Objective: A modified method for screening of six lysosomal storage disorders (LSDs) by tandem ma... more Objective: A modified method for screening of six lysosomal storage disorders (LSDs) by tandem mass spectrometry was presented.Methods: The enzyme activities for six LSDs (Gaucher, Pompe, Krabbe, Fabry, Niemann-Pick A/B and Mucopolysaccharidosis Type I) was measured by using ultra- HPLC and mass spectrometry. After overnight incubation of dried blood spots with three distinct reaction cocktails containing substrates and internal standards, reactions were stopped and online trapping was performed with ultra-HPLC preceding to mass spectrometry. Ultra-HPLC was equipped with online solid phase extraction and Hypersil Gold C8 analytical columns and coupled with TSQ Quantum Access Max mass spectrometry.Results: Activities of acid-s-glucocerebrosidase (ABG), acid glucosidase (GAA), galactocerebroside-s-galactosidase (GALC), acid-galactosidase A (GLA), acid sphingomyelinase (ASM), and α-L-iduronidase (IDU) were obtained from DBSs of patients and healthy individuals. The intraand inter-assay...
Clinical Chemistry and Laboratory Medicine (CCLM), 2021
Objectives Reliable biological variation (BV) data are required for the clinical use of tumor mar... more Objectives Reliable biological variation (BV) data are required for the clinical use of tumor markers in the diagnosis and monitoring of treatment effects in cancer. The European Biological Variation Study (EuBIVAS) was established by the EFLM Biological Variation Working Group to deliver BV data for clinically important measurands. In this study, EuBIVAS-based BV estimates are provided for cancer antigen (CA) 125, CA 15-3, CA 19-9, carcinoembryonic antigen, cytokeratin-19 fragment, alpha‐fetoprotein and human epididymis protein 4. Methods Subjects from five European countries were enrolled in the study, and weekly samples were collected from 91 healthy individuals (53 females and 38 males; 21–69 years old) for 10 consecutive weeks. All samples were analyzed in duplicate within a single run. After excluding outliers and homogeneity analysis, the BVs of tumor markers were determined by CV-ANOVA on trend-corrected data, when relevant (Røraas method). Results Marked individuality was f...
The concept of personalized medicine has become popular within the last decade. However, personal... more The concept of personalized medicine has become popular within the last decade. However, personalized medicine needs correct diagnosis and monitoring of patients which can be done by using personalized reference intervals of laboratory tests. In this paper we proposed a model based on within subject biological variation to calculate the personalized reference intervals of tests requested by physicians for the diagnosis of diseases. We used the data of adult patients admitted to check-up units and calculated the personal reference intervals. If the patients are on steady-state, only a few data are sufficient to calculate the personal reference intervals. The model is very simple and can be used by physicians safely and easily.
In the literature, studies on the oxidant effects of nontransferrin bound iron [NTBI (eLPI assay)... more In the literature, studies on the oxidant effects of nontransferrin bound iron [NTBI (eLPI assay)] during chemotherapy of acute lymphoblastic leukemia and acute myeloblastic leukemia are lacking. We established NTBI and oxidative stress determinants (OSD), iron parameters, high-sensitive C-reactive protein (hs-CRP) levels, liver tests, cumulative chemotherapeutic doses, and transfused blood in 36 children with acute leukemia throughout chemotherapy. These parameters were determined at the beginning and end of chemotherapy blocks (11 time points) and in 20 healthy children using enzyme-linked immunosorbent assay, and colorimetric and fluorometric enzymatic methods. In acute lymphoblastic leukemia, NTBI, OSD, and hs-CRP were higher than controls at 4/11, 7/11, and 9/11 time points (P<0.05). At 3 time points, NTBI and OSD concurrently increased. Ferritin, soluble transferrin receptor, serum iron, and transferrin saturation were higher than in controls at 5 to 11/11 time points (P<...
HbA1c test has been widely used to evaluate glycemic control in patients with diabetes. However, ... more HbA1c test has been widely used to evaluate glycemic control in patients with diabetes. However, there are controversial results regarding the value of HbA1c in the diagnosis of diabetes mellitus (DM). The present study investigates the diagnostic effectiveness of HbA1c in a large patient group. The oral glucose tolerance test and HbA1c results of 6551 patients (4704 healthy, 1345 pre-diabetes, 502 DM) in 12 different medical centers in Turkey between 2010 and 2016 were examined to understand the effectiveness of HbA1c in the diagnosis of DM. Different Roche systems were used for measuring HbA1c via the immunoturbidimetric method. The DM ROC curves revealed the diagnostic sensitivity, specificity, and AUC of 74.5%, 87.1%, and 0.866 (CI 95% 0.858–0.875), respectively, for HbA1c (at the cut-off 41 mmol/mol, 5.9%). For HbA1c at the universal diagnostic decision value of 48 mmol/mol (6.5%), the sensitivity and specificity were determined as 32.4% and 99.9%, respectively. The ROC curves for fasting plasma glucose (FPG) revealed the diagnostic sensitivity, specificity, and AUC of 71.3%, 85.3%, and 0.853 (CI 95% 0.844–0.861), respectively. However, the ROC curve results for pre-diabetes (HbA1c at the cut-off value of 39 mmol/mol, 5.7%) revealed the diagnostic sensitivity, specificity, and AUC of 45.7%, 76.4%, and 0.641, respectively. Furthermore, it was shown that the changes in HbA1c values due to gender and age had no clinical effect on the diagnosis. According to our results, it remains challenging to suggest HbA1c measurements can have a significant contribution to the FPG measurements. It was found that the sensitivity is specifically low in the assessment of the pre-diabetes data. Additionally, considering the problems associated with Hb1Ac measurements, further studies conducted in different regions by using different methods are required.
Acute kidney injury (AKI) is a worldwide health problem and defined by rapid loss of excretory fu... more Acute kidney injury (AKI) is a worldwide health problem and defined by rapid loss of excretory function of the kidney with the accumulation of metabolic end products. For effective treatment and prevent complications the early diagnosis of AKI is crucial. The current analytes used to diagnose AKI are not adequately sensitive and specific and therefore clinicians need new biomarkers. One of the new promising biomarker candidates of renal injury is cofilin-1. Previously, in our laboratory we isolated cofilin-1 in kidney preservation solution prior to transplantation and attempted to measure serum cofilin-1 in renal transplanted patients. However, cofilin-1 was not accurately measured in serum samples due to the methodological issues. In this mini-review, we summarized the current knowledge and concepts both in the literature and our experiences with cofilin-1 as a potential biomarker for the diagnosis and management of AKI.
Perchlorate, thiocyanate, and nitrate can block iodide transport at the sodium iodide symporter (... more Perchlorate, thiocyanate, and nitrate can block iodide transport at the sodium iodide symporter (NIS) and this can subsequently lead to decreased thyroid hormone production and hypothyroidism. NIS inhibitor exposure has been shown to reduce iodide uptake and thyroid hormone levels; therefore we hypothesized that maternal NIS inhibitor exposure will influence both maternal and newborn thyroid function. Spot urine samples were collected from 185 lactating mothers and evaluated for perchlorate, thiocyanate, and nitrate concentrations. Blood and colostrum samples were collected from the same participants in the first 48 h after delivery. Thyroid hormones and thyroid-related antibodies (TSH, fT3, fT4, anti-TPO, anti-Tg) were analyzed in maternal blood and perchlorate was analyzed in colostrum. Also, spot blood samples were collected from newborns ( = 185) between 48 and 72 postpartum hours for TSH measurement. Correlation analysis was performed to assess the effect of NIS inhibitors on t...
The European Federation of Clinical Chemistry and Laboratory Medicine European Biological Variati... more The European Federation of Clinical Chemistry and Laboratory Medicine European Biological Variation Study (EuBIVAS) has been established to deliver rigorously determined data describing biological variation (BV) of clinically important measurands. Here, EuBIVAS-based BV estimates of serum electrolytes, lipids, urea, uric acid, total protein, total bilirubin, direct bilirubin, and glucose, as well as their associated analytical performance specifications (APSs), are presented. Samples were drawn from 91 healthy individuals (38 male, 53 female; age range, 21-69 years) for 10 consecutive weeks at 6 European laboratories. Samples were stored at -80 °C before duplicate analysis of all samples on an ADVIA 2400 (Siemens Healthineers). Outlier and homogeneity analyses were performed, followed by CV-ANOVA on trend-corrected data, when relevant, to determine BV estimates with CIs. The within-subject BV (CV) estimates of all measurands, except for urea and LDL cholesterol, were lower than esti...
The Journal of asthma : official journal of the Association for the Care of Asthma, Jan 6, 2017
Remodeling is a crucial feature of severe asthma and may be associated with activation of the all... more Remodeling is a crucial feature of severe asthma and may be associated with activation of the allergic cascade by immunoglobulin E (IgE). Omalizumab, an anti-IgE monoclonal antibody, effectively targets the severe allergic asthma phenotype. Pregnancy-associated plasma protein-A (PAPP-A) is an insulin-like growth factor binding protein-4 (IGFBP-4) protease, increasing local insulin-like growth factor (IGF)-1 concentrations, which in turn initiating a cascade involved in the regulation of cell growth, differentiation, and proliferation in various tissues. In the present study, we evaluated the effects of omalizumab on serum PAPP-A, IGFBP-4, and IGF-1 levels in subjects with severe allergic asthma. We studied 36 asthmatic subjects and 36 healthy controls. An ultrasensitive enzyme-linked immunosorbent assay (ELISA) kit was used to measure serum PAPP-A levels, and routine commercial ELISA kits were employed to assess serum levels of IGF-1, IGFBP-4 in control subjects and asthmatic subjec...
Vitamin D and intact parathyroid hormone (iPTH) play a crucial role in calcium homeostasis and bo... more Vitamin D and intact parathyroid hormone (iPTH) play a crucial role in calcium homeostasis and bone health of children. Serum level of 25-hydroxyvitamin D (25-OHD) is considered to be the most accurate marker for vitamin D status. However, there have only been a few studies, with limited number of subjects, investigating the relationship between 25-OHD and parathyroid hormone (PTH) in children. The aim of this study was to evaluate the seasonal 25-OHD levels and its associations with intact parathyroid hormone (iPTH) in Turkish children at all pediatric ages; and then to define a critical decision threshold level for 25-OHD deficiency in Turkish children. A retrospective record review of 90,042 children, was performed on serum 25-OHD and for 3525 iPTH levels. They were measured by mass spectrometry method and by electrochemiluminescence immunoassay simultaneously. 25-OHD levels showed a sinusoidal fluctuation througout the year; being significantly higher in summer and autumn (p <...
Clinical chemistry and laboratory medicine, Jan 2, 2018
The complete blood count (CBC) is used to evaluate health status in the contexts of various clini... more The complete blood count (CBC) is used to evaluate health status in the contexts of various clinical situations such as anemia, infection, inflammation, trauma, malignancies, etc. To ensure safe clinical application of the CBC, reliable biological variation (BV) data are required. The study aim was to define the BVs of CBC parameters employing a strict protocol. Blood samples, drawn from 30 healthy subjects (17 females, 13 males) once weekly for 10 weeks, were analyzed using a Sysmex XN 3000 instrument. The data were assessed for normality, trends, outliers and variance homogeneity prior to coefficient of variation (CV)-analysis of variance (ANOVA). Sex-stratified within-subject (CVI) and between-subjects (CVG) BV estimates were determined for 21 CBC parameters. For leukocyte parameters, with the exception of lymphocytes and basophils, significant differences were found between female/male CVI estimates. The mean values of all erythrocyte-, reticulocyte- and platelet parameters diff...
Summary25 (OH) vitamin D3 (25(OH)D) and parathyroid hormone (PTH) are important regulators of cal... more Summary25 (OH) vitamin D3 (25(OH)D) and parathyroid hormone (PTH) are important regulators of calcium homeostasis. The aim of this study was to retrospectively determine the cut–off for sufficient 25(OH)D in a four-season region and the influence of age, seasons, and gender on serum 25(OH)D and PTH levels.Laboratory results of 9890 female and 2723 male individuals aged 38.8±22.1 years who had simultaneous measurements of 25(OH)D and PTH were retrospectively analyzed by statistical softwares. Serum 25(OH)D and PTH levels were measured by a mass spectrometry method and by an electrochemiluminescence immunoassay, respectively.Mean serum 25(OH)D levels showed a sinusoidal fluctuation throughout the year and were significantly (p<0.01) higher in summer and autumn. On the other hand, PTH levels were significantly higher (p<0.01) in women and showed an opposite response to seasonal effects relative to 25(OH)D. Lowest levels of 25(OH)D were detected in people aged between 20 and 40 ye...
Objective: A modified method for screening of six lysosomal storage disorders (LSDs) by tandem ma... more Objective: A modified method for screening of six lysosomal storage disorders (LSDs) by tandem mass spectrometry was presented.Methods: The enzyme activities for six LSDs (Gaucher, Pompe, Krabbe, Fabry, Niemann-Pick A/B and Mucopolysaccharidosis Type I) was measured by using ultra- HPLC and mass spectrometry. After overnight incubation of dried blood spots with three distinct reaction cocktails containing substrates and internal standards, reactions were stopped and online trapping was performed with ultra-HPLC preceding to mass spectrometry. Ultra-HPLC was equipped with online solid phase extraction and Hypersil Gold C8 analytical columns and coupled with TSQ Quantum Access Max mass spectrometry.Results: Activities of acid-s-glucocerebrosidase (ABG), acid glucosidase (GAA), galactocerebroside-s-galactosidase (GALC), acid-galactosidase A (GLA), acid sphingomyelinase (ASM), and α-L-iduronidase (IDU) were obtained from DBSs of patients and healthy individuals. The intraand inter-assay...
Clinical Chemistry and Laboratory Medicine (CCLM), 2021
Objectives Reliable biological variation (BV) data are required for the clinical use of tumor mar... more Objectives Reliable biological variation (BV) data are required for the clinical use of tumor markers in the diagnosis and monitoring of treatment effects in cancer. The European Biological Variation Study (EuBIVAS) was established by the EFLM Biological Variation Working Group to deliver BV data for clinically important measurands. In this study, EuBIVAS-based BV estimates are provided for cancer antigen (CA) 125, CA 15-3, CA 19-9, carcinoembryonic antigen, cytokeratin-19 fragment, alpha‐fetoprotein and human epididymis protein 4. Methods Subjects from five European countries were enrolled in the study, and weekly samples were collected from 91 healthy individuals (53 females and 38 males; 21–69 years old) for 10 consecutive weeks. All samples were analyzed in duplicate within a single run. After excluding outliers and homogeneity analysis, the BVs of tumor markers were determined by CV-ANOVA on trend-corrected data, when relevant (Røraas method). Results Marked individuality was f...
The concept of personalized medicine has become popular within the last decade. However, personal... more The concept of personalized medicine has become popular within the last decade. However, personalized medicine needs correct diagnosis and monitoring of patients which can be done by using personalized reference intervals of laboratory tests. In this paper we proposed a model based on within subject biological variation to calculate the personalized reference intervals of tests requested by physicians for the diagnosis of diseases. We used the data of adult patients admitted to check-up units and calculated the personal reference intervals. If the patients are on steady-state, only a few data are sufficient to calculate the personal reference intervals. The model is very simple and can be used by physicians safely and easily.
In the literature, studies on the oxidant effects of nontransferrin bound iron [NTBI (eLPI assay)... more In the literature, studies on the oxidant effects of nontransferrin bound iron [NTBI (eLPI assay)] during chemotherapy of acute lymphoblastic leukemia and acute myeloblastic leukemia are lacking. We established NTBI and oxidative stress determinants (OSD), iron parameters, high-sensitive C-reactive protein (hs-CRP) levels, liver tests, cumulative chemotherapeutic doses, and transfused blood in 36 children with acute leukemia throughout chemotherapy. These parameters were determined at the beginning and end of chemotherapy blocks (11 time points) and in 20 healthy children using enzyme-linked immunosorbent assay, and colorimetric and fluorometric enzymatic methods. In acute lymphoblastic leukemia, NTBI, OSD, and hs-CRP were higher than controls at 4/11, 7/11, and 9/11 time points (P<0.05). At 3 time points, NTBI and OSD concurrently increased. Ferritin, soluble transferrin receptor, serum iron, and transferrin saturation were higher than in controls at 5 to 11/11 time points (P<...
HbA1c test has been widely used to evaluate glycemic control in patients with diabetes. However, ... more HbA1c test has been widely used to evaluate glycemic control in patients with diabetes. However, there are controversial results regarding the value of HbA1c in the diagnosis of diabetes mellitus (DM). The present study investigates the diagnostic effectiveness of HbA1c in a large patient group. The oral glucose tolerance test and HbA1c results of 6551 patients (4704 healthy, 1345 pre-diabetes, 502 DM) in 12 different medical centers in Turkey between 2010 and 2016 were examined to understand the effectiveness of HbA1c in the diagnosis of DM. Different Roche systems were used for measuring HbA1c via the immunoturbidimetric method. The DM ROC curves revealed the diagnostic sensitivity, specificity, and AUC of 74.5%, 87.1%, and 0.866 (CI 95% 0.858–0.875), respectively, for HbA1c (at the cut-off 41 mmol/mol, 5.9%). For HbA1c at the universal diagnostic decision value of 48 mmol/mol (6.5%), the sensitivity and specificity were determined as 32.4% and 99.9%, respectively. The ROC curves for fasting plasma glucose (FPG) revealed the diagnostic sensitivity, specificity, and AUC of 71.3%, 85.3%, and 0.853 (CI 95% 0.844–0.861), respectively. However, the ROC curve results for pre-diabetes (HbA1c at the cut-off value of 39 mmol/mol, 5.7%) revealed the diagnostic sensitivity, specificity, and AUC of 45.7%, 76.4%, and 0.641, respectively. Furthermore, it was shown that the changes in HbA1c values due to gender and age had no clinical effect on the diagnosis. According to our results, it remains challenging to suggest HbA1c measurements can have a significant contribution to the FPG measurements. It was found that the sensitivity is specifically low in the assessment of the pre-diabetes data. Additionally, considering the problems associated with Hb1Ac measurements, further studies conducted in different regions by using different methods are required.
Acute kidney injury (AKI) is a worldwide health problem and defined by rapid loss of excretory fu... more Acute kidney injury (AKI) is a worldwide health problem and defined by rapid loss of excretory function of the kidney with the accumulation of metabolic end products. For effective treatment and prevent complications the early diagnosis of AKI is crucial. The current analytes used to diagnose AKI are not adequately sensitive and specific and therefore clinicians need new biomarkers. One of the new promising biomarker candidates of renal injury is cofilin-1. Previously, in our laboratory we isolated cofilin-1 in kidney preservation solution prior to transplantation and attempted to measure serum cofilin-1 in renal transplanted patients. However, cofilin-1 was not accurately measured in serum samples due to the methodological issues. In this mini-review, we summarized the current knowledge and concepts both in the literature and our experiences with cofilin-1 as a potential biomarker for the diagnosis and management of AKI.
Perchlorate, thiocyanate, and nitrate can block iodide transport at the sodium iodide symporter (... more Perchlorate, thiocyanate, and nitrate can block iodide transport at the sodium iodide symporter (NIS) and this can subsequently lead to decreased thyroid hormone production and hypothyroidism. NIS inhibitor exposure has been shown to reduce iodide uptake and thyroid hormone levels; therefore we hypothesized that maternal NIS inhibitor exposure will influence both maternal and newborn thyroid function. Spot urine samples were collected from 185 lactating mothers and evaluated for perchlorate, thiocyanate, and nitrate concentrations. Blood and colostrum samples were collected from the same participants in the first 48 h after delivery. Thyroid hormones and thyroid-related antibodies (TSH, fT3, fT4, anti-TPO, anti-Tg) were analyzed in maternal blood and perchlorate was analyzed in colostrum. Also, spot blood samples were collected from newborns ( = 185) between 48 and 72 postpartum hours for TSH measurement. Correlation analysis was performed to assess the effect of NIS inhibitors on t...
The European Federation of Clinical Chemistry and Laboratory Medicine European Biological Variati... more The European Federation of Clinical Chemistry and Laboratory Medicine European Biological Variation Study (EuBIVAS) has been established to deliver rigorously determined data describing biological variation (BV) of clinically important measurands. Here, EuBIVAS-based BV estimates of serum electrolytes, lipids, urea, uric acid, total protein, total bilirubin, direct bilirubin, and glucose, as well as their associated analytical performance specifications (APSs), are presented. Samples were drawn from 91 healthy individuals (38 male, 53 female; age range, 21-69 years) for 10 consecutive weeks at 6 European laboratories. Samples were stored at -80 °C before duplicate analysis of all samples on an ADVIA 2400 (Siemens Healthineers). Outlier and homogeneity analyses were performed, followed by CV-ANOVA on trend-corrected data, when relevant, to determine BV estimates with CIs. The within-subject BV (CV) estimates of all measurands, except for urea and LDL cholesterol, were lower than esti...
The Journal of asthma : official journal of the Association for the Care of Asthma, Jan 6, 2017
Remodeling is a crucial feature of severe asthma and may be associated with activation of the all... more Remodeling is a crucial feature of severe asthma and may be associated with activation of the allergic cascade by immunoglobulin E (IgE). Omalizumab, an anti-IgE monoclonal antibody, effectively targets the severe allergic asthma phenotype. Pregnancy-associated plasma protein-A (PAPP-A) is an insulin-like growth factor binding protein-4 (IGFBP-4) protease, increasing local insulin-like growth factor (IGF)-1 concentrations, which in turn initiating a cascade involved in the regulation of cell growth, differentiation, and proliferation in various tissues. In the present study, we evaluated the effects of omalizumab on serum PAPP-A, IGFBP-4, and IGF-1 levels in subjects with severe allergic asthma. We studied 36 asthmatic subjects and 36 healthy controls. An ultrasensitive enzyme-linked immunosorbent assay (ELISA) kit was used to measure serum PAPP-A levels, and routine commercial ELISA kits were employed to assess serum levels of IGF-1, IGFBP-4 in control subjects and asthmatic subjec...
Vitamin D and intact parathyroid hormone (iPTH) play a crucial role in calcium homeostasis and bo... more Vitamin D and intact parathyroid hormone (iPTH) play a crucial role in calcium homeostasis and bone health of children. Serum level of 25-hydroxyvitamin D (25-OHD) is considered to be the most accurate marker for vitamin D status. However, there have only been a few studies, with limited number of subjects, investigating the relationship between 25-OHD and parathyroid hormone (PTH) in children. The aim of this study was to evaluate the seasonal 25-OHD levels and its associations with intact parathyroid hormone (iPTH) in Turkish children at all pediatric ages; and then to define a critical decision threshold level for 25-OHD deficiency in Turkish children. A retrospective record review of 90,042 children, was performed on serum 25-OHD and for 3525 iPTH levels. They were measured by mass spectrometry method and by electrochemiluminescence immunoassay simultaneously. 25-OHD levels showed a sinusoidal fluctuation througout the year; being significantly higher in summer and autumn (p <...
Clinical chemistry and laboratory medicine, Jan 2, 2018
The complete blood count (CBC) is used to evaluate health status in the contexts of various clini... more The complete blood count (CBC) is used to evaluate health status in the contexts of various clinical situations such as anemia, infection, inflammation, trauma, malignancies, etc. To ensure safe clinical application of the CBC, reliable biological variation (BV) data are required. The study aim was to define the BVs of CBC parameters employing a strict protocol. Blood samples, drawn from 30 healthy subjects (17 females, 13 males) once weekly for 10 weeks, were analyzed using a Sysmex XN 3000 instrument. The data were assessed for normality, trends, outliers and variance homogeneity prior to coefficient of variation (CV)-analysis of variance (ANOVA). Sex-stratified within-subject (CVI) and between-subjects (CVG) BV estimates were determined for 21 CBC parameters. For leukocyte parameters, with the exception of lymphocytes and basophils, significant differences were found between female/male CVI estimates. The mean values of all erythrocyte-, reticulocyte- and platelet parameters diff...
Summary25 (OH) vitamin D3 (25(OH)D) and parathyroid hormone (PTH) are important regulators of cal... more Summary25 (OH) vitamin D3 (25(OH)D) and parathyroid hormone (PTH) are important regulators of calcium homeostasis. The aim of this study was to retrospectively determine the cut–off for sufficient 25(OH)D in a four-season region and the influence of age, seasons, and gender on serum 25(OH)D and PTH levels.Laboratory results of 9890 female and 2723 male individuals aged 38.8±22.1 years who had simultaneous measurements of 25(OH)D and PTH were retrospectively analyzed by statistical softwares. Serum 25(OH)D and PTH levels were measured by a mass spectrometry method and by an electrochemiluminescence immunoassay, respectively.Mean serum 25(OH)D levels showed a sinusoidal fluctuation throughout the year and were significantly (p<0.01) higher in summer and autumn. On the other hand, PTH levels were significantly higher (p<0.01) in women and showed an opposite response to seasonal effects relative to 25(OH)D. Lowest levels of 25(OH)D were detected in people aged between 20 and 40 ye...
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Papers by Mustafa Serteser