During the Network's last webinar “Water quality testing in action: Making your testing program work in the real world” there were some questions to our panelist Dr. Anna Murray that couldn't been answered because of time constraints. She answered them in written for us to share with all of you. ¡Thank you Anna! 

If you missed the event, you can register to watch the recording here.

Question: Would you suggest field blank/duplicate sample for CBTs?

Yes, I suggest using quality control measures with compartment bag tests (CBTs). Field blanks are always useful to test for sources of contamination during sample collection and transport. Field duplicates are also helpful, but the interpretation of them can be difficult due to the semi-quantitative nature of the test. It is possible to do the duplicate comparison by checking for both samples landing within the same diarrheal disease risk category (<1, 1-10, 10-100, >100 MPN/100mL)

During the Network's last webinar “Water quality testing in action: Making your testing program work in the real world” there were some questions to our panelist Dr. Anna Murray that couldn't been answered because of time constraints. She answered them in written for us to share with all of you. ¡Thank you Anna! 

If you missed the event, you can register to watch the recording here.

Question: For quality control measures, after how many samples should you test a blank or duplicate sample, if you are testing many samples?

The decision may come down to time or resources, but with field lab tests, I have used 1 blank per every 20 samples run. (If there are fewer than 20 samples, the minimum would be one at the end of the run of samples. Even better is to do one at the beginning, one at the middle, and one at the end. For field blank samples collected in the field, I would include a minimum of one field blank per team member per week.  

During the Network's last webinar “Water quality testing in action: Making your testing program work in the real world” there were some questions to our panelist Dr. Anna Murray that couldn't been answered because of time constraints. She answered them in written for us to share with all of you. ¡Thank you Anna! 

If you missed the event, you can register to watch the recording here.

Question: Quality control measure is interesting.  Does it mean testing the reagents and testing methods, as well?

Quality control methods can span a wide variety of checks to ensure the quality of your test methods (microbiological methods, chemical methods, or other methods). The ones I presented in the webinar are the basic quality control checks that are typical of field data collection. In laboratory analyses similar methods are used – namely blank samples and duplicate samples. Some additional control samples are also sometimes used, including “positive control” tests, where you test a sample that you know has a certain positive occurrence of the parameter you are testing, or “spiked sample” which has a high concentration of the parameter. These checks will give you a sense of how your procedure is performing. Then if there are issues identified, you can use that indication to investigate the root cause of the problem (protocol, human error, reagents, etc).