Abstract
Background:
Most of the factors causing preanalytical and analytical variation in ammonia measurement have been identified. Biological variation data for ammonia is still lacking. We therefore estimated the components of biological variation (within-subject=CVI and between-subject=CVG), reference change value (RCV) and quality specifications for ammonia in a group of healthy individuals using fresh and frozen plasma samples.
Methods:
Blood samples from 20 healthy subjects were collected in K2EDTA tubes daily over a period of 4 consecutive days from each subject. Each plasma sample was split into two aliquots; one was immediately analyzed as the samples were collected and the other was stored –80 °C until testing at the end of the collection period and analyzed at once in one analytical run. All samples were analyzed in duplicate. Estimations were calculated according to Fraser and Harris methods.
Results:
CVI value for fresh samples (13.78%) was significantly lower than that in frozen samples (18.91%) (p<0.001). However, there was no statistically significant difference in CVG values between fresh (16.91%) and frozen (18.43%) samples (p=0.570). The index of individuality did not exceed 1.4 for fresh and frozen samples. The estimated RCVs were high for both fresh and frozen samples (43.37% and 56.85%, respectively). Quality specifications were established.
Conclusions:
The present study for the first time described the components of biological variation for ammonia in healthy individuals. These data regarding biological variation of ammonia could be useful for a better evaluation of ammonia test results in clinical interpretation and for determining quality specifications based on biological variation.
Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: None declared.
Employment or leadership: None declared.
Honorarium: None declared.
Competing interests: The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.
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