Evaluation of a next generation direct whole blood enzymatic assay for hemoglobin A1c on the ARCHITECT c8000 chemistry system.

BACKGROUND: The utility of HbA1c for the diagnosis of type 2 diabetes requires an accurate, precise and robust test measurement system. Currently, immunoassay and HPLC are the most popular methods for HbA1c quantification, noting however the limitations associated with some platforms, such as imprecision or interference from common hemoglobin variants. Abbott Diagnostics has introduced a fully automated direct enzymatic method for the quantification of HbA1c from whole blood on the ARCHITECT chemistry system. METHODS: Here we completed a method evaluation of the ARCHITECT HbA1c enzymatic assay for imprecision, accuracy, method comparison, interference from hemoglobin variants and specimen stability. This was completed at three independent clinical laboratories in North America and Europe. RESULTS: The total imprecision ranged from 0.5% to 2.2% CV with low and high level control materials. Around the diagnostic cut-off of 48 mmol/mol, the total imprecision was 0.6% CV. Mean bias using reference samples from IFCC and CAP ranged from -1.1 to 1.0 mmol/mol. The enzymatic assay also showed excellent agreement with HPLC methods, with slopes of 1.01 and correlation coefficients ranging from 0.984 to 0.996 compared to Menarini Adams HA-8160, Bio-Rad Variant II and Variant II Turbo instruments. Finally, no significant effect was observed for erythrocyte sedimentation or interference from common hemoglobin variants in patient samples containing heterozygous HbS, HbC, HbD, HbE, and up to 10% HbF. CONCLUSIONS: The ARCHITECT enzymatic assay for HbA1c is a robust and fully automated method that meets the performance requirements to support the diagnosis of type 2 diabetes.

A patient with a high concentration of B-type natriuretic peptide (BNP) but normal N-terminal proBNP concentration: A case report.

OBJECTIVES: A 61-year-old female presented with non-typical chest pain. High levels of plasma B-type natriuretic peptide (BNP; result 3188 ng/L, reference range<100 ng/L, method Abbott Architect) were found, although she did not exhibit dyspnoea or other clinical symptoms of heart failure. Echocardiography did not provide an explanation for the elevated BNP concentrations. In follow-up, the chest pain complaints disappeared but BNP remained elevated at the same levels. The serum N-terminal proBNP (NT-proBNP) concentration appeared to be normal. This led us to doubt the accuracy of the BNP values. DESIGN AND METHODS: Possible interference was investigated with BNP and NT-proBNP assays from different manufacturers, various (auto)antibody tests, sample dilutions, addition of mouse serum and polyethylene glycol (PEG) precipitation. RESULTS: BNP and NT-proBNP concentrations were normal when measured using all other (NT-pro)BNP immunoassays. Serial dilutions of sample and addition of mouse serum did not alter the results. Specific (auto)antibody tests were negative. However, PEG precipitation showed the presence of a high molecular weight immunoreactive protein. CONCLUSIONS: We report a false positive BNP result possibly caused by a macro-BNP. This macro-BNP was only immunoreactive in the Abbott Architect BNP immunoassay. Clinicians should be aware of analytical interference when BNP results are constantly elevated in the absence of (non)cardiac causes.

Validation study of Axis-Shield carbohydrate-deficient transferrin (CDT) on ARCHITECT chemistry analyzer.

BACKGROUND: Carbohydrate-deficient transferrin (CDT) is a biochemical marker used for identifying chronic alcohol intake. We developed and validated an ARCHITECT c8000 (Abbott) instrument application for the Axis-Shield %CDT immunoassay. METHODS: Standard CLSI (Clinical and Laboratory Standards Institute) evaluation protocols were performed. RESULTS: The Axis-Shield %CDT ARCHITECT method was standardized against the Axis-Shield %CDT microtiter test by linear regression analysis (n=50 mean of duplicate, R=0.996). Method comparison by Deming regression revealed a slope of 1.01 and an intercept of -0.03 with Axis-Shield %CDT microtiter test (n=50 in duplicate, R=0.995), and a slope of 0.82 and an intercept of 1.09 with HPLC method (n=47 in duplicate, R=0.990) as the candidate IFCC (International Federation of Clinical Chemistry and Laboratory Medicine) reference method. The predicted medical decision points (MDPs) are both 2.6% and equal the MDP that is generally used for the Axis-Shield %CDT tests. Precision derived from pooled patient sera (low level) and commercially available control material (high level) was excellent. Total variation was 3.2% and 1.8%, respectively. CONCLUSIONS: The Axis-Shield %CDT ARCHITECT method, as one of the first Axis-Shield applications on a large-scale analyzer, is a reliable test for routine %CDT analysis providing precise and well-standardized %CDT results.