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Investigation of alkaline phosphatase discrepancies on the Roche cobas® pro: causes, solutions, and workflow
I Seiden-Long1, K Niemann2, K Moses2
1Alberta Precision Laboratories, Canada; University of Calgary, Cumming School of Medicine, Department of Pathology and Laboratory Medicine, Canada.
Clinical Biochemistry
|April 5, 2026
Summary
High alkaline phosphatase (ALP) discrepancies on Roche Cobas® pro analyzers were investigated. An automated workflow combining dilution and respinning effectively eliminated these spurious results, improving lab accuracy.
Area of Science:
- Clinical Chemistry
- Laboratory Medicine
- Analytical Biochemistry
Background:
- High frequency of delta check flags for alkaline phosphatase (ALP) indicated non-reproducible discrepancies on Roche Cobas® pro analyzers.
- Multi-site studies were initiated to characterize these ALP discrepancies and identify root causes.
Purpose of the Study:
- To characterize the frequency and root causes of spurious alkaline phosphatase (ALP) discrepancies observed on Roche Cobas® pro analyzers.
- To develop and evaluate mitigation strategies for these ALP measurement errors.
Main Methods:
- Alkaline phosphatase (ALP) was measured in duplicate using lithium heparin plasma separator tubes (PST) on Roche cobas® pro c503 and cobas® 8000 c702 analyzers.
- Discrepancies were defined by results exceeding total allowable error (TEa). Three protocols were evaluated: repeat centrifugation, alternative tube types (BD Barricor), and on-board dilutions.
Main Results:
- 563 ALP discrepancies were identified on c503 analyzers, with none on the c702. Discrepancy rates varied by site (0.04-1.51%).
- Repeat centrifugation reduced discrepancies by 99.5%. BD Barricor tubes reduced them by 81.4%. On-board dilutions reduced discrepancies by 95.4%.
- An automated protocol combining dilution with respinning completely eliminated ALP discrepancies.
Conclusions:
- ALP discrepancies were specific to certain Roche Cobas® pro c503 analyzers, suggesting susceptibility to preanalytical plasma contaminants.
- Respinning, dilution, and alternative tube types indicated preanalytical error sources.
- An automated workflow integrating on-board dilution and centrifugation effectively mitigated ALP discrepancies, offering a cost-effective and reliable solution.
