Biomedical Engineering Reference
In-Depth Information
1
Introduction
Dried blood spots (DBS) were introduced by Guthrie and Susie [
1
] in 1963 as a
sampling technique for screening metabolic diseases of neonates in a large popu-
lation. The applications of DBS have been reviewed recently by two research
groups [
2,
3
]. DBS offers many advantages over conventional sampling tech-
niques for blood, plasma, or serum collection [
4
]. These advantages can be sum-
marized as less invasive sampling, simpler storage and handling, less infection
risks through using pretreated sampling cards, and smaller sample volume [
5
] . In
addition to newborn screening, DBS has also been applied in therapeutic drug
monitoring and pharmacokinetics studies [
6-
37
]. All these applications were
based on the sole assumption in which the same size punches from dried blood
spots on sampling paper/cards absorb the same volume of blood regardless of any
differences among test subject genders, matrix lots, disease states, or blood vis-
cosity. Sampling paper/cards are the ultimate carrier of the target analyte in blood.
There have been a few types of sampling paper/cards available specifically
designed for this purpose. Hundred percent cotton filter paper, marketed under the
names of plain filter paper, Guthrie paper, Shleicher & Scheull 903, S & S903,
Whatman 903, or No. 545 filter paper over different times or by different vendors,
has been used successfully over the last few decades for newborn screening.
However, inconsistent extraction was randomly observed between low and high
concentration spots via quality controls, but also between fresh and aged blood
spots [
16,
25
]. Paper pretreatment with chemicals [
25
] and via impregnation [
36
]
provided a solution for unbalanced extraction recoveries. The paper pretreatment
via impregnation of other chemicals is commercialized as multiple products such
as Whatman FTA series for lysing cells, denaturing proteins, and preventing the
growth of microorganisms. FTA series (i.e., FTA, FTA Elute, DMPK cards) was
designed with proprietary formulations so that the paper/cards could be used in
the bioanalysis of drug metabolism and pharmacokinetic samples for better accu-
racy over plain filter paper. Although other factors such as hematocrit [
37
] , blood
volume, and blood distribution have direct impacts on the accuracy and precision
of bioanalytical methods on DBS, in this article we present only the potential
impact of the sampling paper/cards as we have learned from implementing DBS-
LC-MS in our laboratory.
2
Experiments
2.1
Chemicals
Six proprietary compounds were from Abbott Laboratories (North Chicago, IL,
USA). Two stable isotope labeled compounds and additional proprietary com-
pound from Abbott Laboratories were used as the internal standards. HPLC grade
