We switched to N-Hance years ago in order to comply with Massachusetts Water Resources regulations. ImmuAdd contains the preservative thimerosol-a mercury contaminant. We performed a small validation and found that N-Hance performed as well as ImmuAdd. Only one problem: the manufacturer's insert suggests using a transfer pipet to dispense the additive rather than the vial dropper in order to maintain the proper ionic strength. When we open a vial, we always discard the dropper and replace it with a stopper.

2 hours ago, Monique said:

We switched to N-Hance years ago in order to comply with Massachusetts Water Resources regulations. ImmuAdd contains the preservative thimerosol-a mercury contaminant. We performed a small validation and found that N-Hance performed as well as ImmuAdd. Only one problem: the manufacturer's insert suggests using a transfer pipet to dispense the additive rather than the vial dropper in order to maintain the proper ionic strength. When we open a vial, we always discard the dropper and replace it with a stopper.

For reference:

Edited August 19, 20204 yr by AMcCord

2 hours ago, AMcCord said:

For reference:

Wow. I perfectly understand the science, but that is an awful thing to put in a Directions for Use. A savvy Inspector could throw serious doubt on any tests performed using the supplied dropper. And why provide a dropper if it isn't good enough for the test ? The only way to meet this requirement to the fullest is to use a calibrated semiautomatic pipette.

21 hours ago, exlimey said:

Wow. I perfectly understand the science, but that is an awful thing to put in a Directions for Use. A savvy Inspector could throw serious doubt on any tests performed using the supplied dropper. And why provide a dropper if it isn't good enough for the test ? The only way to meet this requirement to the fullest is to use a calibrated semiautomatic pipette.

Or is the question the quality of the disposable pipette that is used for the patient plasma? We do use a disposable intended for Blood Bank use with a statement on the box  'consistent drop size'. I would say that you could present documentation that you've verified volume delivered (on average - since its a disposable) by the pipette vs the dropper in the vial.

22 hours ago, AMcCord said:

Or is the question the quality of the disposable pipette that is used for the patient plasma? We do use a disposable intended for Blood Bank use with a statement on the box  'consistent drop size'. I would say that you could present documentation that you've verified volume delivered (on average - since its a disposable) by the pipette vs the dropper in the vial.

That's an excellent point. It always struck me as slightly odd that such critical testing is done by "drops" - a potentially highly variable volume. One certainly wouldn't see an HIV test kit give instructions like "Dispense two drops". Goes to show that the standard serological (tube) test is extremely tolerant of variation.

On 8/21/2020 at 6:07 AM, exlimey said:

That's an excellent point. It always struck me as slightly odd that such critical testing is done by "drops" - a potentially highly variable volume. One certainly wouldn't see an HIV test kit give instructions like "Dispense two drops". Goes to show that the standard serological (tube) test is extremely tolerant of variation.

True, but I suppose we can also say that there has been years and years worth of testing performed that way with no evidence of harm reported from the practice.