Cut-off Optical Density Research Articles

High False Positive Rate Of An ELISA Screen For The Detection Of Anti-Factor VIII Antibodies In Congenital Hemophilia A

IntroductionAnti-factor VIII antibodies are a serious complication of factor replacement therapy in hemophilia A patients. Neutralizing antibodies could previously only be detected via the functional and gold-standard Bethesda assay with or without the Nijmegen modification. The introduction of an enzyme-linked immunosorbent assay (ELISA) screening test provides a less laborious alternative to the Bethesda assay and also has a high sensitivity. Unlike the Bethesda assay, the ELISA can potentially detect non-neutralizing antibodies, which raise the possibility of false positive screens. As it is important that both clinicians and the coagulation laboratory understand the clinical performance of ELISA screening, this study evaluated the sensitivity and specificity of ELISA and Bethesda assays used in both a laboratory validation study and in subsequent clinical experience. MethodsResults from all active adult and pediatric congenital hemophilia A patients who underwent both Bethesda assay and ELISA in British Columbia, Canada as of July 2013 were included in this study. The sensitivity and specificity were compared to the provincial coagulation laboratory validation study of the GTI Factor 8 Antibody ELISA kit against the classical Bethesda assay conducted in both hemophilia A and normal controls in 2010. Optical density (OD) readings were retrieved for eligible samples and from the laboratory validation study. Results35 samples from 26 different patients were used in the validation study performed in 2010. Of 147 adult and 86 pediatric hemophilia A clinic patients active during the study period, 56 samples from 16 adults and 17 children underwent concurrent Bethesda assay and ELISA screen between November 2010 and June 2013. Since ELISA implementation, 389 ELISA screens and 187 Bethesda assays were performed. ELISA screens resulted in the avoidance of Bethesda assays in 85% (330/389) of samples submitted during that period. Specificities and positive predictive values were lower in the clinical sample due to a larger number of false positives (n=18; 32%) relative to the validation study (n=3; 9%), while sensitivity and negative predictive values remained at 100% (Table 1). Interestingly, 67% (2/3) of false positive ELISA screens in the laboratory setting had Bethesda positive histories; however, in the clinical sample, only 6% (1/18) had a distant history of inhibitors. ODs were available for all validation study samples and for 54 clinical samples. Redefinition of our OD cutoff to improve specificity was prevented by false positive patients with strongly positive ODs.Table 1ELISA pre-clinical and clinical performance summaryData sourceSample sizeSensitivitySpecificityPositive predictive valueNegative predictive valueLaboratory validation study351009057100Clinic561005547100Pediatric331004350100Adult231006840100 ConclusionsThe ELISA screen used in this setting is highly sensitive for anti-factor VIII antibody detection in congenital hemophilia A. However, compared to pre-clinical data, our 2.5 years of clinical experience reveals a high incidence of false positives resulting in a significantly lower specificity. Our approximate cost savings in British Columbia as a result of avoided Bethesda assays due to ELISA screens (n=330) is $90 per test, and may exceed $200 per test in the United States. Additional testing and follow-up on positive ELISA results can be an inconvenience in both time and blood sampling, especially in the pediatric population where inhibitor status is more closely monitored. The cost ramifications of this follow up testing could not be quantified in this study. The potential implications for the detection of non-neutralizing anti-FVIII antibodies in hemophilia A need to be further explored and long-term study and monitoring of these discrepant patients is warranted. Disclosures:No relevant conflicts of interest to declare.

Elevated Immunoglobulin to Tissue KLK11 in Patients With Sjögren Syndrome

We have previously reported that mouse kallikrein (KLK) 22 in the lacrimal and salivary glands is an autoantigen that can induce primary Sjogren syndrome (SS) in rats. In this study, we determine whether the production of antibodies against tissue KLK is specific for SS and whether the antibody can be used as a biomarker for the diagnosis in humans. Sera from 11 patients diagnosed with SS, 8 patients with dry eye disease (DED), and 8 normal age/sex-matched controls (NL) were collected for detecting antibodies against tissue KLK1, KLK11, KLK12, and KLK13 by capture enzyme-linked immunosorbent assay. Anti-KLK11 antibody was significantly higher in the SS than in the DED (P = 0.05) and NL (P < 0.01) groups, with no difference in the level of this antibody between the DED and NL groups. In addition, receiver operating characteristic analysis revealed that, at or above an optical density cutoff point of 0.2695, anti-KLK11 antibody has a sensitivity of 82% and a specificity of 94% to distinguish the SS group from the other groups. Our results suggest that anti-KLK11 might be a novel biomarker for SS in humans. Further investigation is required to confirm this finding and to establish the exact role of KLK11 in the pathogenesis of SS.

An indirect enzyme-linked immunosorbent assay using a recombinant truncated capsid protein of Porcine circovirus-2

Porcine circovirus-2 (PCV-2) serology is commonly used for PCV-2 herd status determination and optimal timing of PCV-2 vaccination programs. The objectives of the current study were to develop an in-house indirect enzyme-linked immunosorbent assay (ELISA) using a recombinant nuclear localization signal truncated capsid (rntCap) protein expressed in an Escherichia coli system and to determine the diagnostic performance of the developed rntCap indirect ELISA in comparison with immunoperoxidase monolayer assays (IPMAs). Based on a receiver operating characteristic (ROC) curve analysis of the rntCap indirect ELISA (n = 90), an optimum cutoff optical density (OD) of 0.330 was determined, which resulted in diagnostic sensitivity, diagnostic specificity, and accuracy of 98.33%, 93.33%, and 96.67%, respectively. Average OD values of the positive (n = 8) and negative sera (n = 8) tested by either purified glutathione-S-transferase (GST) protein or the rntCap protein as the coating antigen revealed that the mean OD values tested by the rntCap indirect ELISA were significantly different from using GST alone (P < 0.005). The correlation between the established rntCap indirect ELISA and the IPMA results demonstrated as the linear regression (Spearman correlation coefficient = 0.772, P < 0.005) indicated that the OD ratio obtained from the rntCap indirect ELISA could be used to predict the levels of the IPMA titers. More samples are needed for enhancing the diagnostic sensitivity, specificity and accuracy. In conclusion, the establishment of the rntCap indirect ELISA could be used as a serodiagnostic assay for large-scale detection of PCV-2 antibodies in swine and has the capability to be produced commercially for routine use in diagnostic laboratories.

Evaluation of serum galactomannan detection for diagnosis of feline upper respiratory tract aspergillosis

Measurement of serum galactomannan (GM), a polysaccharide fungal cell-wall component, is a non-invasive test for early diagnosis of invasive aspergillosis in humans. Feline upper respiratory tract (URT) aspergillosis is an emerging infectious disease in cats. Diagnosis requires biopsy for procurement of tissue specimens for cytological or histological detection of fungal hyphae and for fungal culture. The aim of this study was to evaluate serum GM measurement as a non-invasive diagnostic test for URT aspergillosis in cats. A one-stage, immunoenzymatic sandwich ELISA was used to detect serum GM in 4 groups of cats; Group 1 (URT aspergillosis) – confirmed URT aspergillosis (n=13, sinonasal aspergillosis (SNA) n=6 and sino-orbital aspergillosis (SOA) n=7), Group 2 (URT other) – other URT diseases (n=15), Group 3 (β-lactam) – cats treated with β-lactam antibiotics for non-respiratory tract disease (n=14), Group 4a – healthy young cats (≤1y of age, n=28), Group 4b – healthy adult cats (>1y of age, n=16). One cat with SNA and two cats with SOA caused by an Aspergillus fumigatus-mimetic species, tested positive for serum GM. For a cut-off optical density index of 1.5, the overall sensitivity and specificity of the assay was 23% and 78% respectively. False positive results occurred in 29% of cats in Group 3 and 32% of cats in Group 4a. Specificity increased to 90% when Groups 3 and 4a were excluded from the analysis. Overall, serum GM measurement has a poor sensitivity but is a moderately specific, non-invasive screening test to rule out infection in patients with suspected feline upper respiratory tract aspergillosis.

Diagnosing pulmonary aspergillosis in patients with hematological malignancies: a multicenter prospective evaluation of an Aspergillus PCR assay and a galactomannan ELISA in bronchoalveolar lavage samples

Diagnosing invasive pulmonary aspergillosis (IPA) remains a challenge in patients with hematological malignancies. The clinical significance of testing bronchoalveolar lavage (BAL) samples both with polymerase chain reaction (PCR) and Aspergillus galactomannan ELISA (GM) is unclear, and the BAL cutoff for GM has not been clearly evaluated yet. Using a validated nested PCR assay and a GM ELISA, we prospectively examined BAL samples from 87 hematological patients at high risk of IPA. Of 76 (87%) evaluable patients, 29 patients had proven or probable disease. The receiver operating characteristic (ROC) analysis of GM optical density (OD) cutoff levels yielded a BAL OD of 0.5 to be optimal. We identified 29 probable or proven cases based on this OD. Sensitivity and specificity for BAL GM were 0.79 (95% CI, 0.62-0.9) and 0.96 (95% CI, 0.86-0.99), respectively. For BAL PCR, sensitivity and specificity were 0.59 (95% CI, 0.41-0.75) and 0.87 (95% CI, 0.75-0.94), respectively. Combining BAL GM and PCR for diagnosis showed a sensitivity and specificity rate of 0.55 (95% CI, 0.38-0.72) and 1.0 (95% CI, 0.93-1.0), respectively, if positivity was defined by positive results for both tests. If either positive BAL GM or positive BAL PCR results defined test positivity, the sensitivity was 0.83 (95% CI, 0.65-0.92), and the specificity was 0.83 (95% CI, 0.70-0.91) In terms of optimal sensitivity and specificity, a GM OD cutoff of 0.5 was determined for BAL samples. Positivity for both GM and Aspergillus PCR in BAL makes a pulmonary aspergillosis highly likely.

Serodiagnosis of Syphilis in the Recombinant Era: Reversal of Fortune

Serodiagnosis of Syphilis in the Recombinant Era: Reversal of Fortune

Performance of Commercial Herpes Simplex Virus Type-2 Antibody Tests Using Serum Samples From Sub-Saharan Africa: A Systematic Review and Meta-analysis

Several commercial type-specific serologic tests are available for herpes simplex virus type 2 (HSV-2). Poor specificity of some tests has been reported on samples from sub-Saharan Africa. To summarize the performance of the tests using samples from sub-Saharan Africa, we conducted a systematic review of publications reporting performance of commercially available HSV-2 tests against a gold standard (Western Blot or monoclonal antibody-blocking EIA). We used random-effects meta-analyses to summarize sensitivity and specificity of the 2 most commonly evaluated tests, Kalon gG2 enzyme-linked immunosorbent assay (ELISA), and Focus HerpeSelect HSV-2 ELISA. We identified 10 eligible articles that included 21 studies of the performance of Focus, and 12 of Kalon. The primary analyses included studies using the manufacturers' cut-offs (index value = 1.1). Focus had high sensitivity (random effects summary estimate 99%, 95% confidence interval [CI]: 99%-100%) but low specificity (69%, 95% CI: 59%-80%). Kalon had sensitivity of 95% (95% CI: 93%-97%) and specificity of 91% (95% CI: 86%-95%). Specificity of Focus was significantly lower (P = 0.002) among HIV-positive (54%, 95% CI: 40%-68%) than HIV-negative individuals (69%, 95% CI: 56%-82%). When the cut-off optical density index was increased above the recommended value of 1.1 to between 2.2 and 3.5, the specificity of Focus increased to 85% (95% CI: 77%-92%). Sensitivity and specificity of HSV-2 tests used in sub-Saharan Africa vary by setting, and are lower than reported from studies in the United States and Europe. Increasing the cut-off optical density index may improve test performance. Evaluation of test performance in a given setting may help deciding which test is most appropriate.

Identification of a Novel Fibronectin-Aggrecan Complex in the Synovial Fluid of Knees with Painful Meniscal Injury

Molecular biomarkers associated with knee pain may be useful as diagnostic modalities, prognostic indicators, and surrogate end points for therapeutic trials. The present study describes a novel complex of fibronectin and aggrecan that is present in the affected knee of patients with pain and meniscal abnormality. The present prospective study included thirty patients with knee pain, mechanical symptoms, and magnetic resonance imaging findings that were positive for a meniscal tear who chose arthroscopic partial meniscectomy after unsuccessful nonoperative management. Synovial fluid was aspirated at the time of surgery and was assayed for the fibronectin-aggrecan complex with use of a heterogeneous enzyme-linked immunosorbent assay (ELISA). The results were compared with knee aspirates from ten asymptomatic volunteers with no pain who underwent magnetic resonance imaging of the knee. The mean optical density (and standard deviation) of the fibronectin-aggrecan complex was significantly greater in synovial fluid from knees undergoing arthroscopic surgery as compared with fluid from asymptomatic controls (13.29 ± 8.48 compared with 0.03 ± 0.09; p < 0.001). The mean age in the study group was significantly greater than in control group (46.0 ± 12.6 compared with 38.5 ± 6.0 years; p = 0.02), but controlling for age did not affect the results. Post hoc, an optical density cutoff value of 0.3 distinguished the study group from the control group with 100% accuracy. A novel fibronectin-aggrecan complex is present in the synovial fluid of painful knees with meniscal abnormality. The fibronectin-aggrecan complex may prove to be useful as a clinical biomarker or therapeutic target. Further research is warranted to correlate functional outcome after surgery with the fibronectin-aggrecan complex and other cartilage biomarkers.

Evaluation of Plasmodium vivax ELISA for the blood screen

Plasmodium vivax malaria is the indigenous strain in the Republic of Korea (ROK). Plasmodium vivax can be transmitted through the transfusions of various blood components, which became a severe problem with the safety of blood transfusions and blood-related products in ROK. We evaluated a P.vivax-specific enzyme-linked immunosorbent assay (Genedia Malaria Ab ELISA 2.0, Green Cross, ROK) with blood samples from four groups: 251 samples from P.vivax-infected patients, 39 samples from post-treatment patients upon follow-up, 200 samples from healthy volunteers and 421 samples from domestic travellers to and from high endemic areas of ROK. The positive cases from the ELISA test were confirmed by both Giemsa microscopic and polymerase chain reaction methods. The clinical sensitivity and specificity of detecting P.vivax with ELISA test were 94.4% and 99.0%, respectively. Thirteen of 421 domestic travellers (3.0%) to endemic areas tested positive. The results indicate the effectiveness of detecting antibodies against P.vivax in blood with Genedia Malaria Ab ELISA 2.0 test in a large blood screen setting.

Immune response after a single vaccination against 2009 influenza A H1N1 in hemodialysis patients

Background: Influenza infection is a significant cause of morbidity and mortality in general population. Hemodialysis patients are considered at high risk of influenza infection given their altered immune status. Pandemic influenza virus is new for human beings, so it is hard to predict the response to infection or vaccination. We aimed to evaluate the response to pandemic H1N1 vaccination in hemodialysis patients. Methods: A total of 70 patients on chronic hemodialysis and 20 controls who had been vaccinated against the pandemic influenza virus 5 weeks before the time of blood sampling were included into this study. The anti-H1N1 immunoglobulin G (IgG) antibodies of the patients were studied with enzyme immune assay (EIA) method. Our cut-off optical density (OD) value was 1.503. If the patient's OD value was equal or higher than this value, it was considered as positive. If it was lower, it was considered as negative. Results: The mean OD value was 2.22 ± 0.42 in the patient group and 1.99 ± 0.34 in the control group (p < 0.05). Two of 70 patients and 1 of the controls had negative OD values and they were considered as nonresponsive to vaccination. There was also a negative correlation between the age and OD values in the patient group (r = −0.277, p < 0.05). Conclusion: H1N1 vaccine can be performed safely and cost effectively with a single dose to the risk groups especially to the hemodialysis patients. Evaluation of H1N1 IgG antibody with enzyme-linked immunosorbent assay (ELISA) may be a safe, easy, and cost-effective assay.

Enzyme-Linked Immunosorbent Assay for Measurement of Cytomegalovirus Glycoprotein B Antibody in Serum

Measurement of antibody to cytomegalovirus (CMV) glycoprotein B (gB) is valuable in the assessment of the antibody response to infection and to gB-containing vaccines. For this purpose, an enzyme-linked immunosorbent assay (ELISA) with a recombinant CMV gB molecule as the antigen was evaluated. Sera from 168 anti-CMV IgG-positive and 100 seronegative subjects were used to evaluate the anti-gB antibody assay. A cutoff optical density (OD) that would distinguish gB antibody-positive from -negative sera was established. Titers of antibody to gB determined by endpoint dilution were compared with those calculated using regression analysis. The run-to-run and interoperator reproducibilities of results were measured. The mean OD + 5 standard deviations from 50 anti-CMV IgG antibody-negative sera (0.2472) was used as the cutoff between anti-gB antibody-positive and -negative results. All sera from 100 anti-CMV IgG-seronegative subjects were negative for antibody to gB. All but 1 of 168 sera from seropositive subjects were positive for antibody to gB. Observed antibody levels based on titration to the endpoint were very similar to results calculated using linear regression. The run-to-run consistency of endpoints was excellent, with 38 runs from one operator and 48 runs from another all giving results within 1 dilution of the mean value for each of three anti-CMV IgG antibody-positive serum pools. The geometric mean titer of antibody to gB for 99 sera from seropositive blood donors was 1/10,937. This ELISA gives accurate and reproducible results for the relative quantity of anti-CMV gB IgG in serum over a wide range of antibody levels.

Can Oral Fluid Testing Be Used to Replace Blood-Based HIV Rapid Testing to Improve Access to Diagnosis in South Africa?

Can Oral Fluid Testing Be Used to Replace Blood-Based HIV Rapid Testing to Improve Access to Diagnosis in South Africa?

Evaluation of ELISA in the serodiagnosis of bovine farcy

Mycobacterium farcinogenes is the causal agent of bovine farcy, a chronic infectious disease of zebu cattle in some parts of tropical Africa. Whole cell homologous antigen of M. farcinogenes was used in the standardization and evaluation of an enzyme linked immunosorbent assay (ELISA) for the detection of circulating antibodies against bovine farcy using sera from confirmed bovine farcy and from bovine farcy-free cattle. The cut-off optical density (OD) value was decided at 1.8 using filter 405 nm after one hour of incubation at 37 degrees C. Accordingly, 115 out of 124 (92.7%) serum samples from clinically proven bovine farcy cattle were reported sero-positive. Sera from cattle infected with M. avium and M. paratuberculosis revealed OD value <1.8, indicating the differential diagnostic ability of M. farcinogenes antigen. Our test sensitivity was 92.7% and specificity was 97%, therefore could be routinely employed to support early clinical diagnosis, epidemiological surveys and for screening animals before exportation to farcy-free regions.

Muscarinic-3 acetylcholine receptor autoantibody in patients with systemic sclerosis: contribution to severe gastrointestinal tract dysmotility

Objective:Patients with systemic sclerosis (SSc) complicated by severe gastrointestinal tract (GIT) dysmotility at an early stage are difficult to treat and mortality is high. To clarify the pathogenesis of GIT...

Early Detection of Pregnancy and Embryonic Loss in Dairy Cattle by ELISA Tests

Over a 25-month period 8118 blood samples were assayed for the presence of the serum pregnancy specific-protein B (PSPB) and progesterone (P4) concentrations on three Hungarian large-scale dairy farms. Pregnancy (n = 4085) was checked by BioPRYN assay at 30-36 days post-insemination (PI). Samples from all cows that tested not pregnant and from cows with an optical density (OD) reading in the BioPRYN test that was between 0% and 30% above the cutoff OD value were tested for serum P4 concentration. According to serum P4 concentration, cows were assigned to three categories: high (>4 ng/ml), medium (2-4 ng/ml) and low (<2 ng/ml) serum progesterone. The authors predicted a presumed (low) or possible (medium) late embryonic loss (LEL) or maintenance of the pregnancy (high). A total of 710 LELs were detected (17.4%) and 31.8% of them were predicted because of a low OD value at 30-36 days after insemination. Lower PSPB serum level significantly refers for LEL (p < 0.0001). The prediction rate for the true embryonic loss was 31.8% when OD cutoff from 0% to + 30% of cutoff was examined while it was 62.5% when the threshold was OD cutoff of 0% to 10% of cutoff. The authors conclude that BioPRYN was useful for prediction of a part of LEL in dairy cows and serum P4 concentration in these cows related to the rate of LEL.

Asian Pacific Association for the Study of the Liver consensus statements on the diagnosis, management and treatment of hepatitis C virus infection

Asian Pacific Association for the Study of the Liver consensus statements on the diagnosis, management and treatment of hepatitis C virus infection

Optimization of the Cutoff Value for the Aspergillus Double-Sandwich Enzyme Immunoassay

Many health care centers worldwide use the Platelia Aspergillus enzyme immunoassay (PA-EIA; Bio-Rad Laboratories) for diagnosis of invasive aspergillosis (IA). A cutoff optical density (OD) index of 1.5 was originally recommended by the manufacturer, but in practice, most institutions use lower cutoff values. Moreover, a cutoff OD index of 0.5 was recently approved in the United States. In the present study, we set out to optimize the cutoff level by performing a retrospective analysis of PA-EIA values for samples that had been obtained prospectively from adult patients at risk for IA at 2 European health care centers. In total, 239 treatment episodes were included of which there were 19 episodes of proven IA and 19 episodes of probable IA. Per-episode and per-test analyses and receiver operating characteristic curves were used to determine the optimal cutoff value. In the per-episode analysis, lowering the cutoff OD index for positivity from 1.5 to 0.5 increased the overall sensitivity by 21% (from 76.3% to 97.4%) but decreased the overall specificity by 7% (from 97.5% to 90.5%). Requiring 2 consecutive samples with an OD index > or = 0.5 resulted in the highest test accuracy, with an improved positive predictive value. At a cutoff OD index of 0.5, the antigen test result was positive during the week before conventional diagnosis in 65% of cases and during the week of diagnosis in 79.5% of cases. A cutoff OD index of 0.5--identical to the approved cutoff in the United States--improves the overall performance of the PA-EIA for adult hematology patients.

Sensitivity and specificity of current diagnostic tests for gill‐associated virus in Penaeus monodon

This study reports the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy between a reverse transcriptase-nested polymerase chain reaction (RT-nPCR) and an enzyme-linked immunosorbent assay (ELISA) for the detection of gill-associated virus (GAV) from a sample of 120 Penaeus monodon. Subsequently, the same comparisons were applied to the ELISA and haemagglutination (HA) assays for detection of GAV from a second 120 prawns. The optical density (OD) or dilution cut-off point had a direct influence on the tested parameters. The cut-off OD of 0.5-0.6 with the ELISA produced a sensitivity of 98% compared with RT-nPCR. However, these OD produced the lowest accuracy (85.8% and 86.7%, respectively). The OD cut off of 0.75 resulted in the highest accuracy (91.7%) and NPV (81.3%) while it had the second highest sensitivity (97%) and PPV (93.3%). However, the OD cut off of 0.9 had the highest specificity (80%). With regards to HA, the titre cut off at 8 resulted in the highest sensitivity, specificity and NPV (94%, 100% and 100%, respectively) compared with the ELISA, while the HA titre of 16 gave the highest accuracy (73%) and the second highest specificity (75%). A HA titre of 64 gave the highest PPV (81%). Using the RT-nPCR as the gold standard, the ELISA had an accuracy of 91.7% when using a cut off >0.75 as a positive result. When compared with the ELISA, the HA had an accuracy of 73% when using an HA titre cut off greater than 16 as a positive result. These results indicate that alternative tests for GAV (ELISA and HA) can be used to explore multiple questions about the disease status of P. monodon stocks in a cost-effective manner.

Evaluation of enzyme-linked immunosorbent assay (ELISA) tests and culture for determining Salmonella status of a pig herd

The purpose of this study was to evaluate Salmonella ELISA tests and a culture technique to determine Salmonella status using samples collected from commercial herds. Faecal samples from 15 finisher pigs on each of 40 swine farms were cultured for Salmonella. Sera from the same 600 pigs were analysed for the presence of antibodies to Salmonella by means of two different ELISA kits Salmotype (Salmotype Labordiagnostik, Leipzig, Germany) and IDEXX (Herdchek* Salmonella; IDEXX Laboratories, Schiphol-Rijk, Noord-Holland, The Netherlands). The Salmotype ELISA test demonstrated a moderate ability to differentiate culture-positive pigs from culture-negative pigs while IDEXX was relatively poor in classifying those pigs correctly (The area under the curves were 0.79 and 0.65 for Salmotype and IDEXX respectively). The maximum value of sensitivity plus specificity was gained at the cut-off optical density (OD) > or =25% for Salmotype (sensitivity 0.65, specificity 0.84) and at the OD > or =9% for IDEXX (sensitivity 0.59, specificity 0.69). The maximum herd sensitivity and herd specificity was 0.64 (95% CI 0.49-0.79) and 0.72 (95% CI 0.59-0.86) for the Salmotype test and 0.73 (95% CI 0.59-0.87) and 0.62 (95% CI 0.47-0.77) for the IDEXX. Culture and the ELISA tests showed fair agreement at the herd level (kappa=0.3, P<0.05). Likewise there was significant disagreement between the two ELISA tests at the pig level, but very good agreement between the two ELISA tests (kappa=0.8, P<0.0001) at the herd level. The coating antigens in Salmotype and IDEXX represent only 48% of the antigens of Salmonella isolated in our study and need to be revised based upon the Salmonella serovar distribution in Ontario.

Epitope mapping Candida albicans proteinase (SAP 2).

The continuous epitopes of Candida albicans proteinase SAP 2 were derived by epitope mapping with sera from patients with oral candidiasis (n = 3), necropsy-proven disseminated candidiasis (n = 5), paired sera from patients who had recovered from blood culture-proven disseminated candidiasis (n = 3) and infection due to Candida parapsilosis (n = 2) and Candida tropicalis (n = 2). In C. albicans infection, IgM identified epitopes in amino acid positions 57-61 (QAVPV), 146-151 (SQGTLY) and 346-351 (PYDKCQ) and IgG at position 386-390 (VKYTS). For C. tropicalis IgM and IgG were positive for the same epitopes whilst IgG also detected epitopes at 78-83 (SNNQKL) and 159-164 (GVSIKN). For C. parapsilosis, IgM was positive for SNNQKL and IgG detected no epitopes. Reactivity of two of the epitopes as peptides KTSKRQAVPVTL and SLAQVKYTSASSI was confirmed in an indirect ELISA. At a cut-off optical density of 0.4, IgM against either peptide was associated with survival but present in only about half of the sera (n = 60) from patients who recovered from disseminated candidiasis whilst IgG levels were disappointing. Human recombinant antibodies from a patient who had recovered from disseminated candidiasis against either of these peptides had no activity in a lethal mouse model of candidal infection.