Just when you do use the validity strips, use a dropper instead of dipping the strip into the sample. Using a dropper eliminates the chance of cross-contamination (when the strip is withdrawn from the sample after dipping, color agents from the reagent pads can often "bleed off" onto the neighboring reagent pads, making for erroneous readings).
When using a dropper, draw enough sample to where you can drop thick beads onto each reagent pad (panel). Then after a few seconds, carefully tip the strip on its side to drain off the excess on a paper towel. Now the strip is ready for reading.

Keep us posted of your findings and progress :thumbsup: