Can I ask where the patients take the sample from please? Also has anyone done any comparative tests alongside a full DPD test to check their accuracy. Hopefully not important but many years ago I found that some test strips gave clinically significant false low readings especially if done on non-RO water. Test strips said 0.1ppm actual was 0.45ppm. It seemed that other chems in tap water (post GAC filter) interfered with the tests at the exceedingly low end of the scale that we require resolution to.
We used to have patients do a test with the Serim low range strips by taking a sample from the permeate line by way of a needled septum port, but it wasn't very successful and was discontinued.
We now use the same strips but get patients to test the incoming supply at the kitchen sink pre dialysis, basically checking for an abnormally high incoming level that the carbon stage wouldn't be able to deal with.
We use the higher grade carbon that's over rated for our normal flow rate and chlorine level, so I'm not that concerned about it.
Our patients rinse equipment before use and sample from the dialysate sample port before commencing run up. Not ideal but avoids extra taps and disconnects post carbon filtration. Post carbon would then be checked each visit at 3 months but carbon filters replaced regardless.
I've also had slight concerns as to accuracy of test strips though a recent issue with carbon columns did show a change in colour at just over 0.1ppm total chlorine. Happy staff and patients, remotely testing, will be able to identify issue (if the test is done correctly).