Restless Legs Syndrome (RLS) Discussion Board

badnights wrote: ↑

Mon Jun 15, 2020 7:15 am

Holland, what do you mean by iron saturation? I think I have a handle on transferrin saturation, TIBC & UIBC, iron concentration, & transferrin index, but I thought iron sat was just another term for transferrin sat.

What was your sat. when your ferritin was 452?

Beth,
iron sat=iron/TIBC (Where TIBC is Total Iron Binding Capacity)
Transferrin sat=(iron/transferrin)x70.9

They are usually close and frequently incorrectly considered the same. The difference is that TIBC (a cheap test) is TOTAL iron binding capacity, which is mostly, but not all, due to transferrin. Transferrin Sat (correctly used) means measuring transferrin level directly (a much more expensive test). For the purposes used here, they may be used interchangeably.

Iron Sat when my ferritin was 452 (just prior to my iron infusion last week) was 33% (the doc didn't order a transferrin level, so true transferrin sat is unknown).

badnights wrote: ↑

Mon Jun 15, 2020 7:15 am

I'm being advised against another infusion right now based on a sat. of 52% (and ferritin 308). It's a bit weird - two months post-infusion, my sat. was 44% and serum iron was 123 microg/dL. At that point I was definitely feeling benefits, I had dropped my hydromorphone from 9 to 6 mg daily. Seven and a half months post-infusion, symptoms had been bad again for about 1.5 months, my sat. was 52%, serum iron 140. Quite an increase, I would have expected it to DEcrease.

The cause of the increase has to be that I re-started oral iron 3 weeks before the test (I am kicking my own butt about that now, but I had irrational reasons for not getting tested, stemming from depression). But how can 3 weeks of oral iron cause more of an increase than the infusion did? Maybe my hepcidin is messed up and I absorb iron even when my blood is full of it. I also am convinced I get worse symptoms if I take 2 instead of 3 ferrous sulfate pills/day, but common wisdom is I'm just pooping it out.

Quite aside from that, I think none of the iron numbers we use are being interpreted correctly and they're probably inadequate to guess at status of brain iron. My body tells me the infusion was good for me, that it has worn off and another one is in order - no matter what the numbers are saying.

The difference may have been due to the timing of the blood test and/or the oral iron. Serum iron levels have a diurnal variation and are quite sensitive to recent changes in dietary iron intake. You should have the test done in the morning, fasting and off all iron supplements for several days. The lab doesn't usually tell you this, but it is important if you want accurate ferritin and iron levels.

Doctors are VERY nervous about poisoning their patients with too much iron, and your last iron sat was on the high side. If your last test wasn't done in early AM, fasting, and off iron tablets for several days, I would ask for a repeat test done. Might get an iron sat more acceptable to the doctor ordering your infusions.

You are absolutely correct in saying doctors frequently misinterpret these test results, the most common error is thinking serun ferritin levels reflect brain iron levels. And you are correct that none of these tests correctly reflect brain iron levels.

You are correct that 3 weeks of oral iron is not going to change the total amount of iron in your body, but the iron level measured in your blood is only a tiny portion of the total iron in your body, so iron tablets can easily increase the iron level measured in your blood, while not changing your total iron in your body, most commonly approximated by the ferritin.

I see - the sources I used said (or the way I took notes from them said) that iron/TIBC is transferrin sat and that iron/transferrin is transferrin index. But anyway I know now that your 33% was measuring the same thing as my 44 and 52%. I fasted for over 12 hours and stopped oral iron for 3 days before each. However, if the actual time of day matters, as opposed to my circadian day, that might have had an effect; I went about mid-afternoon. I probably got up around 10, can't remember.

badnights wrote: ↑

Tue Jun 16, 2020 8:12 am

I see - the sources I used said (or the way I took notes from them said) that iron/TIBC is transferrin sat and that iron/transferrin is transferrin index. But anyway I know now that your 33% was measuring the same thing as my 44 and 52%. I fasted for over 12 hours and stopped oral iron for 3 days before each. However, if the actual time of day matters, as opposed to my circadian day, that might have had an effect; I went about mid-afternoon. I probably got up around 10, can't remember.

There is another confounding issue in interpreting these tests: TIBC. Traditionally and most commonly "TIBC" means Total Iron Binding Capacity, however, some sources interpret the "TIBC" as Transferrin Iron Binding Capacity. That may be part of the reason for the confusion in the sources you mentioned.

The afternoon blood draw may have been the problem. Do you remember, or can look on the report, what time of day the previous test was drawn? I suggest a repeat, fasting, early morning, off oral iron supplements.

I will make sure I get there in the morning next time. Early! Ugh. Maybe I'll just stay up all night.