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DBS Knowledge Library

Explore the various applications and resources for HemaSpotTM  technology.  If you are new to dried blood spotting, you can discuss your particular needs with us

Frequently Asked Questions

Are there differences between the paper used in the HemaSpot and HemaForm™ kits? No, both products can have the same grade of absorbent paper.  Both products may have grades other than the grade of paper Spot On Sciences has been recommending – TFN from Sartorius-Stedim.  For example, Whatman’s 903 grade, CF12 grade of paper can both be cut to fit the HemsSpot device platform as can Ahlstrom’s 226 grade of paper.
How soon do I have to use the HemaSpot after opening the sealed packaging? The HemaSpot device will function properly up to 60 minutes after the packaging is opened.  Spot On Sciences recommends applying the sample and closing the device within 15 minutes of opening the packaging.  After 60 minutes, the drying capacity of the device may be compromised.
After a successful sampling and closing of the device, are the sample and the device stable in the trunk of my car? Yes, the device itself is stable.  HemaSpot has been tested in a number of extreme conditions from a baking hot car sitting in the summer sun to a biological freezer set at -80° C.  The device has been submerged under water for at least 12 hours and has even been run over with the full weight of a Ford F-150.  The device and the DBS sample were found to have survived all of these conditions.  However, we don’t recommend any of these conditions for long term storage with the exception of the -80° C freezer.
Can I mail the sampled (used) device through the U.S. Postal Service or other delivery services?

Yes, dried blood spots are accepted by the U.S. Postal Service as safe and may be shipped by standard mail if secured within a secondary container before placing inside the mailer.  The HemaSpot device is considered the secondary container and renders the blood sample safe and secure after closing.

Compared to a traditional DBS card, how many punched samples can you get from a single HemaSpot device and how does that compare to the HemaForm plate? The HemaForm-80 was designed to hold 80uL of WB.  Each blade contains 11.5% of this volume or 9.2uL of WB.  A total of 8 blades may be collected from each HemaForm.  A typical DBS card holds 5 circles with each circle capable of receiving a single drop of blood.  A drop of blood usually means between 25 and 30uL of WB, depending upon hematocrit.  And each sample might allow 3 x 4mm punches.  Thus, assuming all circles are good, about 15 x 4mm punches may be collected from each card.  Each of these 4mm punches represents about 4uL of WB.  Therefore, nearly 60 uL of WB may be recovered from a total of 125 uL WB collected.
What is the expected reproducibility from blade-to-blade, from the HemaSpot HF (accuracy and precision)? Accuracy = (mean-nominal)/nominal*100
Precision = Standard Deviation/Average*100
Expected reproducibility from blade-to-blade should be less than 10% with the proper sample volume applied.  Nominal sample volume is 80 µL (approximately 2-3 drops) of blood.
Are there any specific elution methods you recommend as a starting point to help in assessing likely compatibility with existing systems?

Typically, we use a mixture of water and a water miscible organic solvent, such as methanol or acetonitrile, to elute analytes from the HemaForm blades.  After vortexing or sonicating the blades in 200µL of solvent in deep well plates or conical tubes for 30 to 60 minutes followed by centrifuging at 10,000g for 10 minutes, we are able to draw off 175-180µL of solvent.  Usually, this sample may be injected directly onto an HPLC system for mass spec analysis.

With protein or enzymatic assays, we generally use 200µL of a phosphate buffered solution or simply water to elute these components.  For enzymatic assays, the enzyme substrate is generally added to the PBS solution and the deep well plate is mixed with heating for as much as 48-hours depending upon the activity of the enzyme.  After incubation, the plates may be centrifuged briefly and the liquid decanted and added to an equal volume of cold methanol or acetonitrile to precipitate protein.  Again, after centrifuging to pellet protein, the sample is injected onto the HPLC for analysis.

How much blood can I recover from a single HemSpot blade? How much from an entire HemaForm? To absorb a target volume of 80µL of blood.  A single blade is approximately 11.5% of the total fan, meaning that each blade can carry approximately 9-10µL of blood per blade.
What is the best way to ensure a good finger stick? There are several established methods that can help with blood flow to the fingertips.  Spot On Sciences recommends either holding the selected hand under warm running water for about 1 minute and/or vigorously massaging or rubbing the fingertip.  Remember to select either the middle or ring finger on the non-dominant hand.  Avoid calluses and the “pad” of the fingertip.  The fleshy side of the fingertip is the ideal spot to place the lancet for the finger stick.
What is hematocrit? What are the effects from hematocrit?

Hematocrit is the volume percentage of red blood cells in blood.  Hematocrit (ht or HCT) is also referred to as Packed Cell Volume (PCV) or Erythrocyte Volume Fraction (EVF). Normal HCT levels for adult males is 42-52%. Normal HCT levels for adult females is 36-48%.  Hematocrit is measured by centrifuging whole blood in a heparinized capillary tube (to prevent clotting) to separate the plasma from red blood cells.  HCT is calculated by measuring the lengths of the layers (PCV length/total length).

Hematocrit has an effect on blood viscosity and may influence the flow and spread of a sample onto DBS filter paper.  Spot On Sciences’ HemaForm design reduces the effect of hematocrit by controlling the flow and spread when a sample is applied. (Hematocrit poster data can be supplied)