Reference intervals of serum folate and vitamin B12 developed from data of healthy subjects

 In this study the reference intervals for folate and vitamin B₁₂ were estimated according to the National Committee for Clinical Laboratory Standards Approved Guideline C28-A and International Federation of Clinical Chemistry recommendations. The study included 155 women and 124 men between ages 18–40. The health status was confirmed by history, physical examination and a questionnaire. The central 95% reference intervals of serum folate and vitamin B12 for women, determined non-parametrically, were found to be 3.9–18.1 ng/ml and 101–666.7 pg/ml, respectively. The reference values of serum folate and vitamin B12 for men were also found to be 2,5–17.6 ng/ml and 100–699.57 pg/ml, respectively. We did not observe subclass differences between females and males. Received: 15 April 2000 · Accepted: 15 April 2000     

A practical analytical quality report on the effect of carotenemia on neonatal bilirubin levels

 The effect of haematocrit and β-carotene levels on the serum total bilirubin measurement in two analytical methods was studied as an example of the impact of practical analytical quality in medical decision making. The precision characteristics of the two methods were very similar. Based upon the significant difference in the correlation coefficient in a method comparison study before and after 20% trimming of the data, an interference effect study was performed. Haemoglobin (expressed as haematocrit) and β-carotene were the substances studied to explain the observed differences. The bilirubin test results from the Wako bilirubinometer were easily affected (n=19;X(S): 13.83±2.43;t=–6.17;P=0.000) and more elevated than in the Vitros dry chemistry systems (n=18;X(S): 12.72±2.21;t=–2.48;P=0.017), due to the presence of β-carotene (>200 μg/dl).     

Elastoplastic analysis of nonlinearly hardening variable thickness annular disks under external pressure

Based on von Mises’ yield criterion, deformation theory of plasticity and Swift’s hardening law, elasto-plastic deformation of variable thickness annular disks subjected to external pressure is studied. A nonlinear shooting method using Newton’s iterations with numerically approximated tangent is designed for the solution of the problem. Considering a thickness profile in the form of a general parabolic function, the condition of occurrence of plastic deformation at the inner and outer edges of the annular disk is investigated. A critical disk profile is determined and the corresponding elastic–plastic stresses as well as the residual stress distribution upon removal of the applied pressure are computed and discussed.     

Chaotic predation scheme for age-clustered one predator–one prey Lotka–Volterra

Nonlinear Dynamics - Lotka–Volterra differential equations deal with modeling of predator and prey populations and interrelation of population sizes in a continuous domain. Since all...     

Analysis of a new simple one dimensional chaotic map

In this paper, a new one-dimensional map is introduced, which exhibits chaotic behavior in small interval of real numbers. It is discovered that a very simple fraction in a square root with one variable and two parameters can lead to a period-doubling bifurcations. Given the nonlinear dynamics of one-dimensional chaotic maps, it is usually seen that chaos arises when the parameter raises up to a value, however in our map, which seems reverse, it arises when the related parameter decreases and approaches to a constant value. Since proposing a new map entails solid foundations, the analysis is originated with linear stability analysis of the new map, finding fixed points. Additionally, the nonlinear dynamics analysis of the new map also includes cobweb plot, bifurcation diagram, and Lyapunov analysis to realize further dynamics. This research is mainly consisting of real numbers, therefore imaginary parts of the simulations are omitted. For the numerical analysis, parameters are assigned to given values, yet a generalized version of the map is also introduced.     

The use of split-sample design for performance evaluation of screening kits

Laboratory medicine is an important discipline in health care with its remarkable effect on risk assessment, diagnosis of health, and disease state. This accounts describes a newborn screening approach involving retest, recall, and follow-up procedures. This real life trial emphasizes the need for split-sample design evaluation of newly opened test kits. Quantitative measurements of phenylalanine and neonatal thyroid stimulating hormone (nTSH) were performed in two laboratories. After validation of the calibration in the laboratory that was using the industrially prepared screening kits for the first time, the same real newborn blood spot samples were analyzed for phenylalanine and nTSH measurements in both laboratories and the results obtained were compared non-parametrically, and examined by Deming regression and difference plots. There was no problem with the phenylalanine results: similar results were obtained for the same blood spot cards in both laboratories (P=0.496; bias estimation 0.13). However, the nTSH values were found to be significantly higher in the laboratory that used the nTSH kit for the first time. Although the validation of the calibration of the nTSH kit was valid with the manufactures control materials, spilt-sample results showed that there was a significant difference between the two laboratories (P=0.005; bias estimation 28.6). This study implies that acceptable comparability of split-sample design analysis is needed for testing the analytical performance of industrially prepared tests kits, and this can only be achieved with certified reference materials.Presented at the 8th Conference on Quality in the Spotlight, 17–18 March 2003, Antwerp, Belgium     

Performance evaluation of a G-6-PD assay employing an adapted error grid graph

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is one of the most common genetic diseases, characterized by neonatal jaundice or hemolysis during adulthood. Neonatal screening for this disease has been established in many countries in the Mediterranean and Middle East region but not yet in Turkey. The performance of a new fully quantitative G-6-PD kit employing hemoglobin normalization was statistically evaluated and the cut-off points and reference values for the Izmir region (Aegean coast of Turkey) were established, including a long term performance evaluation of the method. Statistical acceptance of the bias and variation were also clinically evaluated using new tools, such as the Parkes error grid graph. The kit used is particularly suitable for use with Guthrie cards as well as with whole blood samples. We report here on the results of the evaluation, emphasizing the methodology we used for it.Presented at the 9th Conference on Quality in the Spotlight, 18–19 March 2004, Antwerp, Belgium.     

Experimental and analytical investigation of the mechanics of crawl stroke swimming

A three dimensional analytical model for crawl stroke swimming is developed in which the swimmer is modeled as a body and two arms connected to the body at the shoulder joints. Each arm is assumed to consist of three segments. The numerical results obtained from the model are compared with the results of two sets of experiments performed. In the first series of experiments, the tether forces developed in crawl stroke swimming are measured and a linear correlation between the tether force and the stroke rate is obtained. In the second series of experiments, untethered crawl stroke swimming for different arm position angles is recorded. The results are presented in graphical forms and the effect of stroke rate on swimming velocity is discussed.     

Estimation of the biological variation of glucose-6-phosphate dehydrogenase in dried blood spots

Models based on biological variation provide a well-accepted database with reliable information for clinical laboratories for all purposes including screening, diagnosis and follow-up. Newborn screening laboratories use a blood spotted paper matrix to measure the analytes. This matrix medium is certainly different than body fluid matrix medium. After long-term monitoring of the performance of the Glucose-6-Phosphate Dehydrogenase Kit (R&D Diagnostics OSMMR 2000-D G6PD), the results obtained from the variation analysis were statistically evaluated. Analytical coefficient of variation, CV _A, was found to be 5.41%. The CV _A derived from between run assays was 5.32%, while within-subject biological coefficient of variation, CV _I, was 7.26%. Since minimum performance is defined as CV _A< 0.750 CV _I , CV _A should be lower than 5.44%. The analytical bias in calculation of total error was chosen to evaluate the performance of this assay. In this aspect, CV _G, between-subject biological coefficient of variation, was found to be equal to 10.35%. B _A was found to be 4.12%, which is lower than 4.74%, which means that it is acceptable. Therefore, the minimum quality specification for total error allowable is . When the relevant results obtained in this study were substituted in this formula, TE _a was found to be 13.7% for G6PD measurement in dried blood spots on paper filter matrix. It is expected that this figure will be helpful for the performance evaluation of newborn screening laboratories performing G6PD screening. We have been using error grid graphs for the evaluation of our external quality assurance survey results for the last two years, only because there was no data for assays employing filter matrix. Even the TE _a already reported for EDTA whole blood samples used in G6PD assays has been remarkably high, which can easily create the wrong impression that G6PD is not a reliable test to perform from blood spot cards. The present study shows that this assay is adequately reliable even when performed from dried blood spot matrix. However, we believe that the combination of total allowable error, error grid graphs with a well-defined cut off is the best approach to obtain an accurate performance evaluation for this test.Presented at the 10th Conference Quality in the Spotlight, March 2005, Antwerp, Belgium.