Unsuitable Specimens Research Articles

Blood sample quality.

Several lines of evidence now confirm that the vast majority of errors in laboratory medicine occur in the extra-analytical phases of the total testing processing, especially in the preanalytical phase. Most importantly, the collection of unsuitable specimens for testing (either due to inappropriate volume or quality) is by far the most frequent source of all laboratory errors, thus calling for urgent strategies for improving blood sample quality and managing data potentially generated measuring unsuitable specimens. A comprehensive overview of scientific literature leads us to conclude that hemolyzed samples are the most frequent cause of specimen non-conformity in clinical laboratories (40-70%), followed by insufficient or inappropriate sample volume (10-20%), biological samples collected in the wrong container (5-15%) and undue clotting (5-10%). Less frequent causes of impaired sample quality include contamination by infusion fluids (i.e. most often saline or glucose solutions), cross-contamination of blood tubes additives, inappropriate sample storage conditions or repeated freezing-thawing cycles. Therefore, this article is aimed to summarize the current evidence about the most frequent types of unsuitable blood samples, along with tentative recommendations on how to prevent or manage these preanalytical non-conformities.

A comparative study of fine needle aspiration cytology versus non aspiration technique in thyroid lesions

Background: Fine needle aspiration cytology (FNAC) is regarded as the gold standard investigation in the diagnosis of thyroid swellings. But often unsatisfactory specimen, especially mixed with blood, poses an obstacle in proper cytological interpretation. To overcome this problem, an alternative method of fine needle non aspiration cytology (FNNAC) technique was developed which, relies on the capillary pressure only to suck the cells inside the needle bore.Methods: Patients presenting with thyroid swellings from July 2008 to January 2009 were included in the study. 91 patients treated for thyroid lesions entered a prospective comparative evaluation of fine needle cytology with aspiration and non-aspiration techniques in thyroid. The thyroid swelling in every patient was sampled by both the aspiration as well as the non-aspiration technique by a single operator. Both procedures were done using 23G needles. Aspiration was done using a 10ml syringe. Both dry and wet smears were made and stained. All smears were interpreted by a cytologist without knowledge of the technique employed. Apart from the diagnosis, comments were made on the quality of the slides and three qualitative categories are created as unsuitable specimens, diagnostically adequate and diagnostically superior.Results: Non-neoplastic lesions accounted for 92.3%. They comprised mainly of nodular colloid goiter 53.84%, colloid nodules 29.6%, thyroiditis 8.79%, and one case of suppurative lesion. Out of the 7 neoplasms, 2 were follicular neoplasms, 1 was papillary carcinoma, 2 cases of Hurthle cell neoplasm and 1 cellular nodule in an MNG. Diagnostically superior material was obtained in 42 cases (46.15%) of the non-aspiration samples, as compared with 18 cases (19.78%) of aspiration samples which was statistically significant.Conclusions: The FNNAC produces better results in the form of a better quality of the cellularity and less field obscurity by blood. This technique should be used alone or in tandem with FNAC for better diagnostic yield.

Reduction of burden of hemolyzed specimens in a large urban emergency department: A real-world, five years’ experience

In vitro hemolysis may jeopardize patient care because tests results generated using unsuitable specimens may lead to inappropriate patient management. The prevalence of hemolyzed specimens is high in the emergency department (ED). We previously showed that collecting blood by means of a closed system entailing manual aspiration of blood instead of using conventional evacuated systems was effective to cut-down by nearly half the rate of hemolysis. Aim of this real world study was to verify whether longterm replacement of standard evacuated blood collection systems may be really effective to reduce the burden of spurious hemolysis. Starting from May 2014 in the ED of our Hospital vacuum tubes were replaced with S-Monovette serum tubes. We compared data about hemolyzed specimens entered in the two years before the implementation of the new device (i.e., 2012 and 2013) and the two years after introducing SMonovette in manual aspiration mode (i.e. 2015 and 2016). The year 2014 was not considered due to mixed data. The rate of hemolyzed specimens decreased from 4.36% to 3.07% with the use of S-Monovette in manual aspiration mode (Chi squared, 183.8; P<0.001). The likelihood of obtaining hemolyzed specimens was hence reduced by approximately 30% (relative risk, 0.707), with an expected economic saving of approximately 510€/year. The results of this real-world study demonstrate that the use of an alternative closed device encompassing manual aspiration for drawing blood from intravenous catheters may reduce hemolyzed samples by approximately 30%, so representing a valuable perspective for safeguarding patient safety and improving ED efficiency.

Reporting altered test results in hemolyzed samples: is the cure worse than the disease?

The management of laboratory data in unsuitable (hemolyzed) samples remains an almost unresolved dilemma. Whether or not laboratory test results obtained by measuring unsuitable specimens should be made available to the clinicians has been the matter of fierce debates over the past decades. Recently, an intriguing alternative to suppressing test results and recollecting the specimen has been put forward, entailing the definition and implementation of specific algorithms that would finally allow reporting a preanalytically altered laboratory value within a specific comment about its uncertainty of measurement. This approach carries some advantages, namely the timely communication of potentially life-threatening laboratory values, but also some drawbacks. These especially include the challenging definition of validated performance specifications for hemolyzed samples, the need to producing reliable data with the lowest possible uncertainty, the short turnaround time for repeating most laboratory tests, the risk that the comments may be overlooked in short-stay and frequently overcrowded units (e.g. the emergency department), as well as the many clinical advantages of a direct communication with the physician in charge of the patient. Despite the debate remains open, we continue supporting the suggestion that suppressing data in unsuitable (hemolyzed) samples and promptly notifying the clinicians about the need to recollect the samples remains the most (clinically and analytically) safe practice.

The role of European Federation of Clinical Chemistry and Laboratory Medicine Working Group for Preanalytical Phase in standardization and harmonization of the preanalytical phase in Europe

Patient safety is a leading challenge in healthcare and from the laboratory perspective it is now well established that preanalytical errors are the major contributor to the overall rate of diagnostic and therapeutic errors. To address this, the European Federation of Clinical Chemistry and Laboratory Medicine Working Group for Preanalytical Phase (EFLM WG-PRE) was established to lead in standardization and harmonization of preanalytical policies and practices at a European level. One of the key activities of the WG-PRE is the organization of the biennial EFLM-BD conference on the preanalytical phase to provide a forum for National Societies (NS) to discuss their issues. Since 2012, a year after the first Preanalytical phase conference, there has been a rapid growth in the number of NS with a working group engaged in preanalytical phase activities and there are now at least 19 countries that have one. As a result of discussions with NS at the third conference held in March 2015 five key areas were identified as requiring harmonisation. These were test ordering, sample transport and storage, patient preparation, sampling procedures and management of unsuitable specimens. The article below summarises the work that has and will be done in these areas. The goal of this initiative is to ensure the EFLM WG-PRE produces work that meets the needs of the European laboratory medicine community. Progress made in the identified areas will be updated at the next preanalytical phase conference and show that we have produced guidance that has enhanced standardisation in the preanalytical phase and improved patient safety throughout Europe.

Abstract ED02-03: Development of clinical trials incorporating genomic signatures: Lessons learned.

Abstract ED02-03: Development of clinical trials incorporating genomic signatures: Lessons learned.

The prevalence of preanalytical errors in a Croatian ISO 15189 accredited laboratory

The preanalytical phase is the most common source of laboratory errors. The goal of this descriptive study was to analyze the prevalence and type of preanalytical errors in relation to the site of sample collection (inpatient vs. outpatient) and the type of laboratory unit (hematology and coagulation vs. biochemistry). For the biochemistry unit, the data were also analyzed relative to the type of the analysis (stat vs. routine). We retrospectively analyzed the sample and test request form error rate for a 1-year period, from January to December 2008. The frequency of the sample errors differed significantly between the emergency and routine biochemistry unit (0.69% vs. 2.14%; p<0.0001), and between inpatients and outpatients (1.12% vs. 1.36%; p=0.0006). Hemolysis was the most frequent sample error, accounting for 65% of all unsuitable specimens in the emergency biochemistry unit. The total sample error rate did not differ between hematology and coagulation vs. the biochemistry unit. The frequency of test request form errors differed significantly with respect to the sample collection site (p<0.0001), laboratory unit (p<0.0001) and type of the analysis (p<0.0001). Errors in the test request form were least frequent in the outpatient unit (2.98%) and most frequent in the routine biochemistry unit (65.94%). Sample and test request form errors in our laboratory are occurring with a frequency comparable to that reported by others. Continuous educational action is needed for all stakeholders involved in laboratory testing to improve the quality of the preanalytical phase of the total testing process.

Genetic and biochemical heterogeneity of cardiac troponins: clinical and laboratory implications

The contractile sarcomeric pool of skeletal muscle and heart consists of a highly-ordered arrangement of actin thin filaments, tropomyosin and proteins of the troponin complex: troponin I (TnI), troponin T (TnT) and troponin C (TnC). The cardiac myocyte expresses specific isoforms of both TnI and TnT (cTnI and cTnT, respectively), which can be distinguished from skeletal muscle isoforms by rapid and reliable immunoassays. Due to their superior cardiac specificity, cTnI and cTnT have become the recommended biomarkers for the diagnosis of myocardial injury. The most common applications are for risk stratification and diagnosis of acute coronary syndromes, albeit they can also be used for assessing a variety of other myocardial disorders. However, the excellent diagnostic efficiency of cardiac troponin testing is jeopardized by some pre-analytical issues (unsuitable specimens for testing, analyte stability, handling, transportation and storage of specimens prior to analysis), as well as by analytical concerns related to standardization or harmonization of cTnI immunoassays, imprecision at low concentrations, antibody specificity, immunoreactivity of plasma isoforms released in the blood after myocardial injury, interference from autoantibodies, heterophilic antibodies, rheumatoid factor, and human anti-mouse antibodies. In addition, although the influence of some known mutations in cTnT and cTnI on calcium sensitivity and force generation have been readily demonstrated, their influence on current immunoassays is unknown. Most mutations in these proteins may contribute to the development of certain cardiomyopathies, namely hypertrophic and restrictive. In these situations, the phenotype is characterized by the underlying diseases, and the ability to detect cTnT or cTnI is of relatively little clinical significance. However, the cTnT Arg129Lys polymorphism and those observed in the stable domain of cTnI do not significantly alter the functional properties of the molecule within the myocardium and thus are predictably asymptomatic. While the actual prevalence of these polymorphisms in the general population is still unknown, they might be a source of potential analytical problems; modifying the immunogenicity of the molecule and leading to potential false negative results. The goal of this article is to provide an overview on the potential technical and analytical challenges in the measurement of cardiac troponins, along with the significance of polymorphisms in the genes encoding for cTnI and cTnT in both health and disease.

Haemolysis: an overview of the leading cause of unsuitable specimens in clinical laboratories

Prevention of medical errors is a major goal of healthcare, though healthcare workers themselves have not yet fully accepted or implemented reliable models of system error, and neither has the public. While there is widespread perception that most medical errors arise from an inappropriate or delayed clinical management, the issue of laboratory errors is receiving a great deal of attention due to their impact on the quality and efficiency of laboratory performances and patient safety. Haemolytic specimens are a frequent occurrence in clinical laboratories, and prevalence can be as high as 3.3% of all of the routine samples, accounting for up to 40%-70% of all unsuitable specimens identified, nearly five times higher than other causes, such as insufficient, incorrect and clotted samples. This article focuses on this challenging issue, providing an overview on prevalence and leading causes of in vivo and in vitro haemolysis, and tentative guidelines on identification and management of haemolytic samples in clinical laboratories. This strategy includes continuous education of healthcare personnel, systematic detection/quantification of haemolysis in any sample, immediate clinicians warning on the probability of in vivo haemolysis, registration of non-conformity, completing of tests unaffected by haemolysis and request of a second specimen for those potentially affected.

Risk management in the preanalytical phase of laboratory testing

The clinical laboratory is no longer its own limited ecosystem, as it is increasingly integrated with patient care, assisting diagnosis, monitoring therapies and predicting clinical outcomes. Although efforts and resources are continuously focused to achieve a satisfactory degree of analytical quality, there is clear evidence that the preanalytical phase is much more vulnerable to uncertainties and accidents, which can substantially influence patient care. Most errors within the preanalytical phase result from system flaws and insufficient audit of the operators involved in specimen collection and handling responsibilities, leading to an unacceptable number of unsuitable specimens due to in vitro hemolysis, clotting, insufficient volume, wrong container, contamination and misidentification. A reliable approach to overcome this problem entails prediction of accidental events (exhaustive process analysis, reassessment and rearrangement of quality requirements, dissemination of operating guidelines and best-practice recommendations, reduction of complexity and error-prone activities, introduction of error-tracking systems and continuous monitoring of performances), an increase in and diversification of defenses (application of multiple and heterogeneous systems to identify non-conformities), and a decrease in vulnerability (implementation of reliable and objective detection systems and causal relation charts, education and training). This policy, which requires integration between requirements and design, full commitment and interdepartmental cooperation, should make laboratory activity more compliant to the inalienable paradigm of total quality in the testing process.

Recommendations for detection and management of unsuitable samples in clinical laboratories

A large body of evidence attests that quality programs developed around the analytical phase of the total testing process would only produce limited improvements, since the large majority of errors encountered in clinical laboratories still prevails within extra-analytical areas of testing, especially in manually intensive preanalytical processes. Most preanalytical errors result from system flaws and insufficient audit of the operators involved in specimen collection and handling responsibilities, leading to an unacceptable number of unsuitable specimens due to misidentification, in vitro hemolysis, clotting, inappropriate volume, wrong container or contamination from infusive routes. Detection and management of unsuitable samples are necessary to overcome this variability. The present document, issued by the Italian Inter-society SIBioC-SIMeL-CISMEL (Society of Clinical Biochemistry and Clinical Molecular Biology-Italian Society of Laboratory Medicine-Italian Committee for Standardization of Hematological and Laboratory Methods) Study Group on Extra-analytical Variability, reviews the major causes of unsuitable specimens in clinical laboratories, providing consensus recommendations for detection and management.

National survey on the pre-analytical variability in a representative cohort of Italian laboratories

Owing to remarkable advances in automation, laboratory technology and informatics, the pre-analytical phase has become the major source of variability in laboratory testing. The present survey investigated the development of several pre-analytical processes within a representative cohort of Italian clinical laboratories. A seven-point questionnaire was designed to investigate the following issues: 1a) the mean outpatient waiting time before check-in and 1b) the mean time from check-in to sample collection; 2) the mean time from sample collection to analysis; 3) the type of specimen collected for clinical chemistry testing; 4) the degree of pre-analytical automation; 5a) the number of samples shipped to other laboratories and 5b) the availability of standardised protocols for transportation; 6) the conditions for specimen storage; and 7) the availability and type of guidelines for management of unsuitable specimens. The questionnaire was administered to 150 laboratory specialists attending the SIMEL (Italian Society of Laboratory Medicine) National Meeting in June 2006. 107 questionnaires (71.3%) were returned. Data analysis revealed a high degree of variability among laboratories for the time required for check-in, outpatient sampling, sample transportation to the referral laboratory and analysis upon the arrival. Only 31% of laboratories have automated some pre-analytical steps. Of the 87% of laboratories that ship specimens to other facilities without sample preparation, 19% have no standardised protocol for transportation. For conventional clinical chemistry testing, 74% of the laboratories use serum evacuated tubes (59% with and 15% without serum separator), whereas the remaining 26% use lithium-heparin evacuated tubes (11% with and 15% without plasma separator). The storage period and conditions for rerun/retest vary widely. Only 63% of laboratories have a codified procedure for the management of unsuitable specimens, which are recognised by visual inspection (69%) or automatic detection (29%). Only 56% of the laboratories have standardised procedures for the management of unsuitable specimens, which vary widely on a local basis. The survey highlights broad heterogeneity in several pre-analytical processes among Italian laboratories. The lack of reliable guidelines encompassing evidence-based practice is a major problem for the standardisation of this crucial part of the testing process and represents a major challenge for laboratory medicine in the 2000s.

Influence of the needle bore size used for collecting venous blood samples on routine clinical chemistry testing

Despite remarkable advances in technology and laboratory automation, results of laboratory testing still suffer from a high degree of preanalytical variability. Although there is no definitive evidence, the use of small-gauge needles for venipuncture is usually discouraged to reduce the chance of producing unsuitable specimens. The purpose of this investigation was to assess the influence of the needle size used to collect venous blood on the measurement of 14 common analytes, including free hemoglobin, the most representative enzymes, protein-bound substances and electrolytes. Results for venous blood samples collected from 20 fasting voluntary physicians using either a 23- (0.60 mmx19 mm) or 25-gauge-needle (0.50 mmx19 mm) butterfly devices with polyvinyl chloride tubing (1.40 mmx300 mm) were compared with reference specimens collected using a 21-gauge-needle (0.80 mmx19 mm) butterfly device with polyvinyl chloride tubing (1.40 mmx300 mm). All means for paired samples collected using the smaller needles did not differ significantly from the reference specimen by paired Student's t-test analysis. Passing-Bablok regression analysis and Pearson's or Spearman (creatine kinase, aspartate aminotransferase, alanine aminotransferase and chloride) correlation were acceptable for most of the analyses, although a lower correlation coefficient was observed for electrolytes. In addition, when expressed as a percentage of the mean for paired samples, the s(y,x) value exceeded the desirable bias for free hemoglobin, glucose, lactate dehydrogenase, aspartate aminotransferase, sodium, chloride, calcium and magnesium (in samples collected using both 23 G and 25 G needles) and potassium (in samples collected using a 25 G needle). Although Bland-Altman plot analysis and +/-1.96 SD agreement intervals for the set of differences between values was acceptable overall, the bias was rather broad for free hemoglobin and several critical electrolytes (calcium, chloride, potassium, sodium), exceeding the respective limits for desirable bias. The results of our investigation indicate that 23 G needles, if handled correctly, will not introduce any statistically or clinically significant error to the measurement results compared to a 21 G needle. For the 25 G needle, we observed increased variability for potassium compared to a 23 G needle. Small-bore needles of 25 G or less cannot be universally recommended when collecting venous blood for clinical chemistry testing and should be reserved for selected circumstances, such as in patients with problematical venous accesses and newborns. In such cases, however, the bias introduced by the use of smaller needles should always be taken into consideration when interpreting test results.

Outpatient phlebotomy success and reasons for specimen rejection.

To determine the rate with which blood collection is successful on the initial phlebotomy encounter, the rate with which laboratory personnel judge specimens unsuitable for analysis, and the practice characteristics associated with fewer unsuccessful collections and fewer rejected specimens. Clinical laboratories participating in the College of American Pathologists Q-Probes laboratory improvement program prospectively characterized the outcome of outpatient phlebotomies for 3 months or until 20 unsuccessful phlebotomy encounters occurred. By questionnaire, participants provided information about test ordering, patient preparation, and specimen collection. Institutions in the United States (n = 202), Canada (n = 4), Australia (n = 3), and South Korea (n = 1). Percentage of successful encounters and percentage of unsuitable specimens. Of 833289 encounters, 829723 were successful. Phlebotomies were unsuccessful because patients were not fasting as directed (32.2%), phlebotomy orders were missing information (22.5%), patients specimens were difficult to draw (13.0%), patients left the collection area before specimens were collected (11.8%), patients were improperly prepared for reasons other than fasting (6.3%), patients presented at the wrong time (3.1%), or for other reasons (11.8%). Only 2153 specimens (0.3%) were unsuitable; these samples were hemolyzed (18.1%), of insufficient quantity (16.0%), clotted (13.4%), lost or not received in the laboratory (11.5%), inadequately labeled (5.8%), at variance with previous or expected results (4.8%), or unacceptable for other reasons (31.1%). Facilities staffed by laboratory-administered phlebotomists reported higher success rates than facilities staffed by nonlaboratory-administered phlebotomists (P =.002). Most outpatient phlebotomy encounters are successful and result in specimens suitable for laboratory analysis.

Outpatient Phlebotomy Success and Reasons for Specimen Rejection

Abstract Objectives.—To determine the rate with which blood collection is successful on the initial phlebotomy encounter, the rate with which laboratory personnel judge specimens unsuitable for analysis, and the practice characteristics associated with fewer unsuccessful collections and fewer rejected specimens. Design.—Clinical laboratories participating in the College of American Pathologists Q-Probes laboratory improvement program prospectively characterized the outcome of outpatient phlebotomies for 3 months or until 20 unsuccessful phlebotomy encounters occurred. By questionnaire, participants provided information about test ordering, patient preparation, and specimen collection. Setting and Participants.—Institutions in the United States (n = 202), Canada (n = 4), Australia (n = 3), and South Korea (n = 1). Main Outcome Measures.—Percentage of successful encounters and percentage of unsuitable specimens. Results.—Of 833289 encounters, 829723 were successful. Phlebotomies were unsuccessful because pa...

Estudio de calidad y selección de muestras de lavado broncoalveolar (LBA) en neumopatías difusas

Bronchoalveolar lavage (BAL) samples used to study immune or inflammatory response in interstitial lung disease must be representative of the lower respiratory tract. Thus, the selection of suitable samples must be part of routine practice. To assess the incidence of unsuitable BAL samples used for cytology and to determine the relation between parameters related to underlying disease and the quality of samples. One hundred sixty-one patients were enrolled. Seventy-two were HIV positive and had diffuse pulmonary infiltrates, 34 had idiopathic pulmonary fibrosis (IPF), 10 had sarcoidosis, 10 had hypersensitivity pneumonitis, 19 had interstitial lung disease and collagen diseases and 2 had pulmonary eosinophilia. Fourteen individuals formed the control group. The quality study was carried out by staining the BAL samples following a modified Wright-Giemsa technique and evaluating the samples by the selection criteria described by Chamberlain and colleagues (1987). We identified unsuitable samples from 53% of the HIV positive patients, from 35% of the IPF patients and from 21% of the interstitial lung disease patients with associated connective tissue disease. In the other groups, all samples were suitable for analysis. Intolerance of BAL with decreasing percentage of fluid recovered was significantly associated with sample quality, particularly in the IPF group. The cytology results that invalidated the samples differed by group. In all groups, unsuitable specimens had low cell counts. The finding or not of evidence of associated infection in HIV-infected patients, on the other hand, did not appear to determine sample quality in and of itself, although it did in samples related to other entities. We can predict that a high rate of unsuitable BAL samples will come mainly from patients with diffuse lung disease associated to HIV infection, IPF and interstitial lung disease with associated connective tissue disease. Tolerance to the technique influences quality of the specimen obtained and, therefore, should be taken into account in interpreting the findings of cytology. The criteria applied by the various teams using BAL should be unified, and it should be determined whether the exclusion of inappropriate samples affects the final composition of study groups.

Preanalytical phase in coagulation testing: state of the art in the laboratories of the Piedmont region, Italy.

The control of preanalytical variables is critical, particularly for coagulation assays, since this has a direct influence on the quality of results and on their clinical reliability. The aim of the study was to evaluate the extent of information about preanalysis in the laboratories of a large region of northern Italy that perform tests of haemostasis. A questionnaire was sent concerning the number of coagulation analyses per year, the system of blood drawing, the anticoagulants and the tubes in use, the amount of blood collected, the tendency to reject unsuitable specimens, the storage temperatures, the times between collection and analysis, the conditions of tube centrifugation and identification, and the presence of staff specifically occupied in coagulation testing. Complete answers were offered by 136 laboratories (81%; 69 private and 67 public) that reported a total amount of 3,648,000 determinations per year. Statistical analysis was carried out on the findings of the investigation, in order to assess their significance and to detect possible correlations between the variables under consideration. The results show significant attention being given by laboratories to the preanalytical phase. This is also indicated by the large percentage of complete answers obtained. Some of the important positive aspects shown in the study are: (1) the preference for the closed system for blood sampling; (2) the prevalent use of primary tubes for testing; (3) a strong tendency to reject incorrect samples for analysis. On the other hand, a major problem seems to lie in the delay, particularly in some big centres, in processing of specimens, which can be critical for the correct performance of coagulation assays. The data obtained reflect with good reliability the overall situation in coagulation-testing laboratories in northern Italy.

Determination of geomagnetic palaeointensities from the Quaternary West Eifel volcanic field, Germany

SUMMARY Determination of geomagnetic palaeointensities has been attempted for 418 specimens from 51 volcanic units of the Quaternary West Eifel volcanic field. This paper describes the measuring procedure using a modification of the Thellier method, the analysis of the derived data points, the determination of linear segments and the quality of the individual palaeointensity values calculated from the corresponding slopes. According to a series of acceptance and rejection criteria, finally 312 reliable individual palaeointensity results have been obtained. About 73 per cent of the accepted regression lines have correlation coefficients better than 0.990, and less than 10 per cent of the accepted Thellier experiments have quality factors less than 1.0. The carriers of magnetization of the West Eifel volcanic rocks are titanomagnetites with a broad range of titanium contents and oxidation states in a more or less unweathered, mostly foiditic rock matrix. Accompanying rock magnetic experiments allowed a rough classification of the specimens corresponding to the oxidation state of the titanomagnetites. Specimens with highly oxidized titanomagnetites have been the most successful candidates for the Thellier experiments. However, a prediction of the suitability of the specimens for the Thellier experiments by sample selection according to this classification was not always appropriate. Instead, for most volcanic units pilot specimens were first measured to determine the suitability of a specific sample type, the temperature interval from which the evaluation of palaeointensity was possible, and the best laboratory field intensity to keep the slope errors of the Thellier experiments to a minimum. Palaeointensity determination was not possible for 14 volcanic units because only unsuitable specimens were available. For each of the 37 remaining volcanic units at least five successful Thellier experiments have been carried out, leading to a final mean palaeointensity result. These 37 values have relative standard errors of between 4 and 23 per cent, mostly around 10 per cent. Specimens with differing rock magnetic properties from the same volcanic unit yielded consistent palaeointensity values. Therefore, all West Eifel palaeointensity results have to be regarded as reliable estimates of the Earth’s magnetic palaeofield strength. Mean palaeointensities range from 7 to 62 pT with an unexpectedly large number of palaeointensity values less than 30 pT. About half of the low palaeointensity values are associated with intermediate virtual geomagnetic pole latitudes, which may be due to a geomagnetic excursion.

Chapter 7 Brain banking and the human hypothalamus — factors to match for, pitfalls and potentials

The study of an increasing number of processes occurring in the human brain can be carried out on autopsy material. The availability of this material, whether fresh, frozen or fixed, makes it possible to develop methodologies for studying the neuroanatomical and neurochemical aspects of the human brain. It has also become possible in recent years to correlate functional changes with neurochemical changes and with neuroanatomical abnormalities in disease states. Some compounds and structures are damaged irreversibly within minutes after death and some brain components are known to disintegrate within seconds. This led to the widespread idea that autopsy material would not be suitable for basic research purposes and would not supply the necessary answers on the various fundamental questions regarding processes occurring in normal or diseased brain. However, from data published in recent years in which autopsy material has been routinely used, it becomes more and more evident that this is a misconception. There is an increasing number of reports based on the use of normal and pathological human brain tissue obtained by autopsies in spite of the fact that there is a worrying continuous decline in autopsy rate which causes serious concern among scientists world-wide (Anderson and Hill, 1989). It also became evident that when using the proper fixation procedures, sufficient structural integrity is retained in the tissue to allow morphological and morphometrical studies (Swaab and Uylings, 1988). Electron microscopic examination of synaptosomal preparations from post-mortem human brain showed them to be only slightly less pure than preparations from fresh tissue although there was some degree of damage (Hardy et al., 1982). Agonal state effects the stability of brain compounds and causes brain hypoxia. This again forms a tremendous difficulty for the study of human neurological and psychiatric diseases as one of the frequent causes of death is bronchopneumonia which leads to brain hypoxia and results in pronounced lactic acidosis. The Netherlands Brain Bank has succeeded to partly circumvent some of the serious problems encountered in providing human tissue for research by performing rapid autopsies with an average post-mortem delay of 2-4 h. This has become possible by a close collaboration of numerous nursing homes in Amsterdam and its vicinity and with the neuropathologists of the Free University in Amsterdam. We also measure the pH of the tissue as indicator of agonal state in order to reveal unsuitable specimens. The human hypothalamus contains various nuclei manifesting a wide variety of changes in different conditions.(ABSTRACT TRUNCATED AT 400 WORDS)