Age-adjusted D-dimer cut-off leads to more efficient diagnosis of venous thromboembolism in the emergency department: a comparison of four assays.

Essentials Age-adjusted D-dimer cut-offs decrease the false positives in the elderly. Four D-dimer assays were compared in venous thromboembolism outpatients in an emergency ward. Age-adjusted cut-off resulted in improved specificity with maintained sensitivity for all assays. There was a substantial decrease in false positive results, especially in the older population. SUMMARY: Background The study compares different D-dimer assays and age-adjusted cut-offs in outpatients with suspected venous thromboembolism (VTE). The plasma concentration of this sensitive biomarker is increased by activated coagulation, but also by several conditions that are linked to an increased risk of VTE. One such condition is old age, which poses a common clinical problem where many prefer not to analyze D-dimer in elderly patients. Age-adjusted cut-offs have been validated for both deep venous thrombosis (DVT) and pulmonary embolism, aiming to increase specificity without notably decreasing sensitivity. Objectives We evaluated four common D-dimer assays in parallel, with and without applying age-adjusted cut offs for VTE. Patients/methods The prospective single-center study was conducted in 940 outpatients attending the emergency department with clinically suspected pulmonary embolism or DVT. Four automated D-dimer assays were compared (Siemens INNOVANCE® , Roche Tina-quant, Medirox MRX and STA® -Liatest® D-Di PLUS). Results All assays performed with areas under the ROC curve (AUC) > 0.9 and maintained their sensitivities after implementation of age-adjusted cut-offs. Specificities increased by 6-7% and number needed to test decreased by < 0.3. The rate of false positive results decreased by 6% overall and by 10-20% for patients ≥ 70. Conclusions Age-adjusted cut-offs resulted in maintained high sensitivity and a modest improvement in specificity and number needed to test for all evaluated D-dimer assays. There was a significant reduction in false positive results, which reflects avoidable unnecessary imaging without any compromise of clinical safety. This suggests a potential to benefit the management of VTE in elderly patients, both clinically and economically.

Increased levels of an apoptotic product in the sera from women with pre-eclampsia.

Pre-eclampsia is associated with both maternal and foetal complications. Several studies have shown increased trophoblast apoptosis in the placenta of women with this condition. The aim of this study was to investigate whether increased apoptosis can be detected as elevated levels of an apoptotic product in serum samples from women with pre-eclampsia. For this purpose, we used the M30-Apoptosense ELISA assay, which measures a neo-epitope of cytokeratin 18 that is exposed after cleavage by caspases during apoptosis of epithelial cells (M30 antigen). The M30-antigen concentrations were measured in the sera of 15 healthy pregnant women and 15 patients with pre-eclampsia (gestation weeks 24-34). Patients with pre-eclampsia had significantly higher serum M30-antigen concentrations, median 120 U/L, compared to 15 healthy pregnant women matched for pregnancy length, median 104 U/L (p = 0.01). This is consistent with previous findings of increased trophoblast apoptosis in women with pre-eclampsia and raises the possibility that M30-antigen can be used as a serum marker for the severeness of this condition for the mother and child.

How does the MDRD Study equation compare with serum creatinine in routine healthcare? Anatomy of MDRD-eGFR.

The Modification of Diet in Renal Disease Study equation-estimated glomerular filtration rate (MDRD-eGFR) as a marker for chronic kidney disease, with a single decision level for both genders and all adult ages, requires that the calculated quantity is independent of gender and age. In a retrospective study of S-Creatinine concentrations from laboratory information systems of hospitals in the UK and Sweden, comprising about 140,000 results in total, it was found that the MDRD-eGFR indeed differs between genders and that it varies with age more than the S-Creatinine concentration does. If the age compensation is deleted from the algorithm, the relative changes in the MDRD-eGFR decrease and become almost the same as those for S-Creatinine concentrations. The difference between the genders could probably be overcome by increasing the "if female factor". We used Pt-Iohexol and S-Creatinine concentrations measured simultaneously to estimate the performance of the MDRD-eGFR in relation to Pt-Iohexol clearance. The Pt-Iohexol varies considerably between patients with the same S-Creatinine concentrations, a difference that is not reflected in the MDRD-eGFR. It is concluded that the mathematical transformation of S-Creatinine concentrations does not add any diagnostic value. On the contrary, an increased measurement uncertainty is unavoidable with the use of factors and exponents. The uncertainty is greater than any difference between age and gender in adjacent age groups. There is no compensation for the individual relation between S-Creatinine and Iohexol clearance, and the equation does not consider the individual body surface area; it is therefore inadvisable to use the MDRD-eGFR values as the basis for administration of drugs excreted by the kidneys.

The Swedish Blood Pass project.

Manipulation of the blood's oxygen carrying capacity (CaO(2)) through reinfusion of red blood cells, injections of recombinant erythropoietin or by other means results in an increased maximal oxygen uptake and concomitantly enhanced endurance performance. Therefore, there is a need to establish a system--"A Blood Pass"--through which such illegal and unethical methods can be detected. Venous blood samples were taken under standardized conditions from 47 male and female Swedish national and international elite endurance athletes four times during the athletic year of the individual sport (beginning and end of the preparation period and at the beginning and during peak performance in the competition period). In these samples, different hematological values were determined. ON(hes) and OFF(hre) values were calculated according to the formula of Gore et al. A questionnaire regarding training at altitude, alcohol use and other important factors for hematological status was answered by the athletes. There were some individual variations comparing hematological values obtained at different times of the athletic year or at the same time in the athletic year but in different years. However, the median values of all individual hematological, ON(hes) and OFF(hre), values taken at the beginning and the end of the preparation or at the beginning and the end of the competition period, respectively, as well as median values for the preparation and competition periods in the respective sport, were all within the 95% confidence limit (CI) of each comparison. It must be mentioned that there was no gender difference in this respect. This study shows that even if there are some individual variations in different hematological values between different sampling times in the athletic year, median values of important hematological factors are stable over time. It must be emphasized that for each blood sample, the 95% CI in each athlete will be increasingly narrower. The conclusion is that there is a physiological basis for establishing an individual-based "Blood Pass" system, mainly for athletes competing at the international level. On indications of manipulations of hemoglobin concentration and red cell mass by deviations from established "Blood Pass" data, more specific methods can be applied.

A method to estimate the uncertainty of measurements in a conglomerate of instruments/laboratories.

A comparison of the performance, at two concentrations, of the measurement procedures for 23 common components is presented. For each component the within-, pure between- and total variations have been calculated and an imprecision profile indicated. Thus a pragmatic, readily and generally applicable method is advised to describe the performance of laboratories under repeatability and reproducibility conditions. The calculated total variation is compared with the results estimated from the biological variation of the properties. In most cases the within-laboratory variation is better than that given by the reference database, whereas in about half of the procedures the total variation exceeds that of the reference database. The outcome illustrates the transferability problems that multicentre studies and the diagnosis of patients face by measuring samples using a conglomerate of instruments/laboratories that are not aligned. The calculation procedures are detailed in an appendix and the calculation and presentation of the results are made with a custom-made worksheet program.

Are there advantages with U-Albumin/U-Creatinine ratios compared with U-Albumin in monitoring diabetes?

Management of hypertension and diabetes mellitus in primary health care requires occasional assessment of kidney function. Monitoring the urinary albumin excretion every 24 h is often used as a diagnostic gold standard but measurement of U-Albumin concentrations in morning urine either alone or together with U-Creatinine is a well-established surrogate measure. We compared the ratio U-Albumin/U-Creatinine and U-Albumin concentrations measured by commonly used POC (Point of care) instruments with those obtained in a central laboratory and estimated the uncertainty of the results after establishing an uncertainty budget. It is concluded that the presentation of ratios or concentrations on an ordinal scale is less satisfactory than reporting U-Albumin concentration on a ratio scale. Moreover the latter will have the advantage of allowing the physician to adjust the diagnostic sensitivity and specificity to local needs. The present report is a methodological study and does not consider the diagnostic performance of the studied properties per se.

Serum TGF-beta 1 and TNF-alpha levels and cardiac fibrosis in experimental chronic renal failure.

OBJECTIVES: To characterize dynamics of changes of serum levels of TGF-beta1 and TNF-alpha in rats with cardiac fibrosis (CF) occurring during chronic renal failure (CRF), and to reveal the character pf correlations of these factors with amounts of cardiac collagen. DESIGN AND METHODS: CRF was induced by unilateral nephrectomy and by electrocoagulation of 25% of the cortex of remnant kidney. Post-operative checkpoints were 2, 4, and 6 months. Serum TGF-beta1 and TNF-alpha levels were measured by ELISA. RESULTS: CF became pronounced only at 6 months of CRF, while serum TGF-beta1 concentrations reached maximum at 4 months, i.e., at the checkpoint preceding the development of CF. Multiple regression showed cardiac collagen to correlate with both serum TGF-beta1 levels and time from the onset of CRF. Sensitivity and specificity of TGF-beta1 as serum marker of CF were 86% and 75%.

How do conventional markers of lipid disorders compare with apolipoproteins?

Assessment of risk for coronary heart disease (CHD) indicates that apolipoprotein B and apolipoprotein A-I and their ratio are efficient predictors, possibly superior to hitherto used indicators, i.e. S-Cholesterol, S-Triglycerides, S-HDL cholesterol and S-LDL cholesterol. We used the ratio S-Apolipoprotein B/S-Apolipoprotein A-I as the gold standard to compare the diagnostic performance of the other properties based on consecutive routine measurements in patients attending primary health-care or a university hospital. The different cut-offs of the S-Apolipoprotein B/S-Apolipoprotein A-I ratio that were investigated created a prevalence of risk factors that might require intervention in the study group between 10 and 77%. The gender difference prompts for a partitioning related to the gender, whereas the changes related to age were small and were disregarded. The diagnostic sensitivity and specificity were demonstrated in ROC diagrams for the studied properties.

Measurement of blood and plasma coagulation time using free oscillating rheometry.

An assay based on free oscillating rheometry to measure the activity of coagulation factors is described. The method can be used in blood and plasma and is particularly suitable for screening and monitoring coagulation disturbances in point-of-care testing (POCT) in environments where quick analysis with minimal preanalytical work is needed. In this study the endpoint as clotting onset time (COT) is determined by a deviation from initial viscoelastic properties of an oscillating sample. The model system entails the clotting of citrated blood or plasma clotting by repletion of Ca2+. COT was shown to give a dose-dependent response to added thrombin and to be resistant to high concentrations of corn trypsin inhibitor, indicating measurement of the tissue-factor-dependent pathway of coagulation activation. COT in recalcified blood and plasma covariated with prothrombin time (PT) according to Owren, and activated partial thromboplastin time (aPTT). The technique and instrument used proved to be quick and easy to handle, and suitable for POCT as well as for examinations in the laboratory.

Accreditation of medical laboratories. Some reflections from the Nordic Horizon.

Accreditation has been a successful approach to improved quality management in laboratories and applied to a wide variety of medical laboratories. After the initial enthusiastic phase, in which quality improvement is significant, the endurance is threatened by an increasing bureaucracy of the process. A productive balance between the accreditation bodies and the profession needs to be sought. New standards have been suggested by ISO and the profession needs to take the initiative to assure that a global standard specially adopted to the requirements of medical laboratories becomes recognised and used. The new concept of uncertainty may become an important tool to further improve and describe the performance of laboratories by allowing inclusion of pre- and post-analytical sources of uncertainty as well as bias.

Vitamin C plasma concentrations and leg weakness in the forelegs of growing pigs.

Four litters (41 pigs) of cross-bred pigs were studied from 6 to 26 weeks of age. Blood samples were collected at 6, 13, 21 and 26 weeks of age and analysed for contents of vitamin C, calcium (Ca), inorganic phosphorus (P) and alkaline phosphatase (ALP). The pigs were examined clinically for foreleg weakness at the ages of 21 and 26 weeks. At the age of 26 weeks the pigs were slaughtered and the right forelegs were examined macroscopically and selected samples were collected for radiological, histological and ultrastructural examination. The prevalence of foreleg lesions was high, with lesions of dyschondroplasia of the distal growth plate of the ulna in 30 pigs, synovitis of the elbow joint in 24 pigs and osteochondritis dissecans of the elbow joint in 25 pigs. At the ages of 21 and 26 weeks, five pigs had evidently crooked forelegs and 14 pigs (age 21 weeks) and 25 pigs (age 26 weeks) had mildly deformed forelegs. The serum levels of Ca, P and ALP were within normal values for growing-finishing pigs. The range of vitamin C concentrations in plasma showed a wide difference (7.1-49.8 mumol/l) but was not associated with deformed forelegs. The serum concentrations of Ca, P and ALP and the plasma concentration of vitamin C differed significantly (P = 0.05) between age groups and there was a significant (P = 0.001) positive correlation between the levels of vitamin C in plasma and the serum levels of ALP at 6 weeks of age. The aim of the present study was to determine if there was any association between the plasma levels of vitamin C and the extent of crooked or deviated forelegs in growing-finishing pigs. We could not find a vitamin C deficiency during the study and no association between low levels of vitamin C in plasma and the presence of deformed forelegs of these 40 pigs.

International standards in laboratory medicine.

International standards play an important role in establishing quality systems. A considerable number of standards have been created by ISO and CEN for medical laboratories. Standards can be looked upon in a hierarchal manner but most standards are produced in similarly with iterative consultations and review by the intended users. Most standards are suggested by industry and national or international organisations whereas individuals rarely can influence the contents. An exception is illustrated by a conference arranged to influence and improve the suggested standard (ISO 15196) on quality specifications in laboratory medicine. Standards may also influence the methodological practice and the performance of reagents and kits used in analytical work. A good example is the standard on traceability of calibrators (ISO 17511) that illustrates the practical importance of concepts like 'uncertainty in measurements' and 'trueness'. Biological calibrators, e.g., 'WHO biological standards', constitute a special problem since they often cannot be traced to SI. A reference procedure should be defined and referred. This would be more advantageous than to refer to a reference material that can only be traced to a master preparation. This would reduce the uncertainty and guarantee that calibrators of different batches meet certain metrological criteria.

Isolation of antibacteriologically active compounds from species of the Cottidae family.

Antibacteriologically active compounds were isolated from the skin of several species of the fish family Cottidae. Suitable samples were obtained from species living in the Pacific, lakes in North America and the Fenno-Scandinavian peninsula as well as the Baltic sea. The compounds isolated from the skin of Triglops quadricornis (fourhorn sculpin) from the Baltic sea were particularly studied. The activity was partially characterised by chemical and biochemical investigations and the susceptibility of several human and fish pathogens described. The substance or substance(s) are of a high molecular mass, resist proteolytic and glycolytic enzymes, are heat and pH sensitive and water soluble.

Can age and sex related reference intervals be derived for non-healthy and non-diseased individuals from results of measurements in primary health care?

Reference intervals in clinical chemistry are commonly based on results of measurements in reference populations or are taken from the literature. A reference population should represent a defined group of individuals and be as similar as possible to the patients under investigation. Frequently, reference populations have been recruited from institutionalised healthy young people who do not necessarily fulfill these criteria. In the present study we describe the temporal changes in 37 commonly measured quantities in men and women from childhood to late in life. The samples were collected in the primary health care and sorted according to an assumed decision by the physician. The emerging group of individuals forms a reference population that was regarded as "non-diseased" and the results of measurements in this population are reference values. A remaining group of "non-healthy" were likewise identified for comparison. The central 95 percentile was wider than those usually assigned to the quantities whereas the medians almost coincided. In the "non-healthy" group the medians were shifted in a direction that would be expected from pathophysiology aspects.

Does the uncertainty of commonly performed glucose measurements allow identification of individuals at high risk for diabetes?

Revised recommendations for diagnosis of diabetes introduce the intermediary risk group of impaired fasting glucose (IFG), defined as individuals with a fasting blood-glucose concentration between 5.6 and 6.0 mmol/l. We apply the concept of uncertainty to identifiable steps of sampling and measuring blood-glucose. Since many instruments in primary health care measure plasma-glucose and report results as blood-glucose and vice versa, factors affecting the transformation are also considered. The study identifies the measurement procedure as the major source of uncertainty, closely followed by preanalytical sources. The estimated uncertainties indicate that the presently available procedures do not allow identification of IFG by a single investigation. The approach to establish an uncertainty budget can be used to evaluate the clinical usefulness of measurements.

A single high dose of vitamin C counteracts the acute negative effect on microcirculation induced by smoking a cigarette.

Cigarette smoking is associated with marked acute changes in microcirculation including reduced blood flow. We tested the hypothesis that the reduced blood flow velocity is due to the imbalance between prooxidants and antioxidants that occurs as a consequence of smoking and that it can be reduced by an antioxidant. The effect of smoking a single cigarette on nail-fold microcirculation was analyzed in 24 healthy subjects with varying smoking habits. Vital capillary microscopy was used and the blood cell flow velocity in the capillaries was evaluated before and 1-30 min after smoking. Smoking induced a marked decrease in microcirculatory blood flow in 23 of the 24 subjects (40-50% decrease 1-5 min after smoking). This change was reduced by more than 50% in the same subjects after intake of 2 g of vitamin C 2 h before smoking (P < 0.0001 by ANOVA test) with smokers responding similarly to nonsmokers in these experiments. Intake of 1 g of vitamin C had no significant effect on the smoking-induced changes in most of the subjects tested (n = 11). Pretreatment with aspirin had little or no effect on the response to smoking (n = 9). Our results show that treatment with a single high dose of vitamin C can reduce and in some individuals even completely abolish the negative acute effect on microcirculation induced by smoking a single cigarette. This effect of vitamin C is not likely to be mediated by the cyclooxygenase system.