Chance Of False Negative Results Research Articles

Luminescent diagnostics and quantitative assessment of malaria based on a lateral flow immunoassay with cdte quantum dots

A lateral flow immunoassay (LFI) is a simple, low-cost and rapid diagnostic tool to identify various diseases by detecting analytes such as antibodies, parasites, or other relevant biomarkers. However, most LFIs can only confirm the presence or absence of a target analyte being applied as qualitative diagnostic tools. In addtion, the conventional LFIs, which require visual inspection of the test line, may demonstrate insufficient sensitivity for the mild form or early detection of infections and for this reason, the result can be falsely negative. This study presents the results of employing thioglycolic acid capped CdTe quantum dots as a probe to enhance luminescence and subsequently detection sensitivity in LFIs for diagnosis of malaria. The chemical route synthesis of thioglycolic acid capped CdTe quantum dots was optimized systematically by probing optical properties of the quantum dots. These optimized quantum dots of thioglycolic acid capped CdTe have been conjugated with the anti-malaria antibodies against HRP2 protein (P. falciparum) and were then incorporated into LFIs. Further, an image processing code has been developed to carry out the quantification of malaria parasites in terms of the ratio on intensities of control and test lines on the LFIs. The results have been compared with those obtained using the standard, colloidal gold based LFIs. It has been demonstrated that sensitivity and lower detection limits of malaria under low parasite concentration increase significantly due to enhanced luminescence of control and test lines under UV light, owing to the presence of thioglycolic acid capped CdTe quantum dots. It has also been shown that the image processing based quantification of malaria will likely minimize the chances of false negative results under low parasite concentration and assist in early diagnosis of malaria.

Features and diagnostic accuracy of fine needle aspiration cytology of thyroid nodules: retrospective study from Oman.

BACKGROUND: Fine needle aspiration cytology (FNAC) of the thyroid has been a reliable and cost-effective method for diagnosing thyroid disorders. Since FNAC results are usually operator dependent, there is a compelling need to explore FNAC accuracy among Omanis.OBJECTIVE: Describe cytological features of FNAC and assess FNAC accuracy compared to the postsurgical histopathology report.DESIGN: Retrospective diagnostic accuracy studySETTING: Tertiary care center.PATIENTS AND METHODS: Our study included adult Omani adult patients with thyroid nodules who underwent FNAC from 2014 to 2017 and had final pathology results for patients who underwent thyroid surgery. The results were classified according to the UK Royal college of Pathologists ‘Thy’ categories. Accuracy of FNAC was calculated by determining false and true positive and negative results based on histopathology findings.MAIN OUTCOME MEASURES: FNAC accuracy (sensitivity and specificity) compared to the postsurgical histopathology.SAMPLE SIZE: 867 patients with 1359 ultrasound guided FNACs of thyroid nodule; 137 underwent surgery.RESULTS: The mean age of the 867 patients was 43.7 (13.3) years, with a median of 42 years, and 87.8% were females. Out of 1359 FNACs, 1001 (73.7%) were benign (Thy2), 119 (8.8%) were atypia of undetermined significance or follicular lesion of undetermined significance (Thy3a), 31 (2.3%) were follicular neoplasm or suspicious for a follicular neoplasm (Thy3f), 52 (3.8%) were suspicious for malignancy (Thy4), 55 (4%) were malignant (Thy5), 101 (7.4%) as Unsatisfactory (Thy1). Only 137 patients underwent thyroid surgery, and the FNAC reports were compared with their final histopathology reports. The sensitivity, specificity and total accuracy of FNAC were 80.2%, 98.9% and 89.9%, respectively. The positive and negative predictive values of FNAC were 98.6% and 84.3%, respectively.CONCLUSION: Our study findings confirmed that FNAC of the thyroid is a sensitive, specific, and accurate initial tool for the diagnosis of thyroid lesions. Most of the FNACs were benign with a very low malignancy rate. Due to the minimal chance of false negative results and the slow-growing nature of thyroid malignancy, it is important that patients with benign FNAC should have periodic clinical and radiological follow-up.LIMITATIONS: Retrospective design and single-center study, and thyroid nodule size unavailable.CONFLICT OF INTEREST: None.

An approach to axillary swellings cytomorphological (fine needle aspiration cytology) study

Background: The axilla, a triangular area which is located between the upper arm and thorax, contains blood vessels, nerves, lymph nodes, and fat. Axillary swellings can arise from these various mesenchymal tissues present in the axillary area. The most common palpable axillary masses are usually lymph nodes. Fine needle aspiration cytology (FNAC) is the first line investigative technique with differential diagnosis includes reactive hyperplasia, inflammatory conditions, granulomatous disorders and malignancy. FNAC is a rapid, less invasive, less traumatic, and easily accessible and a cheap diagnostic tool to differentiate the benign or the malignant nature of the swelling. Aims and Objectives: Study is undertaken to document the spectrum of axillary lesions. Value of FNAC as a rapid diagnostic tool in diagnosing the axillary lesions. Materials and Methods: Present study is an 18 months cross-sectional study carried out in department of pathology, tertiary care hospital. Patients demographic and clinical data were collected from request forms. Slides were reviewed and analyzed. Data were entered in microsoft excel and analyzed. Results: Out of total 110 cases analyzed, ratio of female to male is 3.07. There were 41.8% benign and 13.6% malignant cases. 42.7% were inflammatory and 1.9% congenital lesions (ectopic breast). The most common lesions encountered are from lymph node (51.8%) (lymphadenitis-most common) followed by soft tissue tumor (Lipoma – most common). Rare lesions include nonhodgkin lymphoma, hodgkin lymphoma, neurofibroma, and chondroid syringoma. Conclusion: FNAC is an outpatient-based accurate, rapid procedure helps in timely diagnosis of various axillary lesions including clinically and radiologically ambiguous cases. It also helps to discriminate benign and malignant lesions with less chances of false negative results.

Deep Convolutional Neural Network Approach for COVID-19 Detection

Coronavirus disease 2019 (Covid-19) is a life-threatening infectious disease caused by a newly discovered strain of the coronaviruses. As by the end of 2020, Covid-19 is still not fully understood, but like other similar viruses, the main mode of transmission or spread is believed to be through droplets from coughs and sneezes of infected persons. The accurate detection of Covid-19 cases poses some questions to scientists and physicians. The two main kinds of tests available for Covid-19 are viral tests, which tells you whether you are currently infected and antibody test, which tells if you had been infected previously. Routine Covid-19 test can take up to 2 days to complete; in reducing chances of false negative results, serial testing is used. Medical image processing by means of using Chest X-ray images and Computed Tomography (CT) can help radiologists detect the virus. This imaging approach can detect certain characteristic changes in the lung associated with Covid-19. In this paper, a deep learning model or technique based on the Convolutional Neural Network is proposed to improve the accuracy and precisely detect Covid-19 from Chest Xray scans by identifying structural abnormalities in scans or X-ray images. The entire model proposed is categorized into three stages: dataset, data pre-processing and final stage being training and classification.

Screening of ZIKA virus infection among dengue-like illness patients with negative RT-PCR for dengue virus in Punjab - Pakistan.

Objective:To detect ZIKV using reverse transcription-polymerase chain reaction (RT-PCR) among clinical samples tested negative for Dengue virus (DENV) by RT-PCR in Punjab, 2016.Methods:A descriptive cross-sectional study was carried out for duration of two months. Total of 506 samples were collected within seven days from onset of illness from all over hospitals of Punjab, Pakistan of which 350 were selected simply randomly to test for presence of ZIKV by using “Trioplex Real-Time RT-PCR Assay (Trioplex)”. Cohen’s kappa coefficient (κ) and 95% confidence interval (CI) were used to assess the degree of concordance between DENV positive results of non-structural protein 1 (NS1) and IgM solid-phase enzyme immunoassay (ELISA).Results:No samples were positive for any ZIKV, DENV or Chikungunya virus (CHIKV) by Trioplex. Among the 350 samples, 26 samples were positive concordant and the degree of concordance between NS1- and IgM-ELISA was 13% and κ coefficient was -0.71 (95% CI -0.79, -0.63).Conclusion:At study time, no samples were positive for ZIKV. Strengthening laboratory capacity to confirm arboviruses for Punjab’s laboratories is warranted. Trioplex RT-PCR has 100% sensitivity so there are nominal chances of false negative results. Establishing syndromic surveillance for Zika and conducting a sero-surveillance survey for Zika in areas with high human and Aedes mosquito density are recommended in Punjab.

Urine Antigen Testing is Equally Sensitive to B. dermatitidis and B. gilchristii Infections.

Blastomycosis is endemic in Wisconsin with Blastomyces dermatitidis and B. gilchristii responsible for infections. Urine antigen testing is a non-invasive diagnostic method for blastomycosis with up to 93% test sensitivity. However, the test's sensitivity has not been evaluated with relationship to B. gilchristii infections. We aimed to assess physician use of the urine antigen assay and its sensitivity to B. gilchristii and B. dermatitidis infections in a retrospective study. Culture confirmed clinical cases of blastomycosis from 2008-2016 were identified within Marshfield Clinic Health System (MCHS) and UW Hospital and Clinics (UWHC) medical records. Clinical data were abstracted from each medical record and included the following: patient demographics, presence of immune compromising and underlying medical conditions, treatment drugs, presence of isolated pulmonary or disseminated disease, death, urine antigen testing, timeframe of testing, and quantitative test values (EIA units or ng/mL). A total of 140 blastomycosis cases were included in this study, with MCHS contributing 114 cases to the study and UWHC contributing 26 cases. The majority of UWHC cases (n=22; 85%) were caused by B. dermatitidis and the majority of MCHS cases (n=73; 64%) were caused by B. gilchristii. UWHC physicians were significantly more likely to treat with multiple drugs during the course of infection and were more likely to prescribe amphotericin B and voriconazole. Urine antigen testing was more frequently used at UWHC (n=24; 92%) than MCHS (n=51; 45%; P < 0.00001). In this study, the urine antigen assay demonstrated 79% sensitivity. Sensitivity was significantly associated with the timeframe of testing (P < 0.05), with most true positive urine antigen tests (83%) being performed ≤ 7 days from diagnosis. In this study, the urine antigen assay was capable of detecting both B. dermatitidis and B. gilchristii at about equal sensitivity. Urine antigen concentration (ng/mL) trended higher in B. dermatitidis infections. This study found that the urine antigen assay is capable of detecting both species of Blastomyces at about the same sensitivity. We recommend continued use of the urine antigen assay for diagnosis of blastomycosis and recommend that the assay be used early in the diagnostic process to minimize the chance of false negative results.

Surgeries in asymptomatic carriers during SARS-COV-2 pandemic: Challenges and future.

Sir, The outbreak of severe acute respiratory syndrome coronavirus (SARS-CoV-2) pandemic lead to around 5,400,000 confirmed cases in more than 210 countries all over the world (26thMay 2020).[1] To avoid burden on the health care system and to avoid disease transmission, most of the hospitals suspended all the elective procedures and are undertaking only emergency procedures. A suspected/confirmed COVID-19 patient for an emergency procedure may be treated with strict adherence to standard operating procedure (SOP) with enhanced personal protective equipment (PPE) put forth by various agencies.[23] If they are symptomatic or with contact history, we will proceed after testing for COVID-19. But what if the patient is an asymptomatic carrier?[4] Does every patient need to undergo “COVID-19” screening for an elective procedure? Even after the COVID-19 screen, are we sure the test result is not false-negative?[3] Are the health care workers always at risk after this pandemic? So, the answer would be to do the best of the best cost-effectively. Firstly, there is around 10–20% chance of false-negative results.[3] Secondly, it is not cost-effective to carry out every elective procedure with SOP in all asymptomatic patients with negative contact history. A better way would be to emphasise on areas where the chances of transmission are more, use equipment which can be reused and sterilised. The most common mode of transmission in the operating area is by aerosol-generating procedures (AGP), that is, intubation, extubation, suction and manual ventilation. Few precautions may be followed while executing these procedures: The term “elective and emergency” needs to be well understood and balanced with the health of the patient in this time of crisis. Indication of surgery needs to be evaluated against the resources. Emergency surgeries in asymptomatic carriers also stand as a risk during the pandemic Symptomatic suspected/confirmed COVID-19 cases posted for elective procedures should be done only after considering the need for surgery. Cosmetic surgeries may be avoided Pre-anaesthetic check-up also needs to be done with N95 masks, goggles, and hand hygiene. Proper history taking and informed consent (regarding asymptomatic carriers and hospital staff is not responsible if they are detected later) should be done[5] The person handling the airway may use a set of seven to eight N-95 masks/month (reused after “mask quarantine” for 3 days or sterilised with ultraviolet radiation or hydrogen peroxide vapor),[6] goggles (reusable), face shield (reusable), and standard PPE in place of enhanced PPE Use a plastic box with preferably suction/vacuum port or two holes in plastic cover, making a room for two hands, over the patient to be intubated or extubated. The mask may also be covered with plastic cover to limit the spread of aerosol. Avoid manual ventilation as and when possible. If required, small tidal volumes with heat moisture exchanger filter (HMEF) may be used[7] Preoxygenation before induction gives some time during desaturation. It reduces mistakes during induction and hence decreases aerosol generation. The routine use of rapid sequence induction using intubating dose of rocuronium or succinylcholine should be encouraged, unless contraindicated. Routine use of videolaryngoscope is preferable Limit the number of people during AGP to two-three (including a trained assistant) to minimise the exposure to AGPs. Safe extubation practices should be adopted (use of intubation box or plastic drapes) Conduct the elective surgeries under regional anaesthesia (sub-arachnoid block, regional blocks) as and when possible. Use second generation supraglottic airway devices whenever feasible Minimise the number of ventilator disconnections to avoid the operating theatre pollution and aerosol spread. A negative pressure operation theatre (OT) is preferable or if not possible increase the number of air exchanges per hour[3] Use of HMEF may be encouraged at the patient end and at the expiratory limb. Routine use of videolaryngoscopes may be encouraged Hand-hygiene before and after the procedure and social distancing need to be followed in OTs. The surgeons performing open abdominal surgeries, ophthalmological surgeries, oropharyngeal surgeries, etc. may also use the N-95 mask with goggles and face shield. Hence, considering precautionary measures would be a better choice for all asymptomatic cases, as the risk of false-negative tests cannot be negated. This adds to the safety along with COVID screening. Although the spread of the virus to people not performing AGP is not guaranteed, this is the best that can be done cost-effectively. However, for any suspicion of COVID-19 status or a confirmed case, PPE is a must. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

What benefits and harms are important for a decision about cervical screening? A study of the perspective of different subgroups of women.

Background: In cervical screening programs, women typically receive information leaflets to support their decision about participation. However, these leaflets are often based on what experts consider important benefits and harms of screening and not what women themselves consider important to know.Objective: To identify which benefits and harms women consider important for making a decision about cervical screening.Design: Cross-sectional study.Setting and participants: Women from the Dutch target group of cervical screening (N=248; 30–60 years), recruited through an online access panel.Main variables studied: Perceived importance of different benefits and harms of cervical screening, assessed through two rating items (“How important is the information about [this harm/benefit] for your decision?” and “For me it is a [benefit/harm] that participating in the screening program leads to [the benefit/harm]”), and one ranking item (“Rank the information according to their importance for your own choice”).Results: Women overall considered the benefits of cervical screening more important than the harms or disadvantages. The most important harm according to women was the chance of false positive results (M=4.88; SD=1.75). Differences between those with lower and higher numeracy/health literacy were found regarding several aspects, e.g. for the chance of false positive results, the chance of false negative results, the chance of overtreatment.Discussion and conclusion: The results suggest that leaflets could include more explicit information about false positive results.

Bayesian latent class analysis of ELISA and RT-rPCR diagnostic accuracy for subclinical Renibacterium salmoninarum infection in Atlantic salmon (Salmo salar) broodstock.

Renibacterium salmoninarum infection causes bacterial kidney disease (BKD) in salmonid freshwater and saltwater life stages, with potentially severe financial loss for the aquaculture industry. Preventing vertical transmission, from infected broodstock to eggs, is key to disease management. As there is no perfect reference standard for detecting R.salmoninarum, we used Bayesian latent class analyses to compare real-time reverse transcriptase PCR (RT-rPCR, mRNA target) and enzyme-linked immunosorbent assay (ELISA; p57 antigen target) diagnostic accuracy for detection in Atlantic salmon broodstock from British Columbia, Canada, and assessed ELISA repeatability. In 2016, 4,544 Atlantic salmon broodstock (no clinical signs of BKD or gross lesions) were sampled for ELISA testing of kidney tissue. Two groups of ELISA positives (n=132) and two groups of a random sample of ELISA negatives (n=137) were then tested with RT-rPCR, and ELISA testing was repeated. ELISA testing of broodstock provided the best diagnostic sensitivity (DSe; less chance of false-negative results). The use of joint RT-rPCR and ELISA testing improved DSe over that from each test alone, if a sample was considered positive when either test result was positive. Using these testing schemes in combination with management practices can decrease the likelihood of vertical transmission from subclinically infected broodstock.

A Multiplex PCR Assay for Differentiating Coconut Rhinoceros Beetle (Coleoptera: Scarabaeidae) From Oriental Flower Beetle (Coleoptera: Scarabaeidae) in Early Life Stages and Excrement.

The coconut rhinoceros beetle, Oryctes rhinoceros (L.), is a major pest of coconut and other palm trees. An incipient coconut rhinoceros beetle population was recently discovered on the island of Oahu, Hawaii and is currently the target of a large, mutiagency eradication program. Confounding this program is the widespread presence of another scarab beetle on Oahu, the oriental flower beetle, Protaetia orientalis (Gory and Percheron 1833). Eggs, early life stages, and fecal excrement of coconut rhinoceros beetle and oriental flower beetle are morphologically indistinguishable, thereby creating uncertainty when such specimens are discovered in the field. Here, we report the development of a multiplex PCR assay targeting cytochrome oxidase I of coconut rhinoceros beetle and oriental flower beetle that can rapidly detect and distinguish between these insects. This assay also features an internal positive control to ensure DNA of sufficient quantity and quality is used in the assay, increasing its reliability and reducing the chances of false negative results.

Bevacizumab as first-line treatment of ovarian cancer: strengths and weaknesses of subgroup analyses

Bevacizumab is approved as first-line treatment for ovarian cancer, in combination with carboplatin-paclitaxel, in patients with FIGO IIIb or IV disease, and as maintenance therapy. The results of subgroup analyses of data from the ICON7 study have resulted in bevacizumab use being restricted to “high-risk” patients in several countries. While a goal of obtaining as much information as possible from clinical trial data is understandable, there are also a number of limitations associated with subgroup analyses. Interpretation can be limited by the multiplicity of statistical tests (increasing the risk of false positive findings) and by low statistical power (increasing the chance of false negative results). In addition, the credibility of subgroup analyses is improved if they are restricted to the primary study outcome and limited to a small number of predefined patient subgroups. Overall, subgroup findings should be considered exploratory and hypothesis-generating. The subgroup analysis in ICON7 had a number of limitations, including post hoc definition of “high-“ and “lowrisk” groups, and questionable applicability of these definitions to clinical practice. Use of residual disease as a determinant of risk status is also problematic. Excessive emphasis on the role of subgroup analyses may lead to misunderstanding of the true results generated by the overall trial data, and support the incorrect selection of patients to be treated with the new or experimental therapy. Caution should be used in translating results of subgroup analysis to clinical practice guidelines.

Diagnosis of Malaria among Blood Donors in Port Harcourt, Nigeria: Microscopy or Rapid Diagnostic Tests?

The two most common techniques available for diagnosis of malaria in Nigeria are microscopy and rapid diagnostic tests (RDTs). However, in diagnosing asymptomatic Plasmodium parasitaemia among donors, the preferred technique should not only be timely but must not compromise diagnosis. It should be more sensitive with minimal chances of false negative results. This study was carried out to compare microscopy and RDTs as effective tools for diagnosis of Plasmodium parasitaemia among blood donors in Port Harcourt. There were 200 donors involved in the study among which 135 (67.5%) tested positive and 65 (32.5%) tested negative on microscopy whereas 30 (15.0%) tested positive and 170 (85.0%) tested negative to RDT with a statistically significant difference between both techniques. Data were analysed using the statistical package epi-info version 7.02. We therefore recommend that microscopy using giemsa-stained blood films remain the method of choice for diagnosis of Plasmodium parasitaemia among blood donors to prevent the spread of transfusion malaria.

Dietary Amino Acids and Blood Pressure: A Cohort Study of Patients With Cardiovascular Disease

Dietary protein has been variably reported to either lower or raise blood pressure. The purpose of this study was to determine whether intakes of specific amino acids differentially associate with blood pressure. Observational cohort study by secondary analysis of clinical trial data. Study of low-fat versus Mediterranean-style diets in patients with prevalent cardiovascular disease. Dietary amino acids. Systolic and diastolic blood pressure. Dietary nutrients and cardiovascular risk factors were assessed at baseline, 3 and 6 months, and then every 6 months for 2 years. Baseline blood pressure was 119 ± 16 (SD)/72 ± 10 (SD) mm Hg (n = 92) and dietary protein intake was 80 ± 31 g/d. Independent amino acid variables (quartiles of intake) were analyzed by generalized estimating equation models with prespecified covariates for time-varying systolic and diastolic blood pressure. The odds of each 1-SD higher systolic or diastolic blood pressure (ie, 16 and 10 mm Hg, respectively) were increased per quartile of intake for methionine (ORs of 1.29 [95% CI, 1.14-1.46] and 1.21 [95% CI, 1.05-1.39], respectively) and alanine (ORs of 1.17 [95% CI, 1.05-1.30] and 1.22 [95% CI, 1.07-1.38], respectively). Quartiles of intake for threonine (ORs of 0.84 [95% CI, 0.74-0.96] and 0.87 [95% CI, 0.75-1.01], respectively) and histidine (ORs of 0.92 [95% CI, 0.86-1.00] and 0.89 [95% CI, 0.82-0.97], respectively) had inverse associations with the same degree of difference in blood pressure. Modest sample-size biases toward the chance of false-negative results; potential for residual confounding; colinearity between amino acids may obscure relevant relationships to blood pressure; associational findings do not establish causality. Intakes of methionine and alanine were associated positively with higher blood pressure, whereas intakes of threonine and histidine had inverse associations. These amino acids merit further study for advancing dietary approaches to blood pressure reduction.

Intra-Operative Assessment of Sentinel Lymph Nodes with Touch Imprint Cytology – Experience on 232 Patients with Breast Cancer.

Abstract IntroductionSentinel lymph nodes (SLNs) are generally evaluated by histology which takes about 3-5 days and axillary clearance is then carried out if SLN is positive for metastasis. This second operation to perform axillary clearance can be avoided, if a reliable intraoperative assessment is available. This will allow the surgeon to proceed to axillary clearance during the primary operation if intra-operative assessment of SLNs is positive. Touch imprint cytology (TIC), is a relatively new technique for intraoperative assessment. This study aimed to evaluate the accuracy and feasibility of TIC in our practice.MethodsThis was a prospective study of 232 patients with breast cancer. SLN biopsy was performed first and sent for TIC while surgeon proceeded with wide local excision or mastectomy. In pathology, nodes less than 5mm were bisected and others were sliced at 2mm intervals.Each cut surface was touched onto a slide allowing the weight of the node to release the cells onto the slide. The slides were assessed by dedicated breast pathologists and the results telephoned to theatre. If TIC was positive, axillary clearance was performed. Permanent histological sections were evaluated with hematoxylin and eosin stain and immuno-histochemical staining. The TIC results were compared with the final histology of the SLN. We calculated the accuracy, sensitivity, specificity, positive predictive and negative predictive value of TIC. The time required for intra-operative assessment was recorded prospectively in the last 30 patients. We also calculated the percentage of patients who were spared from having a second operation for axillary clearance based on the results of TIC.ResultsAccuracy of TIC was 90%. Sensitivity and specificity was 54% and 100% respectively. Positive and negative predictive value was 100% and 88% respectively. On final histology, 52 patients (22%) were node positive. TIC diagnosed metastasis in 28(54%) patients (95% Confidence Interval 0.39-0.67). Thus 28 patients (54%) avoided a second operation. Among patients with falsely negative TIC, micrometastasis was seen in 6/24(25%) patients and isolated tumour cells in 1/24(4%) patient. Average time from harvesting of the nodes to receiving of result of the TIC for each patient was 32 minutes (range 15-53). This was proportional to the number of nodes sent. Average time taken by cytopathologist was 15 minutes. Prolongation of operation time was seen in only 22% patients on an average by 7 minutes (range 2-15).ConclusionsTIC is a simple and feasible technique with prolongation of operation time seen in only 22% patients on an average by 7 minutes. It is a reliable technique with an accuracy of 90%. No patient was subjected to unnecessary axillary clearance. Patients should however be counseled preoperatively about chance of false negative results on TIC and need for a second operation. TIC avoided a second operation for axillary lymph node clearance in 54% patients and thus also avoided delay in the adjuvant treatment of these patients. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1030.

Bioassays for the detection of growth-promoting agents, veterinary drugs and environmental contaminants in food.

Residues of growth-promoting agents, veterinary drugs and environmental contaminants in food products are routinely analyzed with chemical-analytical methods, using physical and spectrometric properties of a compound. Since residue limits are in general based on biological properties of compounds, bioassays offer in theory a good alternative. As a consequence, these assays are much more suitable for the detection of mixtures of compounds with common biological properties, including possibly unknown agonists. Using modern molecular biological techniques, a new generation of bioassays has been developed, showing in general a higher sensitivity and specificity for the target compounds. The CALUX (chemical activated luciferase expression) assay was developed for the detection of polyhalogenated compounds, based on their affinity for the aryl hydrocarbon (Ah) receptor. This paper focuses on the specificity of the assay. The benzimidazole compounds oxfendazole, fenbendazole, febantel, thiabendazole, mebendazole, omeprazole, lanzoprazole and benomyl were shown to give a positive response in the assay. Similar results were obtained with dexamethasone, corticosterone and cortisol, which in addition were able to enhance the response obtained with TCDD. Similarly to the flavonoids alpha- and beta-naphtoflavone, the reported Ah receptor antagonist 4-amino-3-methoxyflavone showed a strong positive response at a concentration of 400 microM, but failed to inhibit the response obtained with TCDD. It is concluded that the chances of false-negative results appear to be minimal and can be recognized. False-positive or, better, unwanted results are in theory more likely to occur. Possible solutions to avoid or detect these type of results are discussed. In general, these kinds of assays offer great possibilities for screening of food samples. In addition to the further optimization of these assays, future work should be focused on the development of rapid, sample and selective extraction procedures.

The use of a microsomal in vitro assay to study phase I biotransformation of chlorobornanes (toxaphene®) in marine mammals and birds : Possible consequences of biotransformation for bioaccumulation and genotoxicity

The factors determining the bioaccumulation of lipophilic compounds in wildlife are often poorly understood, partly because it is difficult to do in vivo experiments with animals such as marine mammals and birds. To evaluate the role of phase I biotransformation in the bioaccumulation process of chlorobornanes (toxaphene®), this was studied in in vitro assays with hepatic microsomes of animals that could be sampled shortly after death. The capacity of microsomes to metabolise a technical toxaphene mixture decreased in the order Phoca vitulina (harbour seal)⪢ Lagenorhynchus albirostris (whitebeaked dolphin)≅ Diomedea immutabilis (Laysan albatross)> Physeter macrocephalus (sperm whale). Harbour seal microsomes metabolised the chlorobornane (CHB) congeners CHB-32 and CHB-62; whitebeaked dolphin and Laysan albatross microsomes only metabolised CHB-32. Metabolism of CHB-26 and CHB-50 was never observed. The negative chemical ionisation (NCI−) mass spectra of some of the hydroxylated metabolites were obtained. The number of peaks in the toxaphene residues of wildlife extracts decreased in the order of increasing in-vitro biotransformation capacity. Thus, the results of the in vitro assays and residue analysis were in accordance, although assays with microsomes of more individuals of the same species are required for a more general conclusion at the species level. Finally, the effect of in vitro biotransformation was evaluated in terms of the genotoxic potential using the Mutatox® assay. Only technical toxaphene and CHB-32 were genotoxic in the direct assay, whereas the addition of rat S9 fraction or microsomes of harbour seal and albatross decreased the genotoxic response. Thus, organisms with a low ability to metabolise chlorobornanes, such as whales, may be most affected by the carcinogenic properties of toxaphene. A hypothetical reaction which fits the experimental results is discussed. Based on these results it is concluded that in vitro assays with microsomes of wildlife animals which died a natural cause can act as a valuable tool to assess the occurrence and effects of phase I metabolism. Some precautions are discussed, that should be taken to reduce the chance of false negative results.