Utility of Dried Serum Spots for Sample Storage and Estimation of Cholesterol Levels

Abstract

Introduction : Dyslipidaemi as are one of the major modifiable risk factors for coronary heart disease. Globally, 80% of deaths due to cardiovascular diseases occur in low and middle in come countries. Screening by biochemical analysis in a good quality central laboratory would be ideal, but the cost and safety of sample transportation in cold chain are concerns in a large developing country like India with limited resources. Transportation of samples in the form of dried serum spots would ease blood processing, storage, and transport. In the present study, the stability of cholesterol in dried serum spots on filter paper at room temperature for different time intervals was studied.

Material & Methods: 100 samples in the laboratory of a tertiary care hospital of south India were analysed.  An aliquot of each serum sample was analyzed immediately and exact 10-[micro] L replicates of the samples were spotted onto 3M Whatman filter paper. After drying, one aliquot was eluted and analyzed on the day of collection. The remaining filter discs were kept in sealed plastic bags and analysed on 7, 14, 21, 28 and 35 days.

Results: Mean and Standard deviation for Cholesterol levels were 147.24+/- 30.62. Bland Altman plots showed the differences in values obtained from fresh and dried serum, within two standard deviations for most of the samples. An Intra class correlation coefficient of 0.98 was evident between dried serum spots and fresh serum. Our Study has given the values of Cholesterol from Dried serum spots within medically allowable error .

Discussion : Dried serum spot collection has advantages compared to conventional blood draws, such as less sample volume is required, convenience of repeating measurements, and easy sample storage and transport. The comparable values between dried serum spots and conventional serum assays supports its usage as an alternative when conventional venous blood draw facilities are not available or accessible. However, precision and accuracy of the results can be improved by opting standard spotting methods and proper storage. The stability, efficient recovery, and excellent correlation with fresh serum samples makes the dried spot assay reliable and convenient method for screening risk factors like cholesterol. Screening patients to identify these risk factors can help prevent cardiovascular diseases and Type 2 Diabetes Mellitus by providing information for early intervention and treatment.