Hi,
The answer to your question " Should low monocytes needs to be concern" ANSWER is "NO not a big concern" and here are few things to back it up.
Monocytes are the type of white blood cells and the function main function of its
1) phagocytosis - process by which the other organisms are engulfed and destroyed
2) antigen presentation - helps other types of cell to find what they should be looking for -like signaling
3)
cytokine production - chemical which helps signaling for other cells where is the infection and where they should look for, Just like 911 services in united states there the call are received at a place and they will dispatched the near by unit as soon as possible.
Most of the MONOCYTES STAYS IN
SPLEEN AND WILL Come out into circulation in case of infection.
-------------------------------------------------------------------------------------------------------------------------------
NOW TO ANSWER " why it changes so drastically in period over a year"
*** (A) MOSTLY THE MONOCYTES WILL BE LOW IN CASE PERSON IS TAKING "STEROIDS" if such is true in your case then its self explanatory for having low monocyte count.
*** (B) Most of the MONOCYTES STAYS IN SPLEEN AND WILL Come out into circulation in case of infection , so the chances are their that you are healthy so the MONOCYTES in your body were stored in spleen and the
blood test may not show as many of them.
As far as isolated / only monocytes count changes is NOT Indicative of any thing wrong in the body.
Hope it helps.