Does anybody know if there is documentation or requirements anywhere indicating the length of time a sample is good for on an Rh Negative pregnant woman who requires her 28 week RHIG injection? We have always said the injection must be within 14 days, but as with many other things, I'm not sure if there is a scientific reason for this or if it is one of those "That's the way it's always been things"  Thanks for your time

I think the antibody screen done at 28 weeks is to make sure that the current pregnancy will not likely be affected by HDFN. A secondary effect is to know not to give RhIG if already clearly sensitized.  The OB guidelines in the US don't require testing at 28 weeks; they can just give the RhIG.  Based on those points, I would not see a need to have the injection time tied to the testing date.  I guess I would want a screen after, say, 25 weeks if they are doing one at all if it is to serve to predict the likelihood of HDFN.  We detected an anti-D in recent years on the 28 week sample of a first pregnancy and the baby was very affected by HDFN after born at 35 6/7 weeks.

When we still saw antibody screen orders prior to antenatal RhIG administration, the OB providers wanted the patients drawn within 7 days of their appointments. I always assumed that this was a recommendation of the American College of OB/Gyn. They stopped ordering those antibody screens several years ago, so I'm again assuming that there is no longer a recommendation for that testing. That particular practice very much follows guidelines.

On 1/17/2019 at 2:11 PM, NicolePCanada said:

Does anybody know if there is documentation or requirements anywhere indicating the length of time a sample is good for on an Rh Negative pregnant woman who requires her 28 week RHIG injection? We have always said the injection must be within 14 days, but as with many other things, I'm not sure if there is a scientific reason for this or if it is one of those "That's the way it's always been things"  Thanks for your time

So they don’t forget?!

On ‎1‎/‎17‎/‎2019 at 3:19 PM, Mabel Adams said:

I think the antibody screen done at 28 weeks is to make sure that the current pregnancy will not likely be affected by HDFN. A secondary effect is to know not to give RhIG if already clearly sensitized.  The OB guidelines in the US don't require testing at 28 weeks; they can just give the RhIG.  Based on those points, I would not see a need to have the injection time tied to the testing date.  I guess I would want a screen after, say, 25 weeks if they are doing one at all if it is to serve to predict the likelihood of HDFN.  We detected an anti-D in recent years on the 28 week sample of a first pregnancy and the baby was very affected by HDFN after born at 35 6/7 weeks.

Thank you Mabel. I understand the why of RhIg. I just wasn't sure if 30 days was an acceptable amount of time to have the sample for or if there was a worry of other antibody formation between the time of draw and the time of injection. Perhaps I am just not explaining myself well enough. Thanks for your response.

On ‎1‎/‎18‎/‎2019 at 7:00 PM, Ensis01 said:

So they don’t forget?!

No Ensis, I'm only asking if there is a specific time between the drawing of the sample and the date of injection mentioned in any standards anywhere. Historically, we have always said it had to be 14 days between sample draw and injection. I'm just wondering if there was a reason. Thanks for your response.

On 1/21/2019 at 7:16 AM, NicolePCanada said:

No Ensis, I'm only asking if there is a specific time between the drawing of the sample and the date of injection mentioned in any standards anywhere. Historically, we have always said it had to be 14 days between sample draw and injection. I'm just wondering if there was a reason. Thanks for your response.

Sorry, my response was written with a combination of tongue in cheek and experience.

When I worked in a transfusion service lab; the hospital policy was that RhIG was to be given within 72 hours, though we tried to get the RhIG to the RN ASAP. The reason was that patients would often discharge themselves, or occasionally boyfriends would insist on them being discharged before the RhIG could be administered. Many of these women would not see a doctor until their due date or there was a problem. At this point the patient would inevitably "clearly remember getting the injection", and as the order was in the system figuring out if the patient had actually received RhIG was difficult to determine satisfactory.

In my opinion your 14 day policy is probably a practical timeline for your patient population based on hospital experience. I would however suggest following up on your eligible patients to see how many of them are (were) non-compliant in receiving RhIG and use that as a guide to determine if your policy needs reevaluating.

Hope that helps.