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Paper-based dried blood spot sampling for HbA1c screening with ion-exchange chromatography
Author
Low, Jackson Kwee Hiang
Supervisor
Wong, Ka Lun
Tan, Swee Ngin
Abstract
Glucose and glycated haemoglobin (HbA1c) are commonly measured as biomarkers in evaluating a patient’s diabetic status. However, glucose concentration continually fluctuates throughout the day and is affected by numerous factors, such as medication, exercise, stress, and food ingestion. Therefore, to avoid misdiagnosis of diabetes, fasting glucose level is required. In contrast, the concentration of HbA1c is an indication of average glucose in the blood over preceding 8-12 weeks. It is stable and does not require fasting hence blood can be sampled at any time of the day. Current methods employed in hospitals are typically immunoassay and chromatographic based. HbA1c is assayed from fresh venous blood which requires the patient to make a trip to outpatient facilities to have their blood drawn. Home-blood sampling would solve the problem but sending whole blood samples is inconvenient and would pose as a biohazard to the public. Also, sample integrity of whole blood samples would be compromised during transportation from home to the clinical laboratory. The concept of dried blood spot (DBS) sampling, i.e. using a cellulose pad to absorb capillary blood and be dried in open air, simplifies the collection and transportation of blood samples. DBS is already approved for mailing and can be safely manipulated and stored in an analytical lab. However, haemoglobin may undergo alterations during the drying and storing process which requires special treatment of either the paper or extractant. This project aims to study the feasibility of analyzing HbA1c from DBS through ionexchange chromatography. HbA1c values have been compared between liquid whole blood and DBS. Different DBS sampling variables such as HbA1c stability, stabilizing reagents, types of extractants, extraction protocols and humidity have been investigated. The %HbA1c in blood can be quantified from DBS samples using commercial cation-exchange chromatograph. The %HbA1c values of the DBSs have been found to increase during the drying process with time. The elevated %HbA1c values of DBSs could be due to positive error caused by the interferents formed during blood oxidation. Moisture and light have been determined to be the main factors that may accelerate the oxidation of the blood samples during DBS sampling. Among all the reagents tested, cysteine has been found to be the best candidate that can minimise the blood oxidation and hence reducing the positive error of DBS HbA1c quantification by ion-exchange chromatography.
Date Issued
2018
Call Number
RB45 Low
Date Submitted
2018