Challenges of In Vitro Glycation when Producing Blood Materials for Hemoglobin A1C Immunoassays.

BACKGROUND: Blood materials are essential for quality control and assurance of hemoglobin A1C (HbA1C) measurements. This study presents an optimal condition for in vitro glycation to prepare blood materials for HbA1C with desired high HbA1C content and commutable with two immunoassays. METHODS: Washed erythrocytes were adjusted to a hematocrit (Hct) of 50 - 55% and glycated in vitro at 37°C for up to 120 hours with various concentrations of D-glucose in phosphate buffer saline to prepare blood materials for HbA1C. After glycation in each condition, glycation of blood material was inhibited and HbA1C level was monitored. The HbA1c in blood materials from in vitro glycation was compared in terms of stability and commutability with blood materials from other preparation methods. RESULTS: Incubation of erythrocytes with 400 mM D-glucose for 15 hours at 37°C resulted in a significant increase (p < 0.001) of HbA1c in blood materials by at least 40% with a remaining Hct between 38% to 42%. Hemoglobin A1C in blood materials was stable at 3.8 ± 0.8°C for 70 days and during transport for 3 days (temperature ranges from 8.1 to 23.5°C), after inhibition by glucose concentration solution. Hemoglobin A1C values in blood materials from in vitro glycation were commutable between enzymatic and turbidimetric immunoassay. CONCLUSIONS: An optimal condition for in vitro glycation by incubation of erythrocytes with 400 mM D-glucose for 15 hours at 37 °C was able to generate HbA1C material with intact erythrocytes that is sufficiently stable and commutable between enzymatic and turbidimetric immunoassay. Therefore, this condition is suitable for the preparation of blood material for HbA1C immunoassays.

Novel potential diagnostic test for Mycobacterium tuberculosis complex using combined immunomagnetic separation (IMS) and PCR-CTPP.

AIMS: To exploit immunomagnetic separation combined with PCR with confronting two-pair primers (IMS-PCR-CTPP) as a rapid method for detection of Mycobacterium tuberculosis complex (MTC) and identification of Mycobacterium bovis from sputum specimens. METHODS AND RESULTS: Monoclonal antibody (mAb) against the mycobacterial antigen, 85B (Ag85B), was coupled with magnetic particles for specific immunomagnetic separation (IMS) of Mycobacterium spp. Immunofluorescence assay indicated the capability of mAb to bind to Ag85B in both the recombinant and the native form. The IMS combined with PCR-CTPP targeting the mycobacterial lep B gene was further implemented using 133 sputum samples with acid-fast bacilli grading from negative to 3+. The results showed the sensitivity and specificity of IMS-PCR-CTPP vs gold standard culture method were 89·9 and 88·6% respectively. CONCLUSIONS: The IMS-PCR-CTPP method shortens the time for tuberculosis (TB) diagnosis from months to a day. This method is also suitable for investigation of MTC and epidemiological study of Myco. bovis in sputum specimens. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first report emphasizing the combination of IMS and PCR-CTPP for the detection of MTC and simultaneous identification of Myco. bovis from sputum. It could be used for TB diagnosis in resource-limited countries with high TB burden.