Microbeads detection using spin-valve planar Hall effect sensors.

In this paper we present a micromagnetic approach to describe the detection of magnetic nanobeads using planar Hall effect sensors. The magnetic beads polarized by a dc magnetic field generate a field, which can affect the magnetization state of spin-valve sensor, leading in principle, to a detectable signal. For magnetic nanobeads we assumed a superparamagnetic behaviour. Three detection geometries are discussed and some specific behaviours were highlighted by micromagnetic simulations. We found that when the polarising field is applied parallel with the sensor surface a very weak signal can be obtained. This is because at working fields, for which the magnetic nanobeads are magnetised, the sensor saturates. We identified other setups that can overcome this shortcoming and deliver a net signal.

[Prospective comparison of the flow chart for laboratory investigations for anaemia from the Dutch College of General Practitioners' guideline 'Anaemia' with a self-developed, substantive and logistical alternative flow chart]. / Prospectieve vergelijking van het stroomschema voor laboratoriumonderzoek van anemie uit de NHG-standaard 'Anemie' met een eigen, inhoudelijk en logistiek alternatief stroomschema.

OBJECTIVE: To compare the flow diagram for the diagnosis of anaemia from the guideline 'Anaemia' from the Dutch College of General Practitioners (NHG) with a substantive and logistical alternative protocol. DESIGN: Prospective. METHOD: For evaluation of anaemia, 124 patients from primary care reported to the laboratories of the St. Elisabeth Hospital in Tilburg (n = 94) and the Scheper Hospital in Emmen (n = 30), the Netherlands. Two flow charts were used: the NHG's flow chart and a self-developed chart in which not mean corpuscular volume, but ferritin concentration occupies the central position. All the laboratory tests mentioned in both flow charts were carried out in every patient with, for practical reasons, the exception of Hgb electrophoresis and bone marrow investigations. General practitioners were approached and patient dossiers were consulted to obtain further clinical data. RESULTS: According to the NHG protocol, on the grounds of the laboratory investigations, 64 (52%) of patients could not be put in a specific category. The majority were patients with normocytary anaemia who did not fulfil the criteria for iron deficiency anaemia or the anaemia of chronic disease. According to the alternative chart, in 36 (29%) patients no diagnosis was made. These were patients in whom no abnormal laboratory findings were observed, other than low haemoglobin values. The majority of the patients had normocytary anaemia, in some cases this was interpreted as the anaemia of chronic disease, but more often the anaemia could not be assigned to a particular category. A large number ofpatients had a raised creatinine value. This value did not appear in the NHG protocol. In 15% of patients, more than one cause for anaemia was found. The NHG protocol did not enable these multiple diagnoses to be made. Accordingly, the NHG protocol was difficult to implement in the laboratory. CONCLUSION: Using the NHG flow diagram a large percentage of patients could not be assigned to a particular category. Using the alternative flow diagram, which procedure is easier to carry out in the laboratory, it was possible to make multiple diagnoses.

Pharmacokinetics of high-dose cytarabine and its deamination product--a reappraisal.

Cytarabine is intracellularly activated and correlations have been established between the pharmacokinetic behaviour of active metabolites and their antileukemic effect. Recently, a good response to high-dose treatment of leukemias has additionally been attributed to a so-called low deamination phenotype of cytarabine inactivation. Consequently, these findings would support plasma level monitoring of cytarabine and its metabolite uracil arabinoside in high-dose cytarabine regimens. This pharmacokinetic study presents data attempting to reevaluate these observations. Thirty-seven patients were treated by 3-h high-dose cytarabine infusions (9 patients 1000 mg/m2, 28 patients 3000 mg/m2) as part of their treatment for acute leukemia. Serial blood samples during and post infusion were analysed for cytarabine (araC) and its deamination product uracil arabinoside (araU) using HPLC with UV-detection. Considerable interindividual variation was observed in end-infusion plasma concentrations of araC (1000 mg/m2: 2.1-fold, 3000 mg/m2: 5.5-fold) and araU (1000 mg/m2: 2.7-fold, 3000 mg/m2: 2.9-fold). The median ratio of end infusion concentrations araU/araC (on a molar basis) was 5.6 (S.D. 3.0), extreme ratio values were 2 and 14. No differences of the araU/araC ratio were found between the two dosages used. Minimum plasma araC concentrations at the end of infusion were 10.5 micromol/l and 22.0 micromol/l at a dose of 1000 and 3000 mg/m2, respectively. In our European study population a "fast" deamination phenotype of cytarabine (araU/araC ratio > 14) was not be observed.

Detection of 3 beta-hydroxysteroid-dehydrogenase deficiency by urinary steroid profiling: solvolysis of urinary samples should be a necessary prerequisite.

A urinary steroid profile from a patient with suspected 3 beta-HSD deficiency was prepared using capillary gas chromatography, employing only enzymatic deconjugation with Helix pomatia juice. In the chromatogram only very small peaks of dehydroepiandrosterone and 5-pregnenetriol were visible apart from other, for the diagnosis non-significant, peaks. However, after repeating the analysis including an additional solvolysis step, highly significant peaks of DHEA and 5-pregnenetriol became apparent, which suggests the necessity for a solvolysis step for a positive proof of 3 beta-HSD deficiency by urinary steroid profiling.

The diagnosis of 21-hydroxylase deficiency in a prematurely born infant on the basis of the urinary steroid excretion pattern.

The urine of a 6-day-old prematurely born female infant (birth weight 1060 g) suspected of having a 21-OH-deficiency showed no steroid abnormalities on capillary GLC analysis. Using GC-MS tetrahydrocortisone (THE) and also 3 alpha, 17 alpha-dihydroxy-5 beta-pregnane-20-one (17-OH-Polone) were absent, but two androstanetriolone peaks were observed. In the urine collected on day 9 THE was absent, but a large amount of 3 alpha, 11 beta-dihydroxy-5-alpha-androstane-17-one (11-HA) was found by GC-MS to be contaminated by a small amount of 17-OH-Polone. The next urine specimen collected on the 22nd day while the child received cortisol therapeutically showed the characteristic steroid profile for the diagnosis 21-OH deficiency, large peaks of 17-OH-Polone, pregnanetriol (P3) and 11-keto-pregnanetriol (11-keto-P3). Over the next few weeks two other compounds were found to have been excreted in relatively large amounts, 3 xi, 16 xi, 17 xi, 20 xi-pregnanetetrol (16-OH-P3) and surprisingly also a 21-hydroxylated compound, namely 3 xi, 20 alpha, 21-trihydroxy-5-pregnene. These same two compounds were also found in the urine of another infant with suspected 21-OH deficiency. The urinary steroid excretion patterns characteristic for 21-OH deficiency are dependent on the maturity and age of the infant. In the prematurely born infant androstanetriolones appear in the urine before 17-OH-Polone. The occurrence of these different steroid excretion patterns is tentatively explained.

Detection of 3 beta-hydroxysteroid dehydrogenase deficiency in a newborn by means of urinary steroid analysis.

A urinary steroid excretion pattern of a 3-wk-old newborn, suffering from 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) deficiency, has been produced, employing capillary gas chromatography and subsequent mass spectrometric identification of the various excreted steroids. The diagnosis could be established, apart from the clinical symptoms, on the basis of a grossly elevated excretion of 16-OH-DHEA and 16-OH-pregnenolone, combined with mass spectrometric identification of the following steroids: 17-OH-preganolone, pregnanetriol, pregnanolone, pregnenetriol and 17-OH-pregnenolone.

Diagnosis of cerebrotendinous xanthomatosis (CTX) and effect of chenodeoxycholic acid therapy by analysis of urine using capillary gas chromatography.

By means of capillary gas chromatography urine samples of patients with cerebrotendinous xanthomatosis (CTX) were investigated before and during treatment by oral administration of chenodeoxycholic acid. The occurrence of various conjugated bile alcohols, presumably glucuronides, was demonstrated, the major compound being 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 23 xi, 25-pentol. In the bile acid fraction norcholic acid and hydroxycholic acid were shown to be present in considerable amounts. In this way the presence of CTX can be demonstrated conclusively. After chenodeoxycholic acid therapy the excretion of both abnormal bile acids as well as of bile alcohols rapidly decreased within a few weeks, showing the effectiveness of the treatment. By early discovery and subsequent therapy it may be possible to prevent the onset of the detrimental symptoms such as mental deficiency, caused by the accumulation of cholestanol and cholesterol in CTX patients.

Potential of descriptive linear discriminant analysis for studying clinical chemical and haematological data from persons with heterozygous sickle cell disease.

To study the potential of multivariate classification methods in order to obtain more insight into abnormal laboratory data from patients with sickle cell disease, we investigated standard haematological and clinical chemical variables of 18 controls and 37 apparently healthy persons with heterozygous sickle cell disease (Hb AS), all women, using both univariate and multivariate classification methods. In the univariate method, those with Hb AS showed decreased serum log aspartate aminotransferase (log AST) activity, mean corpuscular volume and mean corpuscular haemoglobin (MCH) and increased sodium concentration. The multivariate method identified sodium, potassium, urea, uric acid, log AST, alanine aminotransferase and MCH as the variables that produced maximal separation between persons with Hb As and controls. It increased the 'non-error rate' for classification of persons with Hb AS by 16.4% compared with classification based on the variable, MCH, that produced maximal separation by the univariate method. The frequency distribution of percentage Hb S in the Hb AS group proved bimodal with maximal separation at 37.0% Hb S. The subgroup with 37.0% or less (n = 16) was considered to have concomitant heterozygous alpha-thalassaemia-2. In the univariate method the subgroup characterized by greater than 37.0% Hb S (n = 21) had increased serum sodium and uric acid concentrations, perhaps related to sickle cell nephropathy, whereas the subgroup with less than or equal to 37% Hb S did not. The multivariate method added information to the univariate method by additionally identifying abnormalities in serum potassium and urea concentrations in the former subgroup.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigation of applicability of a mid-infrared spectroscopic method using an attenuated total reflection accessory and a new near-infrared transmission method for determination of faecal fat.

In many laboratories, the titrimetric method of Van de Kamer is used for the analysis of faecal fat content of patients suspected of steatorrhoea. We investigated the applicability of a mid-infrared (MIR) spectroscopic method, using an attenuated total reflection (ATR) accessory, and a new near-infrared (NIR) spectroscopic method. For the NIR method, sealed plastic bags containing the stool samples were used as transmission cells. Standardization was obtained using a previously described MIR method, with a NaCl flow-cell, as reference method. Partial least-squares regression was used for the calibration of each method. Full cross-validation of the calibration set was used for the internal validation of each method. Fifteen per cent of the stool samples could not be estimated with the ATR method within reasonable accuracy limits compared with the reference. The standard error of prediction of the NIR method was 1.1 g/dL. We conclude that the new NIR method is a promising technique for routine use. However, further experiments need to be done with triplicate measurements of each sample and the use of an external validation set.

New method for faecal fat determination by mid-infrared spectroscopy, using a transmission cell: an improvement in standardization.

Current techniques used in clinical laboratories for faecal fat determination, such as the Van de Kamer method, are not very accurate or precise. This became apparent when results obtained by different laboratories were compared, and could explain the disappointing performance of near-infrared and mid-infrared spectroscopy since the accuracy of these techniques depends upon the accuracy of the calibration used (i.e. inaccurate wet chemical analysis). In order to improve standardization, we developed and tested a new quantitative method in three laboratories, based on Fourier transform infrared (FT-IR) spectroscopy. Fatty acids were extracted from faecal samples with acidified petroleum ether-ethanol and the extracts were dried and dissolved in chloroform. An infrared spectrum of the extracts was recorded in the range 4000-650 cm(-1), using an infrared transmission cell. Standard mixtures of stearic and palmitic acids (65:35) were used for calibration. Quantification was based on the absorbance band of the CH2 group (2855 cm(-1)) of free fatty acids and fatty acid glycerol esters. The calibration curve showed excellent linearity. The correlation coefficient between the titrimetric Van de Kamer and FT-IR methods was 0.96 (y = 1.12x-0.02, standard error of prediction = 0.89 g% fat). No significant difference was found when the FT-IR results of 28 faecal samples from patients were compared between two different university hospital laboratories. The new FT-IR method, using primary standards, is simple and rapid, and provides satisfactory intra- and inter-laboratory precision for the diagnosis and monitoring of steatorrhoea.

Clinical and functional comparison of bicondylar sledge prostheses retaining all ligaments and constrained total knee replacement.

OBJECTIVE: Comparison of different total knee replacements regarding clinical and functional differences with respect to gait and electromyographic analyses. DESIGN: Retrospective, comparative, clinical and functional study. METHODS: Three groups (control group of 11 healthy subjects, 15 patients with bicondylar sledge prostheses retaining all ligaments (cemented unicondylar prostheses in both the medial and lateral compartment), 15 patients with constrained total knee replacement sacrificing all cruciate and collateral ligaments (cemented total knee prosthesis with intramedullary stems and a large intercondylar tibial post) were compared by clinical evaluation using a number of clinical evaluation scores, a pain scale, surface electromyographic examinations of the lower limb, and gait analysis. RESULTS: Clinical scores revealed significantly worse results for patients with constrained prostheses. Both patient groups had significantly lower clinical scores compared to the control group. Gait analysis and electromyographic parameters revealed no significant differences between both patient groups. Compared to the control group, patients revealed significantly impaired parameters. Electromyography also demonstrated significant differences between patients and controls: mean electromyographic activities were reduced in vastus medialis and lateralis, semitendinosus, tibialis anterior and gastrocnemius. Peak activities were reduced in all muscles but rectus femoris. CONCLUSION: Clinical scores demonstrated significantly better results in bicondylar sledge than in constrained prostheses. Nevertheless, gait and electromyographic analyses did not reveal significant differences. RELEVANCE: Retaining of ligaments in bicondylar sledge prostheses apparently improved the activities of daily living but is not reflected in gait and electromyographic parameters.

Lipids, apolipoprotein-E genotypes and other risk factors of patients with coronary artery disease in Curaçao.

We studied lipids, apolipoprotein-E (apo-epsilon) genotypes and other coronary artery disease (CAD) risk factors of 67 CAD patients (male/female ratio 5) in Curaçao. Compared with 57 controls, male CAD patients had higher cholesterol, triglycerides, LDL-cholesterol, apo-B and decreased HDL-cholesterol and HDL-cholesterol/cholesterol concentrations. Other CAD risk factors were: increased fasting glucose and HbA1c concentrations, decreased creatinine clearance, and increased prevalences of lipoprotein (a) concentration > 500 mg/l, renal disease, hyperhomocysteinaemia, diabetes mellitus type II (DM-II), positive CAD family history and cigarette smoking. Male CAD patients had higher plasma alpha-tocopheroleq. Compared with 29 female controls, female CAD patients had higher fasting plasma glucose and HbA1c concentrations, and prevalence of DM-II. Predicting factors for CAD development in the whole CAD group were: DM-II, cigarette smoking, apo-epsilon 3/epsilon 4 and apo-epsilon 4/epsilon 4 Apo-epsilon 4 was associated with lower HDL- and higher LDL-cholesterol concentrations. There is a need for local studies on improvement of diabetic control, reference values of lipoprotein (a) and homocysteine concentrations, on apolipoprotein (a) phenotypes, causes of hyperhomocysteinaemia, and dietary influences on CAD development in subjects who carry the apo-epsilon 4 allele.

Correlation-induced double-plasmon excitation in simple metals studied by inelastic x-ray scattering.

We report a new type of peaklike structure observed in the tail of the dynamic structure factor of simple metals, measured by inelastic x-ray scattering. Based on the momentum-transfer dependence of the energy position and the intensity of this structure, it has been unambiguously attributed to intrinsic plasmon-plasmon excitations, an electronic correlation effect that was theoretically predicted by many-body perturbation theory of the homogeneous-electron-gas model beyond the random-phase approximation. This signature appears to be largely unaffected by electron-ion interaction effects. Thus a structure that is primarily caused by correlation effects in the electron gas has been found experimentally in the dynamic structure factor of simple metals.

[Clinico-functional results of constrained knee endoprostheses]. / Klinisch-funktionelle Ergebnisse von gekoppelten Kniegelenksendoprothesen.

AIM OF THE STUDY: To assess the clinical and functional outcome after implantation of a constrained knee arthroplasty. MATERIAL AND METHODS: 14 patients with a revision of the primary prostheses with constrained knee arthroplasties ("Genesis constrained" and "Blauth") were evaluated in the operated and non operated leg at an average follow-up of 8.5 months (range 6.5 to 61.4 months). The study included clinical examinations as well as gait analysis and surface electromyography. The results were compared with a group of healthy volunteers. The clinical examinations were scored with the HSS, the Knee Society Score, the Tegner Activity Score, the Patella Score and the Visual Analogue Scale. Gait analysis was performed with a three dimensional motion analysis system. Surface electromyography was evaluated bilaterally from the rectus femoris, vastus medialis and lateralis, semitendinosus, biceps femoris (long head), tibialis anterior and gastrocnemius (medial head). RESULTS: The comparison between the healthy volunteers and the patients showed significant functional deficits in the patient group. The electromyography demonstrated significantly lower peak amplitudes in 5 of 7 muscles. In all parameters--except for knee extension--gait analysis resulted in significant differences between the patient and control group. The comparison between the operated and non operated leg showed a significant difference only for knee extension. The patients revealed a bilateral functional deficit so that gait symmetry was preserved. CONCLUSION: The presented results indicate that the functional deficits may be caused by preoperative deficits and are not only due to the operation. It can be supposed that the gastrocnemius is more important because of the high correlation with the clinical results. The value of pre- and postoperative rehabilitation programs to prevent postoperative functional deficits can be concluded.

Ion-pair liquid chromatography of cytarabine and uracil-arabinoside in human plasma.

An ion-pair high pressure liquid chromatographic method is described for the determination of cytarabine (CAS 147-94-4, araC) in human plasma. Complete separation is achieved within 10 min using a reversed stationary phase and an isocratic eluent containing 0.4 mmol/l heptane sulfonic acid as modifier. Detection by UV-absorption occurs at 270 nm. Quantification of cytarabine and of its main plasma metabolite uracil arabinoside (araU) is achieved by means of internal standardisation using adenine arabinoside (araA). Retention times of araU, araC, and araA are 3.9, 5.9 and 9.4 min, respectively. Detection limits of araC and araU are 10 and 15 ng/ml, resp. During a pharmacokinetic study of high-dose cytarabine treatment no interferences could be observed in plasma samples.

Simultaneous capillary gas chromatographic profiling of medium-and long-chain fatty acid methyl esters with split injection. Correction for injection-related discrimination by the 'bracketing' method.

Split injection-related discrimination can be a source of inaccuracy and imprecision in quantitative capillary gas chromatographic profiling methods for compounds with relatively big differences in boiling points, such as the methyl esters of medium- and long-chain fatty acids prepared from biological materials. We systematically investigated a standard containing equal masses of saturated fatty acid methyl esters, with chain lengths from C5 to C26, under different injection conditions, including injection temperature, sample volume and split ratio. Day-to-day performance was studied under one set of conditions. Normalized peak areas, reciprocal response factors, using either C17 or C23 as an internal standard, and 'bracketed' reciprocal response factors (peak area of each analyte divided by half the sum of the peak areas of two adjacent esters were calculated. In all experiments the bracketed reciprocal response factors were found to be closest to unity with the lowest coefficients of variation.

Infrared analysis of urinary calculi by a single reflection accessory and a neural network interpretation algorithm.

BACKGROUND: Preparation of KBr tablets, used for Fourier transform infrared (FT-IR) analysis of urinary calculus composition, is time-consuming and often hampered by pellet breakage. We developed a new FT-IR method for urinary calculus analysis. This method makes use of a Golden Gate Single Reflection Diamond Attenuated Total Reflection sample holder, a computer library, and an artificial neural network (ANN) for spectral interpretation. METHODS: The library was prepared from 25 pure components and 236 binary and ternary mixtures of the 8 most commonly occurring components. The ANN was trained and validated with 248 similar mixtures and tested with 92 patient samples, respectively. RESULTS: The optimum ANN model yielded root mean square errors of 1.5% and 2.3% for the training and validation sets, respectively. Fourteen simple expert rules were added to correct systematic network inaccuracies. Results of 92 consecutive patient samples were compared with those of a FT-IR method with KBr tablets, based on an initial computerized library search followed by visual inspection. The bias was significantly different from zero for brushite (-0.8%) and the concomitantly occurring whewellite (-2.8%) and weddellite (3.8%), but not for ammonium hydrogen urate (-0.1%), carbonate apatite (0.5%), cystine (0.0%), struvite (0.4%), and uric acid (-0.1%). The 95% level of agreement of all results was 9%. CONCLUSIONS: The new Golden Gate method is superior because of its smaller sample size, user-friendliness, robustness, and speed. Expert knowledge for spectral interpretation is minimized by the combination of a library search and ANN prediction, but visual inspection remains necessary.

Growth and survival of low birthweight infants from 0 to 9 years in a rural area of Ghana. Comparison of moderately low (1,501-2,000 g) and very low birthweight (1,000-1,500 g) infants and a local reference population.

This prospective and descriptive study was conducted to evaluate the growth and survival of 105 low birthweight (LBW, 1,000-2,000 g) infants discharged during a 4-year period from Agogo Hospital, Ghana, and followed from birth until the age of 4-9 years. Thirty-two babies were very low birthweight children (VLBW, 1,000-1,500 g) and 73 (70%) were of moderately low birthweight (MLBW, 1,501-2,000 g). At the age of 3 years, 15 children (14.2%) had not come for follow-up; of the remaining 90 children, nine (10%) had died, five during the first 3 months of life. At follow-up from 4 to 9 years of age, two more children could not be traced and another two had died. Compared to a local reference population and the WHO standard, growth of survivors lagged behind and caught up only slightly during the first 3 years of life. From 3 to 9 years of age, median growth impairment increased, which either suggests impaired growth potential or poor health and inadequate nutrition. This long-term study confirms that LBW (1,000-2,000 g) infants, particularly VLBW children, are at high risk.

Analytical aspects of the automated CKMB1,2 and CKMM1,2,3 isoform determination and its relation to other biochemical markers.

The automated (CK)MB1,2/MM1,2,3 isoform measurement, based on electrophoresis, has been simplified to the point that it has become possible to perform this analysis on a 24-h routine basis. We studied analytical aspects of this analysis and its clinical relevance in relation to other biochemical markers (CK total, CKMB activity, CKMB mass, myoglobin, Troponin I and Troponin T) in patients with acute myocardial infarction (AMI), patients with unstable angina pectoris (UAP), and healthy donors. Furthermore, the additional significance of the analysis was evaluated in patients with clinically unexpected, raised CKMB/CK total activities. The storage of serum at 4 degrees C does not influence the MB2/MB1 ratios, whereas storage at 20 degrees C changes them significantly. MM3/MM1 and normal MB2/MB1 ratios show lower coefficients of variation than increased MB2/MB1 ratios. Between 2 and 30 h after myocardial tissue damage, AMI patients showed a characteristic change in CK isoform patterns. At a mean time of 3.6 h after the onset of symptoms we found raised MB2/MB1 ratios in 94% of these patients. With the information of the CK isoform analysis unexpected abnormal CK activities could explained by CK macro enzymes (Ig-bound and mitochondrial), insufficient CK clearance capacity, enzyme activities 4 h after (re-)infarction and raised CK activity 15 h after skeletal muscle damage. We conclude that the CK isoforms are relatively simply to assess; they are adequate tools with which to indicate the CK kinetics over a period lasting between 2 and 30 h after tissue damage with a single blood sample and a single analysis; the CK isoform analysis has additional value in explaining inappropriate CKMB/CK total activities, and the MB2/MB1 ratios show to be one of the best early parameters for discriminating patients with AMI on admission to hospital.

Evaluation of urinary metanephrine and normetanephrine enzyme immunoassay (ELISA) kits by comparison with isotope dilution mass spectrometry.

Determination of urinary 3-O-methylated catecholamines (metanephrines) is generally considered a principal test for the clinical chemical diagnosis of pheochromocytoma and is currently performed predominantly with chromatographic techniques such as gas-liquid chromatography and HPLC. Enzyme immunoassays based on microtiter plate technology have recently been developed for the quantitative determination of urinary metanephrine (M) and normetanephrine (NM). We compared the results for urinary M and NM determined by these ELISA methods with those obtained by a recently developed isotope dilution mass spectrometric method. From this comparative study we can conclude that the investigated ELISA methods are applicable in the quantification of urinary M and thus can be successfully used to establish the diagnosis of pheochromocytoma. These relatively simple methods can be executed in any clinical laboratory and in time may replace the present, more complicated, chromatographic techniques.