Effect of different test designs of immunoassays on "hook effect" of CA 19-9 measurement

The contribution and perspectives of proteomics to uncover ovarian cancer tumor markers

Despite all the advances in understanding the mechanisms involved in ovarian cancer (OC) development, many aspects still need to be unraveled and understood. Tumor markers (TMs) are of special interest in this disease. Some aspects of clinical management of OC might be improved by the use of validated TMs, such as differentiating subtypes, defining the most appropriate treatment, monitoring the course of the disease, or predicting clinical outcome. The Food and Drug Administration (FDA) has approved a few TMs for OC: CA125 (cancer antigen 125; monitoring), HE4 (Human epididymis protein; monitoring), ROMA (Risk Of Malignancy Algorithm; HE4+CA125; prediction of malignancy) and OVA1 (Vermillion's first-generation Multivariate Index Assay [MIA]; prediction of malignancy). Proteomics can help advance the research in the field of TMs for OC. A variety of biological materials are being used in proteomic analysis, among them tumor tissues, interstitial fluids, tumor fluids, ascites, plasma, and ovarian cancer cell lines. However, the discovery and validation of new TMs for OC is still very challenging. The enormous heterogeneity of histological types of samples and the individual variability of patients (lifestyle, comorbidities, drug use, and family history) are difficult to overcome in research protocols. In this work, we sought to gather relevant information regarding TMs, OC, biological samples for proteomic analysis, as well as markers and algorithms approved by the FDA for use in clinical routine.

Luminescence based enzyme-labeled phage (Phazyme) assays for rapid detection of Shiga toxin producing Escherichia coli serogroups

Most diagnostic approaches for Shiga toxin producing Escherichia coli (STEC) have been designed to detect only serogroup O157 that causes a majority, but not all STEC related outbreaks in the United States. Therefore, there is a need to develop methodology that would enable the detection of other STEC serogroups that cause disease. Three bacteriophages (phages) that infect STEC serogroups O26, O103, O111, O145 and O157 were chemically labeled with horseradish peroxidase (HRP). The enzyme-labeled phages (Phazymes) were individually combined with a sampling device (a swab), STEC serogroup-specific immunomagnetic separation (IMS) beads, bacterial enrichment broth and luminescent HRP substrate, in a self-contained test device, while luminescence was measured in a hand-held luminometer.The O26 and O157 Phazyme assays correctly identified more than 93% of the bacteria tested during this study, the O123 Phazyme assay identified 89.6%, while the O111 and O145 Phazyme assays correctly detected 82.4% and 75.9%, respectively. The decreased specificity of the O111 and O145 assays was related to the broad host ranges of the phages used in both assays. The Phazyme assays were capable of directly detecting between 10(5) and 10(6) CFU/ml in pure culture, depending on the serogroup. In food trials, the O157 Phazyme assay was able to detect E. coli O157:H7 in spinach consistently at levels of 1 CFU/g and occasionally at levels of 0.1 CFU/g. The assay detected 10(0) CFU/100 cm(2) on swabbed meat samples and 10(2) CFU/100 ml in water samples. The Phazyme assay effectively detects most STEC in a simple and rapid manner, with minimal need for instrumentation to interpret the test result.

Tumor markers in clinical practice: General principles and guidelines

Tumor markers are assuming a growing role in all aspects of cancer care, starting from screening to follow-up after treatment, and their judicious application in clinical practice needs a thorough understanding of the basics of pathophysiology, techniques of identification or testing, reasons for out-of-range levels of tumor markers, as well as the knowledge of evidence of their role in any given malignancy. These are, at the most, just an adjunct to diagnosis, and establishing a diagnosis on the basis of tumor markers alone (especially a single result) is fraught with associated pitfalls because of the problem of nonspecificity. In reality an ideal tumor marker does not exist. Detection can be done either in tissue or in body fluids like ascitic or pleural fluid or serum. Clinical uses can be broadly classified into 4 groups: screening and early detection, diagnostic confirmation, prognosis and prediction of therapeutic response and monitoring disease and recurrence. In addition to variable sensitivity and specificity, the prevalence of a particular malignancy may be a major determinant in the application of a particular test as a screening tool. Serum levels, in certain situations, can be used in staging, prognostication or prediction of response to therapy. Monitoring disease is, perhaps, the most common clinical use of serum tumor markers. Rising trend in serum levels may detect recurrence of disease well before any clinical or radiological evidence of disease is apparent ("biochemical recurrence"). Sampling should ideally be repeated after 5-6 half-lives of the marker in question (or the marker with the longest half-life if multiple markers are being considered); but if found elevated, the next sampling after 2-4 weeks, for additional evidence, may be justified.

Development of two ELISA for estrogen and progesterone receptor with sufficient sensitivity for fine needle aspirate and core biopsy

The quantitative determination of estrogen and progesterone receptors (PR and ER) in breast tumor cytosol has been routinely performed in clinical laboratories to aid in the selection between hormonal and chemotherapy and also to predict prognosis. However, the small amount of tissue available from the increasingly popular fine-needle aspiration and core biopsies from breast cancer patients requires more sensitive immunoassays for receptor quantification. We have developed two sensitive immuno-assays for ER and PR on microplate with the use of recently available anti-ER and anti-PR antibodies of higher affinity and a powerful signal magnification agent, namely Amdex. The calibrator was a pooled breast tumor cytosol used as calibrator and calibrated against Abbott kits. The protein concentration of the cytosol and the upper normal cutoffs for our assays were reduced to approximately 0.2 mg/mL and 3 fmol/0.2 mg/mL, respectively. Both assays have sensitivities close to 1 fmol/mL, which are sufficiently sensitive for the receptor quantification in fine-needle aspiration biopsies and cord biopsies of breast tumor.

Development of radioimmunoassays on microplate: application for CA-GI and CA-Br tumor markers

By taking advantage of a newly available microplate counter for radioactivity and the organic solvent-resistant, pigmented microplates, we have successfully established radioimmunoassays (RIA) for both CA-GI and CA-BR on microplate for routine clinical use. In the process of assay development, we found that both pigmented PicoPlate, made of acrylonitrile, and polystyrene Microlite 2 can be coated with antialpha fetoprotein (AFP) and antinerve growth factor (NGF) and used for setting up immunoassays for AFP and nerve growth factors. There were no problems following a test format of either competitive binding or sandwich design. Microlites 2 is recommended over PicoPlate because Microlites 2 is made of polystyrene, which is less expensive and separable into 8-well strips or even single wells. Single-well separation allows for the use of regular gamma counters in case Topcount is unavailable. We also found that the sensitivity of these tests was not significantly affected even though Topcount counts the weaker beta emissions. Similar dose-response curves could also be generated between original Biomira tube assays and assays using PicoPlate or Microlite 2 coated with protein antigens CA-Br and CA-GI. Excellent correlations were also obtained between the microplate assays and the Biomira tube assays for CA-GI and CA-Br using groups of serum specimens from cancer patients. We recommend the development of various RIAs on the microplate: it requires less reagents and less sample handling by the technologists and it can be essentially automated.