Field Validation of Limiting-Antigen Avidity Enzyme Immunoassay to Estimate HIV-1 Incidence in Cross-Sectional Survey in Swaziland.

Reliable and accurate laboratory assays to detect recent HIV-1 infection have potential as simple and practical methods of estimating HIV-1 incidence in cross-sectional surveys. This study describes validation of the limiting-antigen (LAg) avidity enzyme immunoassay (EIA) in a cross-sectional national survey, conducted in Swaziland, comparing it to prospective follow-up incidence. As part of the Swaziland HIV-1 Incidence Measurement Survey (SHIMS), 18,172 individuals underwent counseling and HIV rapid testing in a household-based, population survey conducted from December 2010 to June 2011. Plasma samples from HIV-positive persons were classified as recent infections using an incidence testing algorithm with LAg-Avidity EIA (normalized optical density ≤1.5) followed by viral load (VL ≥1,000 copies/mL). All HIV-seronegative samples were tested for acute HIV-1 infection by nucleic acid amplification test (NAAT) pooling. HIV-seronegative individuals who consented to follow-up were retested ∼6 months later to detect observed HIV-1 seroconversion. HIV-1 incidence estimates based on LAg+VL and NAAT were calculated using assay-specific parameters and were compared with prospective incidence estimate. A total of 5,803 (31.9%) of 18,172 survey participants tested HIV seropositive; of these 5,683 (97.9%) were further tested with LAg+VL algorithm. The weighted annualized incidence from the longitudinal cohort study was 2.4% (95% confidence interval 2.0-2.7). Based on cross-sectional testing of HIV positives with LAg+VL algorithm, overall weighted annualized HIV-1 incidence was 2.5% (2.0-3.0), whereas NAAT-based incidence was of 2.6%. In addition, LAg-based incidence in men (1.8%; 1.2-2.5) and women (3.2%; 2.4-3.9) were similar to estimates based on observed incidence (men = 1.7%, women = 3.1%). Changes in HIV-1 incidence with age in men and women further validate plausibility of the algorithm. These results demonstrate that the LAg EIA, in a serial algorithm with VL, is a cost-effective tool to estimate HIV-1 incidence in cross-sectional surveys.

Clinical and economic impact of the introduction of a nucleic acid amplification assay for Clostridium difficile.

BACKGROUND: The clinical outcomes and cost implications of a diagnostic shift from an EIA- to PCR-based assay for Clostridium difficile infection (CDI) have not been completely described in the literature. METHODS: The impact of the PCR-based assay on the incidence and duration of CDI therapy was compared to the EIA assay for patients with a negative CDI diagnostic result. Secondary clinical and economic outcomes were also evaluated. Independent predictors of receipt of antibiotic therapy were assessed via logistic regression. RESULTS: 141 EIA and 140 PCR patients were included. Significantly more patients were started or continued on anti-CDI antibiotic therapy after a known negative assay result in the EIA group (26 patients vs. 8 patients, P = 0.002). Duration of antibiotic therapy after a known negative result was significantly shorter in the PCR group (1 vs. 4 days, P = 0.029) and a 23% reduction in the number of tests obtained per patient was observed (1.41 ± 0.86 vs. 1.82 ± 1.35, P = 0.007). The over fourfold difference in per-test cost of the EIA assay ($8.33 vs. $42.86, P < 0.0001) was offset by the overall medication costs required for the increased treatment in the EIA group ($546.60 vs. $188.96, P = 0.191). Utilization of the EIA-based CDI assay was associated with increased odds of CDI treatment after a negative test (aOR 4.71, 95% CI 1.93-11.46, P = 0.001). CONCLUSION: The transition from an EIA to PCR-based assay for diagnosing CDI resulted in a significant decrease in the number of patients treated and the duration of treatment in response to a negative test result. This significant decrease in treatment resulted in decreased costs offsetting the utilization of a more expensive molecular test for patients with a negative CDI diagnostic result.

Development and validation of an immunoperoxidase antigen detection test for improved diagnosis of rabies in Indonesia.

Rabies continues to pose a significant threat to human and animal health in regions of Indonesia. Indonesia has an extensive network of veterinary diagnostic laboratories and the 8 National laboratories are equipped to undertake diagnostic testing for rabies using the commercially-procured direct fluorescent antibody test (FAT), which is considered the reference (gold standard) test. However, many of the Indonesian Provincial diagnostic laboratories do not have a fluorescence microscope required to undertake the FAT. Instead, certain Provincial laboratories continue to screen samples using a chemical stain-based test (Seller's stain test, SST). This test has low diagnostic sensitivity, with negative SST-tested samples being forwarded to the nearest National laboratory resulting in significant delays for completion of testing and considerable additional costs. This study sought to develop a cost-effective and diagnostically-accurate immunoperoxidase antigen detection (RIAD) test for rabies that can be readily and quickly performed by the resource-constrained Provincial laboratories. This would reduce the burden on the National laboratories and allow more rapid diagnoses and implementation of post-exposure prophylaxis. The RIAD test was evaluated using brain smears fixed with acetone or formalin and its performance was validated by comparison with established rabies diagnostic tests used in Indonesia, including the SST and FAT. A proficiency testing panel was distributed between Provincial laboratories to assess the reproducibility of the test. The performance of the RIAD test was improved by using acetone fixation of brain smears rather than formalin fixation such that it was of equivalent accuracy to that of the World Organisation for Animal Health (OIE)-recommended FAT, with both tests returning median diagnostic sensitivity and specificity values of 0.989 and 0.993, respectively. The RIAD test and FAT had higher diagnostic sensitivity than the SST (median = 0.562). Proficiency testing using a panel of 6 coded samples distributed to 16 laboratories showed that the RIAD test had good reproducibility with an overall agreement of 97%. This study describes the successful development, characterisation and use of a novel RIAD test and its fitness for purpose as a screening test for use in provincial Indonesian veterinary laboratories.

Strategies to improve the efficiency of celiac disease diagnosis in the laboratory.

The demand for testing to detect celiac disease (CD) autoantibodies has increased, together with the cost per case diagnosed, resulting in the adoption of measures to restrict laboratory testing. We designed this study to determine whether opportunistic screening to detect CD-associated autoantibodies had advantages compared to efforts to restrict testing, and to identify the most cost-effective diagnostic strategy. We compared a group of 1678 patients in which autoantibody testing was restricted to cases in which the test referral was considered appropriate (G1) to a group of 2140 patients in which test referrals were not reviewed or restricted (G2). Two algorithms A (quantifying IgA and Tissue transglutaminase IgA [TG-IgA] in all patients), and B (quantifying only TG-IgA in all patients) were used in each group, and the cost-effectiveness of each strategy was calculated. TG-IgA autoantibodies were positive in 62 G1 patients and 69 G2 patients. Among those positive for tissue transglutaminase IgA and endomysial IgA autoantibodies, the proportion of patients with de novo autoantibodies was lower (p=0.028) in G1 (11/62) than in G2 (24/69). Algorithm B required fewer determinations than algorithm A in both G1 (2310 vs 3493; p<0.001) and G2 (2196 vs 4435; p<0.001). With algorithm B the proportion of patients in whom IgA was tested was lower (p<0.001) in G2 (29/2140) than in G1 (617/1678). The lowest cost per case diagnosed (4.63 euros/patient) was found with algorithm B in G2. We conclude that opportunistic screening has advantages compared to efforts in the laboratory to restrict CD diagnostic testing. The most cost-effective strategy was based on the use of an appropriate algorithm.

Laboratory Evaluation of a Smartphone-Based Electronic Reader of Rapid Dual Point-of-Care Tests for Antibodies to Human Immunodeficiency Virus and Treponema pallidum Infections.

BACKGROUND: Dual point-of-care tests for antibodies to human immunodeficiency virus (HIV) and Treponema pallidum allow for same-day testing and treatment and have been demonstrated to be cost-effective in preventing the adverse outcomes of HIV infection and syphilis. By recording and transmitting data as they are collected, electronic readers address challenges related to the decentralization of point-of-care testing. METHODS: We evaluated a smartphone-based electronic reader using 201 sera tested with 2 dual rapid tests for detection of antibodies to HIV and T. pallidum in Los Angeles, USA, and Lima, Peru. Tests were read both visually and with the electronic reader. Enzyme immunoassay followed by Western blot and T. pallidum particle agglutination were the reference tests for HIV and T. pallidum, respectively. RESULTS: The sensitivities of the 2 rapid tests for detection of HIV were 94.1% and 97.0% for electronic readings. Both tests had a specificity of 100% for detection of HIV by electronic reading. The sensitivities of the 2 rapid tests for detection of T. pallidum were 86.5% and 92.4% for electronic readings. The specificities for detection of T. pallidum were 99.1% and 99.0% by electronic reading. There were no significant differences between the accuracies of visual and electronic readings, and the performance did not differ between the 2 study sites. CONCLUSIONS: Our results show the electronic reader to be a promising option for increasing the use of point-of-care testing programs.

[Selection of Laboratory Procedures to Detect Toxigenic by the 2-Step Method].

The 2-step method is an algorithm to detect toxigenic Clostridium difficile. We herein compared the sensitivities and specificities of an enzyme immunoassay (toxin A/B-EIA), toxigenic culture (TC-EIA), Loop-Mediated Isothermal Amplification assay (LAMP), and Xpert C. difficile (Xpert) with the detection of the toxin B gene by a polymerase chain reaction (PCR). The results obtained showed that the sensitivities and specificities of toxin A/B-EIA, Xpert, TC-EIA, and LAMP were 30 and 100%, 87.2 and 100%, 97.5 and 89.7%, and 95 and 100%, respectively. We also evaluated the turnaround time (TAT) and cost of toxigenic C. difficile detection. Our hospital TAT for toxin A/B-EIA and TC-EIA are 37 min and 5 days, respectively. We estimated the TAT of Xpert, LAMP, and PCR to be 105 min, 5 days, and 6 days, respectively. On the other hand, the cost to detect toxigenic C. difficile increased in the order of TC-EIA, LAMP, Xpert, and PCR. We have never experienced outbreak of Clostridium difficile infection (CDI) in our hospital, and there is less the number of CDI than other place. So we selected TC-EIA that is good sensitivity and low cost per specimen. Hereafter it'll be necessary to solve a problem it takes time, because we have to respond to outbreak of CDI quickly if it happens.

Optimal strategies for the diagnosis of community-onset diarrhea in solid organ transplant recipients: Less is more.

BACKGROUND: Diarrhea, a common complication after solid organ transplant (SOT), is associated with allograft failure and death. No evidence-based guidelines exist for the evaluation of diarrhea in SOT recipients. We performed a cost analysis to derive a testing algorithm for the diagnosis of community-onset diarrhea that minimizes costs without compromising diagnostic yields. DESIGN: A cost analysis was performed on a retrospective cohort of 422 SOT admissions for community-onset diarrhea over an 18-month period. A stepwise testing model was applied on a population level to assess test costs relative to diagnostic yields. RESULTS: Over an 18-month period, 1564 diagnostic tests were performed and 127 (8.1%) returned positive. Diagnostic testing accounted for $95 625 of hospital costs. The tests with the lowest cost per decrease in the false-omission rate (FOR) were stool Clostridium difficile polymerase chain reaction (PCR) ($156), serum cytomegalovirus quantitative PCR ($1529), stool norovirus (NV) PCR ($4673), and stool culture ($6804). A time-to-event analysis found no significant difference in the length of hospital stay between patients with and without NV testing (P=.520). CONCLUSIONS: A stepwise testing strategy can reduce costs without compromising diagnostic yields. In the first-stage testing, we recommend assessment for C. difficile, cytomegalovirus, and food-borne bacterial pathogens. For persistent diarrheal episodes, second-stage evaluation should include stool NV PCR, Giardia/Cryptosporidium enzyme immunoassay, stool ova and parasite, reductions in immunosuppressive therapy, and possibly endoscopy. Although NV testing had a relatively low cost per FOR, we recommend NV testing during second-stage evaluation, as an NV diagnosis may not lead to changes in clinical management or further reductions in length of hospital stay.

Diagnostic evaluation of rapid tests for scrub typhus in the Indian population is needed.

BACKGROUND: Owing to frequent outbreaks witnessed in different parts of the country in the recent past, scrub typhus is being described as a re-emerging infectious disease in India. Differentiating scrub typhus from other endemic diseases like malaria, leptospirosis, dengue fever, typhoid, etc. is difficult due to overlapping clinical features and a lower positivity for eschars in Asian populations. Hence, the diagnosis heavily relies on laboratory tests. DISCUSSION: Costs and the need of technical expertise limit the wide use of indirect immunoperoxidase or immunofluorescence assays, ELISA and PCR. The Weil-Felix test is the most commonly used and least expensive serological test, but lacks both sensitivity and specificity. Hence, the diagnosis of scrub typhus is often delayed or overlooked. With due consideration of the cost, rapidity, single test result and simplicity of interpretation, rapid diagnostic tests have come into vogue. However, evaluation of rapid diagnostic tests for scrub typhus in the Indian population is needed to justify or discourage their use. CONCLUSION: Research studies are needed to find the most suitable test in terms of the rapidity of the result, simplicity of the procedure, ease of interpretation and cost to be used in the Indian populace.

Newborn screening for cystic fibrosis.

Since the late 1970s when the potential of the immunoreactive trypsinogen assay for early identification of infants with cystic fibrosis was first recognised, the performance of newborn blood spot screening (NBS) has been continually assessed and its use has gradually expanded. NBS for cystic fibrosis is a cost-effective strategy and, if standards of care are fully implemented and robust management pathways are in place, has a positive effect on clinical outcomes. In the past decade, NBS has undergone rapid expansion and an unprecedented number of infants with cystic fibrosis have access to early diagnosis and care. Cystic fibrosis NBS has now moved on from the development phase and is entering an era of consolidation. In the future, research should focus on the rationalisation and optimisation of existing programmes, with particular attention to bioethical implications such as unwanted detection of carriers and inconclusive diagnoses.

[New methodological advances: algorithm proposal for management of Clostridium difficile infection]. / Nuevos avances metodológicos: propuesta de algoritmo para el manejo de la infección por Clostridium difficile.

INTRODUCTION: Clostridium difficile infection (CDI) is considered the most common cause of health care-associated diarrhea and also is an etiologic agent of community diarrhea. The aim of this study was to assess the potential benefit of a test that detects glutamate dehydrogenase (GDH) antigen and C. difficile toxin A/B, simultaneously, followed by detection of C. difficile toxin B (tcdB) gene by PCR as confirmatory assay on discrepant samples, and to propose an algorithm more efficient. MATERIAL AND METHODS: From June 2012 to January 2013 at Hospital Infantil Universitario Niño Jesús, Madrid, the stool samples were studied for the simultaneous detection of GDH and toxin A/B, and also for detection of toxin A/B alone. When results between GDH and toxin A/B were discordant, a single sample for patient was selected for detection of C. difficile toxin B (tcdB) gene. RESULTS: A total of 116 samples (52 patients) were tested. Four were positive and 75 negative for toxigenic C. difficile (Toxin A/B, alone or combined with GDH). C. difficile was detected in the remaining 37 samples but not toxin A/B, regardless of the method used, except one. Twenty of the 37 specimens were further tested for C. difficile toxin B (tcdB) gene and 7 were positive. DISCUSSION: The simultaneous detection of GDH and toxin A/B combined with PCR recovered undiagnosed cases of CDI. In accordance with our data, we propose a two-step algorithm: detection of GDH and PCR (in samples GDH positive). This algorithm could provide a superior cost-benefit ratio in our population.

[Utility of Aspergillus-LFD: first experience in Chile]. / Utilidad de la prueba Aspergillus-LFD para el diagnóstico de aspergilosis: primera experiencia en Chile.

The diagnosis of invasive aspergillosis remains a challenge. Detection of galactomannan in serum and bronchoalveolar lavage is a useful tool; however due to methodological and economic reasons, the test frequencies of galactomannan assays vary from daily to weekly, which constitute a risk to the patient. In this study, we aimed to evaluate and correlate the performance of the new kit Aspergillus-LFD with the GM-EIA. Aspergillus-LFD kit represents a fast, economical and simple test; showed a good performance and excellent correlation with GM-EIA kit. Given the above, the Aspergillus-LFD is emerging as an alternative to consider in the early diagnosis of invasive aspergillosis.

Utilidad de la prueba Aspergillus-LFD para el diagnóstico de aspergilosis: primera experiencia en Chile / Utility of Aspergillus-LFD: first experience in Chile

Introduction: Invasive fungal diseases (IFD) by filamentous fungi are a common cause of morbidity and mortality in immunocompromised patients, especially those with myeloid leukemia. In 2011 a protocol for the rapid diagnosis of IFD by filamentous fungi was implemented in Valparaiso Region. Objectives: To describe cases of IFD by filamentous fungi of the Valparaíso Region, since the implementation of rapid diagnosis and to compare results with the period 2004-2009. Materials and Method: Descriptive and prospective study conducted in two public hospitals: Carlos van Buren at Valparaiso and Gustavo Fricke at Viña del Mar. We selected patients with a diagnosis of filamentous fungal diseases considering the EORTC/MSG criteria. Demographics, underlying diseases, risk factors for EFI, galactomannan (GM) results in blood and bronchoalveolar lavage, cultures and biopsies, treatment and overall lethality rates at 30 days were registered. Results: Eighteen patients were detected, 6 with proven and 12 probable IFD. Nine were diagnosed by GM, 8 by culture and two with both methods. In cases which the agent (9/18) was isolated from Rhizopus oryzae was the most frequent. When comparing overall lethality with the period 2004-2009, there was a reduction of 47.8%, which was statistically significant. Conclusions: Compared to data previously published in the region, demographic and comorbidities of patients with IFD caused by filamentous fungi are similar, however the currently rapid diagnosis protocol has improved survival of patients and lethality experienced overall decrease.

Introducción: la enfermedad fúngica invasora (EFI) por hongos filamentosos es una causa frecuente de morbilidad y mortalidad en pacientes inmunocomprometidos, en especial en aquellos con leucemia mieloide. En el 2011 se implementó en la Región de Valparaíso un protocolo de diagnóstico rápido de la EFI por hongos filamentosos. Objetivos: describir los casos de EFI por hongos filamentosos de la Región de Valparaíso, desde la implementación del diagnóstico rápido y compararlos con el período 2004-2009. Materiales y Método: Estudio descriptivo y prospectivo realizado en los hospitales públicos Carlos van Buren de Valparaíso y Gustavo Fricke de Viña del Mar. Se seleccionaron aquellos pacientes con diagnóstico de EFI por hongos filamentosos considerando los criterios EORTC/MSG. Se obtuvieron datos demográficos, enfermedad de base, factores de riesgo para EFI, resultados de galactomanano (GM), cultivos y biopsias, tratamiento y letalidad global a 30 días. Resultados: Se identificaron 18 pacientes, seis con EFI probadas y 12 probables. Nueve fueron diagnosticados con galactomanano, ocho con cultivos y uno con los dos métodos. En los casos en que se aisló el agente (9/18), Rhizopus oryzae fue el más frecuente. Al comparar la letalidad global con la del período 2004-2009, hubo una reducción de 47,8%, la cual fue estadísticamente significativa. Conclusiones: En relación a lo publicado anteriormente en la región, se conservan las características demográficas y de co-morbilidad de los pacientes con EFI por hongos filamentosos; sin embargo, la introducción del nuevo protocolo de diagnóstico rápido se asoció a una disminución en la letalidad global.

Rapid antigen group A streptococcus test to diagnose pharyngitis: a systematic review and meta-analysis.

BACKGROUND: Pharyngitis management guidelines include estimates of the test characteristics of rapid antigen streptococcus tests (RAST) using a non-systematic approach. OBJECTIVE: To examine the sensitivity and specificity, and sources of variability, of RAST for diagnosing group A streptococcal (GAS) pharyngitis. DATA SOURCES: MEDLINE, Cochrane Reviews, Centre for Reviews and Dissemination, Scopus, SciELO, CINAHL, guidelines, 2000-2012. STUDY SELECTION: Culture as reference standard, all languages. DATA EXTRACTION AND SYNTHESIS: Study characteristics, quality. MAIN OUTCOME(S) AND MEASURE(S): Sensitivity, specificity. RESULTS: We included 59 studies encompassing 55,766 patients. Forty three studies (18,464 patients) fulfilled the higher quality definition (at least 50 patients, prospective data collection, and no significant biases) and 16 (35,634 patients) did not. For the higher quality immunochromatographic methods in children (10,325 patients), heterogeneity was high for sensitivity (inconsistency [I(2)] 88%) and specificity (I(2) 86%). For enzyme immunoassay in children (342 patients), the pooled sensitivity was 86% (95% CI, 79-92%) and the pooled specificity was 92% (95% CI, 88-95%). For the higher quality immunochromatographic methods in the adult population (1,216 patients), the pooled sensitivity was 91% (95% CI, 87 to 94%) and the pooled specificity was 93% (95% CI, 92 to 95%); however, heterogeneity was modest for sensitivity (I(2) 61%) and specificity (I(2) 72%). For enzyme immunoassay in the adult population (333 patients), the pooled sensitivity was 86% (95% CI, 81-91%) and the pooled specificity was 97% (95% CI, 96 to 99%); however, heterogeneity was high for sensitivity and specificity (both, I(2) 88%). CONCLUSIONS: RAST immunochromatographic methods appear to be very sensitive and highly specific to diagnose group A streptococcal pharyngitis among adults but not in children. We could not identify sources of variability among higher quality studies. The present systematic review provides the best evidence for the wide range of sensitivity included in current guidelines.

Cost-effectiveness of a modified two-step algorithm using a combined glutamate dehydrogenase/toxin enzyme immunoassay and real-time PCR for the diagnosis of Clostridium difficile infection.

The analytical performance and cost-effectiveness of the Wampole Toxin A/B EIA, the C. Diff. Quik Chek Complete (CdQCC) (a combined glutamate dehydrogenase antigen/toxin enzyme immunoassay), two RT-PCR assays (Progastro Cd and BD GeneOhm) and a modified two-step algorithm using the CdQCC reflexed to RT-PCR for indeterminate results were compared. The sensitivity of the Wampole Toxin A/B EIA, CdQCC (GDH antigen), BD GeneOhm and Progastro Cd RT-PCR were 85.4%, 95.8%, 100% and 93.8%, respectively. The algorithm provided rapid results for 86% of specimens and the remaining indeterminate results were resolved by RT-PCR, offering the best balance of sensitivity and cost savings per test (algorithm ∼US$13.50/test versus upfront RT-PCR ∼US$26.00/test).

Development and validation of assay protocols for use with dried blood spot samples.

Dried blood spots (DBS)--drops of capillary whole blood collected from finger stick--represent a minimally invasive alternative to venipuncture that facilitates the collection of blood samples from research participants in naturalistic, field-based research settings. But the number of validated assays for quantifying biomarkers in DBS samples is relatively low in comparison with serum or plasma. The objective of this review is to discuss the advantages and disadvantages of DBS sampling, and to outline the steps involved in developing and validating an immunoassay for application to DBS samples. These steps include deciding on reagents, preparing calibration and quality control material, evaluating elution protocols, optimizing sample quantity, and assessing multiple aspects of assay performance, including intra- and interassay variation, lower limit of detection, accuracy, stability, and agreement between results from matched DBS and plasma samples. The broader goal of this "how-to" approach is to encourage investigators to validate, implement, and disseminate assay protocols for DBS samples in order to advance field-based research on human biology.

Nonutility of routine testing of stool for ova and parasites in a tertiary care Canadian centre.

BACKGROUND: In many clinical situations, stool examinations for ova and parasites (O&P) are routine in the work-up of patients with acute or chronic diarrhea. Frequently, these tests are found to be negative for pathogens. The purpose of this study was to examine the diagnostic yield of routine stool testing for O&P in a Canadian tertiary care centre and to estimate the potential clinical benefit of a positive result. PATIENTS AND METHODS: All stool samples sent to the central microbiology laboratory at London Health Sciences Centre were reviewed over a 5-year period ending January 2010. Initial screening was done by direct antigen testing using an enzyme immunoassay (EIA) technique followed by direct microscopy for negative results where there was a high index of suspicion and for positive results to rule out any concurrent parasites not included in the EIA kit. Pathogens identified were categorized and their potential susceptibility to metronidazole was estimated. No clinical data were available, as this was purely a utilization study. RESULTS: A total of 5812 stool tests were ordered. Of these, 5681 (97.7%) were completed. The most common reasons for an incomplete test were sample leakage (n = 38) and use of the incorrect collection kit (n = 32). Direct microscopy identified white blood cells in 17% of patients with positive testing. The most common pathogen was Giardia lamblia , which was detected in 45/83 (54%) of positive specimens. Entamoeba histolytica/Entamoeba dispar was identified in 16/83 (19%) and Cryptosporidium spp. in 10/83 (12%) of positive specimens. Microorganisms not thought to be pathogenic were identified in 7/83 (8%). Direct laboratory costs independent of labor were estimated at $1836 per clinically significant organism identified. Of the 77 specimens positive for pathogenic organisms, 62 (81%) were likely to be sensitive to treatment with metronidazole. CONCLUSION: In a tertiary care centre, the diagnostic yield of routine testing of stool for O&P during the evaluation of patients with acute or chronic diarrhea is low. Most clinically significant positive results should be responsive to metronidazole, but empirical treatment is not encouraged. Strategies to identify patients with a higher likelihood of harboring pathogenic parasites and consideration of empiric metronidazole therapy for patients at highest risk merit further research.

A competitive chemiluminescence enzyme immunoassay for rapid and sensitive determination of enrofloxacin.

With alkaline phosphatase (ALP)-adamantane (AMPPD) system as the chemiluminescence (CL) detection system, a highly sensitive, specific and simple competitive chemiluminescence enzyme immunoassay (CLEIA) was developed for the measurement of enrofloxacin (ENR). The physicochemical parameters, such as the chemiluminescent assay mediums, the dilution buffer of ENR-McAb, the volume of dilution buffer, the monoclonal antibody concentration, the incubation time, and other relevant variables of the immunoassay have been optimized. Under the optimal conditions, the detection linear range of 350-1000 pg/mL and the detection limit of 0.24 ng/mL were provided by the proposed method. The relative standard deviations were less than 15% for both intra and inter-assay precision. This method has been successfully applied to determine ENR in spiked samples with the recovery of 103%-96%. It showed that CLEIA was a good potential method in the analysis of residues of veterinary drugs after treatment of related diseases.

1,1'-Oxalyldiimidazole chemiluminescent enzyme immunoassay capable of simultaneously sensing multiple markers.

In order to rapidly and simultaneously quantify and screen trace levels of multiple biomarkers in a single sample, rapid 1,1'-oxalyldiimidazole chemiluminescence (ODI CL) was applied as a biosensor of immunoassays using various enzymes such as alkaline phosphatase (ALP) and horseradish peroxidise (HRP). (1) Fluorescein was formed from the reaction of fluorescein diphosphate (FDP) and immuno-complex conjugated with ALP. (2) Resorufin was formed from the reaction between Amplex Red and H(2)O(2) in the presence of immuno-complex conjugated with HRP. When ODI CL reagents (H(2)O(2) in isopropyl alcohol, ODI in ethyl acetate) were injected in a test tube or strip-well containing fluorescein and resorufin formed from above two reactions a bright CL emission spectrum having two peaks (518 nm for fluorescein and 602 nm for resorufin) was observed. The two peaks can be independently quantified with an appropriate statistical tool capable of deconvoluting multiple emission peaks. In conclusion, we expect that ODI chemiluminescent enzyme immunoassays (CLEIAs) using a couple of enzymes conjugated with antigen or antibody and substrates can rapidly and simultaneously quantify and screen multiple biomarkers in a single sample.

Chemiluminescence-based biosensor for fumonisins quantitative detection in maize samples.

A compact portable chemiluminescent biosensor for simple, rapid, and ultrasensitive on-site quantification of fumonisins (fumonisin B1+fumonisin B2) in maize has been developed. The biosensor integrates a competitive lateral flow immunoassay based on enzyme-catalyzed chemiluminescence detection and a highly sensitive portable charge-coupled device (CCD) camera, employed in a contact imaging configuration. The use of chemiluminescence detection allowed accurate and objective analyte quantification, rather than qualitative or semi-quantitative information usually obtained employing conventional lateral flow immunoassays based on colloidal gold labeling. A limit of detection of 2.5 µgL(-1) for fumonisins was achieved, with an analytical working range of 2.5-500 µgL(-1) (corresponding to 25-5000 µgkg(-1) in maize flour samples, according to the extraction procedure). Total assay time was 25 min, including sample preparation. A simple and convenient extraction procedure, performed by suspending the sample in a buffered solution and rapidly heating to eliminate endogenous peroxidase enzyme activity was employed for maize flour samples analysis, obtaining recoveries in the range 90-115%, when compared with LC-MS/MS analysis. The chemiluminescence immunochromatography-based biosensor is a rapid, low cost portable test suitable for point-of-use applications.

Cost effectiveness analysis of the New Jersey rapid testing algorithm for HIV testing in publicly funded testing sites.

BACKGROUND: Before 2009, New Jersey (NJ) publicly funded counseling and testing sites (CTS) tested for HIV using a single rapid test followed, when positive, by a Western Blot (WB) for confirmation. With this strategy, 74.8% of confirmed positive clients returned to receive test results. To improve the client notification rate at these centers, the New Jersey (NJ) Division of HIV, STD and TB Services (DHSTS) implemented a rapid testing algorithm (RTA) which utilizes a second, different, rapid test to verify a preliminary positive. OBJECTIVE: To compare the cost-effectiveness of the two testing algorithms. STUDY DESIGN: This was a retrospective cost-effectiveness analysis. DATA SOURCES: New Jersey HIV Rapid Testing Support Program (NJHIV) records, DHSTS grant documents, counseling time estimates from an online survey of site supervisors. Costs included test kits and personnel costs from month of RTA implementation through 11/30 in 2008 and 2009. The incremental cost of the RTA was calculated per additional percent of positive clients who were notified and per day earlier notification. RESULTS: In 2008, 215 of 247 clients with a positive rapid HIV test were confirmed positive by WB. 90.9% of clients were notified a mean of 11.4 days after their initial test. 12 refused confirmatory WB. In 2009, 152 of 170 clients with one positive rapid test had a confirmatory second positive rapid test and were notified on the same day. The incremental cost of the RTA was $20.31 per additional positive person notified and $24.31 per day earlier notification or $3.23 per additional positive person and $3.87 per day earlier notification if the WB were eliminated. CONCLUSIONS: The RTA is a cost-effective strategy achieving 100% notification of newly HIV positive clients a mean of 11.4 days earlier compared to standard testing.