Measurement of cholesterol and triglycerides in fresh serum and dried serum after storage at different time intervals

Abstract

Background and Objectives: Non-communicable diseases (NCD) including cardiovascular diseases, diabetes, obesity, cancers, and chronic lung diseases, are growing concerns in developing countries. In a large country such as India, screening for NCD at remote corners of the country is difficult because of limited resources and technical capacity. Measurement in a good quality central laboratory would be ideal, but the cost and safety of chilled sample transportation are concerns. Transportation of samples in the form of dried blood/serum would circumvent the need for blood processing, storage, and shipment at ultralow temperatures. The collection of dried blood/serum spots on filter paper offers a powerful tool in screening programs. Dried serum spot technology offers several advantages over conventional serum assays; as it does not require separation of serum by centrifugation and allows convenient shipment of samples at low cost. Serum spot assays therefore allow a quick and convenient assessment of patients presenting cardiometabolic health risks. . In the present study, the stability of cholesterol and triglycerides in serum dried on filter paper at room temperature for different time intervals is studied. Materials and methods: 100 Samples of Patients coming to the lab for lipid investigations were selected. Blood collected by venipuncture into tubes without anticoagulant was used. Replicates of serum were spotted onto 3M Whatman paper and left at room temp for an hour for drying. Filter discs were transferred to a plastic bag, sealed and stored at room temp for different time periods . Dried blood spots were cut out with scissors and analysed on 7, 14, 21, 28 and 35 days in a Erba semiautoanalyser using commercially available kit. Results Cholesterol values in the 100 samples analyzed ranged from 102 mg/dl to 314 mg/dl.. The mean +/- standard deviation (SD) cholesterol values obtained from fresh serum was 148.33+/-30.68 mg/dl and the mean cholesterol values from corresponding dried serum was 147.86+/-30.67 mg/dl on the same day of drying and subsequently 147.59+/-30.47 (day 7) , 147.3+/-30.52 ( day14) , 146.74+/-30.62 (day 21) , 146.45+/-30.69 (day 28) and 146.41+/-30.66 (day 35). Triglyceride values in the 100 samples ranged from 86 mg/dl to 168 mg/dl. The mean +/- standard deviation (SD) triglyceride values obtained from fresh serum was 113.18 + 18.77 mg/dl and the mean cholesterol values from corresponding dried serum was 112.78 + 18.62 mg/dl on the same day of drying and subsequently 112.52 + 18.63 (day 7) , 112.35 + 18.64 ( day14) , 111.87 + 18.70 (day 21) , 111.63 + 18.72 (day 28) and 111.49 + 18.80 (day 35). A Intra class correlation coefficient of 0.98 for cholesterol and 0.99 for triglycerides was evident between dried serum spots and fresh serum. Bland–Altman plots suggest that the difference in values obtained by the two methods were within the 2 SD limits for most of the samples for Cholesterol and for Triglycerides. Less than 5% of the values were outside the 2 SD limits. Interpretation and conclusion: The comparable values between dried serum spots and serum assays supports the usage of dried blood spot sample collection method 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 blood spot assay reliable and convenient method for screening modifiable risk factors of CVD like cholesterol and Triglycerides.