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PubMed1990

Indium-111 white blood cell scans: sensitivity, specificity, accuracy, and normal patterns of distribution.

The UCLA Hospital experience with indium-111 labeled white blood cells was reviewed. There were a total of 345 consecutive cases covering a broad range of clinical indications. The overall sensitivity of the method was 79%, specificity was 62%, and accuracy was 73%. The sensitivity for suspected osteomyelitis cases was 84%, with a specificity of 65% and an accuracy of 75%. For other cases sensitivity was 77%, specificity was 60%, and accuracy was 72%. Furthermore, patterns of normal distribution were reviewed.

Bacterial Infections↗
PubMed1996

Sensitive, specific quantitative analysis of tacrolimus (FK506) in blood by liquid chromatography-electrospray tandem mass spectrometry.

The capacity of liquid chromatography-tandem mass spectrometry (LC-MS2) to detect and define individual components in a complex mixture has been utilized to develop a quantitative assay of the potent immunosuppressant drug, tacrolimus. Trough blood concentrations were measured in 175 samples obtained over several weeks after liver transplantation from seven patients. The assay was linear over the range of 0.2 to 100 micrograms/L. Imprecision was <8%, and accuracy was 99-101%. The turnaround time for a batch of 20 samples was 2.5 h. No interference from any of the other drugs being administered to the patients was evident. An ELISA also performed on the same samples overestimated the concentrations substantially, as indicated by a plot of the difference between the results for the two methods vs their mean. The favorable characteristics of the LC-MS2 assay, especially its sensitivity and specificity, will facilitate detailed pharmacokinetic studies of tacrolimus, particularly under circumstances in which metabolism is perturbed by either hepatic dysfunction or drug interactions.

Animals↗
PubMed2006

Evaluation of allergenicity of genetically modified soybean protein extract in a murine model of oral allergen-specific sensitization.

BACKGROUND: With the development of genetically modified crop plants there has been a growing interest in the approaches available to assess the potential allergenicity of novel gene products. For additional assessment of the potential allergenicity of expressed proteins, informative data can be generated using animal models. Soybean is one of the major source of protein in human and animal nutrition, and has also been well characterized as a major allergenic source. Advances in biotechnology have resulted in an increasing number of genetically engineered foods, and among these soybean is one of the most widespread. OBJECTIVE: To develop and characterize a murine model of IgE-mediated soybean sensitization induced by intragastric immunization, in the presence of Cholera Toxin, with wild-type soybean extract (wt-SE) or with genetically modified soybean extract (gm-SE). METHODS: Balb/c mice born in our animal facilities, from females fed on soy-free food, were fed with the same soy-free food and used in all the experiments. Mice were sensitized by gavages with soybean extracts, and allergen-specific IgE and IgG responses were studied by direct ELISA and ELISA inhibition. Antigen-specific cell proliferation and cytokine production were evaluated in spleen cell cultures. Results Sensitization with both soybean extracts induced high levels of antigen-specific IgE and IgG1 and low levels of specific IgG2a. Both wt-SE and gm-SE were able to inhibit the binding of specific IgE from mice immunized with gm-SE to the same antigen used for the ELISA coating. A comparable proliferative response was obtained with the homologous as well as with the heterologous extracts. CONCLUSION: In sensitized mice, we observed a predominantly T-helper type 2 (Th2)-type immune response, with increased soybean-specific IgE and IgG1 antibodies and a concomitant increase of IL-4 and IL-5 production. RESULTS: obtained by specific IgE ELISA inhibition and by antigen-specific T cell proliferation demonstrated that wt-SE and gm-SE shared B and T epitopes. The present murine model of soybean sensitization established by the oral route should provide valuable information about risk assessment for food allergy from new proteins of genetically modified foods.

Administration, Oral↗
PubMed2006

Assessing surveillance using sensitivity, specificity and timeliness.

Monitoring ongoing processes of illness to detect sudden changes is an important aspect of practical epidemiology and medicine more generally. Most commonly, the monitoring has been restricted to a unidimensional stream of data over time. In such situations, analytic results from the industrial process monitoring have suggested optimal approaches to monitor the data streams. Data streams including spatial location as well as temporal sequence are becoming available. Monitoring methods that incorporate spatial data may prove superior to those that ignore it. However, analytically, optimal methods for spatial surveillance data may not exist. In the present article, we introduce and discuss evaluation metrics that can be used to compare the performance of statistical methods of surveillance. Our general approach is to generalize receiver operating characteristic (ROC) curves to incorporate the time of detection in addition to the usual test characteristics of sensitivity and specificity. In addition to weighting ordinary ROC curves by two measures of timeliness, we describe three three-dimensional generalizations of ROC curves that result in timeliness-ROC surfaces. Working in the context of surveillance of cases of disease to detect a sudden outbreak, we demonstrate these in an artificial example and in a previously described simulation context and show how the metrics differ. We also discuss the differences and under which circumstances one might prefer a given method.

Anthrax↗
PubMed1997

Cardiac troponin T is a sensitive, specific biomarker of cardiac injury in laboratory animals.

A reliable serum assay that can discriminate between cardiac and skeletal muscle injury is not available for diagnostic use in laboratory animals. We tested and supported the hypotheses that serum cardiac troponin T (cTnT) was widely applicable in laboratory animals as a biomarker of cardiac injury arising from various causes; that it increased in proportion to severity of cardiac injury; and that it was more cardiospecific than creatine kinase (CK) or lactate dehydrogenase (LD) isozyme activities. In canine and rat models of myocardial infarction, cTnT concentration increased 1,000- to 10,000-fold and was highly correlated with infarct size within 3 h of injury. Serum CK and LD isozymes were substantially less effective biomarkers and, in contrast to cTnT, were ineffective markers in the presence of moderate skeletal muscle injury, with resulting serum CK activity > 5,000 U/L. Using these animal models, and mouse and ferret models, we also showed cTnT to be an effective biomarker in doxorubicin cardiotoxicosis, traumatic injury, ischemia, and cardiac puncture. Reference range serum concentrations for all species were at the detection limit of the assay, except those for mice, in which they were slightly increased, possibly because mice were used to generate assay monoclonal antibodies. We conclude that cTnT is a powerful biomarker in laboratory animals for the sensitive and specific detection of cardiac injury arising from various causes.

Animals↗
PubMed1989

[Detection and localization of the ventricular septum defect using color Doppler echocardiography. Sensitivity, specificity, limitations].

In part 1 of this study 50 healthy children and 56 patients with known VSD were examined by color-Doppler-echocardiography to derive criteria for the diagnosis of a VSD by this technique. Using a defined Nyquist velocity the healthy children showed a monochrome ventricular bloodflow pattern. In patients with VSD and an interventricular pressure gradient greater than 15 mm Hg a turquois-yellow jet could be seen additionally in the ventricle with the lower pressure. The same pattern could be observed within the defect itself, except for four patients, in whom the VSD could not be visualized by two-dimensional echocardiography. In these patients, however, the VSD could be localized by tracing the jet to the septal endocardium. In patients with equal left and right ventricular pressures a monochrome transseptal bloodflow could be seen. Its color pattern was not significantly different from the normal bloodflow pattern. In these cases it was difficult to diagnose a small VSD, if the defect itself could not be visualized. Thus, the following criteria for the diagnosis of a VSD by color-Doppler-echocardiography were derived depending on the interventricular pressure gradient: 1) Interventricular pressure gradient greater than 15 mm Hg: visualization of the VSD-jet including its origin at the septal endocardium. 2) Equal left and right ventricular pressures: visualization of the VSD as echo drop-out as well as a transseptal bloodflow. Using these criteria, sensitivity and specificity of color-Doppler-echocardiography in the detection of VSD were evaluated in part II; 234 consecutive patients, of which 119 had a VSD, were examined. All had undergone cardiac catheterisation. A high sensitivity of 98.3% and a specificity of 99.1% were found. Diagnostic problems remain in patients with a small VSD and also in patients with equal left and right ventricular pressures. In particular, multiple VSD with equal left and right ventricular pressures are difficult to visualize completely, as compared to cases with significant interventricular pressure gradients.

Adolescent↗
PubMed1991

Direct haplotype determination by double ARMS: specificity, sensitivity and genetic applications.

We have developed a novel double Amplification Refractory Mutation System (double ARMS) using a highly polymorphic region 5' to the human delta-globin gene as a model system. The double ARMS approach involves using two allele-specific ARMS primers simultaneously during DNA amplification by the polymerase chain reaction (PCR). The resulting system is highly sensitive and more specific than single ARMS. In addition, this approach enables the elucidation of the relationship of polymorphic sites on the same chromosome and thus allows the direct determination of haplotypes. We have also demonstrated that this system can be used in conjunction with inverse PCR, the resulting double ARMS inverse PCR (DARMSI-PCR) may allow haplotype determination on polymorphic sites which are separated further apart than the length limit imposed by PCR. The double ARMS approach has numerous other applications in molecular biology including HLA typing, virology, forensic pathology and the investigation of the phenomenon of chimerism following bone marrow transplantation.

Alleles↗
PubMed1993

The mathematics of measurement: sensitivity, specificity and predictive value of available tests.

The correct clinical interpretation of any laboratory marker requires a good knowledge of its positive and negative predictive values, which are calculated from the sensitivity and the specificity of the test and from the prevalence of the disease. This means that we need a good assay technique in the case of biochemical tests, and a well defined reference sample (control subjects), with the ability to distinguish between a diseased and a healthy subject. In the field of alcohol abuse markers, each of these notions presents some degree of difficulty. There is no perfect solution, and a compromise has to be agreed upon.

Alcoholism↗
PubMed1998

The value of synthetic linear epitope analogues of La/SSB for the detection of autoantibodies to La/SSB; specificity, sensitivity and comparison of methods.

In a previous study it was shown that La/SSB contains four linear epitopes, p147-154, p291-302, p301-318 and p349-364. The aim of the present study was to investigate the value of the synthetic epitope analogues of the La/SSB autoantigen for the detection of antibodies to La/SSB, in comparison with recombinant La and fragments of this protein. A total of 122 sera with anti-La/SSB activity, from patients with primary Sjögren's syndrome (pSS) or systemic lupus erythematosus (SLE), were tested in various peptide-based assays. In addition, 62 sera from pSS or SLE patients with other autoantibody specificities and 95 sera from healthy individuals were used as controls. The autoantibody specificity was identified by counter immunoelectrophoresis and immunoblot. The peptide-based ELISA assays presented sensitivities ranging from 78% to 88-8% and specificities from 69% to 94-3%. Dot blot assays exhibited sensitivities ranging from 93-6% to 97%, but remarkably lower specificities from 56% to 88%. The most sensitive and specific peptide 349GSGKGKVQFQGKKTKF364 was synthesized and attached on a tetramer sequential oligopeptide carrier SOC4 and used for immunoassay development. Assays based on the recombinant native La protein, the La-C terminal (215 aa), and the N-terminal of La with a mutation at base pair 640 (nine adenines instead of eight) were also developed and compared with the SOC4 peptide-based assay. Of anti-La-positive sera, 88.1% were reactive with both the synthetic peptide SOC4-(349-364aa) and the recombinant La protein. Eighty-three percent of sera were reactive with the La N-terminus and 67.8% of sera were reactive with the La C-terminus. Using sera that were anti-Ro-positive but anti-La-negative, 37% were reactive with the recombinant protein, 26% with the La N-terminus, 33% with the La C-terminus and only 11 % with the synthetic peptide. Our results suggest that the synthetic peptide epitopes exhibit high sensitivity and specificity for the detection of anti-La/ SSB antibodies in ELISA and dot blot techniques. The peptide SOC4-(349-364aa) has the same sensitivity for the detection of anti-La/SSB antibodies as the recombinant protein.

Amino Acid Sequence↗
PubMed2000

Regionally specific sensitivity differences in fMRI and PET: where do they come from?

In this paper we report three neuroimaging studies of language that investigate potential sources of inconsistency in measured hemodynamic responses: (1) between sessions for fMRI, including differences in hormonal status, (2) between sessions for PET, and (3) between scanning modalities (PET and fMRI). Differences in evoked responses between sessions of the same modality were small. In particular we did not find any effect of hormone levels when testing during the first and third weeks of the menstrual cycle (although we cannot exclude the possibility that activation in the temporoparietal regions is sensitive to hormonal status). Comparing the two modalities showed that prefrontal regions were more activated in fMRI than in PET. This may relate to task switching between blocks in fMRI that is not induced by PET paradigms or increased error variance in these regions for PET. In contrast, temporal activations were found in PET more than in fMRI. We attribute the lack of temporal activations, in fMRI, to a combination of factors, including susceptibility artifacts, anticipatory activity during the control condition, discontinuous sampling of peristimulus time, and differences in the source, acquisition, and analysis of the measured signals. It is concluded that although there is sufficient reproducibility of results for these paradigms within each modality, the regionally specific differences in sensitivity found between modalities warrant further investigation. These regionally specific differences are important for a properly qualified interpretation of activation profiles in fMRI.

Adult↗
PubMed2002

Specific sensitization to common allergens and pulmonary function in the European Community Respiratory Health Survey.

BACKGROUND: The role of atopy in the evolution to chronic obstructive disease remains controversial. AIM: We aimed to assess the association between individual sensitization to common allergens and lung function. METHOD: We analysed data from 12,687 subjects aged 20 to 44 years, from 34 centres in 15 countries participating in the European Community Respiratory Health Survey (ECRHS). Participants performed a blood test, lung function test, methacholine challenge, and answered an administered questionnaire. The relationships between specific IgE, FEV1 and FEV1/FVC ratio were assessed for each study centre stratified by sex, followed by random effects meta-analysis. RESULTS: Asthmatics sensitized to house dust mite had a lower FEV1 (-119 mL in women and -112 mL in men) and FEV1/FVC ratio (-1.95%, and -2.48%) than asthmatics without sensitization. Asthmatics sensitized to cat had a lower FEV1 (statistically significant for women only) and a lower FEV1/FVC ratio. Asthmatic women sensitized to grass had a lower FEV1 and a lower ratio, and those sensitized to Cladosporium had a lower FEV1. A weak association was found with sensitization to cat and to Cladosporium among non-asthmatic women, which disappeared after adjusting for BHR. CONCLUSION: We conclude that atopy was related to a lower lung function, which was only apparent among asthmatics. This relationship was explained by specific sensitization to cat and to house dust mite, the latter being homogeneous across areas.

Adult↗
PubMed1998

General practitioner screening for melanoma: sensitivity, specificity, and effect of training.

OBJECTIVE: To measure the performance of trained and untrained general practitioners (GPs) in screening men and women aged 50 or more for melanomas. METHODS: GPs trained in melanoma diagnosis, untrained GPs, and skin cancer specialists examined groups of volunteers, each of which included a small number of subjects with prediagnosed suspicious pigmented lesions (SPLs) that were subsequently excised for histopathological examination. RESULTS: Trained and untrained GPs achieved mean sensitivities of 0.73 and 0.71, and mean predictive values of 0.40 and 0.37, respectively, for the detection of prediagnosed SPLs. When the SPLs had been excised and examined histopathologically, reanalysis showed mean sensitivities of 0.98 and 0.95, mean specificities of 0.52 and 0.49, and mean positive predictive values of 0.24 and 0.22 for the detection of subjects with melanomas by trained and untrained GPs respectively. Trained GPs were significantly better than untrained GPs at diagnosing as melanomas SPLs that subsequently proved to be melanomas (p = 0.04). CONCLUSIONS: GPs in this study achieved high sensitivities in screening older Australian men and women for melanomas, but at the cost of low specificities and positive predictive values. Training in melanoma diagnosis had no significant effect on sensitivity, specificity, and positive predictive value for screening. Data from the study were tested in a model of population screening for melanomas, and costs per life year saved for men aged 50-70 ranged from $A11,852 to $A40,259 depending upon the screening interval and whether the GPs excised the SPLs diagnosed, or referred all patients to skin cancer specialists; this would be as cost effective as cervical cancer screening.

Female↗
PubMed2000

Contact sensitizers specifically increase MHC class II expression on murine immature dendritic cells.

Contact sensitivity is a T-cell-mediated immune disease that can occur when low-molecular-weight chemicals penetrate the skin. In vivo topical application of chemical sensitizers results in morphological modification of Langerhans cells (LC). Moreover, within 18 h, LC increase their major histocompatibility complex (MHC) class II antigens expression and migrate to lymph nodes where they present the sensitizer to T lymphocytes. We wanted to determine if such an effect could also be observed in vitro. However, because of the high genetic diversity encountered in humans, assays were performed with dendritic cells (DC) obtained from a Balb/c mouse strain. The capacity of a strong sensitizer, DNBS (2,4-dinitrobenzene sulfonic acid), to modulate the phenotype of bone marrow-derived DC in vitro, was investigated. A specific and marked increase of MHC class II molecules expression was observed within 18 h. To eliminate the use of animals in sensitization studies, the XS52 DC line was tested at an immature stage. A 30-min contact with the strong sensitizers DNBS and oxazolone, or the moderate mercaptobenzothiazole, resulted in upregulation of MHC class II molecules expression, analyzed after 18-h incubation. This effect was not observed with irritants (dimethyl sulfoxide and sodium lauryl sulfate) nor with a neutral molecule (sodium chloride). These data suggested the possibility of developing an in vitro model for the identification of the sensitizing potential of chemicals, using a constant and non animal-consuming material.

Animal Testing Alternatives↗
PubMed1995

Specific sensitivity of CD43 to neutrophil elastase.

CD43 (sialophorin, leukosialin), an O-glycosylated and sialylated membrane protein (surface sialomucin) with antiadhesive properties, is thought to protect circulating leukocytes by preventing cell surface interactions. Although it is resistant to several proteases, the granule enzyme elastase was recently implicated in loss of extracellular CD43 regions from incubated neutrophils. Flow cytometry showed that neutrophil CD43 is cleaved by low levels of neutrophil elastase with half-maximal cleavage at 5 micrograms/mL; pancreatic elastase, in contrast, did not cleave CD43. Related neutrophil granule proteases proteinase-3 and cathepsin-G did not cleave CD43 or required greater than 10-fold higher enzyme levels, respectively. The 115-kD CD43 isoform on T-lymphoid cells, which differs in glycosylation from 135-kD neutrophil CD43, was equally sensitive to neutrophil elastase, suggesting that cleavage susceptibility extends to various leukocytes. Enzymatic removal of sialic acid did not facilitate CD43 cleavage by neutrophil elastase, a feature that distinguishes the action of neutrophil elastase from other proteases. Western blots of elastase-treated neutrophils detected an 83-kD CD43 fragment that, together with the released 52-kD fragment and 40-kD subfragment, accounts for the entire molecule and indicates that CD43 is cleaved at two sites only, releasing the distal approximately 40% of the sialomucin region. The specificity of the CD43 cleaving reaction was shown by the insensitivity of other neutrophil and lymphoid surface proteins to elastase levels that deplete CD43. Exceptions were P-selectin glycoprotein ligand-1 on neutrophils, also a surface mucin, and CD16 (Fc gamma RIII), which was previously characterized as elastase sensitive. The sensitivity and specificity of CD43 cleavage by neutrophil elastase, the very high levels of elastase in human neutrophils and its ready release by stimulating conditions suggest important physiologic/pathologic roles for this CD43 cleaving reaction.

Antigens, CD↗
PubMed1989

Diagnostic studies for systemic necrotizing vasculitis. Sensitivity, specificity, and predictive value in patients with multisystem disease.

Forty patients with multisystem disease and suspected systemic necrotizing vasculitis were evaluated with a protocol designed to confirm the diagnosis with sequential testing. All patients underwent initial laboratory testing. Subsequent studies were individualized to the patient starting with "safe" tests (skin, muscle, rectal biopsies) and progressing to "invasive" tests (arteriography, kidney and lung biopsies). No single laboratory study was found to have adequate predictive value. Skin biopsy, rectal biopsy, and arteriography were insensitive, nonspecific, or had poor predictive values. Muscle biopsy was the most valuable safe procedure (sensitivity, 50%; specificity, 100%; predictive value, 100%; predictive value of negative biopsy, 76%; efficiency, 64%). A diagnostic approach to the patient with possible systemic necrotizing vasculitis is described.

Adult↗
PubMed1985

Screening test for HTLV-III (AIDS agent) antibodies. Specificity, sensitivity, and applications.

The third member of the human T-cell leukemia (lymphotropic) retrovirus family (HTLV-III) is a newly discovered retrovirus that has been closely associated with the acquired immunodeficiency syndrome (AIDS). In our application of an enzyme-linked immunosorbent assay (ELISA) for HTLV-III antibodies, 72 (82%) of 88 patients with AIDS were positive, 14 (16%) were borderline, and two (2%) were negative. In contrast, only 1% of 297 volunteer blood donors were positive, 6% were borderline, and 93% were negative, demonstrating that this ELISA for HTLV-III antibodies is highly specific and sensitive for AIDS (excluding borderline results, 98.6% and 97.3%, respectively). Among persons at high risk for AIDS, 8% had borderline results, with positive and negative results readily distinguished as bimodal distributions that paralleled the temporal and geographic trends in AIDS. None of the 188 laboratory and health care employees working with patients with AIDS or their specimens were positive for HTLV-III antibodies, indicating that current precautions for health care workers appear adequate. This ELISA for HTLV-III antibodies will be a useful screening test among blood donors and populations at risk for AIDS, will aid in the diagnosis of suspected AIDS, and will help in defining the spectrum of diseases that are etiologically related to HTLV-III.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Sensitivity, specificity, and the hybridization isotherms of DNA chips.

Competitive hybridization, at the surface and in the bulk, lowers the sensitivity of DNA chips. Competitive surface hybridization occurs when different targets can hybridize with the same probe. Competitive bulk hybridization takes place when the targets can hybridize with free complementary chains in the solution. The effects of competitive hybridization on the thermodynamically attainable performance of DNA chips are quantified in terms of the hybridization isotherms of the spots. These relate the equilibrium degree of the hybridization to the bulk composition. The hybridization isotherm emerges as a Langmuir isotherm modified for electrostatic interactions within the probe layer. The sensitivity of the assay in equilibrium is directly related to the slope of the isotherm. A simpler description is possible, in terms of c(50) values specifying the bulk composition corresponding to 50% hybridization at the surface. The effects of competitive hybridization are important for the quantitative analysis of DNA chip results, especially when used to study point mutations.

Base Sequence↗