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Specimen collection on filter cards is a convenient way of sample
collection. It enables sample collection in a population where
intensive venous sampling is unethical or impossible (e.g. neonates).
Moreover, it enables non-hospital based sampling and sample shipment
is cheap as no special requirements are necessary for worldwide
Routinely, after a fingerprick with a disposable lancet, a drop of
blood is collected on a filter paper card (whatman 903 collection
cards, also in use as guthrie cards). The blood equally distributes
over the paper (twice the volume, results in twice the area). So if
you always punch out the same amount from the card, you'll always have
the same amount of sample.
Searching pubmed isn't that hard, if you'll look for dried blood spot
analysis some assays can be found.
Just to correct Dr.Srinivas Rao who claimed that "You need to soak the
filter paper in a proper solution
(probably a buffer solution of appropriate pH), homogenize it using
tissue homogenizer, sonicate for few minutes then extract with a
proper solvent (for ex. Liquid Liquid Extraction method) and anlyze
it". Most extractions from dried blood spots are direct extractions in
either an organic solvent or a mixture of water and organic solvents
without the need for homogenizing and buffering, but ofcourse this
depends on the drug.
Rob ter Heine
Rob ter Heine, MSc, PharmD
Department of Pharmacology, Slotervaart Hospital
Amsterdam, The Netherlands
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