The effect of acidification and oxalate concentration on urine calcium measurements in EQAS materials and patient samples

2012 ◽  
Vol 50 (2) ◽  
Author(s):  
Adriaan J. van Gammeren ◽  
Corrie van Haperen ◽  
Aldy W.H.M. Kuypers
Keyword(s):  
Calcium Oxalate ◽  
Quality Assessment ◽  
Calcium Level ◽  
External Quality Assessment ◽  
Urine Samples ◽  
Sodium Oxalate ◽  
Urine Calcium ◽  
External Quality ◽  
External Quality Assessment Scheme ◽  
Before And After

AbstractAn increase in urine calcium compared to the consensus value was observed in some urine samples of the Dutch External Quality Assessment Scheme (EQAS). It appeared that the increase was due to the addition of oxalate by the EQAS organizers and preanalytical acidification of the samples by some of the participants. Because of this observation, the effect of urine acidification on urine calcium level in EQAS and patient samples with added oxalate was investigated.Twenty-four EQAS urine samples and 20 patient urine samples were subject to recovery measurements of urine calcium before and after addition of sodium oxalate and acidification.Differences in urine calcium between acidified and non-acidified samples up to 30.9% have been observed in EQAS samples with added oxalate. Patient samples show differences up to 80%. Differences between acidified and non-acidified samples are minimal for low calcium oxalate levels but increase with higher levels. Samples without added oxalate show equal urine calcium results between acidified and non-acidified samples.Urine calcium results are decreased in non-acidified samples with an excess of oxalate. In case of hyperoxaluria, acidification of patient urine collections and EQAS samples is recommended for correct urine calcium values.

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.

Precision and accuracy of commercial assays for vancomycin therapeutic drug monitoring: evaluation based on external quality assessment scheme

2020 ◽  
Author(s):  
Chao-Yang Chen ◽  
Meng-Ya Li ◽  
Ling-Yun Ma ◽  
Xing-Yu Zhai ◽  
Dao-Huang Luo ◽  
...  
Keyword(s):  
Serum Concentration ◽  
Quality Assessment ◽  
Bacterial Infections ◽  
External Quality Assessment ◽  
Detection Methods ◽  
Therapeutic Drug ◽  
External Quality ◽  
External Quality Assessment Scheme ◽  
Percentage Difference ◽  
Precision And Accuracy

Abstract Background Vancomycin remains a mainstay of the treatment of Gram-positive bacterial infections. It is crucial to accurately determine vancomycin serum concentration for adequate dose adjustment. Objectives To evaluate the precision and accuracy of commercial assay techniques for vancomycin concentration and to assess the comparability of vancomycin detection methods in Chinese laboratories. Methods Human serum samples spiked with known concentrations of vancomycin were provided to laboratories participating in the external quality assessment scheme (EQAS). Assay methods included chemiluminescence, enzyme immunoassay (EIA) and so on. The dispersion of the measurements was analysed and the robust coefficient of variation (rCV), relative percentage difference (RPD) and satisfactory rate for method groups were calculated. Moreover, performance of the Chinese laboratories was assessed. Results A total of 657 results from 75 laboratories were collected, including 84 samples from 10 Chinese laboratories. The median rCV, median RPD and satisfactory rates classified by methods ranged from 1.85% to 15.87%, −14.75% to 13.34% and 94.59% to 100.00%, respectively. Significant differences were seen in precision, between kinetic interaction of microparticles in solution (KIMS) and other methods, and in accuracy, between enzyme-multiplied immunoassay technique (EMIT), fluorescence polarization immunoassay (FPIA) and other techniques. Vancomycin detection in China mainly depended on the chemiluminescence and EMIT methods, which tended to result in lower measurements. Conclusions Although almost all assays in this study achieved an acceptable performance for vancomycin serum concentration monitoring, obvious inconsistencies between methods were still observed. Chinese laboratories were more likely to underestimate vancomycin concentrations. Thus, recognizing inconsistencies between methods and regular participation in vancomycin EQAS are essential.

ORALVEQ: External quality assessment scheme of drugs of abuse in oral fluid

2008 ◽  
Vol 182 (1-3) ◽  
pp. 35-40 ◽  
Author(s):  
M. Ventura ◽  
R. Ventura ◽  
S. Pichini ◽  
S. Leal ◽  
P. Zuccaro ◽  
...  
Keyword(s):  
Quality Assessment ◽  
Oral Fluid ◽  
Drugs Of Abuse ◽  
External Quality Assessment ◽  
External Quality ◽  
External Quality Assessment Scheme
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