Photo by Jan Björkesten
Circles punched out of dried blood samples
Researchers have found evidence to suggest that dried blood samples may sometimes be a suitable alternative to conventional blood sampling.
The team measured levels of 92 proteins in millimeter-sized circles punched out of dried blood samples.
They found that, in many cases, little happens to these proteins when they are allowed to dry.
Most of the proteins remain unaltered after 30 years, or they change only minimally.
However, the proteins can be affected by storage temperatures.
Still, the researchers believe these results suggest dried blood samples could be used more widely—for routine health checks and to set up large-scale biobanks, with patients collecting the blood samples themselves.
“[Y]ou can prick your own finger and send in a dried blood spot by post,” study author Ulf Landegren, MD, PhD, of Uppsala University in Sweden.
“[A]t a minimal cost, it will be possible to build gigantic biobanks of samples obtained on a routine clinical basis. This means that samples can be taken before the clinical debut of a disease to identify markers of value for early diagnosis, improving the scope for curative treatment.”
Dr Landegren and his colleagues discussed these possibilities in a paper published in Molecular and Cellular Proteomics.
The researchers analyzed dried blood samples, measuring levels of 92 proteins that are relevant in oncology. To determine the effects of long-term storage, the team examined what happens to protein detection as an effect of the drying process.
Some of the dried blood samples analyzed had been collected recently, while others had been preserved for up to 30 years in biobanks in Sweden and Denmark. These 2 biobanks keep their dried blood samples at different temperatures: the Swedish one at +4°C and the Danish one at -24°C.
The researchers also looked at wet plasma samples kept at -70°C for corresponding periods of time.
“Our conclusion is that we can measure levels of 92 proteins with very high precision and sensitivity using PEA [proximity extension assay] technology in the tiny, punched-out discs from a dried blood spot,” said study author Johan Björkesten, a doctoral student at Uppsala University.
“The actual drying process has a negligible effect on the various proteins, and the effect is reproducible, which means that it can be included in the calculation.”
The researchers did find that long-term storage affects the detectability of certain proteins more than others.
Most proteins remain completely intact after 30 years or exhibit minimal changes. However, levels of some proteins decrease so that half the quantity remains after a period of between 10 and 50 years.
The researchers also found that a relatively low storage temperature is preferable for proteins that are affected by storage.
Protein detection was less affected when dried blood samples were stored at -24°C than when they were stored at +4°C. Over the 30-year period, detectability was not affected for 34% of proteins stored at +4°C and 76% of proteins stored at -24°C.
However, storing wet plasma at -70°C preserved proteins better than dried blood sample storage at -24°C. Detectability decreased for 5% of the proteins stored wet at -70°C for 45 years, compared to 24% for proteins in dried samples stored at -24°C for 30 years.
The researchers did note, though, that this part of their analysis was complicated by some confounding factors, so this was not a clear, direct comparison between wet and dry samples.
