scholarly journals Challenges in vitamin D analysis / Izazovi u analizi vitamina D

2012 ◽  
Vol 31 (4) ◽  
pp. 326-332 ◽  
Author(s):  
Mustafa Serteser ◽  
Abdurrahman Coskun ◽  
Tamer C Inal ◽  
Ibrahim Unsal
Keyword(s):  
Vitamin D ◽  
Clinical Laboratory ◽  
Direct Detection ◽  
Reference Method ◽  
Detection Methods ◽  
Binding Assays ◽  
External Quality Assessment Scheme ◽  
Specificity And Sensitivity ◽  
Competitive Protein Binding ◽  
Phosphorus Levels

Summary Vitamin D is an important determinant for the regulation of calcium and phosphorus levels and mineralization of the bone. The most reliable indicator of vitamin D status is the measurement of plasma or serum 25OH-D concentration. Several studies reported discrepancies between the results of assays. These high variabilities in 25OH-D measurements are due to used assay technologies and lack of standardization against the reference materials. Different assays have been employed for the measurement of 25OHD levels: Competitive Protein Binding Assays, immunoassays, direct detection methods. Choosing an assay platform is important both for clinical laboratory professionals and researchers, and several factors affect this process. Recently, liquid chromatography and tandem mass spectrometry is an alternative method to traditional assays and provides higher specificity and sensitivity than many assays; therefore, it has been suggested as a candidate reference method for circulating 25OH-D3. Standardization of methods for the quantification of 25OH-D by using the human-based samples would reduce the inter-method variability. The best way for laboratories to demonstrate the accuracy of their results is by participating in the external quality assessment scheme. Standardization of the assays is also required to provide clinicians with the accurate tools to diagnose hypovitaminosis. In addition, assay-specific decision limits are needed to define appropriate thresholds of treatment.

Establishing an Accuracy Basis for the Vitamin D External Quality Assessment Scheme (DEQAS)

2017 ◽  
Vol 100 (5) ◽  
pp. 1277-1287 ◽  
Author(s):  
Carolyn Q Burdette ◽  
Johanna E Camara ◽  
Federica Nalin ◽  
Jeanita Pritchett ◽  
Lane C Sander ◽  
...  
Keyword(s):  
Vitamin D ◽  
Quality Assessment ◽  
External Quality Assessment ◽  
Measurement Procedure ◽  
Binding Assays ◽  
External Quality ◽  
External Quality Assessment Scheme ◽  
Hydroxyvitamin D ◽  
Target Values ◽  
High Concentrations

Abstract Until recently, the Vitamin D External Quality Assessment Scheme (DEQAS) assessed the performance of various assays for the determination of serum total 25-hydroxyvitamin D [25(OH)D] by using a consensus mean based on the all-laboratory trimmed mean (ALTM) of the approximately 1000 participants' results. Since October 2012, the National Institute of Standardsand Technology (NIST), as part of the Vitamin D Standardization Program, has participated in DEQAS by analyzing the quarterly serum sample sets using an isotope dilution LC-tandem MS (ID LC-MS/MS) reference measurement procedure to assign an accuracy-based target value for serum total 25(OH)D. NIST has analyzed90 DEQAS samples (18 exercises × 5 samples/exercise) to assign target values. The NIST-assigned values are compared with the ALTM and the biases assessed for various assays used by the participants, e.g., LC-MS/MS, HPLC, and several ligand-binding assays. The NIST-value assignment process and the resultsof the analyses of the 90 DEQAS samples are summarized. The absolute mean bias between the NIST-assignedvalues and the ALTM was 5.6%, with 10% of the samples having biases >10%. Benefits of the accuracy-based target values are presented, including for sample sets with high concentrations of 25(OH)D2 and 3-epi-25(OH)D3.

scholarly journals Microfluidic-based virus detection methods for respiratory diseases

2021 ◽  
Author(s):  
E. Alperay Tarim ◽  
Betul Karakuzu ◽  
Cemre Oksuz ◽  
Oyku Sarigil ◽  
Melike Kizilkaya ◽  
...  
Keyword(s):  
Direct Detection ◽  
Genetic Material ◽  
Treatment Strategies ◽  
Virus Detection ◽  
Respiratory Viruses ◽  
Detection Methods ◽  
Novel Technologies ◽  
Detection Techniques ◽  
Specificity And Sensitivity ◽  
Intact Virus

AbstractWith the recent SARS-CoV-2 outbreak, the importance of rapid and direct detection of respiratory disease viruses has been well recognized. The detection of these viruses with novel technologies is vital in timely prevention and treatment strategies for epidemics and pandemics. Respiratory viruses can be detected from saliva, swab samples, nasal fluid, and blood, and collected samples can be analyzed by various techniques. Conventional methods for virus detection are based on techniques relying on cell culture, antigen-antibody interactions, and nucleic acids. However, these methods require trained personnel as well as expensive equipment. Microfluidic technologies, on the other hand, are one of the most accurate and specific methods to directly detect respiratory tract viruses. During viral infections, the production of detectable amounts of relevant antibodies takes a few days to weeks, hampering the aim of prevention. Alternatively, nucleic acid–based methods can directly detect the virus-specific RNA or DNA region, even before the immune response. There are numerous methods to detect respiratory viruses, but direct detection techniques have higher specificity and sensitivity than other techniques. This review aims to summarize the methods and technologies developed for microfluidic-based direct detection of viruses that cause respiratory infection using different detection techniques. Microfluidics enables the use of minimal sample volumes and thereby leading to a time, cost, and labor effective operation. Microfluidic-based detection technologies provide affordable, portable, rapid, and sensitive analysis of intact virus or virus genetic material, which is very important in pandemic and epidemic events to control outbreaks with an effective diagnosis.

scholarly journals Accuracy-Based Vitamin D Survey: Six Years of Quality Improvement Guided by Proficiency Testing

2019 ◽  
Vol 143 (12) ◽  
pp. 1531-1538 ◽  
Author(s):  
Patrick Erdman ◽  
Darryl E. Palmer-Toy ◽  
Gary Horowitz ◽  
Andrew Hoofnagle
Keyword(s):  
Vitamin D ◽  
Proficiency Testing ◽  
Clinical Laboratory ◽  
Matrix Effects ◽  
Pearson Correlation ◽  
Correlation Coefficients ◽  
Reference Method ◽  
Serum Samples ◽  
Testing Program ◽  
Target Values

Context.— The goal of the College of American Pathologists Accuracy-Based Proficiency Testing Program is to promote the quality, standardization, and harmonization of clinical laboratory results through proficiency testing specimens that are free from matrix effects, have target values that are traceable to reference methods, and that probe the limitations of current methods. Objective.— To summarize the first 6 years of the Accuracy-Based Vitamin D Survey and highlight key insights from the data generated as it relates to assay performance. Design.— Accuracy-based challenges were created by using pooled human serum samples. Certain samples were derived from participants in an institutional review board–approved protocol in which vitamin D–deficient participants were treated with ergocalciferol (vitamin D2). Reference targets for the survey were set by the Centers for Disease Control and Prevention using isotope-dilution liquid chromatography–tandem mass spectrometry. Each method was compared with the reference method procedure over the course of the program (n = 43 proficiency testing samples). Results.— Linear regression versus the reference method procedure revealed proportional biases across the methods, ranging from 0.0% to 16.7%. Pearson correlation coefficients (r2) ranged from 0.902 to 0.996. Results were influenced by the concentration of 25-hydroxyvitamin D2 as well as the C-3 epimer of 25-hydroxyvitamin D3. During the 6 years, 2 manufacturers altered their assays to match the reference method procedure more closely. Conclusions.— There is considerable bias, both proportional bias and sample-specific matrix effects, affecting many assays. This ongoing accuracy-based proficiency testing program for vitamin D will provide the data needed for laboratories and manufacturers to improve their assays and thereby patient care.

scholarly journals Comparison of Four Commercially Available Point-of-Care Tests to Detect Antibodies against Canine Parvovirus in Dogs

Viruses ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 18
Author(s):  
Michèle Bergmann ◽  
Mike Holzheu ◽  
Yury Zablotski ◽  
Stephanie Speck ◽  
Uwe Truyen ◽  
...  
Keyword(s):  
Test Performance ◽  
Point Of Care ◽  
Reference Method ◽  
Canine Parvovirus ◽  
P Value ◽  
Important Indicator ◽  
Specificity And Sensitivity ◽  
Specific Pathogen ◽  
The One ◽  
Point Of Care Tests

Measuring antibodies to evaluate dogs´ immunity against canine parvovirus (CPV) is useful to avoid unnecessary re-vaccinations. The study aimed to evaluate the quality and practicability of four point-of-care (POC) tests for detection of anti-CPV antibodies. The sera of 198 client-owned and 43 specific pathogen-free (SPF) dogs were included; virus neutralization was the reference method. Specificity, sensitivity, positive and negative predictive value (PPV and NPV), and overall accuracy (OA) were calculated. Specificity was considered to be the most important indicator for POC test performance. Differences between specificity and sensitivity of POC tests in the sera of all dogs were determined by McNemar, agreement by Cohen´s kappa. Prevalence of anti-CPV antibodies in all dogs was 80% (192/241); in the subgroup of client-owned dogs, it was 97% (192/198); and in the subgroup of SPF dogs, it was 0% (0/43). FASTest® and CanTiCheck® were easiest to perform. Specificity was highest in the CanTiCheck® (overall dogs, 98%; client-owned dogs, 83%; SPF dogs, 100%) and the TiterCHEK® (overall dogs, 96%; client-owned dogs, 67%; SPF dogs, 100%); no significant differences in specificity were observed between the ImmunoComb®, the TiterCHEK®, and the CanTiCheck®. Sensitivity was highest in the FASTest® (overall dogs, 95%; client-owned dogs, 95%) and the CanTiCheck® (overall dogs, 80%; client-owned dogs, 80%); sensitivity of the FASTest® was significantly higher compared to the one of the other three tests (McNemars p-value in each comparison: <0.001). CanTiCheck® would be the POC test of choice when considering specificity and practicability. However, differences in the number of false positive results between CanTiCheck®, TiterCHEK®, and ImmunoComb® were minimal.

scholarly journals Prevalence of vitamin D level in the serum of patients living in Erbil city, Iraq, referred to private clinical laboratory and effect of age and sex on it

2018 ◽  
Vol 91 (1) ◽  
Author(s):  
Rabar M. Abdulrahman ◽  
Balen Muhsin Abdul Rahman
Keyword(s):  
Vitamin D ◽  
Clinical Laboratory ◽  
Mediterranean Country ◽  
Hydroxyvitamin D ◽  
Vitamin D Levels ◽  
Study Population ◽  
25 Hydroxyvitamin D ◽  
Country People ◽  
Effect Of Age ◽  
Age And Sex

This retrospective study aimed to determine the levels of 25- hydroxyvitamin D [25-(OH) D] in the individuals that have been referred to two laboratories (Bio Lab and King Lab) and to around 50 private side laboratories that use both Bio Lab and King Lab as a referral lab for their tests, in Erbil city, Iraq. Then show the range of deficiency and its relation with sunlight exposure, sex and age. Out of the total number of cases (N=10823), large percentage (nearly 78%) referred to both clinical laboratory based in Erbil city were found to have a deficiency in vitamin D levels, which means they had 25-(OH) D levels lower than 20 μg/L. This study found the percentage of vitamin D level in the serum of groups insufficient, deficient, adequate, optimal; intoxication were 52.8, 24.1, 11, 12 and 0.2% respectively. When the records have been compared according to gender, the results suggested that there was no difference between male and female within the study population (P>0.05), while there was difference in the grouped ages (P<0.05). Our results indicate that although Erbil is located in a Mediterranean country, people living there should periodically check their 25-(OH) D levels, in order to get appropriate supplements of vitamin D, which eventually prevents secondary chronic disease due to vitamin D deficiency.

Use of spectrophotometric reading for in vitro antifungal susceptibility testing ofAspergillusspp.

1999 ◽  
Vol 45 (10) ◽  
pp. 871-874 ◽  
Author(s):  
Eric Dannaoui ◽  
Florence Persat ◽  
Marie-France Monier ◽  
Elisabeth Borel ◽  
Marie-Antoinette Piens ◽  
...  
Keyword(s):  
Amphotericin B ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Antifungal Susceptibility ◽  
Reference Method ◽  
Antifungal Susceptibility Testing ◽  
Aspergillus Species ◽  
National Committee ◽  
Broth Microdilution Method

A comparative study of visual and spectrophotometric MIC endpoint determinations for antifungal susceptibility testing of Aspergillus species was performed. A broth microdilution method adapted from the National Committee for Clinical Laboratory Standards (NCCLS) was used for susceptibility testing of 180 clinical isolates of Aspergillus species against amphotericin B and itraconazole. MICs were determined visually and spectrophotometrically at 490 nm after 24, 48, and 72h of incubation, and MIC pairs were compared. The agreement between the two methods was 99% for amphotericin B and ranged from 95 to 98% for itraconazole. It is concluded that spectrophotometric MIC endpoint determination is a valuable alternative to the visual reference method for susceptibility testing of Aspergillus species.Key words: antifungal, susceptibility testing, Aspergillus, spectrophotometric reading.

Gold nanoparticles in the clinical laboratory: principles of preparation and applications

2012 ◽  
Vol 50 (2) ◽  
Author(s):  
Hassan M.E. Azzazy ◽  
Mai M.H. Mansour ◽  
Tamer M. Samir ◽  
Ricardo Franco
Keyword(s):  
Gold Nanoparticles ◽  
Clinical Laboratory ◽  
Sensitive Detection ◽  
Detection Methods ◽  
Practical Applications ◽  
Molecular Assays ◽  
Detection Of Biomarkers

AbstractIn order to meet the challenges of effective healthcare, the clinical laboratory is constantly striving to improve testing sensitivity while reducing the required time and cost. Gold nanoparticles (AuNPs) are proposed as one of the most promising tools to meet such goals. They have unique optophysical properties which enable sensitive detection of biomarkers, and are easily amenable to modification for use in different assay formats including immunoassays and molecular assays. Additionally, their preparation is relatively simple and their detection methods are quite versatile. AuNPs are showing substantial promise for effective practical applications and commercial utilization is already underway. This article covers the principles of preparation of AuNPs and their use for development of different diagnostic platforms.

Optimization of Automated Sample Preparation for Vitamin D Determination on a Biomek i7 Workstation

2021 ◽  
pp. 247263032110302
Author(s):  
Anna Bach ◽  
Heidi Fleischer ◽  
Bhagya Wijayawardena ◽  
Kerstin Thurow
Keyword(s):  
Vitamin D ◽  
Sample Preparation ◽  
Reference Method ◽  
Positive Pressure ◽  
Additional Risk Factor ◽  
Serum Samples ◽  
Recovery Rates ◽  
Preparation Methods ◽  
Sample Throughput ◽  
Automated Sample Preparation

Vitamin D belongs to the fat-soluble vitamins and is an integral part of bone metabolism. In the human body, a decreased vitamin D level can be an additional risk factor for diseases like cancer, diabetes, and mental diseases. As a result, an enormous increase in the demand for vitamin D testing has been observed in recent years, increasing the demand for powerful methods for vitamin D determination at the same time. Automation is the key factor in increasing sample throughput. This study compares three fully automated sample preparation methods for the determination of 25(OH)D2 and 25(OH)D3 in plasma and serum samples. Starting from a semiautomated reference method, the method is tested manually and subsequently fully automated on the Biomek i7 Workstation by integrating a centrifuge and a positive pressure extractor into the workstation. Alternatively, the centrifugation for the separation of protein aggregates and supernatant is replaced by a filter plate. Finally, the sample throughput is further increased by using phospholipid removal cartridges. The results show that phospholipid removal significantly increases the recovery rates in liquid chromatography–mass spectrometry. With the phospholipid removal cartridges, recovery rates of 97.36% for 25(OH)D2 and 102.5% for 25(OH)D3 were achieved, whereas with the automated classic automated preparation method, the recovery rates were 83.31% for 25(OH)D2 and 86.54% for 25(OH)D3. In addition to the technical evaluation, the different methods were also examined with regard to their economic efficiency. Finally, the qualitative and quantitative performance of the developed methods is benchmarked with a selected semiautomatic reference method.

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