapy. Conclusions: HIV testing errors and poor practices, particularly those resulting in false positive or false negative diagnoses, do occur but are preventable. Efforts to accelerate HIV diagnosis and linkage to treatment should be complemented by efforts to improve the quality of HIV testing services and strengthen the quality management systems, particularly the use of validated testing algorithms and strategies, retesting people diagnosed with HIV before initiating treatment and providing clear messages to people with HIV on treatment on the risk of a “false negative” test result. 10.7448/IAS.20.7.21755 © 2017 Johnson C C et al; licensee International AIDS Society Published 29 August 2017; Received 16 December 2016; Accepted 7 March 2017; Revised 29 August 2017

Utilizing BD MAX\u2122 Enteric Bacterial Panel to Detect Stool Pathogens from Rectal Swabs

BackgroundThe BD MAX™ Enteric Bacterial Panel (BDM-EBP) is designed and FDA-cleared to detect Salmonella, Shigella, Campylobacter, and Shiga toxin genes stx1/2 from stool samples. However, rectal swabs, which are not FDA-cleared for clinical testing with the BDM-EBP, are common specimens received from pediatric patients for enteric pathogen testing. The purpose of this study was to evaluate the ability of the BDM-EBP to detect stool pathogens from rectal swabs.MethodsRoutine cultures, Shiga toxin testing, and molecular testing with BDM-EBP were performed on 272 sequential rectal swabs collected from August 2015 to December 2015. Discrepant test results were resolved using Verigene® Enteric Pathogens Nucleic Acid Test (EP). 36 challenge samples (13 Salmonella spp., 3 Shigella spp., 10 Campylobacter spp., and 10 Shiga toxin positive Escherichia coli) were tested using reference strains (American Type Culture Collection) and previous patient isolates diluted to103-104 cfu/ml in saline then added to Sample Buffer Tube (SBT) with negative stool matrix delivered via a swab. Limit of detection testing was performed by serial 10 fold dilutions in saline then added to SBT with negative stool matrix provided via a swab.ResultsA total of 272 rectal swab specimens were evaluated and 89 were positive by culture and/or MAX EBP. All discrepant results were BDM-EBP positive and culture negative. 21 of 31 (68%) of the apparent false positive BDM-EBP discrepant results resolved as positive with Nanosphere’s Verigene® EP. After resolution of the discordant results, the Positive Percent Agreement (PPA) and Negative Percent Agreement (NPA) are as follows for each target: Salmonella (n = 4) 100%, PPA and 100%, NPA; Shigella (n = 79) 100%, PPA and 95.3%, NPA; Campylobacter (n = 4) 100%, PPA and 99.6%, NPA; and Shiga toxin producing organisms (n = 2) 100%, PPA and 100%, NPA. 8.8% of the patient samples did not initially yield a result on the BDM-System. Upon repeat, half of the problematic samples resolved, and 4.4% of the total specimen tested did not yield a result. All organisms in the challenge samples were detected. Limits of detection for BDM-EBP testing of rectal swabs were as follows (in cfu/ml in SBT): Salmonella-1.44 × 102; Shigella-5.10 × 100; Campylobacter-1.51 × 101; and Shiga Toxin-1.13 ×103.ConclusionRectal swabs are acceptable samples for detecting Salmonella, Shigella, Campylobacter, and Shiga toxin using BDM-EBP.

Interlaboratory and between-specimen comparisons of diagnostic tests for leptospirosis in sheep and cattle

A study was performed to investigate interlaboratory test agreement between a research and a commercial veterinary diagnostic laboratory on blood and urine samples, and to investigate test agreement between blood, urine, and kidney samples (research laboratory) for leptospirosis diagnosis. Samples were sourced from 399 sheep and 146 beef cattle from a local abattoir. Interlaboratory agreement for real-time quantitative polymerase chain reaction (qPCR) results on urine samples was almost perfect (kappa = 0.90), despite the use of different amplification targets (DNA gyrase subunit B gene vs. 16s ribosomal RNA gene), chemistries (SYTO9 vs. TaqMan probe), and pre-PCR processing. Interlaboratory agreement for microscopic agglutination test (MAT) positivity was almost perfect (kappa = 0.93) for Leptospira borgpetersenii serovar Hardjo subtype Hardjobovis (Hardjobovis) but moderate (kappa = 0.53) for Leptospira interrogans serovar Pomona (Pomona). Among animals that had different titers recorded, higher Hardjobovis and lower Pomona titers were reported by the commercial laboratory than by the research laboratory (P < 0.005). These interlaboratory comparisons can assist researchers and diagnosticians in interpreting the sometimes discrepant test results. Within the research laboratory, the comparison of qPCR results on urine and kidney showed almost perfect agreement (kappa = 0.84), suggesting that the qPCR on these 2 specimens can be used interchangeably. The agreement between MAT positivity and urine and kidney qPCR results was fair (kappa = 0.32 and kappa = 0.33, respectively). However, the prevalence ratio of urine and kidney qPCR positivity in Hardjobovis-seropositive versus Hardjobovis-seronegative sheep indicated that Hardjobovis seropositivity found in sheep may be able to predict shedding or renal carriage.

Irreconcilable Differences in Tests of Hotelling’s Theory of Exhaustible Resources

Empirical tests of the theory of exhaustible resources have provided mixed results regarding empirical validity of the theory. This paper considers differences in the primary testing methodologies and alternative measures of the in situ resource price. We demonstrate that in situ price measures common in the literature are theoretically equivalent for the vertically integrated firm. We also show that empirical shadow price test methodologies imply the same restricted econometric model, while the unrestricted models diverge. We find that the Halvorsen and Smith (1991) test methodology is relatively efficient, and, using data on natural gas wells, reject the unrestricted transition equation of traditional methodology. We conclude that discrepant empirical test results may be an artifact of the econometric testing methodologies rather than a reflection on the validity of the theory.

Tuberculosis ethambutol resistance: Concordance between phenotypic and genotypic test results

embB306 mutations are potential markers for detecting ethambutol resistance in clinical Mycobacterium tuberculosis isolates. However, more recently, embB306 mutations have been found in ethambutol susceptible isolates and an association with broad drug resistance rather than ethambutol resistance has been reported. To further investigate this question, we analyzed the association between embB306 mutations and phenotypic ethambutol resistance among 197 isolates from a drug resistance survey performed in Karakalpakstan, Uzbekistan. 39 strains had an embB306 mutation, out of which seven were ethambutol susceptible, thus, displaying discrepant test results. After re-analysis, the seven isolates were tested ethambutol resistant. All of these strains had an increased ethambutol MIC, however, three strains showed no or weak growth on the critical concentration of 2 microg/ml on Löwenstein-Jensen. In three strains we confirmed the presence of heteroresistant mixed populations which might influence conventional ethambutol testing. Final concordance between molecular and phenotypic EMB testing was high with a sensitivity of 78% and a specificity of 100%. Our results confirm that embB306 mutations are useful markers for predicting ethambutol resistance. Discrepancies between molecular and phenotypic ethambutol resistance test results are most likely caused by problems with conventional susceptibility testing.

High sensitivity of both sequencing and real‐time PCR analysis of KRAS mutations in colorectal cancer tissue

The KRAS mutation status predicts the outcome of treatment with epidermal growth factor receptor targeted agents, and therefore the testing for KRAS mutations has become an important diagnostic procedure. To optimize the quality of this test, we compared the results of the two most commonly used KRAS mutation tests, cycle sequencing and a real-time PCR-based assay, in DNA extracted from formalin-fixed paraffin-embedded (FFPE) colorectal cancer samples of 511 patients. The results were interpreted in the context of the tumour cell percentage and the assay parameters. In 510 samples KRAS mutation status assessment was successful. A KRAS mutation was detected in 201 tumours (39.4%). Sequencing and the real-time PCR-based assay generated the same result in 486 samples (95.3%). The sequencing result was considered false positive in one (0.2%) and false negative in nine samples (1.8%). The assay result was considered false positive in six (1.2%) and false negative in seven samples (1.4%). Explanations for discrepant test results were a higher sensitivity of the assay in samples with a low tumour cell percentage, occurrence of mutations that are not covered by the assay and δ Ct values approximating the cut-off value of the assay. In conclusion, both sequencing and the real-time PCR-based assay are reliable tests for KRAS mutation analysis in FFPE colorectal cancer samples, with a sensitivity of 95.5% (95% confidence interval [CI] 91.7–97.9%) and 96.5% (95% CI 93.0–98.6%), respectively. The real-time PCR based assay is the method of choice in samples with a tumour cell percentage below 30%.

Discrepancy between sperm acrosin activity and sperm morphology: significance for fertilization in vitro

Background In routine semen analysis, discrepancies may occur between sperm acrosin activity test results and sperm acrosomal morphology. Methods Discrepant test results of sperm acrosin activity (spectrophotometric assay) vs. sperm morphology (strict criteria) in the initial diagnostic investigation of 107 infertile couples were evaluated with respect to fertilization rate (% oocytes with 2 pronuclei) further obtained in IVF treatment. Results Acrosin activity positively correlated with sperm morphology (% normal forms) ( r=0.537) and fertilization rate ( r=0.526). ROC curves for the prediction of ≥50% fertilization rate were comparable for acrosin activity and sperm morphology, with optimal cutoff values at 25 μIU/10 6 sperm and 10%, respectively. In multiple regression analysis, sperm acrosin activity ( P=0.002) predicted fertilization rate independently of sperm morphology ( P<0.001) and sperm vitality (eosin–nigrosin stain) ( P=0.03). Acrosin activities ≥25 μIU/10 6 sperm were observed in 36% of severe teratozoospermic samples (≤4% normal spermatozoa) associated with low fertilization rate. Twenty percent of the morphologically normal ejaculates showed a low acrosin activity (<25 μIU/10 6 sperm) and low hypoosmotic swelling test (HOST) scores (31.4±7.6%) and were associated with low fertilization rate. Conclusion The sperm acrosin assay can help to predict sperm fertilizing capacity in IVF independently of sperm morphology.

Multiplex real-time PCR assay for detection of influenza and human respiratory syncytial viruses.

A multiplex real-time PCR assay was developed with a LightCycler instrument for detection of influenza viruses A and B and the human respiratory syncytial virus (HRSV). Detection of each viral product and of an internal control was based on determination of specific melting temperatures by the LightCycler software. The lower limit of detection in the multiplex PCR assay was found to be 50 copies for each viral target. In an evaluation of nasopharyngeal samples collected from hospitalized children (ages, 0 to 3 years) with acute respiratory tract infections during the winter of 2001 to 2002, a viral pathogen was detected by the multiplex PCR test in 139 (66.8%) of 208 cases, including 45 (21.6%) influenza A virus infections, no (0%) influenza B virus infections, 106 (51%) HRSV infections, and 12 (5.8%) coinfections. The multiplex PCR test was compared to rapid antigen detection assays for influenza viruses A and B (Directigen; Becton Dickinson, Sparks, Md.) and HRSV (RSV TestPack; Abbott Laboratories, Abbott Park, Ill.) in 172 and 204 samples, respectively. After resolution of discrepant test results by use of additional PCR assays targeting other viral genes, the sensitivity (Se) and specificity (Sp) of the multiplex PCR assay for influenza A virus were 100 and 97.7% compared to 43.6 and 98.5% for the antigenic test. Similarly, the Se and Sp of the multiplex PCR assay for HRSV were 94.5 and 98.9% compared to 81.6 and 94.7% for the antigenic test. In conclusion, our multiplex real-time PCR assay combines both rapidity and sensitivity for detecting the most important respiratory viral pathogens in children.

Evaluation of the Helicobacter pylori stool antigen test (HpSA) for detection of Helicobacter pylori infection in children

OBJECTIVE: Helicobacter pylori ( H. pylori) infection is usually acquired in early childhood. Noninvasive methods for detection of H. pylori infection are required to study its incidence, transmission, and clearance. They should be easy to perform, inexpensive, and have a high diagnostic accuracy, especially in infants and toddlers. Both serology and the 13C-urea breath test ( 13C-UBT) do not fulfill all these requirements. The aim of this study was to evaluate a new enzyme immunoassay for detection of H. pylori antigen in stool (Premier Platinum HpSA, Meridian Diagnostics, Cincinnati, OH) in a large cohort of children and to compare it to invasive techniques and the 13C-UBT. METHODS: HpSA was performed in 310 stool samples of 274 children divided into three groups. Group A consisted of 145 children and adolescents (0.5–19.8 yr, 66/145 <6 yr) who underwent upper endoscopy for various gastrointestinal symptoms. H. pylori status was defined by histology, culture, and rapid urease test from biopsies of the antrum and corpus. A 13C-UBT was performed in 133 of 145 children. Group B consisted of 22 patients (5.7–16.1 yr) who were retested with both noninvasive tests 8 wk after anti- H. pylori triple therapy. Group C consisted of 129 healthy infants and toddlers (0.9–3.1 yr) who were tested with the 13C-UBT. Children with discrepant or positive test results were retested after 2 and 12 months. Results of the HpSA were read at 450/620 nm by spectrophotometry. An optical density <0.100 was defined as negative, >0.120 as positive, and values between 0.100 and 0.120 were considered as equivocal. RESULTS: In Group A, the HpSA gave false–negative results in five of 45 infected children and false–positive results in four of 100 noninfected children, whereas four patients (2.8%) showed equivocal results. In both infected and noninfected children, no relation between the optical density values and age was found. The 13C-UBT was correct in 132 of 133 children tested. In Group B, there was complete concordance between the HpSA and 13C-UBT: 19 children tested negative and three positive. In Group C, concordant results between the two noninvasive methods were found in 124 of 129 (96%) toddlers (122 negative and two positive). Retesting of five children with discrepant results revealed that, on initial testing, the HpSA was incorrect in two (one false–positive, one false–negative), and the 13C-UBT was incorrect in three (always false–positive). CONCLUSIONS: In symptomatic children, the HpSA revealed a sensitivity of 88.9% (95% CI 77.3–96.3) and a specificity of 94.0% (88.1–97.7) compared to the 13C-UBT, 100% (94.0–100) and 98.9% (94.7–100), respectively. However, in healthy toddlers, the HpSA performed as well as the 13C-UBT with excellent concordance between the two noninvasive tests. There was no age dependency of the stool test results, and changing the cutoff would not have improved accuracy. Thus, the HpSA test seems suitable to monitor the success of anti- H. pylori therapy.

Evaluation of the Helicobacter pylori stool antigen test (HpSA) for detection of Helicobacter pylori infection in children

Helicobacter pylori (H. pylori) infection is usually acquired in early childhood. Noninvasive methods for detection of H. pylori infection are required to study its incidence, transmission, and clearance. They should be easy to perform, inexpensive, and have a high diagnostic accuracy, especially in infants and toddlers. Both serology and the 13C-urea breath test (13C-UBT) do not fulfill all these requirements. The aim of this study was to evaluate a new enzyme immunoassay for detection of H. pylori antigen in stool (Premier Platinum HpSA, Meridian Diagnostics, Cincinnati, OH) in a large cohort of children and to compare it to invasive techniques and the 13C-UBT. HpSA was performed in 310 stool samples of 274 children divided into three groups. Group A consisted of 145 children and adolescents (0.5-19.8 yr, 66/145 <6 yr) who underwent upper endoscopy for various gastrointestinal symptoms. H. pylori status was defined by histology, culture, and rapid urease test from biopsies of the antrum and corpus. A 13C-UBT was performed in 133 of 145 children. Group B consisted of 22 patients (5.7-16.1 yr) who were retested with both noninvasive tests 8 wk after anti-H. pylori triple therapy. Group C consisted of 129 healthy infants and toddlers (0.9-3.1 yr) who were tested with the 13C-UBT. Children with discrepant or positive test results were retested after 2 and 12 months. Results of the HpSA were read at 450/620 nm by spectrophotometry. An optical density <0.100 was defined as negative, >0.120 as positive, and values between 0.100 and 0.120 were considered as equivocal. In Group A, the HpSA gave false-negative results in five of 45 infected children and false-positive results in four of 100 noninfected children, whereas four patients (2.8%) showed equivocal results. In both infected and noninfected children, no relation between the optical density values and age was found. The 13C-UBT was correct in 132 of 133 children tested. In Group B, there was complete concordance between the HpSA and 13C-UBT: 19 children tested negative and three positive. In Group C, concordant results between the two noninvasive methods were found in 124 of 129 (96%) toddlers (122 negative and two positive). Retesting of five children with discrepant results revealed that, on initial testing, the HpSA was incorrect in two (one false-positive, one false-negative), and the 13C-UBT was incorrect in three (always false-positive). In symptomatic children, the HpSA revealed a sensitivity of 88.9% (95% CI 77.3-96.3) and a specificity of 94.0% (88.1-97.7) compared to the 13C-UBT, 100% (94.0-100) and 98.9% (94.7-100), respectively. However, in healthy toddlers, the HpSA performed as well as the 13C-UBT with excellent concordance between the two noninvasive tests. There was no age dependency of the stool test results, and changing the cutoff would not have improved accuracy. Thus, the HpSA test seems suitable to monitor the success of anti-H. pylori therapy.

First Workshop for Detection of Heparin-induced Antibodies: Validation of the Heparin-induced Platelet-activation Test (HIPA) in Comparison with a PF4/Heparin ELISA

No data exist regarding the inter-laboratory reproducibility of the heparin-induced-platelet-activation (HIPA) test, the most widely used functional assay in Germany for the detection of heparin-induced thrombocytopenia (HIT) antibodies. Nine laboratories used an identical protocol to test eight different sera with the HIPA test. Five laboratories also tested the sera with a platelet factor 4 (PF4)/heparin-complex ELISA. Cross-reactivity with danaparoid-sodium was assessed using 0.2 aFXa units instead of heparin in the HIPA test. Two of nine laboratories had no discrepant HIPA test results. Four laboratories differed in one sample, one reported two discrepant results, and two laboratories reported more than two discrepant results. Cross-reactivity with danaparoid-sodium test results differed among laboratories. PF4/heparin ELISA results were identical in all five laboratories. The HIPA test requires strict quality control measures. Using both a sensitive functional assay (HIPA test) and a PF4/heparin ELISA will allow detection of antibodies directed to antigens other than PF4/heparin complexes as well as detection of IgM and IgA antibodies with PF4/heparin specificity.

An evaluation of dipstick-dot immunoassay in the detection of antibodies to HIV-1 and 2 in Zimbabwe.

There is a need, in many developing countries, for simple and inexpensive HIV serology tests for use at the district level of health care. The Programme for Appropriate Technology in Health has developed a simple dipstick ELISA to detect antibodies to HIV-1 and 2, at a cost considerably lower than current ELISAs, which requires no specialized washing or reading equipment. In order to evaluate this dipstick under local conditions we used a panel of 546 sera selected from frozen stocks maintained by the Zimbabwe AIDS Prevention Project in Harare, Zimbabwe. Prior to storage, the sera had been tested by Abbott recombinant peptide HIV-1 and 2 ELISA and Enzygnost synthetic peptide HIV-1 and 2 ELISA. The panel included sera that were positive by both (including symptomatics and asymptomatics), negative by both, and sera showing discrepant test results. The panel was not representative of a "normal' batch of sera in Zimbabwe, and in particular included an abnormally high number of sera showing discrepant results. Thawed sera were retested using the Abbott recombinant peptide HIV-1 and 2 ELISA and concurrently with the synthetic peptide ICL-Dipstick ELISA. Both the sensitivity and specificity of the ICL Dipstick exceeded 99% when using sera that were positive or negative in all 3 plate ELISAs as the gold standard. When using sera that gave discrepant results between the two pre-storage ELISAs, most results with the ICL Dipstick concurred with findings from other test systems, including Western blot and p24 antigen detection. Considering the accuracy, low cost and case of operation of the ICL Dipstick ELISA, this test can be recommended for use for the rapid detection of antibodies to HIV at district level in developing countries.