Sampling Best Practices


Sampling Best Practices for Genetic Testing

Goal: Ensure each sample is clearly marked and in the correct tube

The following have been identified as primary risk factors associated with the success of the sampling process:

  • Static electricity
  • Workspace organization
  • Isolation of sample tube
  • Double checking samples

NOTE: There are many different ways to minimize these risks. Each technician/institute should use the methods that work best in their environment.

Ways to Mitigate the Risk

Dissipate Static:

  • This is not a problem for all samplers. However, for those rooms which have trouble with static, a spritz of distilled water in the air over the work area has been found to solve the problem.

Pre-Plan and Organize

Logging Samples:

  • Enter the strain/line number and the number of mice to be genotyped.
  • Use a bar code on the cage card to download information into the database or write out a sampling plan and mark tags/cards/labels/cages with the date to be sampled.
  • If using a GTCA sample sheet, log into the sheet and enter data.

Suggestions for Preparing Tubes:

  • Select tubes to be used and place in the rack or plate.
  • You can use a different color tube for each different strain.
  • Use a well plate map to mark your place.
  • Number the plate or box, the sample, and/or your map (1 – 12 on top; A – H on sides) or write the ear tag number or animals ID on the tube or label and affix to the tube.
  • Mark on the tube/plate with a sharpie where litters and/or strains/lines start & stop.
  • Use a large standing magnifying glass to see better.
  • Use a pre-numbered plate with plate map to track which tube to put the sample into. When the strip is done, cap it and/or move it to the plate to be sent to the lab.
  • Number the cage cards of the animals to sample and use that number as the animal sample number. This also gives the total number of samples to expect.

Work Space:

  • Set up your work space to contain the plate maps and plates needed.
  • Be sure to have all necessary tools; sharpie, forceps, scissors, spray bottle, capillary tube, ear notcher, other sampling device, tag applicator, etc…
  • Preset for the order you will do things.

For example if tagging and sampling rodents:

  • Read your ear tags or sample IDs and organize in bags as they will be used.
  • Write on each baggy the numbers contained and the strain number they are to be used with.
  • Place what you need to pick up with your right hand on your right and your left on your left.

Isolate sample tube to track where you are in your sampling:

  • Place a capillary tube in the next tube to be filled. Lift it to the next tube and place the sample where the capillary tube was. This will help to mark your spot.
  • Re-cap tubes or block tubes off as they are filled.
  • Place blunt forceps or tweezers around the tube in which to place the sample.

Double Check Samples:

  • With or without a grid map, pre-identify what the last sample number in a row should be, and double check that the numbers match to make sure that you are at the right sample point. A checklist or sheet might help keep track of where you are in the process.
  • When an expected sample is not taken, cross that place off on the grid or sample list, leave the well/tube empty and move on to the next sample.
  • At the beginning of each row (or the end of the row), make sure the plate/tube numbers and the sample numbers line up
  • For large projects where multiple plates are used, use a two person system in which one person does the tail tipping and the other keeps track of and hands to the “tipper” which sample is next.
  • Hold plates up to the light periodically to ensure samples are in place.
  • When finished, hand the plate/box to a second person to confirm there is a sample in each position and to ensure the sample numbers and the plate numbers match.  Be sure any samples/ plate positions crossed off are empty.

GENERAL:

Move methodically and don’t rush.  It is better to send the correct samples and information late than the wrong samples and information on time.