Diagnosing diabetes mellitus: performance of hemoglobin A1c point-of-care instruments in general practice offices.

BACKGROUND: Hemoglobin A1c (Hb A1c) measurement by hospital laboratory instruments, but not by point-of-care (POC) instruments, has been recommended for use to diagnose diabetes mellitus. We evaluated results from 13 Hb A1c external quality assurance (EQA) surveys over a 6-year period in Norway, from both POC instruments used in general practice (GP) offices and instruments in hospital laboratories, against the analytical quality specifications recommended for use of Hb A1c to diagnose diabetes mellitus. METHODS: All GP offices (n = 1288) and hospital laboratories (n = 52) measuring Hb A1c in Norway participated in the EQA survey. The percentage of participants that performed measurements within the quality specifications was calculated. Pooled within-laboratory CVs were estimated for the Afinion, DCA 2000, DCA 2000+, DCA Vantage(TM), and Nycocard Hb A1c Reader instruments and for hospital laboratory instruments. RESULTS: Between 60% to 90% of Afinion and DCA users and hospital laboratories performed Hb A1c measurements within the quality specifications for both trueness (6.0%) and imprecision (CV ≤2.0%) at 2 levels in each EQA survey. The pooled within-laboratory CVs for the Afinion and DCA instruments and hospital laboratories were below the recommended limit of 2.0% for most of the surveys. CONCLUSIONS: A large proportion of GP offices using Afinion and DCA POC instruments to measure Hb A1c fulfill the analytical quality specifications for diagnosing diabetes mellitus, and these instruments demonstrate analytical quality comparable to that of hospital laboratory instruments. When GP offices participate in a stringent quality assurance program and generate Hb A1c measurements that meet analytical quality specifications, these measurements can be recommended for use to diagnose diabetes mellitus.