With the lack of regional differences and the well-standardized status of test results, the RIs derived from this nationwide study can be used for the entire Turkish population.

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Methylenetetrahydrofolate reductase (MTHFR) is important for folate and homocysteine (Hcy) metabolism. MTHFR 677C->T and 1298A->C MTHFR are two most common mutations which can affect folate and total homocysteine (tHcy) status. This study was designed to determine the rate of MTHFR 677C->T and 1298A->C mutations, and their influence on serum folate, Hcy and vitamin B12 status and the reference intervals in 402 healthy Turkish adults. The rate of MTHFR 677C->T or 1298A->C mutations was 50.7% or 54.7%, respectively. The MTHFR 677C->T mutation-specific reference intervals for serum folate and tHcy were characterized by marked shifts in their upper limits. In homozygote subjects for MTHFR 677C->T serum folate concentration was lower and serum tHcy concentration was higher than those in the wild genotype; all subjects had lower serum folate and 54% of the subjects had higher tHcy concentrations than the cutoff values of or=12 micromol/L, respectively. Serum vitamin B12 status was similar in all genotypes. Serum tHcy concentrations were inversely correlated with serum folate and vitamin B12 concentrations in all genotypes. These data show that the rate of MTHFR 677C->T and 1298A->C mutations is very high in Turks and serum folate and tHcy status are impaired by these mutations.

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Kratak sadr`aj: Dijabetes predstavlja ~est metaboli~ki poreme}aj, ~ije mikrovaskularne i makrovaskularne komplikacije doprinose smrti, invaliditetu i skra}enju o~e kivanog `ivotnog veka kod obolelih. Ova bolest podrazumeva velike tro{kove a pored pacijenta i njegove porodice poga|a i javno zdravlje, zajednice i dru{tvo. Dijabetes zahteva sve ve}i deo nacionalnih tro{kova zdravstva. Prevencija razvoja dijabetesa i njegovih komplikacija je va`an problem. U cilju razumevanja mehanizama razvoja i progresije komplikacija u dijabetesu vr{i se istra`ivanje biomarkera. U ovom radu dat je pregled biomarkera koji se preporu~uju u klini~koj praksi i pravilnicima za laboratorijsku medicinu i koji su istra`ivani radi predikcije ili dijagnostikovanja kom plikacija u dijabetesu. U sa`etom obliku su prikazani rezultati nekoliko klini~kih studija.Klju~ne re~i: dijabetes, biomarkeri, klini~ke studije Summary: Diabetes is a common metabolic disorder. Its microvascular and macrovascular complications contribute to death, disabilities, and reduction in life expectancy in diabetes. It is a costly disease, and affects not only the patient and family, but also the public health, communities and society. It takes an increasing proportion of the na tional health care expenditure. The prevention of the development of diabetes and its complications is a major concern. Biomarkers have been investigated for understanding the mechanisms of the development and progression of diabetic com plications. In this paper, the biomarkers which are re com mended in the clinical practice and laboratory medicine guidelines, and which have been investigated for prediction or diagnosis of diabetes complications, have been reviewed. The results of several clinical studies will be summarized.

Simple Statistics in Diagnostic Tests Diagnostic performance of a laboratory test is one of the key elements in decision making on diagnosis, screening, monitoring, risk assessment and prognosis of diseases. Sensitivity, specificity, likelihood ratios, diagnostic odds ratios and receiver operating characteristic curves are the measures of diagnostic accuracy of a test. The pretest probability of a disease or a target condition can be enhanced by the use of these measures, and hence the decision is made with the posttest probability. These measures are also used for analysis and critical appraisal of literature for finding the best evidence in the five-step model of evidence-based medicine approach, as well as for integrating the research results into clinical usage. In this context, the specialists in laboratory medicine should assess the diagnostic performance of a laboratory test as well as its analytical performance in order to take part in the management of health care services and health care resources. The aim of this review is to summarize the simple Statistics in diagnostic tests.

Summary Background There is increasing requests of Vitamin D test in many clinical settings in recent years. However, immunoassay performance is still a controversial topic. Several diagnostic manufacturers have launched automated 25-hydroxyvitamin D (25-OH D) immunoassays in the past decade. We compared the performance of Abbott Architect 25-OH D Vitamin immunoassay with liquid chromatography-tandem mass spectrometry systems (LC-MS/MS) to evaluate immunoassay performance, especially in deficient groups. Methods Eighty human serum samples were analyzed with Architect 25-OH D vitamin kit (Abbott Diagnostics, Lake Forest, IL, USA) and LC-MS/MS systems (Zivak Technology, Istanbul, Turkey). The results of the immunoassay method were compared with the LC-MS/MS using Passing-Bablok regression analysis, Bland-Altman plots and correlation coefficient analysis. We also evaluated results in four levels of D vitamin as a severe deficiency, deficiency, insufficiency, and sufficiency. Results Architect showed 9.59% bias from LC-MS/MS with smaller mean. Passing-Bablok regression analysis demonstrated the value of 0.95 slope and had a constant bias with an intercept value of -4.25. Concordance correlation coefficient showed moderate agreement with the value of 0.918 (95% CI 0.878–0.945). Two methods revealed good interrater agreement (kappa = 0.738). While the smallest bias determined in deficiency (9.95%) group, the biggest was in insufficiency (15.15%). Conclusions Architect 25-OH D vitamin immunoassay can be used in routine measurements but had potential misclassification of vitamin D status in insufficient and deficient groups. Although there are recent standardization attempts in 25-OH D measurements, clinical laboratories must be aware of this method.

In the present study we used patient data to calculate laboratory-specific indirect reference intervals. These values were compared with reference intervals obtained for a healthy group according to recommendations of the International Federation of Clinical Chemistry and Laboratory Medicine and manufacturer suggestions. Laboratory results (422,919 records) from all subjects of 18-45 years of age over a 1-year period were retrieved from our laboratory information system and indirect reference intervals for 40 common analytes were estimated using a modified Bhattacharya procedure. Indirect reference intervals for most of the biochemical analytes were comparable, with small differences in lower [alkaline phosphatase (ALP) (male), alanine aminotransferase (ALT), creatine kinase, iron (male), total iron-binding capacity, folic acid, calcium (female), lactate dehydrogenase (LDH), lipoprotein (a) [Lp(a)], thyroid-stimulating hormone (TSH), total triiodothyronine (T(3)), direct bilirubin, apolipoprotein A-I (apoA-I), glucose, homocysteine, total cholesterol, ferritin, total protein, ceruloplasmin, sodium, blood urea nitrogen (BUN) and uric acid (female)] and/or upper limits [albumin, ALP (male), amylase, apoA-I, creatine kinase-MB (CK-MB), total iron-binding capacity, phosphorus, glucose, total cholesterol, gamma-glutamyltransferase (gamma-GT), magnesium, total protein, high-density lipoprotein cholesterol (HDL-C), total T(3), ALP (male), ALT, aspartate aminotransferase (AST) (male), direct bilirubin (male), creatine kinase, iron, folic acid (female), Lp(a), uric acid and triglycerides], to the reference intervals determined for healthy subjects in our laboratory. The indirect reference intervals, with the exception of a few parameters (creatinine, direct total bilirubin, calcium, BUN and potassium), were not similar to the reference intervals suggested by the manufacturers. We conclude that laboratory-specific reference intervals can be determined from stored data with a relatively easy and inexpensive method. Indirect reference intervals derived from stored data may be particularly suitable for the evaluation of results for the presenting population.