Specifications for trueness and precision of a reference measurement system for serum/plasma 25-hydroxyvitamin D analysis.
BACKGROUND
The divergence in analytical quality of serum/plasma 25-hydroxy-vitamin D analysis calls for defining specifications for a reference measurement system.


METHODS
Fundamentally, in a reference measurement system, there should be a relationship between the analytical specifications for higher- (reference) and lower-order (routine) measurements. Therefore, when setting specifications, we started with limits for routine imprecision (CV(rou)) and bias (B(rou)) using 4 models: (1) the misclassifications in diagnosis, (2) biological variation data (reference interval (RI) and monitoring), (3) expert recommendations, and (4) state-of-the-art performance. Then, we used the derived goals to tailor those for reference measurements and certified reference materials (CRMs) for calibration by setting the limits for CV(ref) at 0.5 CV(rou), B(ref) at 0.33 B(rou)(,) max. uncertainty (U(max)) at 0.33 B(ref).


RESULTS
The established specifications ranged between CV(rou)<or=22%, B(rou)<or=10%, CV(ref)<or=11%, B(ref)<or=3.3%, U(max) 1.1% (model 3) and CV(rou)<or=4%, B(rou)<or=2.6%, CV(ref)<or=2%, B(ref)<or=0.9%, U(max) 0.3% (model 2, monitoring).


CONCLUSIONS
Model 2 (monitoring) gave the most stringent goals, model 3, the most liberal ones. Accounting for state-of-the-art performance and certification capabilities, we used model 2 (RI) to recommend achievable goals: for routine testing, CV(rou)<or=10%, B(rou)<or=5%, for reference measurements, CV(ref)<or=5%, B(ref)<or=1.7%, and for CRMs, U(max) 0.6%.
Stöckl
Dietmar
D
Laboratory for Analytical Chemistry, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium.
Sluss
Patrick M
PM
Thienpont
Linda M
LM
D000293:Adolescent; D000368:Aged; D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards*; D002648:Child; D005260:Female; D006801:Humans; D007753:Laboratories; D008297:Male; D012015:Reference Standards; D012680:Sensitivity and Specificity; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
D014807:Vitamin D; C104450:25-hydroxyvitamin D