Collection of serum samples





The pictures above show an example on how capillary blood samples from the finger can be collected into a serum tube. The finger is first disinfected with alcohol, optionally a thin layer of vaseline or silicon spray added and then the finger punctured. After that the blood usually just drops into the serum tube (e.g. the one from Sarstedt which is shown here, ord. no. 20.1308) when the finger is a bit pressed as in this example (not milked). After some time in upright position (20-60 min) the tube can be centrifuged in a mini centrifuge (also available with power supply from 4 AA batteries) or a manual centrifuge (more expensive and not so convenient). To increase the blood volume warming the hand, using high efficient lancets (e.g. the blue ones from Becton Dickinson, ord. no. 366594 ), wiping off the blood with a tissue to initiate again the blood flow or adding vaseline/silicon spray to inhibit the coagulation of blood in the puncture hole can be helpful procedures. Getting 100 ul serum is usually no problem and can be easily pipetted with an inexpensive 100 ul pipette (around 25USD). Alternatively 50 ul serum and a 50 ul pipette would also be OK.


Storage of serum samples


To make the measurement easier and more reliable please provide samples only in 0.5 mL tubes from Micronic which are provided by VitMin Lab. The important is that the tubes are correctly closed with the Push Caps. For sending the tubes to the lab itís not necessary to put them in boxes. A simple Ziploc bag which needs the smallest volume can be often the best option.

The volume of the serum should be between 50 and 100 ul serum (the best is when the volume in all tubes is approximately the same). With volumes less than 25 ul a measurement might not be possible anymore and volumes above 100 ul causes various handling problems which can also have the risk that a measurement is not possible or errors are increased due to carry over effects.

Tube_volumes_small_size


To be able to measure the samples it is essential that the unique 10 digit code on the bottom of each tube is correctly documented. Since the first digits of the tubes are the same it can be possible to read the last numbers directly by eye but usually itís helpful to use a magnifying lens with LED's (to each shipment one is added).The following pictures show on how this lens can be used:

2D_code_magnifying_lens

Alternatively Apps on a handphone can be used. The pictures below show this for the App 'Magnifier and Microscope from Hantor' and the App 'CortexScan' which is able to read 2D codes (standard QR code reader usually doesn't work). If there should be any problem in using these Apps please send an E-mail to erhardtj@gmail.com. Usually only a simple change in the settings or arrangement is necessary to make the reading of the codes convenient.
2D_code_magnifying_lens


A
nother possibility is the directing reading of the 2D code into Excel with a sensitive scanner. These scanners are already available for less than 150 USD (e.g. Symbol DS9208 from Zebra or Motorola) but probably only useful when the codes of a bigger number of tubes have to be read:




In case that reading the 10 digit code in the field is necessary and hand-phone or lens are difficult to use it can be helpful to write an informative ID together with the last relevant digits of the tube code on the tubes and to enter them for example later at a central place before shipping out the samples. Additional material like labels should never be added to the tube. They might not fit anymore in the measurement racks making the measurement impossible.
Tubes_handwriting

If reading the code from frozen tubes is necessary itís useful to put the tubes on a frozen cool element to avoid thawing of the serum.
Tubes_thaw_protection

The 2D tubes are available in rack and bag form. In rack form the cost are around 40 USD/rack and in bags around 0.27 USD/tube. They have to be added to the 5 USD/sample for the measurement of the 5 proteins. If the tubes are provided in racks the 10 digit code of each tube will be printed on a A4 sheet (or optionally send by E-Mail) in which an informative code can be added and later entered in Excel (the first 5 constant digits are replaced here with #) :

Tubes_racks

 
If an immediate frozen storage is not possible storage in non frozen form for some days is possible. Extensive tests at the CDC in Atlanta have shown that proteins in serum are stable at room temperature for one week. Since the conditions in the field can be much worse (temperature > 25įC or higher risk for bacterial growth) it's better to freeze the serum as soon as possible or at least to keep it in a cool environment. A car battery driven refrigerator or some deep frozen water bottles in the bottom of a good styrofoam box can be helfpul for this.

If anything of the material should be missing or if there is any additional question please send an e-mail to erhardtj@gmail.com. Usually a reply should come in less than 2 days. Otherwise just send a reminder.