Labs for RLS/PLMS

[danielmd06]

My predecessor in a sleep job would order exhaustive laboratory panels for RLS and PLMS...things like HgbA1c, TSH, BMP, CBC, and magnesium on these people. This is in addition to the ferritin and iron studies. I cannot find any evidence for these.

Do any of you guys actually order this amount of serological studies for PLMS? Am I missing something? I see no reason to go beyond ferritin and total iron binding capacity.

---

Members don't see this ad.

 

[michaelrack]

My predecessor in a sleep job would order exhaustive laboratory panels for RLS and PLMS...things like HgbA1c, TSH, BMP, CBC, and magnesium on these people. This is in addition to the ferritin and iron studies. I cannot find any evidence for these.

Do any of you guys actually order this amount of serological studies for PLMS? Am I missing something? I see no reason to go beyond ferritin and total iron binding capacity.

I also order B12- I see a lot of borderline low values in rls, and often prescribe oral b12. I also order folate, but it always comes back normal.

 

[neurologist]

I'd only get all the other stuff if I thought the RLS was secondary to an undiagnosed peripheral neuropathy (which should be apparent from hx and exam).

But for pure primary RLS I just get ferritin.

 

[lidocayne]

I agree with neurologist as stated above. Ferritin is the only lab I check (at least initially).

I'm not aware of any data to suggest checking any other laboratory data in this situation. I can see the logic in the B12 / Folic Acid, but I'd imagine the yield is fairly low for these, and not sure if the increased cost justifies checking it with every RLS case.

 

[michaelrack]

I have found the yield on B12 testing to be fairly high- lots of values in the 200-300 range, oral B12 often helps rls syxs in these pts. This is based on personal experience, I am not aware of any data.

 

[Faebinder]

Vit B12 level has a standard deviation of about a 100. Meaning you 300 could be a 200 and your 200 could be 100. That's why confirmation is done through methylmalonic acid levels.


Having said that... my understanding is that RLS is really related to low iron level... hence the low iron anemia... Anemia of low VitB12 does not necessarily go with anemia of low iron level (you could have both i suppose). My understanding from the texts is that the reason iron is important because it's a cofactor for the making of dopamine, which we know it's lack of or malfunction is a behind the RLS symptoms.

On the other hand, whose to say that Def of vit B12 wont result in overusing iron to make more RBCs and compensate, thus taking away from making dopamine.

 

[michaelrack]

Vit B12 level has a standard deviation of about a 100. Meaning you 300 could be a 200 and your 200 could be 100. That's why confirmation is done through methylmalonic acid levels.

.

That's one way of doing it. Currently, for B12 levels in the 200's I am currently treating with oral b12 500-1000 micrograms daily for one month and then repeating B12- if B12 is below 400 at this point then I will get a methylmalonic acid level (this assumes the initial b12 level was done purely for rls eval)

 

[michaelrack]

Having said that... my understanding is that RLS is really related to low iron level... hence the low iron anemia... Anemia of low VitB12 does not necessarily go with anemia of low iron level (you could have both i suppose). My understanding from the texts is that the reason iron is important because it's a cofactor for the making of dopamine, which we know it's lack of or malfunction is a behind the RLS symptoms.

On the other hand, whose to say that Def of vit B12 wont result in overusing iron to make more RBCs and compensate, thus taking away from making dopamine.

http://www.ncbi.nlm.nih.gov/pubmed/8842380

agree with what you are saying about iron. Circadian rhythms are also involved in RLS, and B12 appears to play a role in circadian rhythms