Effects of spot size on biomarker levels of field-collected dried blood spots: A new algorithm for exact dried blood spot size measurement

A dried sweat spot paper (DSSP) method based on novel mass spectrometry probe labeling for detection and resolution of DL-lactate enantiomers as potential biomarkers for diabetes mellitus

BACKGROUND

Human sweat can be collected non-invasively with low infectivity; however, its application as a determination method has been challenged due to the presence of trace amounts of chiral metabolites. Moreover, its application as a biological fluid for disease diagnosis has not been previously reported. In this study, the human dried sweat spot paper (DSSP) method was proposed for the derivatization of a novel mass spectrometric chiral probe, N-[1-Oxo-5-(triphenylphosphonium) pentyl]-(S)-3-aminopyrrolidine (OTPA), determination and resolution of DL-lactic acid (DL-LA) enantiomers in human elbow sweat.

RESULTS

The methodological validation revealed the resolution (Rs) as 1.78, the limit of detection (S/N = 3) as 20.83 fmol, good linearity (R2 ≥ 0.9996), and the intra-day and intra-day stability with RSD ranging from 0.53 to 10.85 %, while the average recovery rate of D-LA and L-LA were 104.00 % ± 4.68 % and 107.41 % ± 8.34 %, respectively, with high accuracy. In addition, the method was applied for the determination of DL-LA in the sweat on elbow of 10 healthy volunteers and 30 diabetic patients. The results demonstrated that the D/L ratio and L/D ratio were significantly different (p < 0.0001). In addition, a moderate positive linear correlation between the D/L-LA ratio in human sweat and fasting blood glucose level (r = 0.7744, p < 0.0001) was observed, thereby suggesting that the D/L ratio of lactate in human sweat correlate the glucose level in human fasting blood.

SIGNIFICANCE AND NOVELTY

The D/L lactate ratio in human sweat could be used as a potential biomarker for diabetes screening. The method can be used to screen for diabetes by providing a dry sweat paper to test equipment and has the potential to be a non-invasive early-warning diagnostic tool for diabetes.

Dried blood spot based biomarkers in the Health and Retirement Study: 2006 to 2016

INTRODUCTION

The Health and Retirement Study (HRS) has collected biomarker data over multiple waves. Such data can help improve our understanding of health changes in individuals and the causal pathways related to health. There are, however, technical challenges to using the HRS dried blood spots (DBS) biomarker data due to changes over time in assay protocols, platforms, and laboratories. We provide technical and summary information on biological indicators collected as part of the HRS from 2006 to 2016 that should be helpful to users of the data.

METHODS

We describe the opportunities and challenges provided by the HRS DBS data as well as insights provided by the data. The HRS collected DBS from its nationally representative sample of respondents 51 years of age or older from 2006 to 2016. DBS-based biomarkers were collected from half the sample in 2006, 2010, and 2014, and from the other half of the sample in 2008, 2012, and 2016. These DBS specimens were used to assay total and HDL cholesterol, glycosylated hemoglobin, C-reactive protein, and cystatin C from 2006 to 2016, and Interleukin 6 was added in 2014/2016. Samples included approximately 6000 individuals at each wave, and completion rates ranged from 81% to 90%. HRS transformed DBS values into venous blood equivalents to make them more comparable to those of the whole blood-based assays collected in most other studies and to facilitate longitudinal analysis.

RESULTS

Distribution of changes over time by age shows that total cholesterol levels decreased for each age, while HbA1c levels increased. Cystatin C shows a clear age gradient, but a number of other markers do not. Non-Hispanic Black persons and Hispanic respondents have a higher incidence of risk levels of each biomarker except for CRP among non-Hispanic Black older persons.

CONCLUSION

These public-use DBS data provide analysis opportunities that can be used to improve our understanding of health change with age in both populations and among individuals.

Assessment of circulating apoE4 levels from dried blood spot samples in a large survey setting

INTRODUCTION

The apolipoprotein E (APOE) ε4 allele is associated with high risk for Alzheimer's disease. It is unclear whether individual levels of the circulating apoE4 protein in ε4 carriers confer additional risk. Measuring apoE4 protein levels from dried blood spots (DBS) has the potential to provide information on genetic status as well as circulating levels and to include these measures in large survey settings.

METHODS

We developed a multiplex immunoassay to detect apoE4 protein levels in DBS from 15,974 participants, aged 50+ from Wave 6 of the Survey of Health, Ageing and Retirement in Europe (SHARE).

RESULTS

The apoE4 protein signal was presented in two separable distributions. One distribution corresponded to carriers of at least one copy of the ε4 allele. Fieldwork cofounders affected protein levels but did not explain individual differences.

DISCUSSION

Future research should investigate how genotype and apoE4 level interact with lifestyle and other variables to impact cognitive aging.