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Biomedical subjects

A Kallner

Publications and source records attributed to A Kallner.

At least 19 recordsLinked to original sources
PubMed2005

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.

Clinical Laboratory Techniques↗
PubMed2005

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.

Adolescent↗
PubMed2005

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.

Albumins↗
PubMed2005

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%.

Animals↗
PubMed2002

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.

Anticoagulants↗
PubMed2001

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.

Accreditation↗
PubMed2001

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.

Clinical Chemistry Tests↗
PubMed2001

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.

Animals↗
PubMed2001

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.

Animals↗
PubMed2000

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.

Adolescent↗
PubMed1999

[Quality assurance of blood gas analysis--a medical risk zone].

Blood gas analysis is fundamental to all intensive care. Although speed is essential for adequate treatment, prognosis and even survival of the patient, precision and consistency of results are equally important prerequisites for correct clinical decision making. Point-of-care testing (POCT) has become one of the predominant fields of blood gas analysis. Although modern technology and instruments are user friendly, special training and continuous updating of staff education are of paramount importance to the reliability of results. The article consists in an outline of quality requirements and discussion of appropriate procedures for assessing and maintaining quality in blood gas analysis.

Acid-Base Equilibrium↗
PubMed1999

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.

Adult↗
PubMed1999

Serum urate determines antioxidant capacity in middle-aged men - a controlled, randomized diet and exercise intervention study.

OBJECTIVES: To study whether advice on diet and/or exercise, given in order to reduce cardiovascular risk factors in middle-aged men, affects the intake of antioxidants, urate concentration and the total antioxidant capacity in serum. DESIGN: A 6-month randomized controlled intervention study. SETTING: Primary Health Care in Sollentuna, Stockholm, and the Department of Medicine, Karolinska Hospital, Stockholm, Sweden. SUBJECTS: One hundred and fifty-eight healthy men (46.2 +/- 5.0 years) with moderately raised cardiovascular risk factors. INTERVENTIONS: Advice on diet (D, n = 40), exercise (E, n = 39), diet and exercise (DE, n = 39) and a control group (C, n = 39). MAIN OUTCOME MEASURES: Dietary intake, exercise habits, S-urate and the antioxidant capacity in serum (TAOC). RESULTS: After 6 months, changes in dietary and exercise habits were seen in all three intervention groups and favourable effects were seen on BMI, waist circumference, blood pressure, S-cholesterol and fasting insulin. The intake of alpha-tocopherol was decreased in groups D and E (P < 0.01) and beta-carotene was increased in groups D and DE (P < 0.01). In group DE, the intake of vitamin C was increased (P < 0.05). S-urate was reduced in group D from 345 to 325 micromol L-1 (P < 0.05). No significant changes in TAOC were seen in any group. S-urate and TAOC were correlated (r = 0. 58, P < 0.001) and S-urate was correlated to several parameters in the metabolic syndrome. CONCLUSION: Favourable changes in diet and exercise reduced several cardiovascular risk factors but did not affect the total antioxidant capacity in serum. S-urate was a strong determinant of the antioxidant capacity.

Adult↗
PubMed1999

A 50-Hz electromagnetic field impairs sleep.

In view of reports of health problems induced by low frequency (50-60 Hz) electromagnetic fields (EMF), we carried out a study in 18 healthy subjects, comparing sleep with and without exposure to a 50 Hz/1 mu Tesla electrical field. We found that the EMF condition was associated with reduced: total sleep time (TST), sleep efficiency, stages 3 + 4 slow wave sleep (SWS), and slow wave activity (SWA). Circulating melatonin, growth hormone, prolactin, testosterone or cortisol were not affected. The results suggest that commonly occurring low frequency electromagnetic fields may interfere with sleep.

Adolescent↗
PubMed1999

Quality specifications based on the uncertainty of measurement.

The result of a measurement needs to be accompanied by information on the error or uncertainty of the measurement. Either of two very closely related concepts is thus required to indicate the usefulness and relevance of a result for its purpose: decision making. This presentation will outline the difference between the concept of error and that of uncertainty and deal with procedures to estimate the latter. The use of a spreadsheet program will illustrate how the combined uncertainty is estimated in a relatively complex situation with a bearing on laboratory medicine.

Calibration↗