Impact of ISO/TS 20914-based measurement uncertainty on HbA1c diagnostic classification: A real-world comparison of two analytical systems
In brief
Calibration uncertainty put more HbA1c results inside uncertainty bands at three cutoffs
In 30,791 routine tests, including calibration and traceability uncertainty increased the share of results within uncertainty bands in three of four system and threshold analyses. For one system at the 5.7% cutoff, the share rose from 39% to 48%; there was no change at the other system's 5.7% cutoff. The findings highlight how assay and threshold shape interpretation near diagnostic limits.
- Journal
- Clinica chimica acta; international journal of clinical chemistry (Q1)
- Published
- 4 October 2026
- Study design
- Retrospective cohort
- Evidence level
- Level 3, Low (CEBM 3b)
- Authors
- Ahmet Burak Gürpınar, Canan Karadağ, Muzaffer Katar
- PMID
- 42830178
- DOI
- 10.1016/j.cca.2026.122868
Why clinicians should know about it
- Picked for Biochemistry (medical) (top studies of the week, 11 October 2026): HbA1c measurement uncertainty impacts diagnostic classification
Abstract
OBJECTIVES: HbA1c is interpreted using fixed clinical decision limits, but measurement uncertainty (MU) may affect analytical interpretation of results near these thresholds. This study estimated ISO/TS 20914-based MU for two HbA1c analytical systems and evaluated the patient-level impact of including calibration- and traceability-related uncertainty. METHODS: In this retrospective two-center study, 30,791 routine HbA1c results from independent patient cohorts were obtained using Roche cobas c501 and Adams HA-8180 V systems. MU was estimated from within-laboratory reproducibility uncertainty (uRw), calibration- and traceability-related standard uncertainty (ucal), and uncertainty associated with the IFCC-to-NGSP master equation (uME). Decision-limit-specific coverage intervals were calculated at 5.7% and 6.5% HbA1c using a calibration-included MU model (uRw, ucal, and uME) and a calibration-excluded sensitivity analysis (uRw and uME). Patient-level reclassification was evaluated using McNemar's test with Holm adjustment. RESULTS: Roche showed higher uRw than Adams, whereas ucal was higher for Roche (2.35% vs 1.75%). Calibration-included standard MU was 3.77% and 3.76% for Roche at 5.7% and 6.5%, respectively, and 2.47% and 2.45% for Adams. Inclusion of ucal increased the proportion of results within MU coverage intervals from 38.81% to 48.05% for Roche at 5.7%, from 15.45% to 20.76% at 6.5%, and from 10.69% to 15.90% for Adams at 6.5% (all Holm-adjusted P < 0.001). No reclassification occurred for Adams at 5.7%. CONCLUSIONS: Inclusion of calibration- and traceability-related uncertainty materially affected analytical interpretation around clinical decision limits in three of four system-threshold analyses. Patient-level impact depended on both MU budget composition and the distribution of results around the relevant threshold.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.