ABSTRACT
Background: The current clinical dilemma of diabetes mellitus is prevention of micro- and macrovascular complications. These complications are directly linked to the degree of hyperglycaemia in diabetics. For long-term control of the glycaemic state, measurement of glycohaemoglobin in blood is essential, and glycohaemoglobin harmonization is encouraged for significant inter-laboratory variability. Objectives: To evaluate the performance of plasma glycosylated hemoglobin (HbA1c) assay on Primus PDQ and Bio-Rad D10 analyzers with respect to imprecision against the HbA1c goal, recovery and correlation to the HbA1c test on Cobas Integra 800 automated analyzer. Methods: PDQ employs high performance liquid chromotography (HPLC) boronate affinity chromatography. D10 uses HPLC cation-exchange chromatography. Cobas Integra 800 uses an immunoturbidimetric method. Imprecision studies were performed using patient samples and commercial control sera. Each sample was assayed 20 times and run every morning and afternoon for 5 consecutive days to evaluate between-run data. Recovery was assessed using a patient’s sample with low HbA1c level, admixed with another sample containing high HbA1c level. Comparison was made using 60 patient samples on PDQ and D10 using Cobas Integra 800 as the reference system. Ten venous samples from each group of patients with thalassaemia and uraemia were assayed for HbA1c on Cobas Integra 800, PDQ and D10. Results: The within-run coefficients of variation (CVs) on patient samples were 0.5% and 0.6% for PDQ and 1.1% and 1.3% for D10. The between-run CVs were 1.0% and 0.8% for PDQ and 0.3% and 1.2% for D10. PDQ yielded CVs of 1.1% and 0.7% for level 1 (normal) and level 2(abnormal) controls respectively while D10 demonstrated CVs of 0.5% for each level of controls. The between-run CVs for normal and abnormal controls were 1.7% and 0.8% respectively for PDQ, and 1.0% and 0.7% respectively for D10. Mean recovery for PDQ and D10 were 99.7% and 101.7% respectively. Both PDQ and D10 correlated well with Cobas Integra 800 [Cobas800]. HbA1c method by PDQ correlated well with that by D10. Conclusion: Both the HPLC systems demonstrated acceptable data, good recovery and are comparable with our current operating system (Cobas Integra 800). Both these systems appear to be satisfactory analytical alternatives to the Cobas Integra 800.
ABSTRACT
BACKGROUND: HbA1c measurement is currently routinely used to predict long term outcome of diabetes, thus playing a fundamental role in the management of diabetes. The relationship between HbA1c value and long term diabetic complications has been established by a randomised control Diabetes Control and Complications Trial (DCCT) which used high performance liquid chromatography (HPLC) as a reference method for HbA1c assay. To ensure that HbA1c results from a variety HbA1c assay methods are similar to the DCCT values, the American Diabetes Association (ADA) recommended that all laboratories should use methods certified by the National Glycohemoglobin Standardization Programme (NGSP) with interassay coefficient variation (CV) of < 5% (ideally < 3%). The International Federation of Clinical Chemistry (IFCC) working group on HbA1c standardisation has set a CV < 2.5% as a criteria for its reference laboratories. OBJECTIVES: To evaluate the performance of Arkray Adams HA-8160 HbA1c analyser which uses a cation exchange HPLC method and its correlation to HbA1c assay on Cobas Integra 800 which is an immunoturbidimetric method. METHODS: For the imprecision study, patient samples and control material of two levels were analysed on HA-8160 analyser 20 times in a single run (within-run imprecision) and twice a day on five consecutive days (between-run imprecision). For the recovery study, two samples each with high and low values were selected and mixed in ratios of 1:3, 1:1 and 3:1, and were analysed by HA-8160. Sixty samples were analysed by both Cobas Integra 800 and HA-8160 for method comparison study. Ten uraemic samples and ten thalassaemic samples were assayed on Cobas Integra 800 and HA 8160 for interference study. RESULTS: Within-run CVs were 0.6% and 0.7% for medium and high value samples respectively, 0.6% and 0.7% for low and high level controls respectively. Between-run CVs were 0.5% and 0.4% for medium and high value samples respectively, 0.5% and 0.6% for low and high level controls respectively. The mean recovery was 100.1%. A good correlation between the 2 methods (Adams = 1.00 Cobas - 0.11, r = 0.98) was observed. CONCLUSIONS: The Akray Adams HA-8160 HbA1c analyser performed within the target CV of < 2.5% and showed a good correlation with the Cobas Integra 800.