Diagnostic validation and interpretation of longitudinal circulating biomarkers using a biomarker response characteristic plot.

BACKGROUND: Serum-based tumor biomarkers are used to monitor cancer treatment, while clear guidance on the clinical usage is often lacking. We describe a graphical presentation to support diagnostic accuracy studies and clinical interpretation of longitudinal biomarker data. METHODS: A biomarker response characteristic (BReC) plot was designed. To allow demonstration of the BReC plot application, software was developed that supported 1) dynamic generation of BReC plots, and 2) diagnostic accuracy studies of biomarker response-based medical tests. The BReC plot application was demonstrated using serial carcinoembryonic antigen (CEA) and Cyfra 21.1 results from 216 patients with metastasized non-small cell lung cancer, treated with Nivolumab in routine clinical practice. RESULTS: The developed software supported the generation of BReC plots and diagnostic validation of biomarker response-based medical tests by generating the sensitivity, specificity and predictive values. Obtained BReC plots showed a clear relationship between clinical outcome and CEA and Cyfra 21.1 responses. Furthermore, using BReC plots, CEA and Cyfra 21.1 based medical tests were designed with a sensitivity for detection of treatment failure of 0.34 and 0.35 and a specificity of 0.96. CONCLUSIONS: The BReC plot appears to support diagnostic validation studies and the interpretation of longitudinal biomarkers though further validation is warranted.

Endogenous steroid profiling by gas chromatography-tandem mass spectrometry and multivariate statistics for the detection of natural hormone abuse in cattle.

For years it has been suspected that natural hormones are illegally used as growth promoters in cattle in the European Union. Unfortunately there is a lack of methods and criteria that can be used to detect the abuse of natural hormones and distinguish treated from non-treated animals. Pattern recognition of steroid profiles is a promising approach for tracing/detecting the abuse of natural hormones administered to cattle. Traditionally steroids are analysed in urine as free steroid after deconjugation of the glucuronide (and sulphate) conjugates. The disadvantage of this deconjugation is that valuable information about the steroid profile in the sample is lost. In this study we develop a method to analyse steroids at very low concentration levels (ng l(-1)) for the free steroid, glucuronide and sulphate conjugates in urine samples. This method was used to determine concentrations of natural (pro)hormones in a large population (n = 620) of samples from male and female bovine animals and from bovine animals treated with testosterone-cypionate, estradiol-benzoate, dihydroepiandrosterone and pregnenolone. The data acquired were used to build a statistical model applying the multivariate technique 'Soft Independent Modeling of Class Analogy' (SIMCA). It is demonstrated that by using this model the results of the urine analysis can indicate which animal may have had illegal treatment with natural (pro)hormones.

[Becoming a psychiatrist: an intensive induction course for trainee house officers]. / Psychiater worden: een intensieve introductiecursus voor artsen in opleiding.

Since October 2006 the specialist training for house officers in psychiatry in the province of North Holland has started with a one-week intensive induction course. The course has been designed to facilitate the transition to specialist training and to provide trainees with the tools they need for dealing with psychiatric emergencies. Fifteen house officers, divided into three focus groups, were asked for their views on the course. They gave the course a high rating and stated that it had had a positive effect on group-bonding and functioning in their subsequent training.

Calcineurin activity and inhibition in skin and (epi)dermal cell cultures.

Calcineurin (Cn) is the target of the immunosuppressive drugs cyclosporine A (CsA), tacrolimus (Trl), and pimecrolimus (Prl). Trl and Prl are often used topically for treatment of various skin diseases. The Cn inhibitors CsA and Trl are mostly used for maintenance therapy of transplant patients. Their long-term use, however, causes a dramatic increase in skin cancer risk. By using a newly developed assay for Cn measurement in blood, we were able to demonstrate Cn activity in total skin homogenates. A significantly higher activity was found in epidermis compared to dermis. In skin cell cultures, fibroblasts showed the highest activity as compared to keratinocytes and melanocytes. Of the Cn inhibitors, Trl showed stronger inhibition than CsA and Prl (57 and 55% in fibroblast and keratinocyte cultures, respectively). Also, the lowest IC(50) (the half maximal inhibitory concentration) values were found for Trl (0.5 and 1.3 nM in two different fibroblast cultures). Cn activity and its inhibition can thus be studied in dermatological samples. The effects of Cn inhibition in fibroblasts and keratinocytes may be of influence on the overall functioning of the skin immune system.

Development of a method which discriminates between endogenous and exogenous beta-boldenone.

One potential explanation for the presence of beta-boldenone in calf urine is contamination of the sample with feces containing beta-boldenone. It has been demonstrated that after oral and intramuscular administration of beta-boldenone esters, several metabolites are formed and excreted in urine. One of the (minor) metabolites is 6beta-hydroxy-17alpha-boldenone. This paper describes an analytical method that can discriminate between unconjugated boldenone, its glucuronide- and sulphate-conjugates, 6beta-hydroxy-17alpha/beta-boldenone and coprostanol, a marker for fecal contamination. The method was applied to all samples suspected to contain boldenone within the Dutch National Residue Control Plan. Approximately 10,000 samples of urine were screened (LC-MS) in 2004-2005 by VWA-East, one of the official Dutch control laboratories, from which 261 samples were suspected to contain boldenone. These samples were all analyzed for their conjugation state, 6beta-hydroxy-17alpha/beta-boldenone and for the presence of coprostanol. Alfa-boldenone, the major metabolite in bovine urine after boldenone-ester administration, was found in a large number of these samples. The presence of alpha-boldenone was proven also to be a result of fecal contamination. None of the samples tested contained residues of the metabolite 6beta-hydroxy-17alpha/beta-boldenone. Not finding this metabolite indicates that the origin of alpha-boldenone-conjugates is endogenous. The results confirm that the presence of unconjugated beta-boldenone and alpha-boldenone conjugates next to alpha-boldenone are no indicators for illegal administration of boldenone-esters. No indications were obtained that conjugated beta-boldenone can be of endogenous origin.

[In the consultation room, ready knowledge is more important than knowledge that must be looked up]. / In de spreekkamer is parate kennis belangrijker dan opzoekkennis.

Ready knowledge rules the consultation room--there is no time to look things up. The doctor attempts to find the diagnosis on the basis of a network of ready knowledge. The quality of this knowledge network determines the quality of the resultant diagnosis and of the subsequent treatment. The doctor must continually test and maintain his or her knowledge network.

Endogenous occurrence of some anabolic steroids in swine matrices.

Following findings of 17beta-19-nortestosterone (150-200 microg kg(-1)) in pigs of unspecified gender imported into the European Union, a study to determine steroid and hormone levels in swine from six age/gender categories (uncastrated 'old' boars, cryptorchids, one intersex, barrows, gilts and sows) was initiated. Indeed, for some hormones there has been a discussion about their being endo- or exogenous. Tissue and urine samples from swine from each of the six categories were obtained in Belgium, France, the Netherlands and the USA. Samples were analysed in three laboratories. Quantitation was obtained for norandrostenedione, 19-nortestosterone and boldenone. The results give a well-documented overview of the status of the presence of these hormones in swine. The data illustrate that uncastrated 'old' boars produce the highest percentage of 'positive' matrices, followed by the cryptorchids. Concentrations in the matrices of the barrows and the gilts are lower. Also, sow matrices contain low amounts of nor-steroids. Furthermore, urine samples from an intersex pig contains a higher concentration of nortestosterone than sows and can therefore be suspected for illegal use of these hormones. Veterinarians taking samples in pig farms for the analysis of hormones need to be aware of the presence and concentrations of these substances in the different categories.

Effectiveness of basic clinical skills training programmes: a cross-sectional comparison of four medical schools.

OBJECTIVE: Training in physical diagnostic skills is an important part of undergraduate medical education. The objective of this study was to study the outcome of skills training at four medical schools. CONTEXT: At the time of the study, three schools had a traditional lecture-based curriculum and one school had a problem-based learning curriculum with a longitudinal skills training programme. All schools offer extended exposure to clerkships. METHOD: A cross-sectional study in four medical schools was performed, using a written test of skills that has good correlation with actual student performance. The scores attained from four student groups were compared within and between the four medical schools. A total of 859 volunteer students from the later four years at each medical school participated in the study. RESULTS: The mean scores in the traditional medical schools increased with the start of skill training and the hands-on experience offered during the clerkships. Students from the school with the longitudinal skills training programme and the problem-based learning approach had significantly higher mean scores at the start of the clerkships, and maintained their lead in the subsequent clinical years. CONCLUSIONS: Longitudinal skills training seems to offer the students a superior preparation for clerkships as well as influencing the students' learning abilities during the clerkships. The effect of the problem-based learning approach, also related to the innovative philosophy of the curriculum, could not be accounted for.

An Inter- and Intra-University Comparison With Short Case-Based Testing.

Comparisons between PBL and non-PBL medical schools on problem-solving ability often show no differences. This could be either due to the fact that no difference in problem-solving skills exists or that the instruments used are inadequate. In this study a key-feature approach case-based examination was used to compare two medical schools in the Netherlands, one of which has a PBL curriculum (Maastricht) and one which has a program half way a transition from a non-PBL towards a PBL curriculum (Groningen). Differences were found both in proficiency scores and in the pattern of response times, both supporting the assumption that a PBL approach would lead to a higher level of problem solving ability. The effect size, however, is not as large as originally assumed by the PBL proponents. Conclusions must be drawn with caution, but it seems likely that a test based on large numbers of short cases is the most sensitive in detecting differences in problem solving ability between students of different curricula.

Nortestosterone: endogenous in urine of goats, sheep and mares?

For a number of species it is known that nortestosterone, either the alpha- or beta-epimer, can be of endogenous origin. For goats and mares similar results have not yet been published. As a follow-up on the experiments with cattle, a large number of urine samples per animal were collected from pregnant goats, sheep and mares. These samples were analysed for the presence of alpha- and beta-nortestosterone and alpha-estradiol using GC-MS. The results show that in the goats and mares studied alpha-nortestosterone is present during pregnancy. In this study no alpha-nortestosterone could be demonstrated in sheep. From our study and recently published data, however, it is proven that alpha-nortestosterone can occur endogenously.

Confirmational analysis of beta-agonists by cryotrapping gas chromatography-Fourier transform infrared spectrometry.

Cryotrapping gas chromatography-Fourier transform infrared spectrometry has been used for confirmation analysis of the beta-agonists clenbuterol, salbutamol, mabuterol, bromobuterol, cimaterol, cimbuterol and mapenterol in urine and liver samples of veal calves, subsequent to selected ion detection gas chromatography-mass spectrometry. Samples have been analysed as their trimethylsilyl and methylboronate derivatives. Methylboronate derivatives yielded strongly diminished chemical background and interference levels in the infrared chromatograms of standards and samples. The limit of identification for methylboronate derivatives was at the low ppb level in incurred samples. The similarity of analyte and reference spectra, together with the retention time, was found to be a useful criterion for confirmation of unknown compounds.

Liquid chromatographic purification and detection of anabolic compounds.

The role of liquid chromatography within methods of analysis for steroids, related compounds and beta-agonists in biological samples is discussed. Special attention is given to the application of liquid chromatography in sample preparation and extract clean-up. Different forms of liquid chromatography, including immunoaffinity chromatography, are compared and evaluated. Methods for confirmation based on gas chromatography-mass spectrometry and cryotrapping Fourier transform infrared spectrometry are discussed.

Why do elderly people seek professional home care? Methodologies compared.

In order to investigate which characteristics, besides physical limitations, of elderly people living at home contribute to the utilization of professional home care, a study was conducted in which 450 elderly people aged 55 and over, 123 with and 327 without professional home care, were interviewed. To obtain a selection for the interviews, a postal questionnaire, containing questions on functional status and care utilization, sent out to a random sample of the elderly people (55+) living at home (n = 2451), preceded the actual interviews. The oral interviews yielded the same information, plus an inventory of aspects of the mental status, the social network, the socio-economic status and the housing condition. Analysis was performed in three ways: bivariate analysis, logistic regression analysis and discriminant analysis. The bivariate analysis revealed that users of professional care were older, more often female and more often not married. Their social network was less extensive, as they received less informal care and lived alone more often. Besides they had more mental and financial problems. From the regression analysis it appeared that, in addition to the functional status, the amount of informal care and the household composition contributed to the utilization of professional home care. For the other characteristics inventoried, no independent association with the utilization of professional care could be established. With hindsight, it appeared that in this study long interviews hardly had additional value over postal questionnaires, in which the contribution of functional status and informal care to professional care was already discovered.

Conformation and quantification of chloramphenicol in cow's urine, muscle and eggs by electron capture negative ion chemical ionization gas chromatography/mass spectrometry.

A method is described for the determination of residues of the antibiotic chloramphenicol in biological samples. The method is based on gas chromatography/negative ion chemical ionization mass spectrometry and uses (37Cl2)chloramphenicol as internal standard. Selective ion monitoring of four analyte-specific ions enables the determination of chloramphenicol levels in urine of 3 micrograms l-1 with a coefficient of variation of 8%. The limit of detection of the method is 0.1 p.p.b. for urine, muscle and egg.

[The influence of biographical details in case reports on diagnostic judgment]. / De invloed van biografische details in casuïstische mededelingen op het diagnostisch oordeel.

Diagnostic judgment of medical students is influenced by patients they have seen recently. Not only signs and symptoms but also biographic data of the demonstrated patient contribute to this phenomenon. In this study the question is raised whether practising physicians are susceptible to the same influence after reading a case report in a medical journal. A case to be published in this journal was transformed into two patient scripts. The first was based on the same diagnosis and the same signs and symptoms, the second was based on another diagnosis and contained partly similar partly different signs and symptoms. Both scripts contained the same, striking biographic data derived from the original case report. One of the two scripts was presented randomly to a control group of 53 practising doctors before the date of publication. They were asked to rate the probability of 8 diagnoses on a 7-point scale. The experimental group consisted of 16 doctors who stated having read the case report. The scores of both groups were compared using analysis of variance. The experimental group in both cases assigned a significantly higher probability to the diagnosis of the published case report. In the first case they were right, in the second they were wrong. These results are similar to the findings with medical students. The question to be explored further is how to present patient cases in medical education. On one hand they should be attractive with some real life data, on the other hand spectacular biographic data may impair the diagnostic process.

Factors associated with differential utilization of professional care among elderly people: residents of old people's homes compared to elderly people living at home.

To investigate factors that explain differential utilization of professional care among elderly people a study was performed in Maastricht, the Netherlands. For that purpose 657 interviews with elderly people were held. In this article a comparison is made between elderly people living at home, with or without professional home care, and residents of old people's homes. Besides the functional status, as measured by limitations in household activities and activities of daily living, the composition of the household of the elderly person is recognized as a major discriminating factor between the three groups. The role of depressive complaints in care utilization is less prominent than expected from an earlier study. A bivariate analysis clearly showed the frequency of mental problems and the poorly developed social network among elderly persons using professional care. Implications for caregiving and policy planning are discussed.

Multi-immunoaffinity chromatography: a simple and highly selective clean-up method for multi-anabolic residue analysis of meat.

A method for the detection of nortestosterone (NT) in bovine muscle at levels below 1 microgram/kg is described, based on enzymatic digestion of the sample, clean-up by immunoaffinity chromatography after defatting and detection by gas chromatography-mass spectrometry (selected-ion monitoring). The immunoaffinity matrix was prepared after combining the isolated immunoglobulin G fractions from a rabbit antiserum raised against NT and methyltestosterone (MT). Its capacity per millilitre of gel was approximately 10 ng for each of the two steroids. Results for samples containing 0.1 microgram/kg NT and above are described. It is concluded that for multi-residue analysis of samples of muscle at levels as low as 0.1 microgram/kg, multi-immunoaffinity chromatography is a very suitable method of sample clean-up. For purposes of quantification the trideuterated internal standard [16,16,17 alpha-2H3] nortestosterone was synthesized.

Effective monitoring of residues of nortestosterone and its major metabolite in bovine urine and bile.

The results of a newly developed method for the detection and identification of residues of nortestosterone (NT) and one of its major metabolites, 17 alpha-nortestosterone (epiNT) are described. The method is based on sample clean-up by immunoaffinity chromatography and detection by high-performance liquid chromatography and/or gas chromatography-mass spectrometry (selected-ion monitoring). All samples of bile from calves that had been treated with NT contained significant amounts of epiNT (6-18 micrograms/l). The NT content of these samples, if detectable, was below 1 microgram/l. Urine contained, with one exception, less than 1 microgram/l epiNT. NT itself if detectable, was, present in urine or bile at levels below 0.1 microgram/l. The results corresponds well with results obtained with a radioimmunoassay procedure.